Optical device and optical detection system

Abstract

The optical device comprises: a first waveguide that transmits light in a waveguide direction by total reflection; and a second waveguide; the second waveguide comprises: a first reflecting film; a second reflecting film that is opposite to the first reflecting film; and a first optical waveguide layer that is directly connected to or connected with a clearance to the first waveguide, and is located between the first reflecting film and the second reflecting film; the first optical waveguide layer overlaps with an extension line of a center line of the first waveguide; the optical device emits a part of the light transmitted in the first optical waveguide layer to outside of the second waveguide; or the optical device introduces a part of the light incident into the second waveguide into the first optical waveguide layer.

Description

[0001] This application is a divisional application of Chinese patent application filed on August 21, 2017, with application number “201780003619.X” and invention title “Optical Scanning Device, Optical Receiving Device and Optical Detection System”. Technical Field

[0002] This disclosure relates to optical devices and optical detection systems. Background Technology

[0003] In the past, various devices have been proposed that can use light to sweep (i.e. scan) space.

[0004] Patent document 1 discloses a structure capable of scanning light using a drive device that rotates a mirror.

[0005] Patent Document 2 discloses an optical phased array having multiple nano-optical antenna elements arranged in a two-dimensional manner. The disclosed technique involves optically coupling each antenna element to a variable optical delay line (phase shifter). In this optical phased array, a coherent beam is guided by a waveguide to each antenna element, and the phase of the beam is changed by the phase shifter. This allows for variation of the amplitude distribution of the far-field radiation pattern.

[0006] Patent document 3 discloses an optical deflection element comprising: a waveguide having an optical waveguide layer in which light guides the wave inside, and a first distributed Bragg mirror formed on the upper and lower surfaces of the optical waveguide layer; a light inlet for allowing light to enter the waveguide; and a light outlet formed on the surface of the waveguide for allowing light that has entered from the light inlet and guided the wave inside the waveguide to exit.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2013 / 168266

[0010] Patent Document 2: Japanese Patent Publication No. 2016-508235

[0011] Patent Document 3: Japanese Patent Application Publication No. 2013-16591 Summary of the Invention

[0012] This disclosure provides a novel optical device capable of scanning light with a relatively simple structure.

[0013] An optical device according to the present disclosure includes: a first waveguide for transmitting light in the waveguide direction via total internal reflection; and a second waveguide; the second waveguide includes: a first reflective film; a second reflective film opposite to the first reflective film; and a first optical waveguide layer directly connected to or connected with clearance to the first waveguide, located between the first reflective film and the second reflective film; the first optical waveguide layer overlaps with the extension of the centerline of the first waveguide; the optical device emits a portion of the light transmitted within the first optical waveguide layer to the outside of the second waveguide; or, the optical device guides a portion of the light incident into the second waveguide into the first optical waveguide layer.

[0014] The aforementioned inclusive or specific technical solutions can also be implemented by devices, systems, methods, integrated circuits, computer programs, recording media, or any combination thereof.

[0015] According to a technical solution disclosed herein, one-dimensional or two-dimensional scanning via light can be achieved with a relatively simple structure. Attached Figure Description

[0016] Figure 1 This is a perspective view schematically showing the structure of an optical scanning device 100 according to an exemplary embodiment of the present disclosure.

[0017] Figure 2 This is a schematic diagram illustrating the construction of the cross-section of a waveguide element 10 and an example of transmitted light.

[0018] Figure 3 This is a diagram schematically representing the computational model used in this simulation.

[0019] Figure 4A This indicates the calculated refractive index n of the optical waveguide layer 20 when the thickness d is 704 nm. w The result is related to the emission angle θ of light with modulus m = 1.

[0020] Figure 4B This indicates the calculated refractive index n of the optical waveguide layer 20 when the thickness d is 446 nm. w The result is related to the emission angle θ of light with modulus m = 1.

[0021] Figure 5 This is a schematic diagram illustrating an example of an optical scanning device 100 that achieves one-dimensional scanning using a single waveguide element 10.

[0022] Figure 6A This is a cross-sectional view schematically showing an example (comparative example) of a structure in which light is input to waveguide element 10.

[0023] Figure 6BThis is a diagram illustrating an example of a structure in which light is incident on waveguide 10 through optical fiber 7.

[0024] Figure 7 It represents the angle of incidence θ of the light. in Fix, by making the refractive index n of the waveguide w The change causes the light's exit angle θ to change out A graph showing the change in coupling efficiency under varying conditions.

[0025] Figure 8 This is a cross-sectional view schematically illustrating a portion of the construction of an optical scanning device according to an exemplary embodiment of the present disclosure.

[0026] Figure 9 This is a cross-sectional view schematically illustrating another example of the construction of an optical scanning device.

[0027] Figure 10 This is a cross-sectional view schematically illustrating the structure of another example of an optical scanning device.

[0028] Figure 11 It means as Figure 8 The example shown is an example of light incident on an optical waveguide layer 2 sandwiched between two multilayer reflective films.

[0029] Figure 12A Indicates light as Figure 9 The example shown is an example of introducing light into waveguide 1 via grating 5 provided on the surface of waveguide 1.

[0030] Figure 12B This represents an example of light entering from the end face of waveguide 1.

[0031] Figure 12C This illustrates an example where light is input from a laser source 6 located on the surface of waveguide 1 via that surface.

[0032] Figure 13 Indicates that n w1 The d2 dependence of the coupling efficiency of the guided light from waveguide 1 to waveguide 10 when d1 is set to 1.45, wavelength λ is set to 1.27μm, wavelength λ is set to 1.55μm.

[0033] Figure 14 Indicates that n w1 The result of calculations performed using the same method with d1 changed to 0.5μm and 3.48 changed to 0.48.

[0034] Figure 15 The horizontal axis is set to d² / d. cutoff Set the vertical axis to the refractive index ratio (|n w1 -n w2 | / n w1The diagram categorizes cases into those with coupling efficiencies above 0.5 and those with coupling efficiencies below 0.5.

[0035] Figure 16 This is a diagram showing that the center of the optical waveguide layer 2 in waveguide 1 and the center of the optical waveguide layer 20 in waveguide 10 are offset by Δz.

[0036] Figure 17 This is a graph representing the Δz dependence of the coupling efficiency of light from waveguide 1 to waveguide 10.

[0037] Figure 18A Indicates that n w1 The d2 dependency of coupling efficiency when d1 is set to 0.7μm and wavelength λ is set to 1.55μm.

[0038] Figure 18B Indicates that n w1 The d2 dependency of coupling efficiency when λ is set to 3.48, d1 is set to 0.46μm, and wavelength λ is set to 1.55μm.

[0039] Figure 19A This is a diagram illustrating the computational model used in the calculation of light transmission in other modes.

[0040] Figure 19B This is a graph showing the calculated results of light transmission for other modes.

[0041] Figure 20A This is a cross-sectional view showing another embodiment of the optical scanning device.

[0042] Figure 20B This is a graph showing the calculation results of the gap width dependency of coupling efficiency.

[0043] Figure 21A It is a diagram showing the cross-section of a waveguide array that emits light in a direction perpendicular to the exit surface of the waveguide array.

[0044] Figure 21B It is a diagram showing the cross-section of a waveguide array that emits light in a direction different from the direction perpendicular to the exit surface of the waveguide array.

[0045] Figure 22 It is a schematic representation of a waveguide array in three-dimensional space.

[0046] Figure 23A This is a schematic diagram illustrating the situation where diffracted light is emitted from the waveguide array when p is larger than λ.

[0047] Figure 23B This is a schematic diagram illustrating the situation where diffracted light is emitted from the waveguide array when p is smaller than λ.

[0048] Figure 23C This is a schematic diagram illustrating the situation where diffracted light is emitted from the waveguide array when p≒λ / 2.

[0049] Figure 24 This is a schematic diagram illustrating an example of a structure in which the phase shifter 80 is directly connected to the waveguide element 10.

[0050] Figure 25 This is a schematic diagram showing the waveguide array 10A and the phase shifter array 80A viewed from the normal direction (Z direction) of the light exit surface.

[0051] Figure 26 This is a schematic diagram illustrating an example of a structure in which the waveguide of the phase shifter 80 is connected to the optical waveguide layer 20 of the waveguide element 10 via other waveguides 85.

[0052] Figure 27 This diagram illustrates a structural example in which multiple phase shifters 80 arranged in a cascaded manner are inserted into an optical splitter 90.

[0053] Figure 28A This is a perspective view schematically showing an example of the structure of the first adjusting element 60.

[0054] Figure 28B This is a perspective view schematically showing another structural example of the first adjusting element 60.

[0055] Figure 28C This is a perspective view schematically showing another structural example of the adjusting element 60.

[0056] Figure 29 This is a diagram illustrating an example of a structure that combines an adjustment element 60, comprising a heater 68 made of a material with high resistance, with a waveguide element 10.

[0057] Figure 30 This is a diagram illustrating a structural example of a mirror 30 held in place by a support member 70 made of a material that is easily deformable.

[0058] Figure 31 This is a diagram illustrating an example of a structure in which mirrors 30 and / or 40 are moved by electrostatic forces occurring between the electrodes.

[0059] Figure 32 This is a diagram illustrating a structural example in which the electrode 62 that generates gravity is positioned in a location that does not obstruct the transmission of light.

[0060] Figure 33 This is a diagram showing an example of a piezoelectric element 72 containing piezoelectric material.

[0061] Figure 34A It means to use Figure 33A diagram showing an example of the structure of the support member 74a of the piezoelectric element 72, which has a single piezoelectric element.

[0062] Figure 34B This is a diagram illustrating an example of the state in which the support member 74a deforms when a voltage is applied to the piezoelectric element 72.

[0063] Figure 35A It means to use Figure 33 A diagram showing an example of the structure of the support member 74b of the piezoelectric element 72, which has a double piezoelectric element configuration.

[0064] Figure 35B This is a diagram illustrating an example of the deformation of the support member 74a when a voltage is applied to the piezoelectric elements 72 on both sides.

[0065] Figure 36 It means to Figure 34A The figure shows an example of an actuator with support member 74a arranged on both sides of mirror 30.

[0066] Figure 37A This diagram illustrates the tilting of the front end that occurs in a single piezoelectric actuator.

[0067] Figure 37B This diagram shows an example of connecting two single piezoelectric support members 74a with different directions of extension and retraction in series.

[0068] Figure 38 This diagram illustrates an example of a structure in which multiple support components (i.e., auxiliary substrates) 52 for holding the first mirror 30 are driven together by an actuator.

[0069] Figure 39 This is a diagram illustrating a structural example where the first mirror 30 among multiple waveguide elements 10 is a plate-shaped mirror.

[0070] Figure 40 This is a diagram illustrating an example of a structure from which wiring 64 is taken out together from the electrodes 62 of each waveguide element 10.

[0071] Figure 41 This is a diagram illustrating an example of a structure in which a portion of the electrodes 62 and wiring 64 are shared.

[0072] Figure 42 This is a diagram illustrating an example of a structure in which a common electrode 62 is configured for multiple waveguide elements 10.

[0073] Figure 43 This is a schematic diagram illustrating an example of a structure that ensures a large area for configuring the phase shifter array 80A and integrates the waveguide array in a smaller manner.

[0074] Figure 44This is a diagram showing a structural example where two phase shifter arrays 80Aa and 80Ab are respectively arranged on both sides of waveguide array 10A.

[0075] Figure 45A This is a structural example of a waveguide array where the arrangement direction d1 and the extension direction d2 of the waveguide elements 10 are not orthogonal.

[0076] Figure 45B This is a structural example of a waveguide array where the arrangement spacing of waveguide elements 10 is not fixed.

[0077] Figure 46 This is a diagram illustrating a structural example of an optical scanning device 100 that integrates components such as an optical splitter 90, a waveguide array 10A, a phase shifter array 80A, and a light source 130 on a circuit board (i.e., a chip).

[0078] Figure 47 This is a schematic diagram illustrating a situation where a two-dimensional scan is performed by irradiating a laser beam or the like into the distance from the optical scanning device 100.

[0079] Figure 48 This is a block diagram illustrating a structural example of a LiDAR system 300 capable of generating such ranging images.

[0080] Figure 49 This is a diagram showing the general structure of a total reflection waveguide.

[0081] Figure 50 This is a diagram showing the electric field intensity distribution of a total reflection waveguide.

[0082] Figure 51 This is a diagram showing the general structure of a slow optical waveguide.

[0083] Figure 52 This is a diagram showing the electric field intensity distribution of a slow optical waveguide. Detailed Implementation

[0084] Before describing the embodiments of this disclosure, the understanding that forms the basis of this disclosure will be explained.

[0085] The inventors of this application have discovered that in conventional optical scanning devices, there is a technical problem that makes it difficult to scan space with light without complicating the structure of the device.

[0086] For example, the technology disclosed in Patent Document 1 requires a drive device to rotate the mirror. Therefore, the structure of the device becomes complex, and there is a technical problem of poor vibration robustness.

[0087] In the optical phased array described in Patent Document 2, optical branches need to be guided into multiple column waveguides and multiple row waveguides to direct the light toward multiple antenna elements arranged in a two-dimensional pattern. Therefore, the wiring of the waveguides used to guide the light becomes very complex. Furthermore, the range of the two-dimensional scan cannot be increased. Moreover, to make the amplitude distribution of the emitted light in the far field vary two-dimensionally, phase shifters need to be connected to each of the multiple antenna elements arranged in a two-dimensional pattern, and phase control wiring needs to be installed on the phase shifters. This causes the phase of the light incident on the multiple antenna elements arranged in a two-dimensional pattern to change by different amounts. Therefore, the structure of the elements becomes very complex.

[0088] According to the structure in Patent Document 3, by changing the wavelength of the light incident on the light-deflecting element, a larger one-dimensional scan can be performed by the emitted light. However, a mechanism for changing the wavelength of the light incident on the light-polarizing element is required. If such a mechanism is incorporated into a light source such as a laser, there is a technical problem that the structure of the light source becomes complicated.

[0089] The inventors of this application, addressing the aforementioned technical problems in the prior art, have researched structures for solving these problems. They have discovered that the aforementioned technical problems can be solved by using a waveguide element having a pair of opposing mirrors and an optical waveguide layer sandwiched between these mirrors. One of the mirrors in the waveguide element has a higher light transmittance than the other, causing a portion of the light transmitted in the optical waveguide layer to be emitted outwards. The direction (or emission angle) of the emitted light can be varied by adjusting the refractive index and / or thickness of the optical waveguide layer, as described later. More specifically, by varying the refractive index and / or thickness, the composition of the wave vector of the emitted light along the longer direction of the optical waveguide layer can be varied. This enables one-dimensional scanning.

[0090] Furthermore, two-dimensional scanning can also be achieved when using an array of multiple waveguide elements. More specifically, by imparting an appropriate phase difference to the light supplied to the multiple waveguide elements, the direction in which the light emitted from the multiple waveguide elements mutually reinforces each other can be changed by adjusting this phase difference. Through the change in phase difference, the component of the wave vector of the emitted light that intersects the direction along the longer direction of the optical waveguide layer changes. Thus, two-dimensional scanning can be achieved. Furthermore, in performing two-dimensional scanning, it is not necessary to change at least one of the refractive index and thickness of the multiple optical waveguide layers by different amounts. That is, by imparting an appropriate phase difference to the light supplied to the multiple optical waveguide layers and simultaneously changing at least one of the refractive index and thickness of the multiple optical waveguide layers by the same amount, two-dimensional scanning can be performed. Thus, according to the embodiments of this disclosure, two-dimensional scanning of transmitted light can be achieved with a relatively simple structure.

[0091] The above basic principles can be applied not only to the emission of light but also to the reception of optical signals. By changing at least one of the refractive index and thickness of the optical waveguide layer, the direction of the light that can be received can be changed one-dimensionally. Furthermore, if the phase difference of the light is changed by multiple phase shifters respectively connected to multiple waveguide elements arranged in one direction, the direction of the light that can be received can be changed two-dimensionally.

[0092] The optical scanning device and optical receiving device of the present disclosure can, for example, be used as antennas in a LiDAR (Light Detection and Ranging) system. Compared with radar systems that use radio waves such as microwaves, LiDAR systems can detect the distance distribution of objects with higher resolution because they use short-wavelength electromagnetic waves (visible light, infrared, or ultraviolet light). Such a LiDAR system can be mounted in mobile bodies such as automobiles, UAVs (Unmanned Aerial Vehicles), and AGVs (Automated Guided Vehicles) as a collision avoidance technology.

[0093] <Structure Example of an Optical Scanning Device>

[0094] The following is an example illustrating the structure of an optical scanning device for performing two-dimensional scanning.

[0095] Figure 1 This is a perspective view schematically illustrating the structure of an optical scanning device 100 according to an exemplary embodiment of the present disclosure. The optical scanning device 100 includes components in a first direction (…). Figure 1 A waveguide array comprising multiple waveguide elements 10 regularly arranged in the Y direction (as in the first direction). The multiple waveguide elements 10 are an example of multiple second waveguides. Each of the multiple waveguide elements 10 has a second direction (intersecting the first direction)... Figure 1 The waveguide elements 10 extend in the X direction. While transmitting light in the second direction, they also direct light out in a third direction D3, intersecting the plane formed by the first and second directions. The plane formed by the first and second directions is an imaginary plane parallel to the first and second directions. In this embodiment, the first direction (Y direction) and the second direction (X direction) are orthogonal, but they may not be orthogonal. In this embodiment, the waveguide elements 10 are arranged at equal intervals in the Y direction, but they do not necessarily need to be arranged at equal intervals.

[0096] Furthermore, the orientation of the structures shown in the accompanying drawings is set for ease of explanation, and the embodiments disclosed herein do not limit the orientation in actual implementation. In addition, the shape and size of the entirety or a portion of the structures shown in the drawings are not limited to the actual shape and size.

[0097] Each of the multiple waveguide elements 10 has a first mirror 30 and a second mirror 40 (hereinafter sometimes simply referred to as mirrors) facing each other, and an optical waveguide layer 20 located between the mirrors 30 and 40. The mirrors 30 and 40 each have a reflecting surface at their interface with the optical waveguide layer 20 that intersects a third direction D3. The mirrors 30 and 40, as well as the optical waveguide layer 20, have a shape extending in a second direction (X direction). Furthermore, as described later, the multiple first mirrors 30 of the multiple waveguide elements 10 may also be multiple portions of a third mirror integrally formed. Furthermore, the multiple second mirrors 40 of the multiple waveguide elements 10 may also be multiple portions of a fourth mirror integrally formed. Moreover, the multiple optical waveguide layers 20 of the multiple waveguide elements 10 may also be multiple portions of an optical waveguide layer integrally formed. Multiple waveguides can be formed at least by (1) each first mirror 30 being separately constructed from the other first mirror 30, (2) each second mirror 40 being separately constructed from the other second mirror 40, or (3) each optical waveguide layer 20 being separately constructed from the other optical waveguide layer 20. "Separately constructed" means not only physically setting up space, but also separating the components by sandwiching materials with different refractive indices. The reflecting surfaces of the first mirror 30 and the second mirror 40 are positioned approximately parallel to each other. At least the first mirror 30 of the two mirrors 30 and 40 has the characteristic of transmitting a portion of the light transmitted in the optical waveguide layer 20. In other words, the first mirror 30 has a higher light transmittance with respect to the light than the second mirror 40. Therefore, a portion of the light transmitted in the optical waveguide layer 20 is emitted from the first mirror 30 to the outside. Such mirrors 30 and 40 can be, for example, multilayer mirrors formed by multilayer films (sometimes called "multilayer reflective films") made of dielectrics.

[0098] By controlling the phase of the light input to each waveguide element 10, at least one of the refractive index and thickness of the optical waveguide layer 20 of these waveguide elements 10 can be changed synchronously (simultaneously), thereby enabling two-dimensional scanning of light.

[0099] In order to achieve such two-dimensional scanning, the inventors of this application conducted a detailed analysis of the operating principle of the waveguide element 10. By synchronously driving multiple waveguide elements 10 based on the results, two-dimensional scanning of light was successfully achieved.

[0100] like Figure 1As shown, if light is input into each waveguide element 10, the light exits from the exiting surface of each waveguide element 10. The exiting surface is located on the opposite side of the reflecting surface of the first mirror 30. The direction D3 of the emitted light depends on the refractive index, thickness, and wavelength of the optical waveguide layer. In this embodiment, at least one of the refractive index and thickness of each optical waveguide layer is controlled synchronously so that the light emitted from each waveguide element 10 is approximately in the same direction. Therefore, the X-direction component of the wave vector of the light emitted from the multiple waveguide elements 10 can be varied. In other words, the direction D3 of the emitted light can be varied along... Figure 1 The direction 101 shown changes.

[0101] Furthermore, since the light emitted from the multiple waveguide elements 10 is directed in the same direction, the emitted light interferes with each other. By controlling the phase of the light emitted from each waveguide element 10, the direction in which the light reinforces each other due to interference can be changed. For example, when multiple waveguide elements 10 of the same size are arranged at equal intervals in the Y direction, light with a phase difference of a certain amount is input into the multiple waveguide elements 10. By changing their phase differences, the Y-direction component of the wave vector of the emitted light can be changed. In other words, by changing the phase difference of the light introduced into the multiple waveguide elements 10 respectively, the direction D3 in which the light reinforces each other due to interference can be changed along... Figure 1 The direction 102 shown changes. This enables two-dimensional scanning using light.

[0102] The operating principle of the optical scanning device 100 will be explained in more detail below.

[0103] <Operating Principle of Waveguide Elements>

[0104] Figure 2 This is a schematic diagram illustrating the cross-sectional structure of a waveguide element 10 and an example of transmitted light. Figure 2 In the middle, will be with Figure 1 The direction perpendicular to the X and Y directions is defined as the Z direction, schematically representing a cross-section parallel to the XZ plane of waveguide element 10. A pair of mirrors 30 and 40 are disposed within waveguide element 10, sandwiching optical waveguide layer 20. Light 22, introduced from one end of the optical waveguide layer 20 in the X direction, is positioned on the upper surface of the optical waveguide layer 20. Figure 2 The first mirror 30 on the upper surface and the mirror 30 on the lower surface (in the middle) Figure 2 The light is repeatedly reflected by the second mirror 40 on the lower surface of the first mirror 30 while propagating within the optical waveguide layer 20. The light transmittance of the first mirror 30 is higher than that of the second mirror 40. Therefore, a portion of the light can be output primarily from the first mirror 30.

[0105] In conventional waveguides such as optical fibers, light propagates along the waveguide through repeated total internal reflection. In contrast, in the waveguide element 10 of this embodiment, light propagates through repeated reflections by mirrors 30 and 40 disposed above and below the optical waveguide layer 20. Therefore, light incident at an angle closer to perpendicular to the mirrors 30 or 40 can be transmitted without being constrained by the light propagation angle (the angle of incidence at the interface between the mirrors 30 or 40 and the optical waveguide layer 20). That is, light incident at an angle smaller than the critical angle of total internal reflection (i.e., an angle closer to perpendicular) can also be transmitted. Therefore, the light propagation speed (group velocity) in the light propagation direction is significantly lower than the speed of light in free space. Consequently, the waveguide element 10 has the property that the light propagation conditions vary considerably with changes in the wavelength of the light, the thickness of the optical waveguide layer 20, and the refractive index of the optical waveguide layer 20.

[0106] The transmission of light through waveguide element 10 will be explained in more detail. The refractive index of the optical waveguide layer 20 will be set as n. w Let the thickness of the optical waveguide layer 20 be d. Here, the thickness d of the optical waveguide layer 20 is the dimension of the optical waveguide layer 20 in the normal direction of the reflecting surface of mirror 30 or 40. If the interference condition of light is considered, the transmission angle θ of the light with wavelength λ... w It satisfies the following equation (1).

[0107] [Formula 1]

[0108] 2dn w cosθ w =mλ (1)

[0109] M is the mode number. Equation (1) is equivalent to the condition for light within the optical waveguide layer 20 to form a standing wave in the thickness direction. When the wavelength λ within the optical waveguide layer 20... g For λ / n w At that time, the wavelength λ in the thickness direction of the optical waveguide layer 20 can be considered to be... g’ It is λ / (n) w cosθ w When the thickness d of the optical waveguide layer 20 is equal to the wavelength λ in the thickness direction of the optical waveguide layer 20... g’ Half of λ / (2n) w cosθ w When the integer multiples of ) are equal, a standing wave is formed. Based on this condition, equation (1) is obtained. In addition, m in equation (1) represents the number of antinodes of the standing wave.

[0110] When mirrors 30 and 40 are multilayer mirrors, light also penetrates into the interior of the mirror during reflection. Therefore, strictly speaking, it is necessary to add the term corresponding to the optical path length of the light penetration to the left side of equation (1). However, due to the refractive index n of the optical waveguide layer 20... wThe influence of thickness d is much greater than the influence of light intrusion into the mirror, so the basic operation can be explained by equation (1).

[0111] The exit angle θ of light transmitted within the optical waveguide layer 20 when it passes through the first mirror 30 and exits to the outside (typically air) can be described according to Snell's rule, as in the following equation (2).

[0112] [Formula 2]

[0113] sinθ=n w sinθ w (2)

[0114] Equation (2) can be derived from the wavelength λ / sinθ of the light on the air side of the light emission surface and the wavelength λ / (n) of the light on the waveguide element 10 side in the direction of light propagation. w sinθ w It is obtained by using conditions that are equal.

[0115] From equations (1) and (2), the emission angle θ can be described as shown in equation (3) below.

[0116] [Formula 3]

[0117]

[0118] According to equation (3), by changing the wavelength λ of light and the refractive index n of the optical waveguide layer 20, w And a certain thickness d of the optical waveguide layer 20 can change the direction of light emission.

[0119] For example, in n w With a refractive index of 2, d = 387 nm, λ = 1550 nm, and m = 1, the emission angle is 0°. If the refractive index is changed by n from this state... w =2.2, then the emission angle changes by approximately 66°. On the other hand, if the thickness is changed to d = 420 nm without changing the refractive index, the emission angle changes by approximately 51°. If the wavelength is changed to λ = 1500 nm without changing the refractive index and thickness, the emission angle changes by approximately 30°. Thus, by changing the wavelength λ of the light and the refractive index n of the waveguide layer 20... w The thickness d of the optical waveguide layer 20 can significantly change the direction of light emission.

[0120] Based on this principle, it is conceivable to control the emission direction of light by setting a wavelength-changing mechanism that alters the wavelength of light propagating within the optical waveguide layer 20. However, if the wavelength-changing mechanism is incorporated into a light source such as a laser, the structure of the light source becomes complex.

[0121] Therefore, the optical scanning device 100 of this embodiment controls the refractive index n of the optical waveguide layer 20. w The direction of light emission is controlled by one or both of the thickness d. In this embodiment, the wavelength λ of the light remains constant during operation. The wavelength λ is not particularly limited. For example, the wavelength λ can be included in the wavelength range of 400 nm to 1100 nm (from visible light to near-infrared light), which is typically achieved by photodetectors or image sensors that detect light by absorbing it with silicon (Si), providing high detection sensitivity. In other examples, the wavelength λ can be included in the wavelength range of near-infrared light, which has relatively low transmission loss in optical fibers or Si waveguides. These wavelength ranges are just one example. The wavelength range of the light used is not limited to the wavelength range of visible light or infrared light; for example, it can also be the wavelength range of ultraviolet light. In this embodiment, wavelength control is not performed, but wavelength variation control can be performed in addition to control of refractive index and / or thickness.

[0122] The inventors of this application have verified through optical analysis that the emission of light in a specific direction as described above is indeed possible. The optical analysis was performed using calculations from Cybernetic's DiffractMOD. This simulation, based on Rigorous Coupled-Wave Analysis (RCWA), accurately calculates the effects of wave optics.

[0123] Figure 3 This diagram schematically illustrates the computational model used in this simulation. In this model, a second mirror 40, an optical waveguide layer 20, and a first mirror 30 are sequentially stacked on a substrate 50. Both the first mirror 30 and the second mirror 40 are multilayer mirrors containing multiple dielectric films. The second mirror 40 has a structure in which six layers of a low-refractive-index layer 42 (relatively low refractive index) and six layers of a high-refractive-index layer 44 (relatively high refractive index) are alternately stacked (totaling 12 layers). The first mirror 30 has a structure in which two layers of a low-refractive-index layer 42 and two layers of a high-refractive-index layer 44 (totaling 4 layers) are alternately stacked (totaling 4 layers). An optical waveguide layer 20 is disposed between mirrors 30 and 40. The medium other than the waveguide element 10 and the substrate 50 is air.

[0124] Using this model, the optical response to the incident light is investigated while varying the incident angle. This corresponds to investigating the degree of coupling between the incident light from the air and the optical waveguide layer 20. Under the condition that the incident light is coupled to the optical waveguide layer 20, the reverse process also occurs: the light transmitted within the optical waveguide layer 20 exits outward. Therefore, determining the incident angle when the incident light is coupled to the optical waveguide layer 20 is equivalent to determining the exit angle when the light transmitted within the optical waveguide layer 20 exits outward. If the incident light is coupled to the optical waveguide layer 20, losses occur within the optical waveguide layer 20 due to light absorption and scattering. That is, under conditions of significant loss, the incident light is strongly coupled to the optical waveguide layer 20. If there is no light loss due to absorption, etc., the sum of the transmittance and reflectance is 1; however, if there is loss, the sum of the transmittance and reflectance becomes less than 1. In this calculation, in order to take into account the effect of light absorption, an imaginary part is introduced into the refractive index of the optical waveguide layer 20, and the value obtained by subtracting the sum of transmittance and reflectance from 1 is calculated as the magnitude of the loss.

[0125] In this simulation, it is assumed that substrate 50 is Si, low-refractive-index layer 42 is SiO2 (thickness 267 nm), and high-refractive-index layer 44 is Si (thickness 108 nm). The magnitude of the loss when incident with light of wavelength λ = 1.55 μm is calculated under various changes in the angle of incidence.

[0126] Figure 4A This represents the refractive index n of the optical waveguide layer 20 when the thickness d is 704 nm. w The result shows the relationship between the emission angle θ of light with modulus m = 1 and the emission angle θ. White lines indicate greater losses. For example... Figure 4A As shown, in n w Near n = 2.2, the emission angle of light with a modulus m = 1 is θ = 0°. w Among substances with a refractive index of 2.2, lithium niobate is an example.

[0127] Figure 4B This represents the refractive index n of the optical waveguide layer 20 when the thickness d is 446 nm. w The result is related to the emission angle θ of light with modulus m = 1. For example... Figure 4B As shown, in n w Near 3.45, the emission angle of light with a modulus m = 1 is θ = 0°. In a region with a modulus close to n... w Among substances with a refractive index of 3.45, silicon (Si) is an example.

[0128] By adjusting the thickness d of the optical waveguide layer 20 in this way, it is possible to design a specific refractive index n for the optical waveguide layer 20. wThe emission angle θ of light with a specific modulus (e.g., m=1) is 0°.

[0129] like Figure 4A and Figure 4B As shown, it can be confirmed that the emission angle θ changes significantly with the change in refractive index. As will be discussed later, the refractive index can be changed through various methods, such as carrier injection, electro-optical effects, and thermo-optical effects. The change in refractive index caused by such methods is about 0.1, which is not very large. Therefore, up to this point, we have considered that the emission angle does not change so much under such a small change in refractive index. However, as... Figure 4A and Figure 4B As shown, it can be seen that near the refractive index where the emission angle θ = 0°, if the refractive index increases by 0.1, the emission angle θ changes from 0° to approximately 30°. Thus, in the waveguide element 10 of this embodiment, even a small change in refractive index can significantly adjust the emission angle.

[0130] Similarly, by Figure 4A and Figure 4B The comparison shows that the emission angle θ changes significantly corresponding to the change in the thickness d of the optical waveguide layer 20. As described later, the thickness d can be changed, for example, by an actuator connected to at least one of the two mirrors. Even if the change in thickness d is small, the emission angle can be adjusted considerably.

[0131] Thus, in order to change the direction of light emitted from waveguide element 10, it is only necessary to adjust the refractive index n of optical waveguide layer 20. w And / or the thickness d can be changed. To achieve this, the optical scanning device 100 of this embodiment includes a first adjustment element that changes at least one of the refractive index and thickness of the optical waveguide layer 20 in each waveguide element 10. An example of the structure of the first adjustment element will be described later.

[0132] As described above, if waveguide element 10 is used, then by adjusting the refractive index n of the optical waveguide layer 20... w By changing at least one of the thickness d, the emission direction of light can be significantly altered. This allows the emission angle of light emitted from mirror 30 to vary along the direction of waveguide element 10. To achieve such one-dimensional scanning, an array of waveguide elements 10 is not required; at least one waveguide element 10 is sufficient.

[0133] Figure 5This diagram schematically illustrates an example of an optical scanning device 100 that achieves one-dimensional scanning using a single waveguide element 10. In this example, a beam spot extending in the Y direction is formed. By changing the refractive index of the optical waveguide layer 20, the beam spot can be moved along the X direction. This achieves one-dimensional scanning. Because the beam spot extends in the Y direction, even scanning in a uniaxial direction can scan a relatively large area that extends two-dimensionally. This method can also be used in applications where two-dimensional scanning is not required. Figure 5 The structure shown.

[0134] In the case of achieving two-dimensional scanning, such as Figure 1 As shown, a waveguide array with multiple waveguide elements 10 arranged in a specific pattern is used. When the phase of light propagating within the multiple waveguide elements 10 satisfies a specific condition, the light is emitted in a specific direction. If this phase condition changes, the emission direction of the light also changes in the arrangement direction of the waveguide array. That is, by using a waveguide array, two-dimensional scanning can be achieved. More specific examples of structures used to achieve two-dimensional scanning will be described later.

[0135] As described above, by using at least one waveguide element 10 to change at least one of the refractive index and thickness of the optical waveguide layer 20 in the waveguide element 10, the emission direction of light can be changed. However, there is room for improvement regarding the structure for efficiently guiding light into the waveguide element 10. The waveguide element 10 of the embodiments of this disclosure differs from a conventional waveguide that utilizes total internal reflection of light (hereinafter sometimes referred to as a "total internal reflection waveguide"), and has a waveguide structure in which the optical waveguide layer is sandwiched between a pair of mirrors (e.g., multilayer reflective films) (hereinafter sometimes referred to as a "reflective waveguide"). The coupling of light into such reflective waveguides has not been sufficiently studied until now. The inventors of this application have conceived of a new structure for efficiently guiding light into the optical waveguide layer 20.

[0136] Figure 6A This is a cross-sectional view schematically illustrating an example (comparative example) of a structure in which light is indirectly input into the optical waveguide layer 20 via air and mirror 30. In this comparative example, propagating light is indirectly introduced from the outside into the optical waveguide layer 20, which is a waveguide element 10 that serves as a reflective waveguide, via air and mirror 30. To introduce light into the optical waveguide layer 20, the reflection angle θ of the guided light inside the optical waveguide layer 20 is... w It needs to satisfy Snell's law (n in sinθ in =n w sinθ w Here, n in It is the refractive index of the external medium, θ in It is the angle of incidence of the propagating light, n w This is the refractive index of the optical waveguide layer 20. The incident angle θ is adjusted by taking this condition into account. inThis allows for maximizing the coupling efficiency of light. Furthermore, in this example, a portion of the first mirror 30 is provided with a reduced number of multilayer reflective films. By inputting light from this portion, the coupling efficiency can be improved. However, in such a structure, it is necessary to adjust the coupling efficiency according to the change in the transmission constant (θ) of the optical waveguide layer 20. wav The change in the incident angle θ of light onto the optical waveguide layer 20 causes the light to change. in change.

[0137] Even if the transmission constant of the optical waveguide layer 20 changes, in order to maintain the state where light can always couple with the waveguide, there is a method to partially incident the beam with an angularly extended direction, reducing the number of layers in the multilayer reflective film. As an example of such a method, such as... Figure 6B As shown, the angle θ relative to the normal direction of mirror 30 was investigated. in The coupling efficiency is calculated when light is indirectly incident on the waveguide element 10 from the outside via air and mirror 30 using an inclined optical fiber 7. For simplicity, the light is considered as a ray. The aperture number (NA) of a typical single-mode fiber is approximately 0.14. Converted to angles, this is approximately ±8 degrees. The range of the incident angle of the light coupled to the waveguide is the same as the spread angle of the light emitted from the waveguide. The spread angle θ of the emitted light... div It is represented by the following formula (4).

[0138] [Formula 4]

[0139]

[0140] Here, L is the transmission length, λ is the wavelength of light, and θ is the wavelength of light. out It is the angle of light emission. If we assume L is greater than 10 μm, then θ div Even at a relatively high level, the degree is less than 1 degree. Therefore, the coupling efficiency of light from fiber 7 is less than 1 / 16 × 100 ≈ 6.3%. Furthermore, in Figure 7 The expression in the middle represents the calculation of the incident angle θ of light. in Fix, by making the refractive index n of the waveguide w The change causes the light's exit angle θ to change out The result of the change in coupling efficiency. Coupling efficiency represents the ratio of the energy of the guided light to the energy of the incident light. Figure 7 The results shown are obtained by adjusting the incident angle θ. in The coupling efficiency was calculated by setting the angle to 30°, the waveguide film thickness to 1.125 μm, and the wavelength to 1.55 μm. In this calculation, the refractive index n was set... w The emission angle θ is varied within the range of 1.44 to 1.78. out It varies within the range of 10° to 65°. For example... Figure 7As shown, in such a structure, the coupling efficiency is at most less than 7%. Furthermore, if the emission angle θ is... out If the emission angle changes by more than 20° from the point where the coupling efficiency peaks, the coupling efficiency will further decrease to less than half.

[0141] Thus, if the propagation constant is changed by altering the refractive index of the waveguide to achieve optical scanning, the coupling efficiency will further decrease. To maintain coupling efficiency, the incident angle θ of the light needs to be adjusted according to the change in the propagation constant. in Changes. However, the introduction causes the incident angle θ of the light to change. in Variations in the mechanism lead to increased complexity in the device structure, which is not preferable. The inventors of this application conceived of a method to fix the angle of light incidence by providing a region with a waveguide whose refractive index and thickness are maintained at a constant level in the front section of a region with a waveguide that varies in refractive index or thickness.

[0142] Furthermore, two important factors are considered when considering the coupling of guided light in two different waveguides. The first is the propagation constant of the transmitted light, and the second is the electric field intensity distribution of the mode. The closer these factors are in the two waveguides, the higher the coupling efficiency. The propagation constant β of the transmitted light in the waveguide, if considered in geometric optics for simplicity, is expressed as β = k·sinθ. w =(2πn) w sinθ w Let ) / λ represent the wave number, and let the waveguide angle be θ. w Let the refractive index of the waveguide layer be n. w In a total internal reflection waveguide, since total internal reflection is used to trap the guided light within the waveguide layer, n, which is the condition for total internal reflection, is satisfied. w sinθ w >1. On the other hand, in a slow optical waveguide, light is trapped within the waveguide by multiple layers of reflective films located above and below it, and a portion of the guided light passes through these multiple reflective films and exits, so the value is n. w sinθ w <1. In a total internal reflection waveguide and a slow optical waveguide that emits a portion of the guided light, the transmission constant cannot be equal. Regarding the electric field intensity distribution, Figure 49 The electric field intensity distribution within the total reflection waveguide shown has the following characteristics: Figure 50 Such peak values ​​decrease monotonically outside the waveguide. However, in Figure 51 In a slow optical waveguide as shown, the electric field intensity distribution becomes Figure 52 As shown, the peak value remains constant within the waveguide, but due to the reflection of the guided light through the dielectric multilayer film via light interference, it varies. Figure 52As shown, the electric field intensity penetrates deeply into the dielectric multilayer film and varies oscillatoryly. As such, the propagation constant and electric field intensity distribution of the guided light differ significantly in total internal reflection waveguides and slow optical waveguides. Therefore, direct connection between total internal reflection waveguides and slow optical waveguides has not been considered. The inventors of this application have discovered that it is possible to directly connect total internal reflection waveguides to optical waveguide layers with variable refractive index and / or variable thickness.

[0143] This disclosure includes the equipment described in the following items.

[0144] [Project 1]

[0145] An optical scanning device includes: a first waveguide; and a second waveguide connected to the first waveguide; the second waveguide includes: a first mirror having a multilayer reflective film; a second mirror having a multilayer reflective film opposite to the multilayer reflective film of the first mirror; and an optical waveguide layer located between the first mirror and the second mirror, and transmitting light input to and transmitted in the first waveguide; the first mirror has a higher light transmittance than the second mirror, and emits a portion of the light transmitted within the optical waveguide layer to the outside of the optical waveguide layer; and further includes an adjustment element for changing the direction of light emitted from the second waveguide by changing at least one of the refractive index and thickness of the optical waveguide layer.

[0146] [Project 2]

[0147] As described in Project 1, the optical scanning device comprises a material whose refractive index changes with respect to light transmitted in the optical waveguide when a voltage is applied; the adjustment element changes the refractive index of the optical waveguide by applying a voltage to the optical waveguide, thereby changing the direction of light emitted from the second waveguide.

[0148] [Project 3]

[0149] As described in Project 1 or 2, the first waveguide has two opposing multilayer reflective films and an optical waveguide layer sandwiched between the two multilayer reflective films.

[0150] [Project 4]

[0151] As described in Project 3, the light transmittance of the two opposing multilayer reflective films is lower than that of the first mirror.

[0152] [Project 5]

[0153] As described in any one of items 1 to 4, the optical scanning device, where the refractive index of the first waveguide is n... w1 Let the refractive index of the optical waveguide layer of the second waveguide be n. w2 hour,

[0154] |n w1 -n w2 | / n w1 <0.4.

[0155] [Project 6]

[0156] As described in any one of items 1 to 5, the optical scanning device, when the refractive index of the optical waveguide layer of the second waveguide is n... w2 Let the thickness of the optical waveguide layer of the second waveguide be d2, and let the wavelength of the light input to the first waveguide be λ, then the following conditions are met:

[0157] 0.95×mλ / (2n w2 ) <d2<1.5×mλ / (2n w2 ).

[0158] [Project 7]

[0159] As described in any one of items 1 to 6, the optical scanning device wherein the first waveguide transmits light input into the first waveguide via total internal reflection, and also satisfies the following conditions:

[0160] 1.2×mλ / (2n w2 ) <d2<1.5×mλ / (2n w2 ).

[0161] [Project 8]

[0162] As described in any one of items 1 to 7, the optical scanning device, where the refractive index of the first waveguide is n... w1 Let the refractive index of the optical waveguide layer of the second waveguide be n. w2 When, n w1 >n w2 .

[0163] [Project 9]

[0164] In the optical scanning device described in any one of items 1 to 8, the optical waveguide layer of the second waveguide is connected to the first waveguide via a gap; when the wavelength of the light input to the first waveguide is λ, the product of the refractive index of the gap and the width of the gap is λ / 6.5 or less.

[0165] [Project 10]

[0166] As described in any one of items 1 to 9, in the optical scanning device, when the deviation between the center of the thickness direction of the first waveguide and the center of the thickness direction of the second waveguide is Δz, and the difference between the thickness of the optical waveguide layer of the first waveguide and the thickness of the optical waveguide layer of the second waveguide is Δd, the following conditions are met:

[0167] -Δd / 2 < Δz < Δd / 2.

[0168] [Project 11]

[0169] As described in any one of items 1 to 10, the first waveguide has two opposing multilayer reflective films and an optical waveguide layer sandwiched between the two multilayer reflective films; one of the two multilayer reflective films has a portion with a film thickness thinner than the adjacent portion; the optical waveguide layer transmits light incident on the portion and inputs it to the end face of the optical waveguide layer of the second waveguide.

[0170] [Project 12]

[0171] As described in any one of items 1 to 10, the first waveguide has a grating on a portion of its surface, transmits light incident into the grating, and inputs it to the end face of the optical waveguide layer of the second waveguide.

[0172] [Project 13]

[0173] As described in any one of items 1 to 10, the first waveguide transmits light incident from the end face of the first waveguide and inputs it to the end face of the optical waveguide layer of the second waveguide.

[0174] [Project 14]

[0175] The optical scanning device as described in any one of items 1 to 10 further comprises a third waveguide connected to the first waveguide and transmitting light incident from the outside and inputting it into the first waveguide.

[0176] [Project 15]

[0177] As described in Project 14, the first waveguide has two opposing multilayer reflective films and an optical waveguide layer sandwiched between the two multilayer reflective films; the third waveguide transmits light through total internal reflection and inputs it into the first waveguide.

[0178] [Project 16]

[0179] As described in item 14 or 15, the optical scanning device has a grating on a portion of its surface, transmits light incident on the grating, and inputs it to the end face of the first waveguide.

[0180] [Project 17]

[0181] As described in item 14 or 15, the optical scanning device transmits light incident from the end face of the third waveguide and inputs it to the end face of the first waveguide.

[0182] [Project 18]

[0183] An optical scanning device includes a plurality of waveguide units arranged in a first direction; each of the plurality of waveguide units has: a first waveguide; and a second waveguide connected to the first waveguide and transmitting light in a second direction intersecting the first direction; the second waveguide has: a first mirror having a multilayer reflective film; a second mirror having a multilayer reflective film opposite to the multilayer reflective film of the first mirror; an optical waveguide layer located between the first mirror and the second mirror, transmitting light input to and transmitted in the first waveguide; the first mirror has a higher light transmittance than the second mirror, and emits a portion of the light transmitted within the optical waveguide layer to the outside of the optical waveguide layer; and further includes a first adjustment element that changes the direction of light emitted from each second waveguide by changing at least one of the refractive index and thickness of the optical waveguide layer of each second waveguide.

[0184] [Project 19]

[0185] The optical scanning device as described in Item 18 further includes a second adjustment element that changes the direction of light emitted from each of the second waveguides by adjusting the phase difference of light transmitted from the first waveguide to the second waveguide of the plurality of waveguide units.

[0186] [Project 20]

[0187] The optical scanning device as described in Item 19 further includes a plurality of phase shifters, each having a waveguide respectively connected to the first waveguide of the plurality of waveguide elements; the waveguide of each phase shifter includes a material whose refractive index changes in response to the application of voltage or a change in temperature; the second adjustment element changes the refractive index within the waveguide by applying a voltage to the waveguide of each phase shifter or by changing the temperature of the waveguide, thereby changing the phase difference of the light transmitted from the plurality of phase shifters to the plurality of waveguide elements.

[0188] [Project 21]

[0189] In the optical scanning device described in Item 19 or 20, when the component of the wave vector of the light emitted from each second waveguide in the second direction is defined as the X component and the component in the first direction is defined as the Y component, the first adjustment element changes the X component of the wave vector, and the second adjustment element changes the Y component of the wave vector.

[0190] [Project 22]

[0191] The optical scanning device as described in any one of items 19 to 20 further comprises: a light source that emits light with a wavelength of λ in free space; and an optical splitter that splits the light from the light source and directs it to the waveguides of the plurality of phase shifters.

[0192] [Project 23]

[0193] An optical receiving device includes: a first waveguide; and a second waveguide connected to the first waveguide; the second waveguide includes: a first mirror having a multilayer reflective film; a second mirror having a multilayer reflective film opposite to the multilayer reflective film of the first mirror; and an optical waveguide layer located between the first mirror and the second mirror for transmitting light; the first mirror has a higher light transmittance than the second mirror, guiding a portion of the light incident on the first mirror into the optical waveguide layer; a portion of the light incident from the first mirror into the optical waveguide layer is input into the first waveguide; and further includes an adjustment element for changing at least one of the refractive index and thickness of the optical waveguide layer.

[0194] [Project 24]

[0195] A lidar system comprising: an optical scanning device as described in any one of items 1 to 22; a photodetector for detecting light emitted from the optical scanning device and reflected from an object; and a signal processing circuit for generating distance distribution data based on the output of the photodetector.

[0196] [Project 25]

[0197] An optical scanning device includes: a waveguide array comprising a plurality of waveguide elements arranged in a first direction and transmitting light in a second direction intersecting the first direction, the waveguide array emitting light from the plurality of waveguide elements in a third direction intersecting a plane formed by the first and second directions; and a first adjustment element for changing the third direction of the light emitted from the plurality of waveguide elements; each of the plurality of waveguide elements having: a first mirror having a reflective surface intersecting the third direction and extending in the second direction; a second mirror, The device includes a reflective surface facing the reflective surface of the first mirror and extending in the second direction; and an optical waveguide layer located between the first mirror and the second mirror, transmitting light in the second direction; the first mirror has a higher light transmittance than the second mirror, and emits a portion of the light transmitted within the optical waveguide layer to the outside of the optical waveguide layer; the first adjustment element changes the third direction of the light emitted from the plurality of waveguide elements by changing at least one of the refractive index and thickness of the optical waveguide layer of each waveguide element.

[0198] [Project 26]

[0199] In the optical scanning device described in Item 25, when the component of the wave vector of the light emitted in the third direction is defined as the X component in the second direction and the component in the first direction is defined as the Y component, the first adjustment element changes the X component of the wave vector by changing at least one of the refractive index and the thickness of the optical waveguide layer of each waveguide element; and changes the Y component of the wave vector when the phase difference of the light supplied to two adjacent waveguide elements among the plurality of waveguide elements changes.

[0200] [Project 27]

[0201] The optical scanning device described in item 25 or 26 has the first direction and the second direction described above being orthogonal.

[0202] [Project 28]

[0203] As in any one of items 25 to 27, the optical scanning device comprises a plurality of waveguide elements arranged at equal intervals in the first direction.

[0204] [Project 29]

[0205] As described in any one of items 25 to 28, the optical scanning device, when the center-to-center distance between two adjacent waveguide elements in the first direction is p, and the center wavelength of the light transmitted in the optical waveguide layer of each waveguide element in free space is λ, satisfies the relationship λ / 2≤p≤λ / sin10°.

[0206] [Project 30]

[0207] In any one of the optical scanning devices described in items 25 to 29, at least one of the first and second mirrors comprises a dielectric multilayer film.

[0208] [Project 31]

[0209] The optical scanning apparatus as described in any one of items 25 to 30 further comprises: a plurality of phase shifters respectively connected to the plurality of waveguide elements and each including a waveguide, the waveguide being directly or via another waveguide connected to the optical waveguide layer of a corresponding one of the plurality of waveguide elements; and a second adjustment element that changes the third direction of the light emitted from the plurality of waveguide elements by changing the phase difference of the light transmitted from the plurality of phase shifters to the plurality of waveguide elements respectively.

[0210] [Project 32]

[0211] As described in Item 31, in the optical scanning device, the waveguide of each phase shifter contains a material whose refractive index changes in response to the application of voltage or the change of temperature; the second adjustment element changes the refractive index within the waveguide by applying voltage to the waveguide of each phase shifter or by changing the temperature of the waveguide, and thus changes the phase difference of the light transmitted from the plurality of phase shifters to the plurality of waveguide elements.

[0212] [Project 33]

[0213] When the component of the wave vector of light transmitted in the third direction is defined as the X component in the second direction and the component in the first direction is defined as the Y component, the first adjustment element changes the X component of the wave vector; the second adjustment element changes the Y component of the wave vector.

[0214] [Project 34]

[0215] As in any one of items 31 to 33, the optical scanning device has the plurality of phase shifters located on both sides of the plurality of waveguide elements relative to the second direction.

[0216] [Project 35]

[0217] The optical scanning device as described in any one of items 31 to 34 further comprises: a light source that emits light with a wavelength of λ in free space; and an optical splitter that splits the light from the light source and directs it to the waveguides of the plurality of phase shifters.

[0218] [Project 36]

[0219] As described in any one of items 31 to 35, the optical scanning device comprises: a fifth mirror having a reflective surface intersecting the third direction, extending along the second direction, and connected to the first mirror of a corresponding waveguide element among the plurality of waveguide elements; and a sixth mirror having a reflective surface facing the reflective surface of the third mirror, extending along the second direction, and connected to the second mirror of a corresponding waveguide element among the plurality of waveguide elements; the waveguide of each phase shifter is directly connected to the optical waveguide of the corresponding waveguide element among the plurality of waveguide elements; the light transmittance of the fifth and sixth mirrors is lower than that of the first mirror.

[0220] [Project 37]

[0221] As in any one of items 25 to 36, in the optical scanning apparatus, the optical waveguide layer of each waveguide element comprises a material whose refractive index changes relative to light transmitted in the optical waveguide layer when a voltage is applied; the first adjustment element has a pair of electrodes sandwiching the optical waveguide layer, and by applying a voltage to the pair of electrodes, the refractive index of the optical waveguide layer changes.

[0222] [Project 38]

[0223] As described in Item 37, in the optical scanning device, the optical waveguide layer of each waveguide element comprises a semiconductor material; a p-type semiconductor is included between one of the pair of electrodes or between one of the electrodes and the optical waveguide layer; an n-type semiconductor is included between the other of the pair of electrodes or between the other of the electrodes and the optical waveguide layer; the first adjustment element injects carriers into the semiconductor material by applying a voltage to the pair of electrodes, thereby changing the refractive index of the optical waveguide layer.

[0224] [Project 39]

[0225] As described in Item 37, in the optical scanning device, the optical waveguide layer of each waveguide element contains an electro-optical material; the first adjustment element changes the refractive index of the electro-optical material by applying a voltage to the pair of electrodes.

[0226] [Project 40]

[0227] As described in Item 37, in the optical scanning device, the optical waveguide layer of each waveguide element contains liquid crystal material; the first adjustment element applies a voltage to the pair of electrodes, thereby causing the refractive index of the liquid crystal material to change anisotropically, and causing the refractive index of the optical waveguide layer to change.

[0228] [Project 41]

[0229] As in any one of items 25 to 36, in the optical scanning device, the optical waveguide layer of each waveguide element comprises a thermo-optical material whose refractive index changes with temperature; the first adjustment element has a pair of electrodes sandwiching the optical waveguide layer, and the thermo-optical material is heated by applying a voltage to the pair of electrodes, thereby causing the refractive index of the optical waveguide layer to change.

[0230] [Project 42]

[0231] As in any one of items 25 to 36, in the optical scanning device, the optical waveguide layer of each waveguide element comprises a thermo-optical material whose refractive index changes with temperature; the first adjustment element has a heater that is in contact with or disposed near the optical waveguide layer; and the refractive index of the optical waveguide layer is changed by heating the thermo-optical material by the heater.

[0232] [Project 43]

[0233] As described in any one of items 25 to 36, in the optical scanning device, the optical waveguide layer of each waveguide element comprises a gaseous or liquid material; the first adjustment element has an actuator connected to at least one of the first mirror and the second mirror of each waveguide element; the actuator changes the thickness of the optical waveguide layer by changing the distance between the first mirror and the second mirror.

[0234] [Project 44]

[0235] As described in item 43, the optical scanning device has a pair of electrodes; one of the pair of electrodes is fixed to the first mirror; the other of the pair of electrodes is fixed to the second mirror; by applying a voltage to the pair of electrodes, an electrostatic force is generated between the electrodes, and the distance between the first mirror and the second mirror changes.

[0236] [Project 45]

[0237] As described in Project 43, the optical scanning device includes an actuator comprising a piezoelectric material, which, by deforming the piezoelectric material, causes a change in the distance between the first mirror and the second mirror.

[0238] [Project 46]

[0239] As described in item 43, the optical scanning device has a support member for supporting the first mirror or the second mirror of each waveguide element, and the distance between the first mirror and the second mirror changes by moving the support member.

[0240] [Project 47]

[0241] In the optical scanning device described in Project 43, at least one of the first mirror and the second mirror of each waveguide element is part of a plate-shaped mirror; the actuator changes the distance between the first mirror and the second mirror by moving the plate-shaped mirror.

[0242] [Project 48]

[0243] In the optical scanning device as described in any one of items 25 to 46, at least one of the first mirror and the second mirror of each waveguide element is part of a plate-shaped mirror.

[0244] [Project 49]

[0245] An optical receiving device includes: a waveguide array comprising a plurality of waveguide elements arranged in a first direction and transmitting light in a second direction intersecting the first direction, and transmitting light incident on the plurality of waveguide elements from a third direction intersecting both the first and second directions in the second direction; and a first adjustment element for adjusting the direction of the receivable light; each of the plurality of waveguide elements having: a first mirror having a reflective surface intersecting the third direction and extending in the second direction; a second mirror having a reflective surface facing the reflective surface of the first mirror and extending in the second direction; and an optical waveguide layer located between the first mirror and the second mirror for transmitting light in the second direction; the first adjustment element thereby changing the direction of the receivable light by changing at least one of the refractive index and thickness of the optical waveguide layer of each waveguide element.

[0246] [Project 50]

[0247] The optical receiving device as described in Item 49 further comprises: a plurality of phase shifters respectively connected to the plurality of waveguide elements, including waveguides respectively directly or via other waveguides connected to the optical waveguide layer of a corresponding waveguide element of the plurality of waveguide elements; and a second adjustment element that changes the direction of the receivable light by changing the phase difference of the light output from the plurality of waveguide elements through the plurality of phase shifters respectively.

[0248] [Project 51]

[0249] In the optical receiving device described in item 49 or 50, when the component of the wave vector of the light incident on the plurality of waveguide elements in the second direction is defined as the X component and the component in the first direction is defined as the Y component, the first adjustment element changes the X component of the wave vector of the receivable light, and the second adjustment element changes the Y component of the wave vector of the receivable light.

[0250] [Project 52]

[0251] A LiDAR system comprises: a light scanning device as described in any one of items 25 to 48; a light detector for detecting light emitted from the light scanning device and reflected from an object; and a signal processing circuit for generating distance distribution data based on the output of the light detector.

[0252] The optical scanning device according to an embodiment of this disclosure includes: a first waveguide; and a second waveguide connected to the first waveguide. The second waveguide includes: a first mirror having a multilayer reflective film; a second mirror having a multilayer reflective film opposite to the multilayer reflective film of the first mirror; and an optical waveguide layer located between the first and second mirrors, transmitting light input to and transmitted within the first waveguide. The first mirror has a higher light transmittance than the second mirror, and a portion of the light transmitted within the optical waveguide layer is emitted to the outside of the optical waveguide layer. It also includes an adjustment element that changes the direction of light emitted from the second waveguide by changing at least one of the refractive index and thickness of the optical waveguide layer.

[0253] In the above technical solution, the "second waveguide" is equivalent to the "waveguide element" in the above embodiment. In the embodiments of this disclosure, a first waveguide with a constant refractive index and thickness is provided at the front end of the second waveguide, and light is input into the first waveguide. The first waveguide transmits the input light and inputs it from the end face of the second waveguide. The first waveguide and the second waveguide can be directly connected to each other at their end faces, or there can be a gap between their end faces. In this specification, "the first waveguide and the second waveguide are connected" means that they are positioned in a way that allows light to be transmitted and received between the first waveguide and the second waveguide. The form of "the first waveguide and the second waveguide are connected" includes not only the form in which the first waveguide and the second waveguide are directly connected (i.e., in contact), but also the form in which they are configured with a gap that is sufficiently short compared to the wavelength of the transmitted light. Furthermore, in this disclosure, "directly connected" A to B means that a part of A is in contact with a part of B without a gap, so that light can be transmitted and received between A and B.

[0254] According to the above structure, by placing the first waveguide in front of the second waveguide (waveguide element), even if the incident angle of the light incident on the first waveguide is kept constant, the decrease in coupling efficiency (i.e., energy loss) caused by scanning can be suppressed.

[0255] Furthermore, a third waveguide can be provided at the front end of the first waveguide. This third waveguide is connected to the first waveguide, allowing light transmitted in the third waveguide to be input into the first waveguide. In one embodiment, the third waveguide can be a total reflection waveguide, and the second waveguide can be a reflective waveguide.

[0256] In this disclosure, "light" refers to electromagnetic waves that include not only visible light (wavelength from about 400 nm to about 700 nm), but also ultraviolet light (wavelength from about 10 nm to about 400 nm) and infrared light (wavelength from about 700 nm to about 1 mm). In this disclosure, ultraviolet light is sometimes referred to as "ultraviolet light" and infrared light is sometimes referred to as "infrared light".

[0257] In this disclosure, the term "scanning" of light refers to changing the direction of light. "One-dimensional scanning" refers to changing the direction of light linearly along a direction intersecting that direction. "Two-dimensional scanning" refers to changing the direction of light two-dimensionally along a plane intersecting that direction.

[0258] The embodiments of this disclosure will now be described in more detail. Sometimes, necessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of substantially the same structures are sometimes omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the inventors have provided the drawings and the following description to enable those skilled in the art to fully understand this disclosure, but these are not intended to limit the subject matter of the claims. In the following description, the same reference numerals are used for the same or similar constituent elements in the drawings.

[0259] (Implementation Method)

[0260] Figure 8 This is a cross-sectional view schematically illustrating a portion of the structure of an optical scanning device according to an exemplary embodiment of the present disclosure. The optical scanning device includes a waveguide 1 and a second waveguide (waveguide element) 10 connected to the first waveguide. The waveguide 10 includes a first mirror 30 having a multilayer reflective film, a second mirror 40 having a multilayer reflective film opposite to the multilayer reflective film of the first mirror 30, and an optical waveguide layer 20 located between the first mirror 30 and the second mirror 40. The waveguide 1 transmits input light in the waveguide direction. The optical waveguide layer 20 transmits light input into and transmitted within the waveguide 1. The optical waveguide layer 20 transmits light in the same direction as the waveguide direction of the waveguide 1. The first mirror 30 has a higher light transmittance than the second mirror 40, and a portion of the light transmitted within the optical waveguide layer 20 is emitted to the outside of the optical waveguide layer 20. Although in Figure 8 Although not explicitly stated, the optical scanning device 100 also includes an adjustment element that changes at least one of the refractive index and thickness of the optical waveguide layer 20. The optical waveguide layer 20 may contain, for example, a material whose refractive index changes for light transmitted within it when a voltage is applied. The adjustment element changes the refractive index of the optical waveguide layer 20 by applying a voltage, thereby changing the direction of light emitted from the waveguide 10.

[0261] Waveguide 1 has two opposing multilayer reflective films 3 and 4, and an optical waveguide layer 2 sandwiched between the two multilayer reflective films 3 and 4. To ensure lossless propagation of the guided light, the multilayer reflective films 3 and 4 of waveguide 1 preferably have a higher reflectivity (lower transmittance) than the multilayer reflective film (first mirror 30) on the light-emitting side of waveguide 10. Therefore, the thickness of the multilayer reflective films 3 and 4 is preferably greater than the thickness of the first mirror 30. The refractive index of waveguide 1, i.e., the refractive index of the optical waveguide layer 2 of waveguide 1, remains constant or varies by an amount different from the refractive index of the optical waveguide layer 20. Furthermore, the thickness of the optical waveguide layer 2 remains constant or varies by an amount different from the thickness of the optical waveguide layer 20. Waveguide 1 is directly connected to the optical waveguide layer 20 of waveguide 10. For example, the end face of the optical waveguide layer 2 of waveguide 1 is connected to the end face of the optical waveguide layer 20 of waveguide 10. In this example, the multilayer reflective film 3 has a portion 3a that is thinner than the adjacent portion (i.e., has lower reflectivity). Light is input from this portion 3a (also called the "light input portion 3a"). By inputting light from a region with low reflectivity in this way, light can be efficiently guided into the optical waveguide layer 2. The optical waveguide layer 2 transmits the light incident on the light input portion 3a and inputs it to the end face of the optical waveguide layer 20 of the waveguide 10. Thus, light can be transmitted from the optical waveguide layer 2 to the optical waveguide layer 20 and exit from the mirror 30.

[0262] In waveguide 10, because light needs to be emitted, the reflectivity of the multilayer reflective film of the first mirror 30 is lower than that of the multilayer reflective film of the second mirror 40. In waveguide 1, in order to prevent light from escaping, the reflectivity of the multilayer reflective films 3 and 4 is designed to be the same as that of the second mirror 40.

[0263] With this configuration, the optical scanning device, as described later, is able to emit light efficiently from waveguide 10.

[0264] Figure 9 This is a cross-sectional view schematically illustrating another example of the structure of an optical scanning device. In this example, waveguide 1 does not have multilayer reflective films 3 and 4. Waveguide 1 transmits light through total internal reflection. Waveguide 1 has a grating 5 on a portion of its surface. Light is input via the grating 5. In this example, the portion with the grating 5 functions as a light input section. By providing the grating 5, light is easily guided into waveguide 1. In the absence of multilayer reflective films 3 and 4, as in this example, the design is such that the waveguide angle θ... w1 The total internal reflection condition is met. In this case, the refractive index of waveguide 1 remains unchanged or changes by an amount different from that of optical waveguide layer 20. Furthermore, the thickness of waveguide 1, i.e., the thickness of optical waveguide layer 2, remains unchanged or changes by an amount different from that of optical waveguide layer 20. Moreover, waveguide 1 is directly connected to the optical waveguide layer 20 of waveguide 10. Furthermore, optical waveguide layer 20 directs light in the same direction as the waveguide direction of waveguide 1.

[0265] Figure 10This is a cross-sectional view schematically illustrating another example of the structure of an optical scanning device. The optical scanning device in this example also includes a waveguide 1' connected to waveguide 1. Waveguide 1 is a reflective waveguide, having two opposing multilayer reflective films 3 and 4 and an optical waveguide layer 2 between them. On the other hand, waveguide 1' is a total internal reflection waveguide that transmits light through total internal reflection. The refractive index of waveguide 1' does not change or changes by an amount different from that of the optical waveguide layer 20. Furthermore, the thickness of waveguide 1', i.e., the thickness of the optical waveguide layer 2', does not change or changes by an amount different from that of the optical waveguide layer 20. Furthermore, waveguide 1' is directly connected to the optical waveguide layer 20 of waveguide 10. Furthermore, the optical waveguide layer 20 transmits light in the same direction as the waveguide direction of waveguide 1'. Waveguide 1' and... Figure 9 Similarly, waveguide 1 in the example has a grating 5' on a portion of its surface. Light from the light source is input into waveguide 1' via the grating 5'. In this example, the portion with the grating 5' functions as a light input section. The refractive index or thickness of the optical waveguide layer 20 of waveguide 10 is modulated by an adjustment element (modulation element) not shown. On the other hand, waveguide 1 does not have such a modulation function. To suppress the emission of light from waveguide 1, the reflectivity of the mirrors (multilayer reflective films 3, 4) of waveguide 1 is set to be higher than the reflectivity of the first mirror 30 of waveguide 10. The reflectivity of the first mirror 30 of waveguide 10 is set to be lower than the reflectivity of the second mirror 40. With this structure, light input into waveguide 1' is transmitted in waveguide 1' and waveguide 1 and then input into waveguide 10. While the light is further transmitted in the optical waveguide layer 20 of waveguide 10, it is emitted to the outside via the first mirror 30.

[0266] Figure 11 and Figures 12A to 12C This is a diagram illustrating an example of how light is input into waveguide 1 in a structure where light is input into waveguide 1. Figure 11 like Figure 8 The example shown illustrates an instance of light incident onto a waveguide layer 2 sandwiched between two multilayer reflective films. As shown, by incidenting light onto a thinner portion (a portion with lower reflectivity) 3a of the multilayer reflective films, light can be efficiently guided into the waveguide layer 2. Figure 12A Indicates as Figure 9 As shown in the example, light is introduced into waveguide 1 through grating 5 provided on the surface of waveguide 1. Figure 12B This represents an example of light being input from the end face of waveguide 1. Figure 12C This illustrates an example where light is input from a laser source 6 located on the surface of waveguide 1 via that surface. Figure 12CSuch a structure is disclosed, for example, in M. Lamponi et al., “Low-Threshold Heterogeneously Integrated InP / SOI Lasers With a Double Adiabatic Taper Coupler,” IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 24, NO. 1, JANUARY 1, 2012, pp. 76-78. The entire disclosure of that document is incorporated herein by reference. Based on the above structure, light can be efficiently incident into waveguide 1.

[0267] Figures 11 to 12C The light input method shown is used in Figure 10 This can also be applied to the structure of waveguide 1' shown. Figure 10 In the example shown, a grating 5' is provided on a portion of the surface of waveguide 1', but the grating 5' may not be provided. For example, it is possible to... Figure 12B or Figure 12C The light input method shown is applied to waveguide 1'. In the process of... Figure 12B When the light input method shown is applied to waveguide 1', waveguide 1' transmits light incident from its end face to the end face of waveguide 1'. Figure 12C When the light input method shown is applied to waveguide 1', light is input from a laser source disposed on the surface of waveguide 1' via that surface. Waveguide 1' transmits the input light to its end face. Furthermore, waveguide 1' does not need to be a total internal reflection waveguide; it can also be... Figure 11 A reflective waveguide as shown.

[0268] like Figure 8 , Figure 9 As shown, let the refractive index of the optical waveguide layer 2 of waveguide 1 be n. w1 Let the refractive index of the optical waveguide layer 20 of waveguide 10 be n. w2 Let θ be the exit angle of the light from waveguide 10, and let θ be the reflection angle of the guided light in waveguide 1. w1 Let θ be the reflection angle of the guided light in waveguide 10. w2 In addition, such as Figure 10 As shown, let the refractive index of the optical waveguide layer 2' of waveguide 1' be n. w3 Let θ be the reflection angle of the guided wave light in waveguide 1'. w3 In this embodiment, in order to extract light from waveguide 10 to the outside (e.g., an air layer with a refractive index of 1), n ​​must be satisfied. w2 sinθ w2 =sinθ<1.

[0269] <Principle of waveguide optical coupling>

[0270] The following is for reference Figure 8 , Figure 9 This section explains the principle of waveguide light coupling between waveguides 1 and 10. For simplicity, the light propagating within waveguides 1 and 10 is approximated as light rays. It is assumed that light is completely reflected at the interfaces between the multilayer reflective films on the top and bottom of waveguide 10 and the optical waveguide layer 20, and at the interfaces between the multilayer reflective films on the top and bottom of waveguide 1 and the optical waveguide layer 2 (or the interface between the optical waveguide layer 2 and the external medium). Let the thickness of the optical waveguide layer 2 in waveguide 1 be d1, and the thickness of the optical waveguide layer 20 in waveguide 10 be d2. The conditions for the existence of propagating light in each of waveguides 1 and 10 are expressed by the following equations (5) and (6).

[0271] 2d1n w1 cosθ w1 =mλ (5)

[0272] 2d2n w2 cosθ w2 =mλ (6)

[0273] Here, λ is the wavelength of light, and m is an integer greater than or equal to 1.

[0274] If Snell's rule is considered with respect to the interface of waveguides 1 and 10, then equation (7) holds.

[0275] n w1 sin(90°-θ w1 ) = n w2 sin(90°-θ w2 (7)

[0276] If equation (7) is transformed, we can obtain the following equation (8).

[0277] n w1 cosθ w1 =n w2 cosθ w2 (8)

[0278] When equations (5) and (8) hold, and d1 and d2 are equal, then in n w2 Equation (6) also holds true under varying conditions. That is, even with a change in the refractive index of the optical waveguide layer 20, light can still be transmitted efficiently from the optical waveguide layer 2 to the optical waveguide layer 20.

[0279] In deriving the above equation, light is considered as a ray for simplicity. However, since the thicknesses d1 and d2 are approximately equal to the wavelength λ (even if they are relatively long, they are less than 10 times the wavelength), the guided light exhibits wave-like properties. Therefore, strictly speaking, the refractive index n mentioned above... w1 nw2 The refractive index is not the material refractive index of waveguide layers 2 and 20, but the effective refractive index needs to be considered. Furthermore, even when the thickness d1 of waveguide layer 2 is not the same as the thickness d2 of waveguide layer 20, or when equation (8) is not strictly satisfied, light can still be guided from waveguide layer 2 to waveguide layer 20. This is because the transmission of light from waveguide layer 2 to waveguide layer 20 occurs via the near field. That is, if the electric field distribution in waveguide layer 2 overlaps with the electric field distribution in waveguide layer 20, light is transmitted from waveguide layer 2 to waveguide layer 20.

[0280] The above discussion is about Figure 10 The same applies to the guided light between waveguide 1' and waveguide 1 in the example shown.

[0281] <Calculation Results>

[0282] To confirm the effectiveness of this embodiment, the inventors of this application made various changes to the conditions and calculated the light coupling efficiency. In the calculations, they used FIMMWAVE from Photon Design.

[0283] First, such as Figure 8 As shown, the coupling efficiency is calculated for waveguides 1 and 10, which are sandwiched between multiple reflective films. In the following calculations, the order of the light mode transmitted from waveguide 1 to waveguide 10 is m = 2. However, as long as the order of the light modes in waveguides 1 and 10 is the same, the light couples through the same principle. Therefore, the order of the light modes is not limited to m = 2.

[0284] Figure 13 Indicates that n w1 The coupling efficiency of the guided light from waveguide 1 to waveguide 10 is dependent on d2 when d1 is set to 1.27 μm and wavelength λ is set to 1.45 μm. The horizontal axis represents the cutoff film thickness d when d2 is used in the case that the guided light is assumed to be a ray. cutoff (=mλ / (2n w2 The value of n is divided by 1. The vertical axis represents the coupling efficiency with the peak value normalized to 1. The calculation is performed from the lower limit of the cutoff condition where the guided light can no longer exist to the upper limit where the light is emitted outward. Furthermore, for n... w2 Calculations were performed for values ​​of 1.3, 1.6, 1.9, 2.2, and 2.5. The center of waveguide 1 in the thickness direction is the same as the center of waveguide 10 in the thickness direction. Based on... Figure 13 The results shown indicate that d² / d cutoff The larger the value, the higher the coupling efficiency. As d² / d... cutoff As the size decreases, the module can no longer exist, and the coupling efficiency decreases.

[0285] Figure 14 Indicates that n w1 The result of calculations performed using the same method, changing d1 to 0.5 μm and setting d1 to 3.48. In this case, although the order of the light mode transmitted from waveguide 1 to waveguide 10 is also m=2, as mentioned above, the order of the light mode is not limited to m=2. According to Figure 14 It can be seen that d2 / d cutoff The larger the value of d² / d, the higher the coupling efficiency. cutoff As the size decreases, the module can no longer exist, and the coupling efficiency decreases.

[0286] exist Figure 13 and Figure 14 In d2 / d cutoff The existence of modes (i.e., guided wave coupling) at values ​​lower than 1 is due to the leakage of light reflected by the multilayer reflective film, making the effective thickness of the optical waveguide layer 2 thicker than d2. The upper limit of d2 is the value at which light is no longer emitted to the outside. This value is d2 when the guided wave light is considered as a ray, assuming that the multilayer reflective films above and below each waveguide cause complete reflection of the light at the interface with the waveguide. In this case, the following equation (9) is satisfied.

[0287] n w2 sinθ w2 =1 (9)

[0288] According to equations (6), (9), and d cutoff =mλ / (2n) w2 The following equation (10) holds true.

[0289]

[0290] The effective refractive index of the guided light becomes less than n due to the leakage of light reflected by the multilayer reflective film. w2 Low. Therefore, the upper limit of d2 becomes larger than that of equation (6).

[0291] In the structure of this embodiment, the preferred coupling efficiency is compared to Figure 6B The structure shown becomes more efficient. For example, if the coupling efficiency is higher than that of the structure shown. Figure 7 The condition shown is that the peak value is higher than 7%, then according to Figure 13 , 14 The result is that, as long as

[0292] 0.95×d cutoff <d2<1.5×d cutoff

[0293] (0.95×mλ / (2n w2 ) <d2<1.5×mλ / 2n w2 ))

[0294] That's fine.

[0295] Figure 15 Let the horizontal axis be d² / d cutoff Let the vertical axis represent the refractive index ratio (|n) w1 -n w2 | / n w1 The diagram categorizes cases into those with coupling efficiencies above 0.5 and those below 0.5. Under the condition of a coupling efficiency of 0.5 (50%) or higher, as long as the refractive index is less than 0.4 and 0.95×d... cutoff <d2<1.5×d cutoff That's fine.

[0296] In this embodiment, the refractive index n of waveguide 1 w1 The refractive index n of waveguide 10 w2 large (n) w1 >n w2 However, this disclosure is not limited to such a structure; it can also be n. w1 ≤n w2 .

[0297] Figure 16 This diagram shows a structure where the center of the optical waveguide layer 2 in waveguide 1 is offset by Δz from the center of the optical waveguide layer 20 in waveguide 10. The sign of Δz is as follows: Figure 16 As shown, it is considered positive when the centerline of the optical waveguide layer 20 in the thickness direction of waveguide 10 is closer to the light emission side (the side of the first mirror 30) than the centerline of the optical waveguide layer 2 in the thickness direction of waveguide 1. Let the absolute value of the difference between the thickness d1 of the optical waveguide layer 2 in waveguide 1 and the thickness d2 of the optical waveguide layer 20 in waveguide 10 be Δd. When Δz = Δd / 2, the lower part of the optical waveguide layer 2 in waveguide 1 (opposite to the light emission side) is aligned with the lower part of the optical waveguide layer 20 in waveguide 10 in the Z direction.

[0298] Figure 17 This is a graph representing the Δz dependence of the coupling efficiency of light from waveguide 1 to waveguide 10. Figure 17 Let n be the result. w1 Given 2.2, wavelength λ = 1.55 μm, and n... w2 2.2. Let Δd be 0.12μm, and the coupling efficiency is obtained by changing Δz. Figure 17 The coupling efficiency shown is normalized to the value when Δz = 0. When the centerlines of the optical waveguide layers 2 and 20 in the thickness direction are offset in the Z direction, the coupling efficiency is low when Δz is zero (0). However, when -Δd / 2 < Δz < Δd / 2, the coupling efficiency becomes more than 90% of the coupling efficiency when Δz is 0, and a relatively high coupling efficiency can be maintained.

[0299] Regarding Figure 9 As shown in the example, waveguide 1 guides light through total internal reflection. The basic principle is the same: the guided light propagating in waveguides 1 and 10 can couple with each other. Regarding... Figure 9 The structure shown also yielded the d² dependency of the coupling efficiency of the guided light from waveguide 1 to waveguide 10 through calculation. Figure 18A Indicates that n w1 The d2 dependency of coupling efficiency when d1 is set to 0.7μm and wavelength λ is set to 1.55μm. Figure 18B Indicates that n w1 The dependence of coupling efficiency on d2 when λ is set to 3.48, d1 to 0.46 μm, and wavelength λ to 1.55 μm. Similar to the example above, under the condition of applying a coupling efficiency of 7% or higher, as long as...

[0300] 0.95×d cutoff <d2<1.5×d cutoff

[0301] That is, 0.95×mλ / (2n w2 ) <d2<1.5×mλ / 2n w2 ))

[0302] That's fine.

[0303] Furthermore, under the condition of applying a coupling efficiency of 50% or higher, as long as it is 1.2×d cutoff <d2<1.5×d cutoff (i.e., 1.2×mλ / 2n) w2 ) <d2<1.5×mλ / n w2 That's fine.

[0304] exist Figure 9 In the structure, it can be n w1 >n w2 It can also be n w1 ≤n w2 .

[0305] As described above, the order of the modes of light transmitted from waveguide 1 to waveguide 10 is not limited to m = 2. For example, if in n w1 =1.883, d1=0.3μm, n w2 Used under the conditions of d = 1.6 and d2 = 0.55 μm Figure 19A Such model calculations are as follows Figure 19B As shown, the light is coupled to the waveguide.

[0306] Next, we will study the case where there is a clearance between waveguide 1 and waveguide 10.

[0307] Figure 20A This is a cross-sectional view showing a modified example of this embodiment. In this example, the optical waveguide layer 20 of waveguide 10 is connected to waveguide 1 via a gap (e.g., a void). Thus, even when there is a gap between waveguide 1 and waveguide 10, since light is coupled in the near field by the guided wave mode, as long as the gap width (width in the X direction) is sufficiently small compared to the wavelength λ, the guided light couples with waveguides 1 and 10. This is as follows... Figure 6A or Figure 6B That is different from the method of coupling the propagating light to the waveguide mode in free space.

[0308] Figure 20B This is a graph showing the calculation results of the gap width dependency of coupling efficiency. Figure 20B The coupling efficiency in the calculation is the value normalized to 1 when the clearance is 0 μm. In the calculation, let n... w1 Let n be 3.48. w2 Given a value of 1.5, d1 = 0.9 μm, d2 = 1.1 μm, the refractive index of the gap is 1, and the wavelength λ is 1.55 μm. Based on... Figure 20B The normalized coupling efficiency is above 50% when the gap is below 0.24 μm. If we consider cases where the gap is a medium other than air, and where the wavelength λ differs from 1.55 μm, then as long as the optical length of the gap (the product of the gap's refractive index and its width) is below λ / 6.5, the normalized coupling efficiency will be above 50%. This optical length of the gap is independent of the parameters of waveguides 1 and 10.

[0309] like Figure 10 As shown in the example, when light is input from waveguide 1' to waveguide 1, there can also be a clearance between the end face of waveguide 1' and the end face of waveguide 1. As mentioned above, the optical length of the clearance (the product of the refractive index of the clearance and the width of the clearance) is set to, for example, λ / 6.5 or less.

[0310] Next, a structure for achieving two-dimensional light scanning using a combination of multiple sets of waveguides 1 and 10 of this embodiment (referred to as "waveguide units" in this disclosure) will be described. The light scanning device capable of performing two-dimensional scanning includes multiple waveguide units arranged in a first direction and adjustment elements (e.g., a combination of actuator and control circuitry) for controlling each waveguide unit. The adjustment elements change at least one of the refractive index and thickness of the optical waveguide layer 20 in each waveguide unit. This allows the direction of light emitted from each waveguide 10 to change. Furthermore, by inputting light with appropriately adjusted phase differences into the waveguides 10 of the multiple waveguide units, as shown in the reference... Figure 1 As explained, two-dimensional scanning of light is possible. The following describes in more detail the implementation method for achieving two-dimensional scanning.

[0311] <Principle of operation of two-dimensional scanning>

[0312] In a waveguide array in which a plurality of waveguide elements (second waveguides) 10 are arranged in one direction, the emission direction of light changes due to the interference of light emitted from each waveguide element 10. By adjusting the phase of the light supplied to each waveguide element 10, the emission direction of light can be changed. Hereinafter, the principle will be described.

[0313] Figure 21A FIG. is a cross-sectional view of a waveguide array showing light emitted in a direction perpendicular to the emission surface of the waveguide array. In Figure 21A It also describes the amount of phase shift of the light transmitted in each waveguide element 10. Here, the amount of phase shift is a value based on the phase of the light transmitted in the leftmost waveguide element 10. The waveguide array of the present embodiment includes a plurality of waveguide elements 10 arranged at equal intervals. In Figure 21A In, the dashed arcs represent the wavefronts of the light emitted from each waveguide element 10. The straight line represents the wavefront formed by the interference of light. The arrow represents the direction of the light emitted from the waveguide array (i.e., the direction of the wave vector). In Figure 21A In the example of, the phases of the light transmitted in the optical waveguide layers 20 of each waveguide element 10 are all the same. In this case, the light is emitted in a direction perpendicular to both the arrangement direction (Y direction) of the waveguide elements 10 and the extending direction (X direction) of the optical waveguide layer 20 (Z direction).

[0314] Figure 21B FIG. is a cross-sectional view of a waveguide array showing light emitted in a direction different from the direction perpendicular to the emission surface of the waveguide array. In Figure 21B In the example of, the phases of the light transmitted in the optical waveguide layers 20 of the plurality of waveguide elements 10 differ by a certain amount in the arrangement direction In this case, the light is emitted in a direction different from the Z direction. By changing this the component of the Y direction of the wave vector of the light can be changed.

[0315] The direction of the light emitted from the waveguide array to the outside (here assumed to be air) can be quantitatively discussed as follows.

[0316] Figure 22 FIG. is a perspective view schematically showing a waveguide array in a three-dimensional space. In a three-dimensional space defined by mutually orthogonal X, Y, and Z directions, let the region where light is emitted to air and the boundary surface of the waveguide array be Z = z0. This boundary surface includes the emission surfaces of the respective waveguide elements 10. In Z < z0, a plurality of waveguide elements 10 are arranged at equal intervals in the Y direction, and the plurality of waveguide elements 10 extend in the X direction respectively. When Z > z0, the electric field vector E(x, y, z) of the light emitted to air is represented by the following equation (11).

[0317] [Formula 5]

[0318] E(x, y, z) = E0exp[-j(k)] x x+k y y+k z z)] (11)

[0319] Where E0 is the amplitude vector of the electric field, k x k y and k z These are the wavenumbers in the X, Y, and Z directions, respectively, where j is the imaginary unit. In this case, the direction of the light emitted into the air is related to the wavenumber in the X, Y, and Z directions. Figure 22 The wave vector (k) is indicated by a thick arrow in the middle. x k y k z Parallel. The magnitude of the wave vector is represented by the following equation (12).

[0320] [Formula 6]

[0321]

[0322] Based on the boundary conditions of the electric field at Z = z0, the wave vector component k parallel to the boundary surface... x and k y The wavelengths of the light in the X and Y directions of the waveguide array are respectively consistent with the wavelengths of the light in the X and Y directions of the waveguide array. This is the same as Snell's rule in equation (2), which states that in the boundary surface, the wavelength of the light on the air side has the same wavelength as the wavelength of the light on the waveguide array side in the same plane direction.

[0323] k x The wavenumber is equal to that of the light transmitted in the optical waveguide layer 20 of the waveguide element 10 extending along the X direction.

[0324] In the above Figure 2 In the waveguide element 10 shown, k x Using equations (2) and (3), the following equation (13) is used.

[0325] [Formula 7]

[0326]

[0327] k y This is derived from the phase difference of light between two adjacent waveguide elements 10. Let the center of each of the N waveguide elements 10 arranged at equal intervals in the Y direction be y. q(q=0,1,2,…,N-1), let the distance (center-to-center distance) between two adjacent waveguide elements 10 be p. At this time, the electric field vector (equation (11)) of the light emitted into the air in the boundary surface (Z=z0) is y q and y q+1 The following relationship is satisfied by equation (14).

[0328] [Formula 8]

[0329] E(x, y) q+1 ,z0)=exp[-jk y (y q+1 -y q E(x, y) q ,z0)=exp[-jk y p]E(x,y q ,z0) (14)

[0330] If the settings are configured so that the phase difference between any two adjacent waveguide elements 10 becomes (If certain), then k y It is represented by the following equation (15).

[0331] [Formula 9]

[0332]

[0333] In this case, y q The phase of light at that location becomes That is, phase Along the Y direction is constant Or increase proportionally Or reduce Even if the waveguide elements 10 arranged along the Y direction are not equally spaced, as long as they are set so that relative to the desired k y y q and y q+1 The phase difference at is That's fine. In this case, y q The phase of light at that location becomes If we use the k obtained from equations (14) and (15) respectively x and k y Then, according to equation (12), k is derived. z Therefore, the direction of light emission (the direction of the wave vector) can be obtained.

[0334] For example, such as Figure 22 As shown, let the wave vector of the emitted light be (k). x k y k z ) and the vector (0, k) projected onto the YZ plane.y k z The angle between the wave vector and the YZ plane is θ. θ is the angle between the wave vector and the YZ plane. Using equations (12) and (13), θ is expressed by the following equation (16).

[0335] [Formula 10]

[0336]

[0337] Equation (16) is exactly the same as Equation (3) when the emitted light is parallel to the XZ plane. According to Equation (16), the X component of the wave vector varies depending on the wavelength of the light, the refractive index of the optical waveguide layer 20, and the thickness of the optical waveguide layer 20.

[0338] Similarly, as Figure 22 As shown, let the wave vector (k) of the emitted light (0th order light) be... x k y k z ) and the vector (k) projected onto the XZ plane. x ,0,k z The angle between the wave vector and the XZ plane is α0. α0 is the angle between the wave vector and the XZ plane. Using equations (12) and (13), α0 is expressed by the following equation (17).

[0339] [Formula 11]

[0340]

[0341] According to equation (17), the Y component of the wave vector of light varies with the phase difference of the light. And change.

[0342] In this way, it can also replace the wave vector (k) x k y k z The direction of light emission is determined using θ and α0 obtained from equations (16) and (17), respectively. In this case, the unit vector representing the direction of light emission can be expressed as (sinθ, sinα0, (1-sin 2 α0-sin 2 θ) 1 / 2 In the emission of light, these vector components must all be real numbers, so they satisfy sin 2 α0+sin 2 θ≤1. According to sin 2 α0≤1-sin 2 θ=cos 2As can be seen from θ, the emitted light varies within an angular range satisfying -cosθ ≤ sinα0 ≤ cosθ. Since -1 ≤ sinα0 ≤ 1, when θ = 0°, the emitted light varies within an angular range of -90° ≤ α0 ≤ 90°. However, if θ increases, cosθ becomes smaller, so the angular range of α0 becomes narrower. When θ = 90° (cosθ = 0), light is emitted only at α0 = 0°.

[0343] The two-dimensional scanning of light in this embodiment can be achieved as long as there are at least two or more waveguide elements 10. However, when the number of waveguide elements 10 is small, the expansion angle Δα of α0 described above becomes larger. If the number of waveguide elements 10 increases, Δα becomes smaller. This can be explained as follows. For simplicity, consider the case where θ = 0° in Figure 22 That is, consider the case where the emission direction of light is parallel to the YZ plane.

[0344] Assume that light with the same emission intensity and the above-mentioned phase is emitted from N (N is an integer of 2 or more) waveguide elements 10 respectively. At this time, the absolute value of the amplitude distribution of the total light (electric field) emitted from the N waveguide elements 10 is proportional to F(u) represented by the following equation (18) in the far field.

[0345] [Equation 12]

[0346]

[0347] where u is represented by the following equation (19).

[0348] [Equation 13]

[0349]

[0350] α is the angle formed by the line connecting the observation point and the origin in the YZ plane and the Z axis. α0 satisfies equation (17). F(u) in equation (18) is N (maximum) when u = 0 (α = α0), and 0 when u = ±2π / N. If the angles satisfying u = -2π / N and 2π / N are set as α1 and α2 (α1 < α0 < α2) respectively, the expansion angle of α0 becomes Δα = α2 - α1. The peak in the range of -2π / N < u < 2π / N (α1 < α < α2) is usually called the main lobe. There are multiple smaller peaks called side lobes on both sides of the main lobe. If the width of the main lobe Δu = 4π / N is compared with Δu = 2πpΔ(sinα) / λ obtained from equation (19), then Δ(sinα) = 2λ / (Np). If Δα is small, then Δ(sinα) = sinα2 - sinα1 = [(sinα2 - sinα1) / (α2 - α1)]Δα ≒ [d(sinα) / dα]α＝α0Δα =cosα0Δα. Therefore, the extended angle is represented by the following equation (20).

[0351] [Formula 14]

[0352]

[0353] Therefore, the more waveguide elements 10 there are, the smaller the spread angle Δα can be, enabling high-precision optical scanning even at a distance. The same discussion applies in... Figure 22 It can also be applied to the case where θ≠0°.

[0354] <Diffraction light emitted from the waveguide array>

[0355] From the waveguide array, in addition to zero-order light, higher-order diffracted light can also be emitted. For simplicity, consider... Figure 22 In the case where θ = 0°, the direction of the diffracted light is parallel to the YZ plane.

[0356] Figure 23A This is a schematic diagram illustrating the diffracted light emitted from the waveguide array when p is larger than λ. In this case, if there is no phase shift (α0 = 0°), then... Figure 23A The solid arrows shown emit 0th-order and ±1-order diffracted light (and, depending on the value of p, even higher-order diffracted light). If a phase shift (α0 ≠ 0°) is applied from this state, then... Figure 23A As shown by the dashed arrows, the emission angles of the 0th-order and ±1st-order beams change in the same direction of rotation. Although beam scanning can also be performed using higher-order beams such as ±1st-order beams, only the 0th-order beam is used in cases where the device is constructed more simply. To avoid a decrease in the gain of the 0th-order beam, the emission of higher-order beams can be suppressed by making the distance p between two adjacent waveguide elements 10 smaller than λ. Even if p > λ, only the 0th-order beam can be used by physically blocking the higher-order beams.

[0357] Figure 23B This diagram illustrates the situation where diffracted light is emitted from a waveguide array when p is smaller than λ. In this case, without a phase shift (α0 = 0°), since the diffraction angle exceeds 90 degrees, there is no higher-order diffracted light, and only the 0th-order light is emitted forward. However, when p is a value close to λ, if a phase shift is introduced (α0 ≠ 0°), sometimes ±1-order light is emitted depending on the emission angle.

[0358] Figure 23CThis is a schematic diagram illustrating the situation where diffracted light is emitted from a waveguide array when p ≒ λ / 2. In this case, even with a phase shift (α0 ≠ 0°), ±1-order light is not emitted, or if it is emitted, it is emitted at a considerably large angle. When p < λ / 2, even with a phase shift, higher-order light is not emitted. However, there is no particular benefit from further reducing p. Therefore, p can be set to, for example, λ / 2 or higher.

[0359] Figures 23A to 23C The relationship between the 0th order light and the ±1st order light emitted into the air can be quantitatively explained as follows. Since F(u) in equation (18) is F(u) = F(u + 2π), it is a periodic function of 2π. When u = ±2mπ, F(u) = N (maximum). At this time, ±m order light is emitted at an emission angle α satisfying u = ±2mπ. The peak value near u = ±2mπ (m ≠ 0) (peak width Δu = 4π / N) is called the grating lobe.

[0360] If we only consider the ±1st order light (u=±2π) in the higher order light, then the emission angle α± of the ±1st order light satisfies the following equation (21).

[0361] [Formula 15]

[0362]

[0363] According to the condition that no +1 light is emitted, sinα + >1, therefore p<λ / (1―sinα0). Similarly, according to the condition that no -1 order light is emitted, sinα － Since p < -1, we get p < λ / (1+sinα0).

[0364] The conditions for whether a zero-order ray with an emission angle α0 (>0) emits ±1-order rays are classified as follows: When p ≥ λ / (1―sinα0), both ±1-order rays are emitted. When λ / (1+sinα0) ≤ p < λ / (1―sinα0), no +1-order ray is emitted, but a -1-order ray is emitted. When p < λ / (1+sinα0), neither ±1-order rays are emitted. In particular, if p < λ / (1+sinα0), then... Figure 22 Even when θ≠0°, it does not emit ±1 light. For example, to achieve a unilateral scan of more than 10 degrees without emitting ±1 light, with α0=10°, it is sufficient to satisfy the relationship p≤λ / (1+sin10°)≒0.85λ. If combined with the above conditions for the lower limit related to p, it is sufficient to satisfy λ / 2≤p≤λ / (1+sin10°).

[0365] However, to satisfy the condition of not emitting ±1 order light, p needs to be very small. This makes the fabrication of the waveguide array difficult. Therefore, regardless of the presence or absence of ±1 order light, the 0th order light is assumed to be emitted at 0° < α0 < α. max The scan is performed within the angular range. It is assumed that the ±1 order light does not exist within this angular range. To satisfy this condition, when α0 = 0°, the emission angle of the +1 order light must be α. + ≧α max (that is, sinα) + =(λ / p)≧sinα max ), in α0=α max At that time, the emission angle of the -1st order light must be α. － ≤0 (i.e., sinα) － =sinα max -(λ / p)≤0). Based on these constraints, we get p≤λ / sinα. max .

[0366] Based on the above discussion, the maximum value of the emission angle α0 of the 0th order light in the case where ±1 order light does not exist within the scanning angle range is α0. max It satisfies the following equation (22).

[0367] [Formula 16]

[0368]

[0369] For example, in the absence of ±1 order light within the scanning angle range, in order to achieve a single-sided scan of more than 10 degrees, as α max =10°, as long as the relationship p≤λ / sin10°≒5.76λ is satisfied. If combined with the above conditions for the lower limit related to p, then λ / 2≤p≤λ / sin10° can be satisfied. Since the upper limit of p (p≒5.76λ) is large enough compared to the upper limit in the case of not emitting ±1 light (p≒0.85λ), the fabrication of the waveguide array is relatively easy. Here, in the case where the light used is not a single wavelength, let the center wavelength of the light used be λ.

[0370] Because of the above, in order to scan a wider angular range, the distance p between waveguides needs to be reduced. On the other hand, in order to reduce the spread angle Δα of the emitted light in equation (20) when p is small, the number of waveguide arrays needs to be increased. The number of waveguide arrays is appropriately determined according to the application and the required performance. For example, the number of waveguide arrays can be 16 or more, and depending on the application, it can be 100 or more.

[0371] Phase control of light introduced into the waveguide array

[0372] To control the phase of the light emitted from each waveguide element 10, a phase shifter that changes the phase of the light can be introduced at the stage before the light is introduced into the waveguide element 10. The optical scanning device 100 of this embodiment includes multiple phase shifters respectively connected to multiple waveguide elements 10, and a second adjustment element for adjusting the phase of the light transmitted in each phase shifter. Each phase shifter includes a waveguide directly or via another waveguide connected to the optical waveguide layer 20 of a corresponding one of the multiple waveguide elements 10. The second adjustment element changes the direction (third direction D3) of the light emitted from the multiple waveguide elements 10 by changing the phase difference of the light transmitted from the multiple phase shifters to the multiple waveguide elements 10. In the following description, similar to a waveguide array, the multiple phase shifters arranged together are sometimes referred to as a "phase shifter array".

[0373] Figure 24 This is a schematic diagram illustrating an example of a structure where the phase shifter 80 is directly connected to the waveguide element 10. Figure 24 In the diagram, the portion enclosed by the dashed frame corresponds to phase shifter 80. Phase shifter 80 has a pair of opposing mirrors (5th mirror 30a and 6th mirror 40a, hereinafter sometimes simply referred to as mirrors) and a waveguide 20a disposed between mirrors 30a and 40a. In this example, waveguide 20a is constructed from components shared with the optical waveguide layer 20 of waveguide element 10 and is directly connected to the optical waveguide layer 20. Similarly, mirror 40a is also constructed from components shared with mirror 40 of waveguide element 10 and is connected to mirror 40. Mirror 30a has a lower transmittance (higher reflectance) than mirror 30 of waveguide element 10. Mirror 30a is connected to mirror 30. In phase shifter 80, to prevent light emission, the transmittance of mirror 30a is designed to be the same low value as mirrors 40 and 40a. That is, the transmittance of the 5th mirror 30a and the 6th mirror 40a is lower than the transmittance of the 1st mirror 30. The waveguides 1 or 1' mentioned above can also function as phase shifters.

[0374] Figure 25 This is a schematic diagram of the waveguide array 10A and the phase shifter array 80A viewed from the normal direction (Z direction) of the light exit surface. Figure 25 In the example shown, all phase shifters 80 and all waveguide elements 10 have the same transmission characteristics. Each phase shifter 80 and each waveguide element 10 can be of the same length or of different lengths. When the lengths of the phase shifters 80 are equal, their respective phase shifts can be adjusted simply by using a driving voltage. Furthermore, by constructing the phase shifters 80 with equally spaced lengths, equally spaced phase shifts can be achieved with the same driving voltage. Moreover, the optical scanning device 100 also includes an optical splitter 90 that splits the light to supply the multiple phase shifters 80, a first driving circuit 110 that drives each waveguide element 10, and a second driving circuit 210 that drives each phase shifter 80. Figure 25The straight arrows in the diagram represent light input. Two-dimensional scanning can be achieved by independently controlling the first drive circuit 110 and the second drive circuit 210, which are set separately. In this example, the first drive circuit 110 functions as a component of the first adjustment element, and the second drive circuit 210 functions as a component of the second adjustment element.

[0375] As described later, the first driving circuit 110 modulates the angle of light emitted from the optical waveguide layer 20 by changing (modulating) the refractive index or thickness of the optical waveguide layer 20 of each waveguide element 10. The second driving circuit 210, as described later, modulates the phase of light transmitted inside the waveguide 20a by changing the refractive index of the waveguide 20a of each phase shifter 80. The optical splitter 90 can be constructed either as a dielectric waveguide that transmits light through total internal reflection, or as a reflective waveguide similar to the waveguide element 10.

[0376] Alternatively, after controlling the phase of each beam split by the optical splitter 90, the individual beams can be introduced into the phase shifter 80. In this phase control, for example, a simple phase control structure implemented by adjusting the length of the waveguide to the phase shifter 80 can be used. Alternatively, a phase shifter with the same function as the phase shifter 80 that can be controlled by an electrical signal can be used. In this way, for example, the phase can be adjusted before the light is introduced into the phase shifter 80 to supply light of equal phase to all phase shifters 80. This adjustment simplifies the control of each phase shifter 80 by the second drive circuit 210.

[0377] Figure 26 This diagram schematically illustrates an example of a structure in which the waveguide of the phase shifter 80 is connected to the optical waveguide layer 20 of the waveguide element 10 via another waveguide 85. The other waveguide 85 could also be one of the waveguides 1 described above. Furthermore, the other waveguide 85 could also be... Figure 10 Waveguides 1 and 1' are shown. Each phase shifter 80 can have the same characteristics as... Figure 24 The phase shifter 80 shown has the same structure, but it can also have different structures. Figure 26 In this context, the phase shifter 80 will use symbols to represent the amount of phase shift. A simplified representation. The same representation is sometimes used in later diagrams. In phase shifter 80, a dielectric waveguide that utilizes total internal reflection to transmit light can be employed. In this case, it is not necessary... Figure 24 Mirrors 30a and 40a as shown.

[0378] Figure 27 This diagram illustrates a structural example where multiple phase shifters 80 arranged in a cascaded manner are inserted into an optical splitter 90. In this example, multiple phase shifters 80 are connected along the path of the optical splitter 90. Each phase shifter 80 imparts a certain phase shift to the transmitted light. By ensuring that the phase shift introduced by each phase shifter 80 to the transmitted light is constant, the phase difference between two adjacent waveguide elements 10 becomes equal. Therefore, the second adjustment element can send a common phase control signal to all phase shifters 80. This results in a simplified structure.

[0379] To enable efficient light transmission between the optical splitter 90, phase shifter 80, and waveguide element 10, a dielectric waveguide can be used. In a dielectric waveguide, an optical material with a higher refractive index than the surrounding material and lower light absorption can be used. For example, materials such as Si, GaAs, GaN, SiO2, TiO2, Ta2O5, AlN, and SiN can be used. Furthermore, to enable light transmission from the optical splitter 90 to the waveguide element 10, one of the aforementioned waveguides can also be used. Furthermore, to enable light transmission from the optical splitter 90 to the waveguide element 10, a dielectric waveguide can also be used. Figure 10 Waveguides 1 and 1' are shown.

[0380] In the phase shifter 80, a mechanism is needed to change the optical path length in order to impart a phase difference to the light. In this embodiment, the refractive index of the waveguide of the phase shifter 80 is modulated to change the optical path length. This allows adjustment of the phase difference of the light supplied to the waveguide element 10 from two adjacent phase shifters 80. More specifically, a phase shift can be imparted by modulating the refractive index of the phase-shifting material within the waveguide of the phase shifter 80. Specific examples of the structure for refractive index modulation will be described later.

[0381] <Example of the first adjusting element>

[0382] Next, a structural example of the first adjustment element for adjusting the refractive index or thickness of the optical waveguide layer 20 of the waveguide element 10 will be described. First, a structural example in the case of adjusting the refractive index will be described.

[0383] Figure 28A This is a perspective view schematically showing an example of the structure of the first adjusting element 60 (hereinafter sometimes simply referred to as the adjusting element). Figure 28AIn the example shown, an adjustment element 60 with a pair of electrodes 62 is incorporated into the waveguide element 10. An optical waveguide layer 20 is sandwiched between the pair of electrodes 62. The optical waveguide layer 20 and the pair of electrodes 62 are disposed between a first mirror 30 and a second mirror 40. The entire side surface (the surface parallel to the XZ plane) of the optical waveguide layer 20 is in contact with the electrodes 62. The optical waveguide layer 20 contains a refractive index modulation material that modulates the refractive index of light transmitted in the optical waveguide layer 20 when a voltage is applied. The adjustment element 60 also has wiring 64 extending from the pair of electrodes 62 and a power supply 66 connected to the wiring 64. By turning on the power supply 66 and applying a voltage to the pair of electrodes 62 via the wiring 64, the refractive index of the optical waveguide layer 20 can be modulated. Therefore, the adjustment element 60 can also be referred to as a refractive index modulation element.

[0384] Figure 28B This is a perspective view schematically illustrating another structural example of the first adjustment element 60. In this example, only a portion of the side surface of the optical waveguide layer 20 contacts the electrode 62. All other points are not in contact with the electrode. Figure 28A The structures shown are identical. In this way, even with a structure that partially changes the refractive index of the optical waveguide layer 20, the direction of the emitted light can be changed.

[0385] Figure 28C This is a perspective view schematically illustrating another structural example of the first adjustment element 60. In this example, a pair of electrodes 62 have a layered shape that is substantially parallel to the reflective surfaces of mirrors 30 and 40. One electrode 62 is sandwiched between the first mirror 30 and the optical waveguide layer 20. The other electrode 62 is sandwiched between the second mirror 40 and the optical waveguide layer 20. With this structure, transparent electrodes can be used in the electrodes 62. This structure offers the advantage of easier manufacturing.

[0386] exist Figures 28A to 28C In the example shown, the optical waveguide layer 20 of each waveguide element 10 contains a material whose refractive index changes relative to the light transmitted in the optical waveguide layer 20 when a voltage is applied. The first adjustment element 60 has a pair of electrodes 62 sandwiching the optical waveguide layer 20, and the refractive index of the optical waveguide layer 20 is changed by applying a voltage to the pair of electrodes 62. The voltage can be applied by the first driving circuit 110 described above.

[0387] Here, examples of materials that can be used in each of the constituent elements are given.

[0388] In the materials of mirrors 30, 40, 30a, and 40a, for example, multilayer films formed of dielectrics can be used. Mirrors using multilayer films can be fabricated, for example, by periodically forming multiple films with different refractive indices, each having an optical thickness of 1 / 4 wavelength. High reflectivity can be obtained with such multilayer film mirrors. Materials used as films include, for example, SiO2, TiO2, Ta2O5, Si, SiN, etc. The mirrors are not limited to multilayer film mirrors; they can also be formed from metals such as Ag and Al.

[0389] In the electrode 62 and wiring 64, a variety of conductive materials can be used. For example, metallic materials such as Ag, Cu, Au, Al, Pt, Ta, W, Ti, Rh, Ru, Ni, Mo, Cr, Pd, etc., or inorganic compounds such as ITO, tin oxide, zinc oxide, IZO (registered trademark), SRO, etc., or conductive polymers such as PEDOT, polyaniline, etc., can be used.

[0390] In the material of the optical waveguide layer 20, various transparent materials such as dielectrics, semiconductors, electro-optical materials, and liquid crystal molecules can be used. Examples of dielectrics include SiO2, TiO2, Ta2O5, SiN, and AlN. Examples of semiconductor materials include Si-based, GaAs-based, and GaN-based materials. Examples of electro-optical materials include lithium niobate (LiNbO3), barium titanate (BaTiO3), lithium tantalate (LiTaO3), zinc oxide (ZnO), lead lanthanum zirconate titanate (PLZT), and potassium niobate tantalate (KTN).

[0391] Methods for modulating the refractive index of the optical waveguide layer 20 include, for example, methods utilizing carrier injection effects, electro-optical effects, birefringence effects, or thermo-optical effects. Examples of each method are described below.

[0392] The carrier injection effect can be achieved by utilizing a semiconductor pin junction structure. In this method, a structure is used where a semiconductor with a low doping concentration is sandwiched between p-type and n-type semiconductors, and the refractive index is modulated by injecting carriers into the semiconductor. In this structure, the optical waveguide layer 20 of each waveguide element 10 contains semiconductor material. One side of a pair of electrodes 62 may contain a p-type semiconductor, and the other side may contain an n-type semiconductor. The first adjustment element 60 injects carriers into the semiconductor material by applying a voltage to the pair of electrodes 62, causing a change in the refractive index of the optical waveguide layer 20. This can be achieved by simply fabricating the optical waveguide layer 20 with undoped or low-doped semiconductors and placing the p-type and n-type semiconductors in contact with them. Alternatively, a composite structure can be created where the p-type and n-type semiconductors are in contact with the low-doped semiconductors, and a conductive material contacts the p-type and n-type semiconductors. For example, if Si is implanted with 10… 20 cm -3 With approximately 0.1 charge carriers, the refractive index of Si changes by about 0.1 (for example, refer to "Free charge carrier-induced refractive index modulation of crystalline Silicon" 7). th IEEE International Conference on Group IV Photonics, pp. 102-104, 1-3 Sept. 2010). When this method is employed, as... Figures 28A to 28C The material of the pair of electrodes 62 can be p-type semiconductors or n-type semiconductors. Alternatively, the pair of electrodes 62 can also be made of metal, and p-type or n-type semiconductors can be included in the layer between the electrodes 62 and the optical waveguide layer 20 or in the optical waveguide layer 20 itself.

[0393] The method of utilizing electro-optical effects can be achieved by applying an electric field to the optical waveguide layer 20 containing electro-optical materials. In particular, if KTN is used as the electro-optical material, a large electro-optical effect can be obtained. Since the dielectric constant of KTN increases significantly at temperatures slightly higher than the phase transition temperature from tetragonal to cubic, this effect can be utilized. For example, according to "Low-Driving-Voltage Electro-Optic Modulator With Novel KTa1-xNbxO3 Crystal Waveguides" Jpn.J.Appl.Phys., Vol.43, No.8B (2004), the electro-optical constant g = 4.8 × 10⁻⁶ is obtained for light with a wavelength of 1.55 μm. －15 m 2 / V 2Therefore, if an electric field of, for example, 2 kV / mm is applied, the refractive index changes by 0.1 (=gn). 3 E 3 Approximately 2). Thus, in the structure utilizing the electro-optical effect, the optical waveguide layer 20 of each waveguide element 10 contains an electro-optical material such as KTN. The first adjustment element 60 changes the refractive index of the electro-optical material by applying a voltage to a pair of electrodes 62.

[0394] In the method utilizing the birefringence effect of liquid crystals, the refractive index of the liquid crystal can be anisotropically changed by driving the optical waveguide layer 20 containing liquid crystal material with electrodes 62. This allows modulation of the refractive index relative to the light transmitted in the optical waveguide layer 20. Since liquid crystals typically have a birefringence difference of about 0.1 to 0.2, a refractive index change equivalent to the birefringence difference can be obtained by changing the orientation direction of the liquid crystal with an electric field. Thus, in the structure utilizing the birefringence effect of liquid crystals, the optical waveguide layer 20 of each waveguide element 10 contains liquid crystal material. The first adjustment element 60 changes the refractive index of the liquid crystal material anisotropically by applying a voltage to a pair of electrodes 62, thereby changing the refractive index of the optical waveguide layer 20.

[0395] Thermo-optical effects are the effects of refractive index changing with the temperature of a material. To achieve thermo-optical effect-based actuation, the refractive index can also be modulated by heating the optical waveguide layer 20 containing thermo-optical materials.

[0396] Figure 29 This diagram illustrates an example of a structure combining an adjustment element 60, comprising a heater 68 made of a material with high resistance, with a waveguide element 10. The heater 68 can be positioned near the optical waveguide layer 20. Heating is achieved by applying voltage to the heater 68 via wiring 64 containing a conductive material by turning on a power supply 66. Alternatively, the heater 68 can be placed in contact with the optical waveguide layer 20. In this structural example, the optical waveguide layer 20 of each waveguide element 10 comprises a thermo-optical material whose refractive index changes with temperature. The first adjustment element 60 has a heater 68 that is in contact with or positioned near the optical waveguide layer 20. The first adjustment element 60 changes the refractive index of the optical waveguide layer 20 by heating the thermo-optical material with the heater 68.

[0397] Alternatively, the optical waveguide layer 20 itself can be made of a high-resistivity material, and heated by directly clamping the optical waveguide layer 20 with a pair of electrodes 62 and applying a voltage. In this case, the first adjustment element 60 has a pair of electrodes 62 clamping the optical waveguide layer 20. The first adjustment element 60 heats the thermo-optical material (e.g., a high-resistivity material) in the optical waveguide layer 20 by applying a voltage to the pair of electrodes 62, causing a change in the refractive index of the optical waveguide layer 20.

[0398] As a high-resistivity material used in heater 68 or optical waveguide layer 20, a semiconductor or a metal material with high resistivity can be used. Examples of semiconductors include Si, GaAs, or GaN. Furthermore, metals with high resistivity include iron, nickel, copper, manganese, chromium, aluminum, silver, gold, platinum, or alloys combining these materials. For example, the temperature dependence of the refractive index of Si for light with a wavelength of 1500 nm, dn / dT, is 1.87 × 10⁻⁶. －4 (K －1 (Refer to "Temperature-dependent refractive index of silicon and germanium", Proc. SPIE 6273, Optomechanical Technologies for Astronomy, 62732J). Therefore, changing the temperature by 500°C can cause a change in refractive index of approximately 0.1. If a heater 68 is placed near the optical waveguide layer 20 and localized heating is performed, even a large temperature change such as 500°C can be achieved relatively quickly.

[0399] The response speed of the refractive index change caused by carrier injection depends on the carrier lifetime. Typically, since the carrier lifetime is on the order of nanoseconds (ns), a response speed of about 100 MHz to 1 GHz can be obtained.

[0400] When using electro-optical materials, an electric field is applied to induce electron depolarization, resulting in a change in refractive index. The rate at which this depolarization occurs is typically very high; in materials such as LiNbO3 and LiTaO3, the response time is on the order of femtoseconds (fs), enabling high-speed driving exceeding 1 GHz.

[0401] When using thermo-optical materials, the response speed of refractive index change is determined by the rate of temperature rise and fall. A rapid temperature rise can be achieved by locally heating only the vicinity of the waveguide. Furthermore, if the heater is shut off while the temperature is locally rising, the temperature can be rapidly reduced by dissipating heat to the surrounding area. A response speed of around 100 kHz can be achieved in some cases.

[0402] In the above example, the first adjustment element 60 changes the X component of the wave vector of the emitted light by simultaneously changing the refractive index of each optical waveguide layer 20 by a certain value. In refractive index modulation, the modulation amount depends on the material properties; to obtain a larger modulation amount, a higher electric field or liquid crystal alignment is required. On the other hand, the direction of the light emitted from the waveguide element 10 also depends on the distance between mirrors 30 and 40. Therefore, the thickness of the optical waveguide layer 20 can also be changed by changing the distance between mirrors 30 and 40. An example of a structure that changes the thickness of the optical waveguide layer 20 will be described below.

[0403] To change the thickness of the optical waveguide layer 20, the optical waveguide layer 20 can be made of a deformable material such as a gas or liquid. The thickness of the optical waveguide layer 20 can be varied by moving at least one of the mirrors 30 and 40 that sandwich the optical waveguide layer 20. In order to maintain the parallelism between the upper and lower mirrors 30 and 40, a structure that minimizes the deformation of mirrors 30 or 40 can be adopted.

[0404] Figure 30 This diagram illustrates a structural example where a support member 70 made of a easily deformable material holds the mirror 30. The support member 70 may comprise a thinner component or a thinner frame that is relatively easily deformable compared to the mirror 30. In this example, the first adjustment element has an actuator connected to the first mirror 30 of each waveguide element 10. The actuator changes the thickness of the optical waveguide layer 20 by varying the distance between the first mirror 30 and the second mirror 40. Furthermore, the actuator may be connected to at least one of the first mirror 30 and the second mirror 40. Various actuators utilizing electrostatic force, electromagnetic induction, piezoelectric materials, shape memory alloys, or heat can be used as actuators to drive the mirror 30.

[0405] In structures utilizing electrostatic forces, the actuator in the first adjusting element moves mirrors 30 and / or 40 using the attractive or repulsive forces between electrodes generated by electrostatic forces. Examples of such structures are described below.

[0406] Figure 31This diagram illustrates an example of a structure in which mirrors 30 and / or 40 are moved by electrostatic forces generated between the electrodes. In this example, transparent electrodes 62 are provided between mirror 30 and the optical waveguide layer 20, and between mirror 40 and the optical waveguide layer 20. Support members 70 disposed on both sides of mirror 30 are fixed at one end to mirror 30 and at the other end to a housing (not shown). By applying positive and negative voltages to the pair of electrodes 62, an attractive force is generated, reducing the distance between mirrors 30 and 40. If the voltage application is stopped, a restoring force occurs in the support members 70 that hold the mirrors, and the distance between mirrors 30 and 40 returns to its original length. The electrodes 62 that generate this attractive force do not need to be located on the entire surface of the mirror. The actuator in this example has a pair of electrodes 62, one of which is fixed to the first mirror 30, and the other of which is fixed to the second mirror 40. The actuator applies a voltage to a pair of electrodes 62, generating an electrostatic force between the electrodes, thus changing the distance between the first mirror 30 and the second mirror 40. Furthermore, the application of the voltage to the electrodes 62 is controlled by the aforementioned drive circuit 110 (e.g., Figure 25 )conduct.

[0407] Figure 32 This diagram illustrates a structural example where the attractive electrode 62 is positioned in a location that does not obstruct light transmission. In this example, it is not necessary for the electrode 62 to be transparent. As shown, the electrode 62 fixed to each of the mirrors 30 and 40 does not need to be a single electrode; it can be divided into segments. By measuring the electrostatic capacitance of a portion of the divided electrodes, feedback control can be performed, such as measuring the distance between mirrors 30 and 40 and adjusting the parallelism of mirrors 30 and 40.

[0408] Alternatively, instead of using the electrostatic force between the electrodes, the mirrors 30 and / or 40 can be driven by electromagnetic induction that causes the magnetic body in the coil to generate attraction or repulsion.

[0409] In actuators utilizing piezoelectric materials, shape memory alloys, or thermal deformation, the phenomenon of material deformation caused by externally applied energy is utilized. For example, lead zirconate titanate (PZT), a representative piezoelectric material, expands and contracts by applying an electric field in the polarization direction. The distance between mirrors 30 and 40 can be directly changed using this piezoelectric material. However, since the piezoelectric constant of PZT is approximately 100 pm / V, even when an electric field of, for example, 1 V / μm is applied, the displacement is very small, approximately 0.01%. Therefore, sufficient mirror movement distance cannot be obtained when using such a piezoelectric material. Therefore, structures called single piezoelectric elements or double piezoelectric elements can be used to increase the amount of displacement.

[0410] Figure 33 This diagram shows an example of a piezoelectric element 72 containing piezoelectric material. The arrows indicate the direction of displacement of the piezoelectric element 72, and the size of the arrows indicates the amount of displacement. For example... Figure 33 As shown, since the displacement of the piezoelectric element 72 depends on the length of the material, the displacement in the surface direction is greater than the displacement in the thickness direction.

[0411] Figure 34A It means to use Figure 33 The diagram shows a structural example of a support member 74a for the piezoelectric element 72, which has a single piezoelectric element configuration. This support member 74a has a configuration where one layer of piezoelectric element 72 and one layer of non-piezoelectric element 71 are stacked. By fixing such a support member 74a to at least one of mirrors 30 and 40 and deforming it, the distance between mirrors 30 and 40 can be varied.

[0412] Figure 34B This diagram illustrates an example of the deformation of the support member 74a caused by applying a voltage to the piezoelectric element 72. When a voltage is applied to the piezoelectric element 72, only the piezoelectric element 72 elongates in the planar direction, causing the support member 74a to flex as a whole. Therefore, the displacement can be increased compared to the case without the non-piezoelectric element 71.

[0413] Figure 35A It means to use Figure 33 The diagram shows a structural example of a support member 74b with a double piezoelectric element 72. This support member 74b has a structure in which two layers of piezoelectric elements 72 are stacked with a single layer of non-piezoelectric element 71 between them. By fixing such a support member 74b to at least one of mirrors 30 and 40 and deforming it, the distance between mirrors 30 and 40 can be varied.

[0414] Figure 35B This diagram illustrates an example of the deformation of the support member 74a caused by applying voltage to the piezoelectric elements 72 on both sides. In the dual piezoelectric element structure, the displacement directions in the upper and lower piezoelectric materials 72 are opposite. Therefore, when using a dual piezoelectric element structure, the displacement amount can be further increased compared to a single piezoelectric element structure.

[0415] Figure 36 It means to Figure 34A The diagram shows an example of an actuator with support member 74a arranged on both sides of mirror 30. By deforming support member 74a in a manner that causes beam flexion by such a piezoelectric actuator, the distance between mirror 30 and mirror 40 can be varied. Alternatively, Figure 34A The support member 74a shown is used Figure 35A The support component 74b is shown.

[0416] Furthermore, because the single piezoelectric actuator is deformed in an arc shape, therefore... Figure 37AAs shown, the front end tilts on the side that is not fixed. Therefore, if the rigidity of mirror 30 is low, it is difficult to keep mirror 30 and mirror 40 parallel. Thus, as... Figure 37B As shown, two single piezoelectric support members 74a with different directions of extension and retraction can also be connected in series. Figure 37B In the example, in the support member 74a, the directions of deflection are opposite in the telescoping region and the stretching region. As a result, it is possible to prevent tilting at the front end on the unfixed side. By using such a support member 74a, tilting of mirrors 30 and 40 can be suppressed.

[0417] Similarly, by bonding materials with different coefficients of thermal expansion, beam structures capable of flexural deformation can also be achieved. Furthermore, beam structures can also be constructed using shape memory alloys. Both can be used to adjust the distance between mirrors 30 and 40.

[0418] Alternatively, the optical waveguide layer 20 can be made into a sealed space, and the distance between the mirror 30 and the mirror 40 can be changed by changing the volume of the optical waveguide layer 20 by sucking or discharging the air or liquid inside using a small pump.

[0419] As described above, the actuator in the first adjustment element can vary the thickness of the optical waveguide layer 20 through various configurations. This thickness variation can be performed individually on each of the multiple waveguide elements 10, or uniformly on all of the waveguide elements 10. In particular, when all the waveguide elements 10 have identical configurations, the distance between the mirrors 30 and 40 of each waveguide element 10 is controlled to be constant. Therefore, one actuator can drive all the waveguide elements 10 simultaneously.

[0420] Figure 38 This diagram illustrates an example of a structure in which an actuator drives multiple support members (i.e., auxiliary substrates) 52 that hold the first mirror 30 together. Figure 38 In this embodiment, the second mirror 40 is a plate-shaped mirror. Mirror 40 can also be divided into multiple mirrors as described above. The support member 52 is made of a light-transmitting material and has single piezoelectric actuators on both sides.

[0421] Figure 39 This diagram illustrates a structural example where the first mirror 30 of a plurality of waveguide elements 10 is a single plate-shaped mirror. In this example, the second mirror 40 is divided according to each waveguide element 10. Alternatively, as shown... Figure 41 and Figure 42 As in the example, at least one of the mirrors 30 and 40 of each waveguide element 10 may be a plate-shaped mirror portion. The actuator may also change the distance between mirrors 30 and 40 by moving the plate-shaped mirror.

[0422] <Refractive index modulation for phase shift>

[0423] Next, the structure for adjusting the phase of the plurality of phase shifters 80 by the second adjustment element will be described. The phase adjustment in the plurality of phase shifters 80 can be achieved by changing the refractive index of the waveguide 20a in the phase shifter 80. This refractive index adjustment can be achieved by a method already described that is exactly the same as the method for adjusting the refractive index of the optical waveguide layer 20 of each waveguide element 10. For example, the reference can be applied as is. Figures 28A to 29 The structure and method of refractive index modulation are explained. (Regarding...) Figures 28A to 29 In the description, it is sufficient to simply replace waveguide element 10 with phase shifter 80, first adjustment element 60 with second adjustment element, optical waveguide layer 20 with waveguide 20a, and first drive circuit 110 with second drive circuit 210. Therefore, detailed explanation of refractive index modulation in phase shifter 80 is omitted.

[0424] Each phase shifter 80's waveguide 20a comprises a material whose refractive index changes with the application of voltage or temperature. The second adjustment element changes the refractive index within the waveguide 20a by applying voltage to it or by changing its temperature. Thus, the second adjustment element can change the phase difference of light transmitted from the multiple phase shifters 80 to the multiple waveguide elements 10 respectively.

[0425] Each phase shifter 80 can be configured to achieve a phase shift of at least 2π during the period before light passes through. The length of waveguide 20a can be increased if the change in refractive index per unit length of the waveguide 20a of the phase shifter 80 is small. For example, the size of the phase shifter 80 can range from several hundred micrometers (μm) to several millimeters (mm), or even more, depending on the situation. Correspondingly, the length of each waveguide element 10 can be, for example, a value from tens of μm to approximately tens of millimeters.

[0426] <Structure for synchronous drive>

[0427] In this embodiment, the first adjusting element drives each waveguide element 10 to make the direction of light emitted from the plurality of waveguide elements 10 consistent. To make the direction of light emitted from the plurality of waveguide elements 10 consistent, for example, it is possible to provide a driving unit separately in each waveguide element 10 and drive them synchronously.

[0428] Figure 40 This is a diagram illustrating an example of a structure from which wiring 64 is taken out together from the electrodes 62 of each waveguide element 10. Figure 41 This is a diagram illustrating an example of a structure in which a portion of the electrodes 62 and wiring 64 are of the same type. Figure 42 This is a diagram illustrating an example of a structure in which a shared electrode 62 is configured relative to multiple waveguide elements 10. Figures 40-42In the diagram, straight arrows represent light input. By forming structures like those shown in these figures, the wiring to drive the waveguide array 10A becomes simple.

[0429] According to the structure of this embodiment, optical scanning can be performed two-dimensionally with a simple device structure. For example, when synchronously driving a waveguide array composed of N waveguide elements 10, if separate independent drive circuits are provided, N drive circuits are required. However, if the electrodes or wiring are designed to be common as described above, it can be operated with a single drive circuit.

[0430] When a phase shifter array 80A is provided at the front end of the waveguide array 10A, N drive circuits are still needed to enable each phase shifter 80 to operate independently. However, by means of... Figure 27 As in the example, the phase shifters 80 can be cascaded, and can be operated with a single drive circuit. That is, in the structure of this disclosure, two-dimensional optical scanning can be achieved using two to 2N drive circuits. Furthermore, the waveguide array 10A and the phase shifter array 80A can be operated independently, so their wiring will not interfere with each other and can be easily routed out.

[0431] <Manufacturing Method>

[0432] The waveguide array, phase shifter array 80A, and the dielectric waveguides connecting them can be manufactured using high-precision microfabrication processes such as semiconductor processing, 3D printing, self-organization, and nanoimprinting. These processes allow the necessary components to be integrated into a smaller area.

[0433] In particular, the use of semiconductor processes offers advantages such as high processing precision and high mass production capability. With semiconductor processes, various materials can be deposited on a substrate through methods such as evaporation, sputtering, CVD, and coating. Furthermore, micro-processing is performed using photolithography and etching. Substrate materials can include, for example, Si, SiO2, Al2O2, AlN, SiC, GaAs, and GaN.

[0434] <Variation Example>

[0435] Next, a variation of this embodiment will be described.

[0436] Figure 43This diagram schematically illustrates an example of a structure that ensures a large area for configuring the phase shifter array 80A while integrating a small waveguide array. With this structure, sufficient phase shift can be ensured even with only a small change in refractive index in the waveguide material constituting the phase shifter 80. Furthermore, when the phase shifter 80 is thermally driven, a wider spacing can be achieved, thus reducing the impact on adjacent phase shifters 80.

[0437] Figure 44 This diagram illustrates a structural example where two phase shifter arrays 80Aa and 80Ab are respectively arranged on both sides of a waveguide array 10A. In this example, the optical scanning device 100 has two optical splitters 90a and 90b, and two phase shifter arrays 80Aa and 80Ab on both sides of the waveguide array 10A. Figure 44 The arrows representing straight lines, indicated by dotted lines, indicate the light transmitted in optical splitters 90a and 90b and phase shifters 80a and 80b. Phase shifter array 80Aa and optical splitter 90a are connected to one side of waveguide array 10A, and phase shifter array 80Ab and optical splitter 90b are located on the other side of waveguide array 10A. The optical scanning device 100 also includes an optical switch 92 that switches the light supply to optical splitter 90a and optical splitter 90b. By switching the optical switch 92, the light supply from... Figure 44 The state of the input light to the left-side waveguide array 10A, and the state of the light from... Figure 44 The state of the light input to the waveguide array 10A from the right side.

[0438] According to the structure of this modified example, it has the advantage of being able to expand the scanning range with respect to the X direction of light emitted from the waveguide array 10A. In the structure where light is input to the waveguide array 10A from one side, by driving each waveguide element 10, the direction of the light can be scanned from the front direction (+Z direction) along a certain direction, either the +X direction or the -X direction. In contrast, in this modified example, when light is input from a single side to the waveguide array 10A, the direction of the light can be scanned from the front direction (+Z direction) along a certain direction, either the +X direction or the -X direction. Figure 44 When light is input to the left optical splitter 90a, it can scan the light along the +X direction from the front. On the other hand, when light is input from the right optical splitter 90b, it can scan the light in the -X direction from the front. That is, in Figure 44 In its structure, when viewed from the front, it can direct light towards Figure 44 The light is scanned in both left and right directions. Therefore, compared to a structure that inputs light from one side, the scanning angle range can be expanded. The optical switch 92 is controlled by an electrical signal by a control circuit (e.g., a microcontroller unit) that is not shown. According to this structural example, the driving of all components can be controlled by electrical signals.

[0439] The above description only pertains to waveguide arrays where the arrangement direction of waveguide elements 10 and the direction in which waveguide elements 10 extend are orthogonal. However, these directions do not need to be orthogonal. For example, alternative directions can also be used. Figure 45A The structure shown. Figure 45A This example illustrates a waveguide array where the arrangement direction d1 and the extension direction d2 of the waveguide elements 10 are not orthogonal. In this example, the light emission surfaces of each waveguide element 10 may not be in the same plane. Even with such a structure, by appropriately controlling each waveguide element 10 and each phase shifter, the light emission direction d3 can be varied two-dimensionally.

[0440] Figure 45B This illustrates a waveguide array structure where the arrangement spacing of waveguide elements 10 is not fixed. Even with such a structure, two-dimensional scanning is possible by appropriately setting the phase shift amount introduced by each phase shifter. Figure 45B In the structure, the arrangement direction d1 of the waveguide array and the extension direction d2 of each waveguide element 10 can also be non-orthogonal.

[0441] <Application Example>

[0442] Figure 46 This diagram illustrates an example of the structure of an optical scanning device 100, which integrates components such as an optical splitter 90, a waveguide array 10A, a phase shifter array 80A, and a light source 130 on a circuit board (i.e., a chip). The light source 130 can be, for example, a light-emitting element such as a semiconductor laser. In this example, the light source 130 emits light of a single wavelength λ in free space. The optical splitter 90 splits the light from the light source 130 and directs it to the waveguides of multiple phase shifters. Figure 46 In the structural example, an electrode 62a and multiple electrodes 62b are provided on the chip. For the waveguide array 10A, a control signal is supplied from electrode 62a. For the multiple phase shifters 80 in the phase shifter array 80A, control signals are respectively sent from the multiple electrodes 62b. Electrodes 62a and 62b can be connected to a control circuit (not shown) that generates the aforementioned control signals. The control circuit can also be provided... Figure 46 The chip shown can also be placed on other chips in the optical scanning device 100.

[0443] like Figure 46 As shown, by integrating all components onto a single chip, large-area optical scanning can be achieved with a small device. For example, components can be integrated onto a chip of approximately 2mm × 1mm. Figure 46 All components are shown.

[0444] Figure 47This is a schematic diagram illustrating a two-dimensional scan performed by irradiating a laser beam or similar object from an optical scanning device 100 into a distant location. The two-dimensional scan is performed by moving the beam spot 310 in both horizontal and vertical directions. For example, by combining it with the well-known Time of Flight (TOF) method, a two-dimensional ranging image can be obtained. The TOF method is a method of determining distance by irradiating a laser, observing the reflected light from an object, and calculating the time of flight of the light.

[0445] Figure 48 This is a block diagram illustrating the structure of a LiDAR (Light Detection and Ranging) system 300, an example of a light detection system capable of generating such a ranging image. The LiDAR system 300 includes a light scanning device 100, a light detector 400, a signal processing circuit 600, and a control circuit 500. The light detector 400 detects light emitted from the light scanning device 100 and reflected from an object. The light detector 400 may be, for example, an image sensor sensitive to the wavelength λ of the light emitted from the light scanning device 100, or a light-receiving element including a photodiode, etc. The light detector 400 outputs an electrical signal corresponding to the amount of light received. The signal processing circuit 600 calculates the distance to the object based on the electrical signal output from the light detector 400 and generates distance distribution data. The distance distribution data is data representing a two-dimensional distribution of distances (i.e., a ranging image). The control circuit 500 is a processor that controls the light scanning device 100, the light detector 400, and the signal processing circuit 600. The control circuit 500 controls the timing of the illumination of the light beam from the light scanning device 100 and the timing of the exposure and signal readout of the photodetector 400, and instructs the signal processing circuit 600 to generate the ranging image.

[0446] In 2D scanning, the frame rate for acquiring ranging images can be selected from, for example, 60fps, 50fps, 30fps, 25fps, 24fps, etc., which are commonly used in motion imaging. Furthermore, considering applications in automotive systems, a higher frame rate results in a higher frequency of acquiring ranging images, leading to more accurate obstacle detection. For example, when traveling at 60 km / h, a frame rate of 60fps allows for image acquisition whenever the vehicle moves approximately 28cm. A frame rate of 120fps allows for image acquisition whenever the vehicle moves approximately 14cm. A frame rate of 180fps allows for image acquisition whenever the vehicle moves approximately 9.3cm.

[0447] The time required to acquire a ranging image depends on the beam scanning speed. For example, to acquire a 100×100 resolution image at 60fps, beam scanning is required at a speed of less than 1.67μs per point. In this case, the control circuit 500 controls the emission of the beam by the optical scanning device 100 and the signal storage and readout by the photodetector 400 at an operating speed of 600kHz.

[0448] <Application Examples of Light Receiving Devices>

[0449] The optical scanning device disclosed herein can also be used as an optical receiving device with a substantially similar structure. The optical receiving device includes a waveguide array 10A identical to that of the optical scanning device, and a first adjustment element 60 for adjusting the direction of the receivable light. Each first mirror 30 of the waveguide array 10A transmits light incident from a third direction to the opposite side of the first reflecting surface. Each optical waveguide layer 20 of the waveguide array 10A transmits light transmitted through the first mirror 30 in a second direction. The first adjustment element 60 can change the direction of the receivable light by changing at least one of the refractive index and thickness of the optical waveguide layer 20 of each waveguide element 10. Furthermore, when the optical receiving device includes a plurality of phase shifters 80, or 80a and 80b, identical to those of the optical scanning device, and a second adjustment element that changes the phase difference of the light output from the plurality of waveguide elements 10 through the plurality of phase shifters 80, or 80a and 80b, the direction of the receivable light can be changed two-dimensionally.

[0450] For example, it can constitute Figure 46 The light source 130 in the optical scanning device 100 shown is replaced by an optical receiving device in the receiving circuit. If light of wavelength λ is incident on the waveguide array 10A, the light is transmitted to the optical splitter 90 via the phase shifter array 80A, and is finally concentrated at a certain point before being transmitted to the receiving circuit. The intensity of the light concentrated at this point can represent the sensitivity of the optical receiving device. The sensitivity of the optical receiving device can be adjusted by adjustment elements respectively installed in the waveguide array 10A and the phase shifter array 80A. In the optical receiving device, for example in Figure 22 In this configuration, the directions of the wave vectors (thick arrows) are reversed. The incident light has a light component in the direction in which the waveguide element 10 extends (X direction) and a light component in the direction in which the waveguide element 10 is arranged (Y direction). The sensitivity of the light component in the X direction can be adjusted by an adjustment element installed in the waveguide array. On the other hand, the sensitivity of the light component in the direction in which the waveguide element 10 is arranged can be adjusted by an adjustment element installed in the phase shifter array 80A. The phase difference of the light when the sensitivity of the optical receiving device is maximized is determined by the phase difference of the light. The refractive index n of the optical waveguide layer 20 wGiven the thickness d, we can know θ and α0 (Equations (16) and (17)). Therefore, we can determine the incident direction of the light. The above embodiments and variations can be appropriately combined.

[0451] Industrial availability

[0452] The optical scanning device and optical receiving device of the present disclosure can be used, for example, in lidar systems installed in vehicles such as automobiles, UAVs, and AGVs.

[0453] Label Explanation

[0454] 1 Waveguide

[0455] 2. Optical waveguide layer

[0456] 3. Multilayer reflective film

[0457] 4. Multilayer reflective film

[0458] 5. Grating

[0459] 6. Laser source

[0460] 7 fiber optics

[0461] 10. Waveguide Components (Waveguides)

[0462] 20 optical waveguide layers

[0463] 30 First Frame

[0464] 40 Second Mirror

[0465] 42 Low Refractive Index Layer

[0466] 44 High Refractive Index Layer

[0467] 50 substrates

[0468] 52 Support Components (Auxiliary Baseboard)

[0469] 60 Adjustment Components

[0470] 62 electrodes

[0471] 64 wiring

[0472] 66 power supply

[0473] 68 heater

[0474] 70 Support Components

[0475] 71 Non-piezoelectric elements

[0476] 72 piezoelectric elements

[0477] 74a, 74b support components

[0478] 80, 80a, 80b phase shifters

[0479] 90, 90a, 90b optical splitters

[0480] 92 optical switch

[0481] 100 light scanning equipment

[0482] 110 waveguide array drive circuit

[0483] 130 light source

[0484] 210 phase shifter array drive circuit

[0485] 310 beams

[0486] 400 photodetectors

[0487] 500 control circuit

[0488] 600 signal processing circuit

Claims

1. An optical device, characterized in that, have: The first waveguide transmits light in the waveguide direction via total internal reflection; and Second waveguide; The aforementioned second waveguide possesses: First reflective film; A second reflective film, opposite to the first reflective film described above; and The first optical waveguide layer is directly connected to the first waveguide or connected with clearance, and is located between the first reflective film and the second reflective film. The aforementioned first optical waveguide layer overlaps with the extension of the centerline of the aforementioned first waveguide; The aforementioned optical device will emit a portion of the light transmitted within the first optical waveguide layer to the outside of the second waveguide. Alternatively, the aforementioned optical device may guide a portion of the light incident on the second waveguide into the first optical waveguide layer.

2. An optical device, characterized in that, have: The first waveguide transmits light in the waveguide direction via total internal reflection; Second waveguide; and Third waveguide; The aforementioned second waveguide possesses: First reflective film; A second reflective film, opposite to the first reflective film described above; and The first optical waveguide layer is located between the first reflective film and the second reflective film. The aforementioned third waveguide possesses: Third reflective film; A fourth reflective film, opposite to the third reflective film described above; and The second optical waveguide layer is located between the third reflective film and the fourth reflective film. The second optical waveguide layer is directly connected to or connected with clearance to the first waveguide, and transmits the light transmitted in the first waveguide. The first optical waveguide layer is directly connected to the second optical waveguide layer, and transmits the light transmitted in the second optical waveguide layer. The extensions of the centerlines of the first optical waveguide layer and the second optical waveguide layer overlap. The second optical waveguide layer mentioned above overlaps with the extension of the centerline of the first waveguide mentioned above; The aforementioned optical device will emit a portion of the light transmitted within the first optical waveguide layer to the outside of the second waveguide. Alternatively, the aforementioned optical device may guide a portion of the light incident on the second waveguide into the first optical waveguide layer.

3. The optical device as described in claim 1 or 2, characterized in that, The first optical waveguide layer transmits the light in the same direction as the waveguide direction of the first waveguide.

4. The optical device as described in claim 1 or 2, characterized in that, The first waveguide and the second waveguide mentioned above are integrated on the chip.

5. The optical device as described in claim 1 or 2, characterized in that, Let the refractive index of the first waveguide relative to the aforementioned light be n. w1 Let the refractive index of the first optical waveguide layer relative to the aforementioned light be n. w2 When, n w1 and n w2 satisfy |n w1 -n w2 | / n w1 <0.4。 6. The optical device as described in claim 1 or 2, characterized in that, Let the refractive index of the first optical waveguide layer relative to the aforementioned light be n. w2 Let the thickness of the first optical waveguide layer be d2, the wavelength of the light in free space be λ, and when m is an integer greater than or equal to 1, n w2 and d2 satisfies 0.95×mλ / (2n) w2 ) <d2<1.5×mλ / (2n w2 )。 7. The optical device as described in claim 6, characterized in that, n w2 And d2 also satisfies 1.2×mλ / (2n) w2 ) <d2<1.5×mλ / (2n w2 )。 8. The optical device as described in claim 1 or 2, characterized in that, Let Δz be the offset between the centers of the first waveguide and the first optical waveguide layer along their thickness direction, and let Δd be the difference between the absolute values ​​of the thickness of the first optical waveguide layer and the thickness of the first waveguide layer. Δz satisfies... -Δd / 2 < Δz < Δd / 2.

9. The optical device as described in claim 1 or 2, characterized in that, The first optical waveguide layer is connected to the first waveguide with a clearance. Let the wavelength of the light in the aforementioned gap be λ, and let the optical length of the aforementioned gap satisfy λ / 6.5 or less.

10. The optical device as described in claim 1 or 2, characterized in that, Let the refractive index of the first waveguide relative to the aforementioned light be n. w1 Let the refractive index of the first optical waveguide layer relative to the aforementioned light be n. w2 When, n w1 and n w2 Satisfying n w1 >n w2 .

11. The optical device as described in claim 1 or 2, characterized in that, The first waveguide has a grating on a portion of its surface and transmits the light incident on the grating.

12. The optical device as described in claim 1 or 2, characterized in that, The first waveguide transmits the light incident from the end face of the first waveguide.

13. An optical device, characterized in that, It has multiple waveguide units; The aforementioned waveguide units each possess: The first waveguide transmits light in the second direction via total internal reflection; and Second waveguide; The aforementioned second waveguide possesses: First reflective film; A second reflective film, positioned opposite the first reflective film; and The first optical waveguide layer is directly connected to the first waveguide or connected with clearance, and is located between the first reflective film and the second reflective film. The aforementioned first optical waveguide layer overlaps with the extension of the centerline of the aforementioned first waveguide; The aforementioned optical device will emit a portion of the light transmitted within the first optical waveguide layer to the outside of the second waveguide. Alternatively, the aforementioned optical device may guide a portion of the light incident on the second waveguide into the first optical waveguide layer.

14. An optical device, characterized in that, It has multiple waveguide units; The aforementioned waveguide units each possess: The first waveguide transmits light to the second direction via total internal reflection; Second waveguide; and Third waveguide; The aforementioned second waveguide possesses: First reflective film; A second reflective film, positioned opposite the first reflective film; and The first optical waveguide layer is located between the first reflective film and the second reflective film. The aforementioned third waveguide possesses: Third reflective film; A fourth reflective film, positioned opposite the aforementioned third reflective film; and The second optical waveguide layer is located between the third reflective film and the fourth reflective film. The second optical waveguide layer is directly connected to or connected with clearance to the first waveguide, and transmits the light transmitted in the first waveguide. The first optical waveguide layer is directly connected to the second optical waveguide layer, and transmits the light transmitted in the second optical waveguide layer. The extensions of the centerlines of the first optical waveguide layer and the second optical waveguide layer overlap. The second optical waveguide layer mentioned above overlaps with the extension of the centerline of the first waveguide mentioned above; The aforementioned optical device will emit a portion of the light transmitted within the first optical waveguide layer to the outside of the second waveguide. Alternatively, the aforementioned optical device may guide a portion of the light incident on the second waveguide into the first optical waveguide layer.

15. The optical device as claimed in claim 13, characterized in that, The optical device adjusts the phase of the light transmitted to the second waveguide in each of the plurality of waveguide units.

16. The optical device as claimed in claim 15, characterized in that, It also has multiple phase shifters; The aforementioned multiple phase shifters each have a fourth waveguide connected to the corresponding first waveguide; The fourth waveguide of each phase shifter comprises a material whose refractive index changes in response to the application of voltage or temperature. The aforementioned optical device changes the refractive index of the fourth waveguide by applying a voltage to the fourth waveguide of each phase shifter or by changing the temperature of the fourth waveguide of each phase shifter, and adjusts the phase of the light transmitted to the second waveguide in each of the plurality of waveguide units.

17. The optical device as claimed in claim 16, characterized in that, It also has: The light source emits the aforementioned light; and The optical splitter directs the optical path from the aforementioned light source to the fourth waveguide of each of the plurality of phase shifters.

18. The optical device according to any one of claims 13 to 17, characterized in that, It also features an integrally formed fifth reflective film; The first reflective film of each of the aforementioned waveguide units is a part of the aforementioned fifth reflective film.

19. The optical device according to any one of claims 13 to 17, characterized in that, It also features an integrally formed sixth reflective film; The second reflective film of each of the aforementioned waveguide units is a part of the aforementioned sixth reflective film.

20. The optical device as claimed in claim 1, characterized in that, The first optical waveguide layer has an end face that is directly connected to the end face of the first waveguide.

21. A light detection system, characterized in that, have: The optical device according to any one of claims 1 to 19; A photodetector detects light emitted from the aforementioned optical device and reflected from an object; and The signal processing circuit generates distance distribution data based on the output of the aforementioned photodetector.

Images