Lighting device

Abstract

The optical device includes: a first waveguide extending in a first direction; and a second waveguide extending in the first direction; the second waveguide includes: a first mirror having a first reflecting surface; a second mirror having a second reflecting surface opposite to the first reflecting surface; and an optical waveguide layer between the first mirror and the second mirror; at least one of the first waveguide and the second waveguide has one or more gratings in a part of a region where the first mirror, the second mirror, and the first waveguide overlap when viewed from a direction perpendicular to the first reflecting surface; the one or more gratings are away from an end of the first mirror or the second mirror in the overlapping region in the first direction by a distance longer than at least one of a thickness of the first mirror and a thickness of the second mirror.

Description

[0001] This application is a divisional application of the invention patent application filed on February 7, 2020, with application number 202080016865.0 and title "Optical Device". Technical Field

[0002] This invention relates to optical devices. Background Technology

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

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

[0005] Patent document 2 discloses an optical phased array having multiple nanophotonic antenna elements arranged in a two-dimensional pattern. Each antenna element is optically coupled to a variable optical delay line (i.e., a phase shifter). In this optical phased array, a coherent beam is guided to each antenna element through a waveguide, and the phase of the beam is shifted by the phase shifter. This allows for a variation in the amplitude distribution of the far-field radiation pattern.

[0006] Patent document 3 discloses an optical deflection element comprising: an optical waveguide having an optical waveguide layer having light guided internally 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 optical waveguide; and a light outlet formed on the surface of the optical waveguide for emitting light that has entered from the light inlet and guided within the optical waveguide.

[0007] Patent document 4 discloses an optical scanning device comprising a first waveguide that allows light to propagate via total internal reflection and a second waveguide that allows light to propagate between two multilayer reflective films. The first waveguide and the second waveguide are connected.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2013 / 168266

[0011] Patent Document 2: Japanese Patent Publication No. 2016-508235

[0012] Patent Document 3: Japanese Patent Application Publication No. 2013-16591

[0013] Patent Document 4: International Publication No. 2018 / 061514 Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] The purpose of this invention is to provide a new optical device that can achieve optical coupling between waveguides with a relatively simple structure.

[0016] Methods used to solve problems

[0017] An optical device according to a technical solution of the present invention includes: a first waveguide extending along a first direction; and a second waveguide extending along the first direction; the second waveguide includes: a first mirror having a first reflecting surface; a second mirror having a second reflecting surface facing the first reflecting surface; and an optical waveguide layer between the first mirror and the second mirror; at least one of the first waveguide and the second waveguide has one or more gratings in a portion of the overlapping area of ​​the first mirror, the second mirror and the first waveguide when viewed from a direction perpendicular to the first reflecting surface; the one or more gratings are located in the first direction at a distance from the end of the first mirror or the second mirror in the overlapping area that is longer than at least one of the thickness of the first mirror and the thickness of the second mirror.

[0018] The inclusiveness or specific form of the present invention can also be achieved by means of devices, systems, methods or any combination thereof.

[0019] Invention Effects

[0020] According to a technical solution of the present invention, optical coupling between waveguides can be achieved with a relatively simple structure. Attached Figure Description

[0021] Figure 1 This is a perspective view schematically illustrating an example of an optical scanning device.

[0022] Figure 2 This is a schematic diagram illustrating the construction of a waveguide element's cross-section and an example of propagated light.

[0023] Figure 3A 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.

[0024] Figure 3B 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.

[0025] Figure 4 This is a stereoscopic diagram schematically representing an example of a waveguide array in three-dimensional space.

[0026] Figure 5 This is a schematic diagram of the waveguide array and phase shifter array viewed from the normal direction (Z direction) of the light emission surface.

[0027] Figure 6This is a diagram schematically illustrating an example of an optical device in which the shape of the end of the first mirror is changed through processing.

[0028] Figure 7 This is a graph showing the relationship between the change in the thickness of the optical waveguide layer and the diffusion angle of the emitted light from the first mirror.

[0029] Figure 8A This is a diagram schematically illustrating an exemplary embodiment of an optical device according to the present invention.

[0030] Figure 8B Viewed from the Z direction Figure 8A The diagram shows the connection between the total reflection waveguide and the slow optical waveguide.

[0031] Figure 9 This is a diagram schematically illustrating an example of an optical device with a longer distance from the interface to the grating.

[0032] Figure 10A It is a schematic representation Figure 8A A diagram of the first modified example of the optical device shown.

[0033] Figure 10B It is a schematic representation Figure 8A A diagram of the second variation of the optical device shown.

[0034] Figure 10C It is a schematic representation Figure 8A The figure shows a third variation of the optical device.

[0035] Figure 11A It is a schematic representation Figure 8A The diagram shows the fourth variation of the optical device.

[0036] Figure 11B It is a schematic representation Figure 8A The diagram shows the fifth variation of the optical device.

[0037] Figure 12 This is a diagram illustrating a structural example of an optical scanning device that integrates components such as beam splitters, waveguide arrays, phase shifter arrays, and light sources on a circuit board.

[0038] Figure 13 This is a schematic diagram illustrating a situation where a two-dimensional scan is performed by irradiating a laser beam or similar object from a light scanning device into a distant location.

[0039] Figure 14 This is a block diagram representing a structural example of a LiDAR system capable of generating ranging images. Detailed Implementation

[0040] In this specification, "at least one of refractive index, thickness, and wavelength" refers to at least one selected from the group consisting of the refractive index of the optical waveguide layer, the thickness of the optical waveguide layer, and the wavelength input to the optical waveguide layer. To change the direction of light emission, any one of the refractive index, thickness, and wavelength can be controlled individually. Alternatively, any two or all of these three can be controlled to change the direction of light emission. The wavelength of the light input to the optical waveguide layer can also be controlled, either instead of controlling the refractive index or thickness.

[0041] 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, thickness, and wavelength, the direction of the receivable light can be changed one-dimensionally. Furthermore, if the phase difference of the light is changed by multiple phase shifters connected to multiple waveguide elements arranged in one direction, the direction of the receivable light can be changed two-dimensionally.

[0042] The optical scanning device and optical receiving device of the present invention can be used as antennas for optical detection systems such as LiDAR (Light Detection and Range) systems. Compared with radar systems that use electromagnetic waves such as millimeter waves, 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 LiDAR systems can be installed, for example, in automobiles and UAVs (Unmanned Aerial Vehicles). i Mobile vehicles such as drones (AGVs) and guided vehicles (AGVs) can be used as one of the collision avoidance technologies. In this specification, optical scanning devices and optical receiving devices are sometimes collectively referred to as "optical devices." Furthermore, devices used in optical scanning devices or optical receiving devices are also sometimes referred to as "optical devices."

[0043] <Structure Example of an Optical Scanning Device>

[0044] The structure of a two-dimensional scanning optical scanning device will be described below as an example. However, there are instances where necessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of substantially the same structures may be 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 the invention, but these are not intended to limit the subject matter of the claims. In the following description, the same or similar constituent elements are given the same reference numerals.

[0045] In this invention, "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 specification, ultraviolet light may be referred to as "ultraviolet light" and infrared light as "infrared light".

[0046] In this invention, "scanning" based on 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.

[0047] Figure 1 This is a perspective view schematically illustrating an example of an optical scanning device 100 according to an embodiment. The optical scanning device 100 includes a waveguide array comprising a plurality of waveguide elements 10. The plurality of waveguide elements 10 each have a first direction (…). Figure 1 The shape extends in the X direction (of the first direction). Multiple waveguide elements 10 extend in a second direction (of the second direction) intersecting the first direction. Figure 1 The waveguide elements 10 are regularly arranged in the Y direction. Multiple waveguide elements 10 propagate light in the first direction and simultaneously emit light in a third direction D3, intersecting an imaginary plane parallel to the first and second directions. In this invention, the first direction (X direction) and the second direction (Y direction) are orthogonal, but they may not be orthogonal. In this invention, the multiple waveguide elements 10 are arranged at equal intervals in the Y direction, but they do not necessarily need to be arranged at equal intervals.

[0048] Furthermore, the orientation of the structures shown in the accompanying drawings of this application is set for ease of explanation and is not intended to limit the orientation during implementation. In addition, the shape and size of the entirety or a portion of the structures shown in the drawings do not limit the actual shape and size.

[0049] Each of the multiple waveguide elements 10 has a first mirror 30 and a second mirror 40 (hereinafter, each may be simply referred to as a "mirror") 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 that extends along a first direction (X direction).

[0050] Furthermore, as described later, the plurality of first mirrors 30 of the plurality of waveguide elements 10 can also be multiple parts of a mirror integrally formed. Additionally, the plurality of second mirrors 40 of the plurality of waveguide elements 10 can also be multiple parts of a mirror integrally formed. Furthermore, the plurality of optical waveguide layers 20 of the plurality of waveguide elements 10 can also be multiple parts of an optical waveguide layer integrally formed. Multiple waveguides can be formed by at least (1) each first mirror 30 being separately formed from the other first mirrors 30, or (2) each second mirror 40 being separately formed from the other second mirrors 40, or (3) each optical waveguide layer 20 being separately formed from the other optical waveguide layers 20. "Separately formed" includes not only physically setting up space, but also separating the components by sandwiching materials with different refractive indices in between.

[0051] The reflecting surfaces of the first mirror 30 and the second mirror 40 are positioned approximately parallel to each other. Of the two mirrors 30 and 40, at least the first mirror 30 has the property of transmitting a portion of the light propagating in the optical waveguide layer 20. In other words, the first mirror 30 has a higher light transmittance than the second mirror 40. Therefore, a portion of the light propagating in the optical waveguide layer 20 is emitted from the first mirror 30 to the outside. Such mirrors 30 and 40 can, for example, be multilayer mirrors formed of a dielectric-based multilayer film (also known as a "multilayer reflective film").

[0052] By controlling the phase of the light input to each waveguide element 10, the refractive index or thickness of the optical waveguide layer 20 of these waveguide elements 10, or the wavelength of the light input to the optical waveguide layer 20, can be changed synchronously and simultaneously, enabling light-based two-dimensional scanning.

[0053] In order to achieve such two-dimensional scanning, the inventors of this invention analyzed the operating principle of the waveguide element 10. Based on their findings, they successfully achieved light-based two-dimensional scanning by synchronously driving multiple waveguide elements 10.

[0054] like Figure 1 As shown, if light is input to each waveguide element 10, the light is emitted from the emission surface of each waveguide element 10. The emission 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 invention, at least one of the refractive index, thickness, and wavelength 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 wavenumber 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.

[0055] 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 through 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 to each of the multiple waveguide elements 10. By changing this phase difference, the Y-direction component of the wavenumber 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 emitted light reinforces each other through interference can be changed along... Figure 1 The direction 102 shown changes. This enables light-based two-dimensional scanning.

[0056] The operating principle of the optical scanning device 100 is explained below.

[0057] <Operating Principle of Waveguide Elements>

[0058] Figure 2 This is a schematic diagram illustrating the construction of a cross-section of a waveguide element 10 and an example of propagated 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 of waveguide element 10 parallel to the XZ plane. In waveguide element 10, a pair of mirrors 30 and 40 are arranged to sandwich the 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 disposed on the lower surface ( Figure 2 The light is repeatedly reflected by the second mirror 40 (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.

[0059] 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 invention, light propagates through repeated reflections by mirrors 30 and 40 disposed above and below the optical waveguide layer 20. Therefore, there is no restriction on the propagation angle of the light. Here, the propagation angle of the light is the angle of incidence pointing towards the interface between mirror 30 or 40 and the optical waveguide layer 20. Light incident at an angle closer to perpendicular to mirror 30 or 40 can also propagate. That is, light incident at an angle smaller than the critical angle of total internal reflection can also propagate. Therefore, the group velocity of light in the propagation direction is significantly lower than the speed of light in free space. Thus, the waveguide element 10 has the property that the propagation conditions of light vary significantly with changes in the wavelength of light, the thickness of the optical waveguide layer 20, and the refractive index of the optical waveguide layer 20. The waveguide element 10 is also referred to as a "reflective waveguide" or a "slow-light waveguide."

[0060] The emission angle θ of light emitted from waveguide element 10 into the air is represented by the following equation (1).

[0061] [Formula 1]

[0062]

[0063] According to equation (1), by changing the wavelength λ of light in the air and the refractive index n of the optical waveguide layer 20, w Any one of the thicknesses d of the optical waveguide layer 20 can change the direction of light emission.

[0064] 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 changes to d = 420 nm without changing the refractive index, the emission angle changes by approximately 51°. If the wavelength changes 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 A change in any one of the thicknesses, including d, of the optical waveguide layer 20 can cause a significant change in the direction of light emission.

[0065] Therefore, in the optical scanning device 100 of the present invention, the wavelength λ of the light input to the optical waveguide layer 20 and the refractive index n of the optical waveguide layer 20 are controlled. wThe light emission direction can be controlled by at least one of the following: the thickness d of the optical waveguide layer 20. The wavelength λ of the light can also remain constant during operation. In this case, light scanning can be achieved with a simpler structure. 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 provides high detection sensitivity using photodetectors or image sensors that typically detect light by absorbing it with silicon (Si). In another example, the wavelength λ can be included in the wavelength range of near-infrared light, from 1260 nm to 1625 nm, where transmission loss in optical fibers or Si waveguides is relatively small. 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.

[0066] In order to change the direction of the emitted light, the optical scanning device 100 may have a first adjustment element that changes at least one of the refractive index, thickness and wavelength of the optical waveguide layer 20 in each waveguide element 10.

[0067] As described above, if waveguide element 10 is used, then by adjusting the refractive index n of the optical waveguide layer 20... w A change in at least one of the thickness d and wavelength λ can significantly alter the direction of light emission. This allows the emission angle of light emitted from mirror 30 to vary along the direction of waveguide element 10. Such one-dimensional scanning can be achieved by using at least one waveguide element 10.

[0068] To adjust the refractive index of at least a portion of the optical waveguide layer 20, the optical waveguide layer 20 may also contain a liquid crystal material or an electro-optical material. The optical waveguide layer 20 can be sandwiched between a pair of electrodes. By applying a voltage to the pair of electrodes, the refractive index of the optical waveguide layer 20 can be changed.

[0069] To adjust the thickness of the optical waveguide layer 20, at least one actuator can be connected to at least one of the first mirror 30 and the second mirror 40. By changing the distance between the first mirror 30 and the second mirror 40 using at least one actuator, the thickness of the optical waveguide layer 20 can be varied. If the optical waveguide layer 20 is formed of a liquid, its thickness can be easily varied.

[0070] <Principles of Two-Dimensional Scanning>

[0071] In a waveguide array consisting of multiple waveguide elements 10 arranged in one direction, the direction of light emission changes due to interference of light emitted from each waveguide element 10. The direction of light emission can be changed by adjusting the phase of the light supplied to each waveguide element 10. The principle is explained below.

[0072] Figure 3AThis is a diagram showing a cross-section of a waveguide array that emits light in a direction perpendicular to the exit surface of the waveguide array. Figure 3A The diagram also records the phase shift of the light propagating in each waveguide element 10. Here, the phase shift is a value based on the phase of the light propagating in the waveguide element 10 at the left end. The waveguide array of the present invention includes a plurality of waveguide elements 10 arranged at equal intervals. Figure 3A In the diagram, the dashed arcs represent the wavefronts of light emitted from each waveguide element 10. Straight lines represent the wavefronts formed by light interference. Arrows indicate the direction of light emitted from the waveguide array (i.e., the direction of the wavenumber vector). Figure 3A In the example shown, the phase of the light propagating in the optical waveguide layer 20 of each waveguide element 10 is the same. In this case, the light is emitted in a direction (Z direction) that is perpendicular to both the arrangement direction (Y direction) of the waveguide elements 10 and the direction in which the optical waveguide layer 20 extends (X direction).

[0073] Figure 3B This is a diagram showing a 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. Figure 3B In the example shown, the phase of the light propagating in the optical waveguide layer 20 of the multiple waveguide elements 10 differs by a certain amount (Δφ) in each of the arrangement directions. In this case, the light is emitted in a direction different from the Z direction. By changing this Δφ, the Y-direction component of the light wavenumber vector can be changed. If the center-to-center distance between two adjacent waveguide elements 10 is p, then the light emission angle α0 is represented by the following equation (2).

[0074] [Formula 2]

[0075]

[0076] exist Figure 2 In the example shown, the direction of light emission is parallel to the XZ plane. That is, α0 = 0°. Figure 3A and Figure 3B In the example shown, the direction of the light emitted from the optical scanning device 100 is parallel to the YZ plane. That is, θ = 0°. However, typically the direction of the light emitted from the optical scanning device 100 is neither parallel to the XZ plane nor to the YZ plane. That is, θ ≠ 0° and α0 ≠ 0°.

[0077] Figure 4 This is a stereoscopic diagram schematically representing an example of a waveguide array in three-dimensional space. Figure 4 The thick arrows shown indicate the direction of light emitted from the optical scanning device 100. θ is the angle between the emitted light direction and the YZ plane. θ satisfies equation (1). α0 is the angle between the emitted light direction and the XZ plane. α0 satisfies equation (2).

[0078] Phase control of light introduced into the waveguide array

[0079] To control the phase of light emitted from each waveguide element 10, a phase shifter that changes the phase of the light can be provided, for example, at the front end where light is introduced into the waveguide element 10. The optical scanning device 100 of the present invention includes a plurality of phase shifters connected to each of the plurality of waveguide elements 10, and a second adjustment element for adjusting the phase of light propagating in each phase shifter. Each phase shifter includes a waveguide directly connected to or via another waveguide of the optical waveguide layer 20 in a corresponding one of the plurality of waveguide elements 10. The second adjustment element changes the direction (i.e., the third direction D3) of the light emitted from the plurality of waveguide elements 10 by changing the phase difference of the light propagating from the plurality of phase shifters to the plurality of waveguide elements 10. In the following description, similar to a waveguide array, the plurality of phase shifters arranged together may be referred to as a "phase shifter array".

[0080] Figure 5 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 5 In the example shown, all phase shifters 80 have the same propagation characteristics, and all waveguide elements 10 have the same propagation characteristics. Each phase shifter 80 and each waveguide element 10 can also have the same length, or the lengths can be different. When the lengths of each phase shifter 80 are equal, for example, the phase shift amount can be adjusted by the driving voltage. Furthermore, by constructing a structure in which the lengths of each phase shifter 80 change in equal steps, equal-step phase shifts can be applied with the same driving voltage. Furthermore, the optical scanning device 100 also includes a beam splitter 90 that branches 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 5 The straight arrows shown indicate the light input. Two-dimensional scanning can be achieved by independently controlling the first drive circuit 110 and the second drive circuit 210, which are respectively provided. 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.

[0081] The first driving circuit 110 changes the angle of light emitted from the optical waveguide layer 20 by changing at least one of the refractive index and thickness of the optical waveguide layer 20 in each waveguide element 10. The second driving circuit 210 changes the phase of light propagating inside the optical waveguide 20a by changing the refractive index of the optical waveguide 20a in each phase shifter 80. The beam splitter 90 can be constructed from a waveguide in which light propagates through total internal reflection, or from a reflective waveguide similar to the waveguide element 10.

[0082] Alternatively, the phases of the individual beams branched by the beam splitter 90 can be controlled before guiding each beam to the phase shifter 80. This phase control can be achieved, for example, using a simple phase control structure implemented by adjusting the length of the waveguide up to the phase shifter 80. Alternatively, a phase shifter with the same function as the phase shifter 80, controllable by an electrical signal, can be used. In this way, the phase can be adjusted before being guided to the phase shifter 80 to supply equal-phase light to all phase shifters 80. This adjustment simplifies the control of each phase shifter 80 by the second drive circuit 210.

[0083] An optical device having the same structure as the optical scanning device 100 described above can also be used as an optical receiving device. Details regarding the operating principle and method of the optical device are disclosed in U.S. Patent Application Publication No. 2018 / 0224709. The entire disclosure of that document is incorporated herein by reference.

[0084] <Connection of Total Internal Reflection Waveguide and Slow Optical Waveguide>

[0085] Next, an example of inputting light from a total internal reflection waveguide to a slow optical waveguide by connecting a total internal reflection waveguide and a slow optical waveguide will be described.

[0086] Figure 6 This is a schematic cross-sectional view illustrating an example of an optical device connecting a total reflection waveguide 1 and a slow light waveguide 10. In this specification, the total reflection waveguide 1 is sometimes referred to as "first waveguide 1," and the slow light waveguide 10 as "second waveguide 10." The shape of the end portion 30e of the first mirror 30 will be described without considering this aspect. Figure 6 The optical device shown.

[0087] In the total internal reflection waveguide 1, at least the front end has a structure extending in the X direction. The slow optical waveguide 10 is connected to the total internal reflection waveguide 1. The optical waveguide layer 20 in the slow optical waveguide 10 internally includes a portion comprising the front end of the total internal reflection waveguide 1. The refractive index of the optical waveguide layer 20 is lower than that of the total internal reflection waveguide 1. When viewed from the Z direction, in the connection region 111 where the total internal reflection waveguide 1 and the slow optical waveguide 10 overlap, the total internal reflection waveguide 1 has a grating 15 whose refractive index varies periodically with a period p along the X direction. The connection region 111 can also be described as the region where the first mirror 30, the second mirror 40, and the total internal reflection waveguide 1 overlap when viewed from the Z direction. Figure 6The illustrated grating 15 has four recesses arranged in the X direction. In practice, more recesses can be provided in the grating 15. Convexes can also be provided instead of recesses. The number of recesses or convexes arranged in the X direction in the grating 15 is preferably four or more, for example. Furthermore, the number of recesses or convexes can be four or more and 64 or less. In one example, the number of recesses or convexes can be eight or more and 32 or less. In another example, the number of recesses or convexes can be eight or more and 16 or less. The number of recesses or convexes can be adjusted according to the diffraction efficiency of each recess or convex. The diffraction efficiency of each recess or convex depends on its depth or width, etc. Therefore, the number of recesses or convexes is adjusted according to their dimensions so that good characteristics can be obtained as a whole in the grating 15.

[0088] The total reflection waveguide 1 has a first surface 1s1 facing the reflecting surface of the first mirror 30 and a second surface 1s2 facing the reflecting surface of the second mirror 40 in the connection region 111. Figure 6 In the example shown, grating 15 is disposed on the first surface 1s1 of the total reflection waveguide 1. Grating 15 may also be disposed on the second surface 1s2. Grating 15 may be disposed on at least one of the first surface 1s1 and the second surface 1s2 of the total reflection waveguide 1.

[0089] The grating 15 is not limited to being disposed at the interface between the total internal reflection waveguide 1 and the slow optical waveguide 10, but can also be disposed at other locations. Furthermore, multiple gratings can be disposed. In the connection region 111 where the total internal reflection waveguide 1 and the slow optical waveguide 10 overlap when viewed from a direction perpendicular to the reflecting surface of the first mirror 30, at least a portion of the total internal reflection waveguide 1 and the slow optical waveguide 10 may include at least one grating. The refractive index of each grating varies periodically along the X-direction extending from the total internal reflection waveguide 1 and the slow optical waveguide 10.

[0090] In the total reflection waveguide 1, the portion located outside the optical waveguide layer 20 can be supported by other dielectric layers or sandwiched between two dielectric layers.

[0091] The length of the connecting region 111 can be, for example, approximately 3 μm to 50 μm. Within the connecting region 111 of this size, a grating 15 with approximately 8 to 32 periods can be formed. The length of the non-connecting region 112 can be, for example, approximately 100 μm to 5 mm. The length of the connecting region 111 can be, for example, a fraction of a percent to a fraction of a tenth of the length of the non-connecting region 112. However, it is not limited to this length, and the dimensions of each component can be determined according to the required characteristics.

[0092] In the connection region 111, the first mirror 30 may not have a higher transmittance than the second mirror 40. Similarly, in the non-connection region 112 of the slow waveguide 10, outside of the connection region 111, and also in the region close to the connection region 111, the first mirror 30 may not have a higher transmittance than the second mirror 40. The connection region 111 is provided to improve the coupling efficiency of light. Therefore, in the vicinity of the connection region 111, the slow waveguide 10 does not necessarily need to emit light.

[0093] Let the propagation constant of the waveguide mode of total reflection waveguide 1 be β1 = 2πn. e1 / λ, let the propagation constant of the waveguide mode of the slow optical waveguide 10 be β2=2πn e2 / λ. λ is the wavelength of light in air. n e1 and n e2 These are the effective refractive indices (also called equivalent refractive indices) in total internal reflection waveguide 1 and slow-light waveguide 10, respectively. Light propagating within total internal reflection waveguide 1 does not couple with the external air. The effective refractive index of such a waveguide mode is n. e1 >1. On the other hand, a portion of the light propagating in the optical waveguide layer 20 of the slow waveguide 10 is emitted into the external air. The effective refractive index of such a waveguide mode is 0. <n e2 <1. Therefore, β1 and β2 are very different. As a result, the coupling efficiency of waveguide light from total reflection waveguide 1 to slow light waveguide 10 is usually low.

[0094] In the connection region 111, when the total internal reflection waveguide 1 is equipped with a grating 15, diffraction caused by the grating 15 occurs. In this case, the propagation constant β1 of the waveguide mode of the total internal reflection waveguide 1 is shifted to an integer multiple of the reciprocal lattice 2π / p. For example, if β1 is shifted to β1-(2π / p) by -1 diffraction, β1-(2π / p) = β2 can be made possible by appropriately setting p. In this case, since the two propagation constants of the connection region 111 are consistent, the waveguide light is coupled from the total internal reflection waveguide 1 to the slow light waveguide 10 with high efficiency. According to β1-(2π / p) = β2, the period p is represented by the following equation (3).

[0095] [Formula 3]

[0096]

[0097] Because of 0 <n e2 <1, so the period p satisfies the following equation (4).

[0098] [Formula 4]

[0099]

[0100] In the slow optical waveguide 10, the same waveguide mode exists in the connected region 111 and the non-connected region 112 outside of it, so the waveguide light is coupled with high efficiency.

[0101] In the above example, a grating is provided in the entire connection region 111 where the first waveguide 1 and the second waveguide 10 overlap. However, the construction of the optical device of the present invention is not limited to such a construction. The grating may also be provided only in a part of the connection region 111, for example, in the part of the connection region 111 close to the front end of the first waveguide 1. In other words, the grating may not be provided in the part of the connection region 111 far from the front end of the first waveguide 1. In one embodiment of the present invention, one or more gratings are provided in a first direction at a position that is longer than at least one of the thickness of the first mirror 30 and the thickness of the second mirror 40 from the interface between the medium (e.g., air) in contact with both the optical waveguide layer 20 and the first waveguide 1 in the first direction. According to the research of the inventors of the present invention, with such a construction, good light emission characteristics can be easily achieved even when the thickness of the optical waveguide layer 20 is non-uniform.

[0102] In the example above, it is assumed that the thickness of the optical waveguide layer 20 is constant along the X direction. However, in reality, the thickness of the optical waveguide layer 20 may vary along the X direction for various reasons. The effects of variations in the thickness of the optical waveguide layer 20 along the X direction will be explained in detail below. In the following description, the number of gratings is one, but the number of gratings can also be two or more.

[0103] Figure 7 This is a figure showing an example of the calculated results relating the rate of change of the thickness of the optical waveguide layer 20 to the diffusion angle of the emitted light from the first mirror 30. Figure 7 In the example, the rate of change of thickness of the optical waveguide layer 20 ranges from 0 nm / mm to 100 nm / mm. Here, "rate of change of thickness" refers to the amount of change in thickness relative to a displacement of 1 mm along the length direction of the optical waveguide layer 20, i.e., the first direction. 0 nm / mm means that the thickness of the optical waveguide layer 20 does not change substantially along the X direction. 100 nm / mm means that the thickness of the optical waveguide layer 20 changes by 100 nm relative to a displacement of 1 mm along the length direction of the optical waveguide layer 20.

[0104] In this calculation, the thickness of the optical waveguide layer 20 is set to 2.15 μm, the refractive index is set to 1.68, and it is assumed that the thickness of the optical waveguide layer 20 varies along the X-direction. The complex amplitude of the light emitted from the exit surface of the first mirror 30 is calculated, and the angular spectrum of the emitted light at a distance is calculated by applying a two-dimensional discrete Fourier transform to it. In the following description, the diffusion angle of the emitted light is assumed to be the full width at half maximum (FWHM) of the emitted light in the angular spectrum.

[0105] like Figure 7 As shown, when the thickness of the optical waveguide layer 20 varies at a rate of approximately 10 nm / mm, the spread angle of the emitted light is roughly the same as when the thickness of the optical waveguide layer 20 is constant. However, when the thickness of the optical waveguide layer 20 varies at a rate of 20 nm / mm or more, the spread angle of the emitted light increases approximately monotonically relative to the tilt of the optical waveguide layer 20. This spread of emitted light is due to the disordered phase distribution of the light emitted from the first mirror 30 caused by the non-uniform thickness of the optical waveguide layer 20. If the spread angle of the emitted light is large, the rectilinear propagation of the emitted light is lost. In particular, in the connection region 111 where the total internal reflection waveguide 1 connects to the slow optical waveguide 10, the intensity of the light emitted from the first mirror 30 is higher than that of the portion where the light further propagates from the connection region 111. Therefore, if the thickness of the optical waveguide layer 20 in the connection region 111 is not constant, the stronger emitted light may over-spread when light is emitted from the first mirror 30 in the connection region 111.

[0106] The variation in the thickness of the optical waveguide layer 20 can be attributed to changes in the shape of the end of the first mirror 30 through processing. For example... Figure 6 As shown, the end 30e of the first mirror 30 may be tilted, for example, through etching. Furthermore, warping of the first mirror 30 and / or the second mirror 40 may be considered as another reason for the thickness variation of the optical waveguide layer 20.

[0107] The following describes an example of an optical device that suppresses the effects of variations in the thickness of the optical waveguide layer 20.

[0108] Figure 8A This is a diagram schematically illustrating an exemplary embodiment of an optical device according to the present invention. The medium surrounding the optical device is, for example, air. The interface 20i between the medium and the optical waveguide layer 20, which is in contact with both the optical waveguide layer 20 and the total reflection waveguide 1, surrounds the total reflection waveguide 1. In this embodiment, the ends of the first mirror 30 and the second mirror 40 in the X direction coincide. Therefore, the end face 20i of the connection region 111 in this embodiment is a surface that passes through the ends of the first mirror 30 and the second mirror 40 and is parallel to the Y and Z directions. This end face 20i is the end of the connection region 111 in this embodiment. Furthermore, in this embodiment, the interface 20i between the medium and the optical waveguide layer 20 coincides with the end face 20i of the connection region 111. Figure 8A As shown, grating 15 and Figure 6Compared to the example shown, this one is located further inside the optical waveguide layer 20, away from the end 30e of the first mirror 30. From a reliability standpoint, if the length of the inclined portion of the end 30e of the first mirror 30 projected in the X direction exceeds the thickness of the first mirror 30, such a first mirror 30 is not used in optical devices. Therefore, in the first mirror 30 actually used in optical devices, the length of the inclined portion of the end 30e projected in the X direction is less than or equal to the thickness of the first mirror 30. The thickness of the first mirror 30 can be, for example, 3 μm. The same applies to the case where the second mirror 40 has an end face near the end face 20i similar to that of the first mirror 30. Therefore, in order to suppress the effects of variations in the thickness of the optical waveguide layer 20, the grating 15 can be configured to be positioned away from the end face 20i in the X direction by a distance longer than at least one of the thicknesses of the first mirror 30 and the second mirror 40. In other words, the distance L0 from end face 20i to grating 15 in the X direction is longer than at least one of the thickness of the first mirror 30 and the thickness of the second mirror 40. Here, the distance L0 from end face 20i to grating 15 refers to the distance between the end of grating 15 that is closer to end face 20i and end face 20i.

[0109] Figure 8B Observing from the Z direction Figure 8A The diagram shows the connection between the total internal reflection waveguide 1 and the slow optical waveguide 10. Figure 8B In the example shown, outside the optical waveguide layer 20 in the total internal reflection waveguide 1, the total internal reflection waveguide 1 includes a portion whose width monotonically increases as it approaches the slow optical waveguide 10. That is, a portion of the total internal reflection waveguide 1 has a tapered structure 1t. The width w of the total internal reflection waveguide 1 at the portion farther from the optical waveguide layer 20 is... w It is narrower than the width wc of the total reflection waveguide 1 in the connection region 111, which serves as the coupling part. Width w w It can be the width w c For example, it is about 1 / 100 to 1 / 2. In the total reflection waveguide 1, there is a conical structure 1t between the narrower waveguide section 1w and the wider waveguide section 1c. If such a structure is adopted, it is possible to suppress the reflection of light propagating in the narrower waveguide section 1w when it is incident on the wider waveguide section 1c.

[0110] Furthermore, the warpage of the first mirror 30 and / or the second mirror 40 is minimized near the center of the first mirror 30 and / or the second mirror 40 in the X direction. Therefore, the grating 15 can also be located near the center of the first mirror 30 and / or the second mirror 40 in the X direction within the optical waveguide layer 20. On the other hand, when the distance L0 from the end face 20i to the grating 15 is shorter, the probability of defects and / or particles occurring in the portion of the optical waveguide layer 20 within the total internal reflection waveguide 1 decreases. Therefore, the distance L0 from the end face 20i to the grating 15 and the length L of the grating 15 are both relatively small. gThe total L0+L g It can also be shorter than either half the length of the first mirror (30°) or half the length of the second mirror (40°). L0+L g Equivalent to Figure 8A The length of the connecting region 111 shown. Figure 8A The overall length of each of the first mirror 30 and the second mirror 40 shown is not particularly limited; for example, it can be greater than 300 μm and less than 10 mm. In one example, the length can be greater than 1 mm and less than 5 mm, for example, about 2 mm.

[0111] The connecting region 111 can be divided into a first connecting region 111a without the grating and a second connecting region 111b containing the grating 15. The length of the first connecting region 111a is L0, and the length of the second connecting region 111b is L... g The length L0 of the first connection region 111a can be, for example, 3 μm or more and 1 mm or less. The length L0 can also be 10 μm or more and 1 mm or less. In other examples, the length L0 can be set to 150 μm or more and 1 mm or less.

[0112] Next, an example of an optical device with a longer distance L0 from the end face 20i to the grating 15 will be described.

[0113] Figure 9This is a diagram schematically illustrating an example of an optical device where the distance L0 from end face 20i to grating 15 is longer. The distance L0 from end face 20i to grating 15 can, for example, be set to a value longer than the attenuation distance required for the intensity of light propagating in the slow optical waveguide 10 along the X direction to attenuate to 1 / e times. e is the base of the natural logarithm. This attenuation distance can, for example, be from about 150 μm to about 200 μm or more. This attenuation distance can be more than a fraction of the length of the overlapping region of the first mirror 30 and the second mirror 40 when viewed from the Z direction. When equation (3) is not satisfied, the light propagating in the total reflection waveguide 1 does not propagate to the non-connected region 112, but is reflected by the end face 1e of the total reflection waveguide 1 located within the optical waveguide layer 20. A portion of the reflected light leaks into the optical waveguide layer 20 in the connected region 111 and propagates in the -X direction. Thus, light propagating in the -X direction within the optical waveguide layer 20 can be emitted rearward from the first mirror 30 in the connected region 111. Furthermore, when the optical waveguide layer 20 contains liquid crystal material or electro-optical material, by adjusting the refractive index of the optical waveguide layer 20 to satisfy equation (3), the emission direction of light can be switched from rear to front, and vice versa. "Front" refers to the emission direction of light emitted from the slow optical waveguide 10 having a +X component from the total internal reflection waveguide 1 towards the slow optical waveguide 10. "Rear" refers to the emission direction of light emitted from the slow optical waveguide 10 having a -X component from the slow optical waveguide 10 towards the total internal reflection waveguide 1. Next, a modified example of the connection between the total internal reflection waveguide 1 and the slow optical waveguide 10 via the grating 15 will be described. (Refer to...) Figures 10A to 10C and Figure 11A and Figure 11B The following variation illustrates that the grating 15 is located further inside than the waveguide layer 20. Figure 8A The examples shown are common.

[0114] Figures 10A to 10C It is a schematic representation Figure 8A A cross-sectional view of a modified example of the optical device shown. Figures 10A to 10C In the example shown, the total internal reflection waveguide 1 is supported by a dielectric layer 51, which in turn is supported by a second mirror 40. The second mirror 40 is shared by both the total internal reflection waveguide 1 and the slow-light waveguide 10. The dielectric layer 51 is formed, for example, from SiO2. The refractive index n of the dielectric layer 51 is... sub The refractive index n of the total reflection waveguide 1 w1 Small. Therefore, light propagating in the total internal reflection waveguide 1 does not leak into the dielectric layer 51. The dielectric layer 51 may also not be supported by the second mirror 40. In areas other than the connection region 111 and the non-connection region 112, the second mirror 40 may be replaced with a structure made of the same material as the dielectric layer 51. In this modified example, the end face of the connection region 111 is a surface that passes through the end of the first mirror 30 and is parallel to the Y and Z directions. This end face is the end of the connection region 111 in this embodiment.

[0115] exist Figure 10A In the example shown, the total internal reflection waveguide 1 has a grating 15 in the first surface 1s1. Figure 10B In the example shown, the total internal reflection waveguide 1 has a grating 15 in the second surface 1s2. Figure 10C In the example shown, the total reflection waveguide 1 has a grating 15 on both the first surface 1s1 and the second surface 1s2.

[0116] Thus, the total reflection waveguide 1 can also have a grating 15 on at least one of the first surface 1s1 and the second surface 1s2.

[0117] Figure 11A and Figure 11B It is a schematic representation Figure 8A Cross-sectional views of other variations of the optical device shown. Figure 11A and Figure 11B In the example shown, with Figures 10A to 10C Similarly, in the example shown, the total reflection waveguide 1 is supported by the dielectric layer 51, which is supported by the second mirror 40.

[0118] exist Figure 11A and Figure 11B In this example, the grating 15 is not located on the total reflection waveguide 1, but rather on the reflecting surface of the first mirror 30 and / or the second mirror 40. Figure 11A In the example shown, the slow waveguide 10 has a grating 15 on the reflecting surface of the first mirror 30. Figure 11B In the example shown, the slow waveguide 10 has a grating 15 on the reflecting surface of the second mirror 40.

[0119] exist Figure 11A and Figure 11B In the example shown, the distance in the Z direction between the total internal reflection waveguide 1 and the first mirror 30 and / or the second mirror 40 is relatively short. Therefore, the evanescent light in the total internal reflection waveguide 1 is diffracted by the grating 15. As a result, similar to the example above, the coupling efficiency of the waveguide light from the total internal reflection waveguide 1 to the slow-light waveguide 10 can be improved. Thus, the slow-light waveguide 10 can also have the grating 15 on at least one of the reflecting surfaces of the first mirror 30 and the second mirror 40.

[0120] like Figure 8A , Figures 10A to 10C and Figure 11A and Figure 11B As shown, at least one of the total reflection waveguide 1 and the slow optical waveguide 10 has a grating 15 at a portion of the overlapping part of the total reflection waveguide 1 and the slow optical waveguide 10 when viewed from the Z direction.

[0121] in addition, Figure 9 The total reflection waveguide 1 shown can also be as follows: Figures 10A to 10C and Figure 11A and Figure 11B As shown, it is supported by the dielectric layer 51 on the second mirror 40.

[0122] Next, the functions that the constituent elements of the aforementioned optical device may have will be explained.

[0123] At least a portion of the optical waveguide layer 20 may also have a structure capable of adjusting the refractive index and / or thickness. By adjusting the refractive index and / or thickness, the X-direction component of the light emitted from the first mirror 30 changes.

[0124] To adjust the refractive index of at least a portion of the optical waveguide layer 20, the optical waveguide layer 20 may also contain a liquid crystal material or an electro-optical material. The optical waveguide layer 20 can be sandwiched between a pair of electrodes. By applying a voltage to the pair of electrodes, the refractive index of the optical waveguide layer 20 can be changed.

[0125] In the optical waveguide layer 20, the refractive index in the connecting region 111 and the refractive index in the non-connecting region 112 can be adjusted simultaneously. However, if the refractive index in the connecting region 111 is adjusted, the condition of equation (3) may change. As a result, the coupling efficiency of waveguide light from the total reflection waveguide 1 to the slow light waveguide 10 may decrease. Therefore, the refractive index in the connecting region 111 can also be kept constant, so that only the refractive index in the non-connecting region 112 can be adjusted. Even if the refractive indices in the connecting region 111 and the non-connecting region 112 are different, the effect of waveguide light reflection occurring at the interface between the connecting region 111 and the non-connecting region 112 is relatively small.

[0126] In this case, the portion of the optical waveguide layer 20 sandwiched between the aforementioned pair of electrodes (also referred to as the "first pair of electrodes") is different from the portion that overlaps with the total reflection waveguide 1 when viewed from a direction perpendicular to the reflecting surface of the first mirror 30. By applying a voltage to the pair of electrodes by a control circuit (not shown), the refractive index of at least a portion of the aforementioned non-connected region 112 can be adjusted.

[0127] As long as the conditions of Equation (3) are met as designed, it is acceptable. However, in reality, due to manufacturing errors, there are cases where the conditions of Equation (3) are not fully met. To compensate for such cases, the optical device can also be given the function of adjusting the refractive index of the connection region 111 in addition to adjusting the refractive index in the non-connection region 112.

[0128] In this case, a second pair of electrodes can be provided in addition to the first pair of electrodes described above. At least a portion of the optical waveguide layer 20 that overlaps with the total internal reflection waveguide when viewed from the Z direction is sandwiched between the second pair of electrodes. The control circuit can independently adjust the refractive index of the portion of the optical waveguide layer located between the first pair of electrodes and the portion located between the second pair of electrodes by independently applying voltages to the first pair of electrodes and the second pair of electrodes.

[0129] To adjust the thickness of the optical waveguide layer 20, at least one actuator can be connected to at least one of the first mirror 30 and the second mirror 40. The control circuit can change the thickness of the optical waveguide layer 20 by controlling the distance between the first mirror 30 and the second mirror 40 through at least one actuator. If the optical waveguide layer 20 is formed of a liquid, its thickness can be easily varied.

[0130] At least one of the aforementioned actuators can be connected to at least one of the first mirror 30 and the second mirror 40 in the unconnected region 112. The actuators can change the thickness of the optical waveguide layer 20 in the unconnected region 112. In this case, the conditions of equation (3) remain unchanged.

[0131] The aforementioned at least one actuator can also be two actuators. One actuator can be connected to at least one of the first mirror 30 and the second mirror 40 in the connection region 111. The other actuator can be connected to at least one of the first mirror 30 and the second mirror 40 in the non-connection region 112. With two actuators, the thickness of the optical waveguide layer 20 in the connection region 111 and the thickness of the optical waveguide layer 20 in the non-connection region 112 can be varied separately. Thus, compensation can be performed even when the conditions of equation (3) are not satisfied, as designed.

[0132] Two-dimensional optical scanning can also be performed by constructing an optical device having multiple sets of total internal reflection waveguides 1 and slow optical waveguides 10. Such an optical scanning device has multiple waveguide units arranged in the Y direction. Each waveguide unit has the aforementioned total internal reflection waveguide 1 and slow optical waveguide 10. In this optical scanning device, multiple phase shifters are connected to multiple waveguide units respectively. Each phase shifter includes a waveguide directly connected to or via another waveguide of one of the corresponding total internal reflection waveguides of the multiple waveguide units. By changing the phase difference of the light passing through the multiple phase shifters, the Y-direction component of the light emitted from the optical scanning device can be changed. An optical receiving device can be constructed using the same structure.

[0133] <Application Example>

[0134] Figure 12This diagram illustrates an example of the structure of an optical scanning device 100, which integrates components such as a beam splitter 90, a waveguide array 10A, a phase shifter array 80A, and a light source 130 on a circuit board (e.g., 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 beam splitter 90 branches the light from the light source 130 and directs it into the waveguides of multiple phase shifters. Figure 12 In the example shown, electrode 62A and multiple electrodes 62B are provided on the chip. For waveguide array 10A, a control signal is supplied from electrode 62A. For multiple phase shifters 80 in phase shifter array 80A, control signals are transmitted from multiple electrodes 62B respectively. Electrode 62A and multiple electrodes 62B can be connected to a control circuit (not shown) that generates the aforementioned control signals. The control circuit can be located in... Figure 12 The chip shown can also be placed on other chips in the optical scanning device 100.

[0135] like Figure 12 As shown, by integrating all components onto a single chip, large-area optical scanning can be achieved with a small device. For example, it is possible to integrate such components onto a chip of approximately 2mm × 1mm. Figure 12 All components are shown.

[0136] Figure 13 This is a schematic diagram illustrating a two-dimensional scan performed by irradiating a laser beam or similar light source from an optical scanning device 100 into a distant location. The two-dimensional scan is performed by moving the light 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 calculates the time of flight of light and determines the distance by irradiating a laser and observing the reflected light from an object.

[0137] Figure 14This is a block diagram illustrating the structure of a LiDAR 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 light emitted from the light scanning device 100, or a light detector including a light-receiving element such as a photodiode. 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, generating 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 beam irradiated from the light scanning device 100, as well as the timing of the exposure and signal readout of the photodetector 400, and instructs the signal processing circuit 600 to generate a ranging image.

[0138] 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, at a frame rate of 60fps, an image can be acquired whenever the vehicle moves approximately 28cm. At a frame rate of 120fps, an image can be acquired whenever the vehicle moves approximately 14cm. At a frame rate of 180fps, an image can be acquired whenever the vehicle moves approximately 9.3cm.

[0139] The time required to acquire a ranging image depends on the beam scanning speed. For example, to acquire an image with a resolution of 100×100 points at 60 fps, the beam needs to be scanned at a speed of less than 1.67 μs per point. In this case, the control circuit 500 controls the beam emission by the optical scanning device 100 and the signal accumulation and readout by the photodetector 400 at an operating speed of 600 kHz.

[0140] <Examples of applications for optical receiving equipment>

[0141] The optical scanning device of the present invention 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 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 side opposite to the first reflecting surface. Each optical waveguide layer 20 of the waveguide array 10A propagates light transmitted through the first mirror 30 in a second direction. The first adjustment element 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 in each waveguide element 10, and the wavelength of the light. 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.

[0142] For example, it can constitute Figure 12 The light source 130 in the illustrated optical scanning device 100 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 beam splitter 90 via the phase shifter array 80A, and finally concentrated to a single point before being transmitted to the receiving circuit. The intensity of the light concentrated at this single point can be said to represent the sensitivity of the optical receiving device. The sensitivity of the optical receiving device can be adjusted by adjustment elements respectively assembled to the waveguide array and the phase shifter array 80A. In the optical receiving device, for example in... Figure 4 In this configuration, the directions of the wavenumber vector (thick arrow in the figure) are reversed. The incident light has a light component in the direction in which the waveguide element 10 extends (X direction in the figure) and a light component in the direction in which the waveguide element 10 is aligned (Y direction in the figure). The sensitivity of the light component in the X direction can be adjusted by an adjustment element assembled to the waveguide array 10A. On the other hand, the sensitivity of the light component in the direction in which the waveguide element 10 is aligned can be adjusted by an adjustment element assembled to the phase shifter array 80A. The sensitivity of the light is adjusted based on the phase difference Δφ of the light when the sensitivity of the optical receiving device is maximized, and the refractive index n of the optical waveguide layer 20. w And the thickness d, can know Figure 4 The values ​​θ and α0 are shown. Therefore, the incident direction of the light can be determined.

[0143] The above-described implementation methods can be combined appropriately.

[0144] Finally, the aforementioned optical devices can be summarized into the following items.

[0145] The optical device of the first item comprises: a first waveguide extending along a first direction; and a second waveguide connected to the first waveguide; the second waveguide comprises: a first mirror having a first reflective surface; a second mirror having a second reflective surface facing the first reflective surface; and an optical waveguide layer between the first mirror and the second mirror, internally including a portion comprising the front end of the first waveguide. At least one of the first waveguide and the second waveguide has one or more gratings in a portion of the overlapping connection area of ​​the first mirror, the second mirror, and the first waveguide when viewed from a direction perpendicular to the first reflective surface. The one or more gratings are located in the first direction at a distance from the end of the first mirror or the second mirror in the connection area that is longer than at least one of the thicknesses of the first mirror and the second mirror.

[0146] In this optical device, even if an inclined portion is formed on the end closer to the connection area of ​​the first mirror and / or the second mirror, the light propagating in the first waveguide can be coupled to the second waveguide with high efficiency through the grating without being affected by the inclined portion.

[0147] In the optical device of the second item, in the optical device of the first item, the connection region includes a first region extending from the end to the one or more gratings and a second region containing the one or more gratings. The sum of the length of the first region in the first direction and the length of the second region in the first direction is shorter than either half the length of the first mirror in the first direction or half the length of the second mirror in the first direction.

[0148] In this optical device, the effects of defects and / or particles occurring inside the optical waveguide layer on the optical coupling from the first waveguide to the second waveguide can be suppressed.

[0149] In the optical device of the third item, in the optical device of the first or second item, the distance from the aforementioned end to the aforementioned one or more gratings is longer than the distance required for the intensity of light propagating in the aforementioned second waveguide along the aforementioned first direction to be attenuated by 1 / e times (e is the base of the natural logarithm).

[0150] In this optical device, when light propagating in the first waveguide is not coupled to the second waveguide via a grating, a portion of the light propagates in the optical waveguide layer of the connection region in a direction from the second waveguide toward the first waveguide. As a result, a portion of the light is emitted rearward from the first mirror and / or the second mirror.

[0151] In the optical device relating to item 4, in any of items 1 to 3, the transmittance of the first mirror is higher than that of the second mirror. A portion of the light entering the optical waveguide layer from the first waveguide to the second waveguide exits via the first mirror.

[0152] In this optical device, light is emitted through the first mirror.

[0153] Regarding the optical device of item 5, in the optical device of any one of items 1 to 4, when the effective refractive index of the waveguide mode of the light propagating in the first waveguide is n... e1 If the wavelength of the light in air is λ, then the period of each of the above-mentioned one or more gratings is greater than λ / n. e1 Less than λ / (n) e1 -1).

[0154] In this optical device, by appropriately setting the period of the grating, light propagating in the first waveguide can be coupled to the second waveguide with high efficiency via the grating.

[0155] Industrial availability

[0156] The optical scanning device and optical receiving device of the present invention can be used, for example, in applications such as lidar systems mounted on vehicles such as automobiles, UAVs, and AGVs.

[0157] Label Explanation

[0158] 10. Waveguide components, optical waveguides

[0159] 11 Optical waveguide

[0160] 10A waveguide array

[0161] 15, 15a, 15b, 15c, 15m gratings

[0162] 20 Optical waveguide layers

[0163] 30. First Frame

[0164] 40 Mirror 2

[0165] 51 Dielectric layer

[0166] Electrodes 62a, 62b, 62A, and 62B

[0167] More than 73 partition walls

[0168] 80 Phase Shifter

[0169] 80A Phase Shifter Array

[0170] 90 beam splitter

[0171] 100 optical scanning equipment

[0172] 111 Connection Area

[0173] 112 Non-connected areas

[0174] 110 Waveguide Array Driving Circuit

[0175] 130 light source

[0176] 210 Driving circuit for phase shifter array

[0177] 310 beam spot

[0178] 400 photodetector

[0179] 500 control circuit

[0180] 600 Signal Processing Circuit

Claims

1. An optical device, wherein, have: The first waveguide extends along the first direction; and The second waveguide extends along the first direction mentioned above; The aforementioned second waveguide possesses: The first mirror has a first reflecting surface; The second mirror has a second reflecting surface facing the first reflecting surface described above; and The optical waveguide layer between the first mirror and the second mirror mentioned above; At least one of the first waveguide and the second waveguide has one or more gratings in a portion of the overlapping area of ​​the first mirror, the second mirror and the first waveguide when viewed from a direction perpendicular to the first reflecting surface. The aforementioned one or more gratings are separated from the ends of the aforementioned first mirror or the aforementioned second mirror in the aforementioned overlapping region by a distance in the aforementioned first direction that is longer than at least one of the thickness of the aforementioned first mirror and the thickness of the aforementioned second mirror.

2. The optical device as described in claim 1, wherein, The aforementioned overlapping area includes a first region extending from the end of the first mirror or the second mirror to the one or more gratings and a second region containing the one or more gratings; The sum of the length of the first region in the first direction and the length of the second region in the first direction is shorter than either half the length of the first mirror in the first direction or half the length of the second mirror in the first direction.

3. The optical device as described in claim 1 or 2, wherein, The distance from the end of the first or second mirror to one or more gratings is longer than the distance required for the intensity of light propagating in the second waveguide along the first direction to be attenuated by 1 / e times, where e is the base of the natural logarithm.

4. The optical device as described in claim 1 or 2, wherein, The transmittance of the first mirror is higher than that of the second mirror. A portion of the light entering the optical waveguide layer of the first waveguide and then entering the second waveguide is emitted through the first mirror.

5. The optical device as described in claim 1 or 2, wherein, Let the effective refractive index of the waveguide mode of the light propagating in the first waveguide be n. e1 Let the wavelength of light in air be λ. The period of each of the above-mentioned gratings is greater than λ / n e1 Less than λ / (n) e1 -1).

Images