Optical Devices and Optical Detection Systems

Abstract

This optical device is provided with: a plurality of optical waveguides that each extend in a first direction and are arranged side by side in a second direction interesting the first direction; and a planar optical waveguide directly or indirectly connected to the plurality of optical waveguides. The plurality of optical waveguides propagate light along the first direction. The planar optical waveguide is provided with a first mirror and a second mirror facing each other and extending along the first direction and the second direction and an optical waveguide layer positioned between the first mirror and the second mirror.

Description

[Technical field]

[0001] The present disclosure relates to optical devices and optical detection systems. [Background technology]

[0002] Conventionally, various devices capable of scanning a space with light have been proposed.

[0003] Patent Document 1 discloses a configuration in which scanning by light can be performed using a driving device that rotates a mirror.

[0004] Patent Document 2 discloses an optical phased array having multiple nanophotonic antenna elements arranged two-dimensionally. Each antenna element is optically coupled to a variable optical delay line (i.e., a phase shifter). In this optical phased array, a coherent optical beam is guided to each antenna element by a waveguide, and the phase of the optical beam is shifted by the phase shifter. This allows the amplitude distribution of the far-field radiation pattern to be changed.

[0005] Patent Document 3 discloses an optical deflection element including a waveguide having an optical waveguide layer through which light is guided and first distributed Bragg reflectors formed on the upper and lower surfaces of the optical waveguide layer, a light inlet for admitting light into the waveguide, and a light outlet formed on the surface of the waveguide for exiting the light that is incident from the light inlet and guided within the waveguide. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2013 / 168266 [Patent Document 2] Special Publication No. 2016-508235 [Patent Document 3] JP 2013-16591 A Summary of the Invention [Problem to be solved by the invention]

[0007] One aspect of the present disclosure provides a novel optical device that can achieve scanning by light with a relatively simple configuration. [Means for solving the problem]

[0008] An optical device according to one embodiment of the present disclosure comprises a plurality of optical waveguides each extending in a first direction and aligned in a second direction intersecting the first direction, and a planar optical waveguide connected directly or indirectly to the plurality of optical waveguides, the plurality of optical waveguides propagating light along the first direction, the planar optical waveguide comprising a first mirror and a second mirror facing each other and extending along the first direction and the second direction, and an optical waveguide layer located between the first mirror and the second mirror.

[0009] The general or specific aspects of the present disclosure may be realized by a device, a system, a method, or any combination thereof. Effect of the Invention

[0010] According to one aspect of the present disclosure, one-dimensional scanning or two-dimensional scanning using light can be achieved with a relatively simple configuration. [Brief description of the drawings]

[0011] FIG. 1 is a perspective view that typically illustrates the configuration of an optical scanning device previously considered by the present inventor. FIG. 2 is a diagram illustrating an example of a cross-sectional structure of one waveguide element and propagating light. FIG. 3A is a diagram showing a cross section of a waveguide array that emits light in a direction perpendicular to an emission surface of the waveguide array. FIG. 3B is a diagram showing a cross section of a waveguide array that emits light in a direction different from a direction perpendicular to the emission surface of the waveguide array. FIG. 4 is a perspective view illustrating a waveguide array in a three-dimensional space. FIG. 5 is a schematic diagram of a waveguide array and a phase shifter array viewed from the normal direction (Z direction) of a light emitting surface. FIG. 6A is a perspective view diagrammatically illustrating an optical device in a comparative example. FIG. 6B is a perspective view diagrammatically illustrating the configuration on the right of FIG. 6A. 7 is a diagram illustrating a schematic view of a light beam being emitted from the optical device in FIG. 6A. FIG. 8A is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in a comparative example. FIG. 8B is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in a comparative example. FIG. 8C is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in a comparative example. FIG. 9A is a diagram illustrating an optical device according to the first embodiment. FIG. FIG. 9B is a perspective view diagrammatically illustrating the planar optical waveguide of FIG. 9A. 10 is a diagram illustrating a schematic view of how light is emitted from the optical device in FIG. 9A. FIG. 11A is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in the first embodiment. FIG. 11B is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in the first embodiment. FIG. 11C is a diagram showing an example of the intensity distribution of light propagating between two mirrors and an example of the intensity distribution of light emitted into the distance in the first embodiment. [Figure 12] Figure 12 is a Multiple 13 is a diagram showing the period dependence of the crosstalk rate occurring between a number of optical waveguides 11. FIG. 13A is a diagram illustrating a first modified example of the optical device in the first embodiment. FIG. FIG. 13B is a diagram illustrating a second modified example of the optical device in the first embodiment. FIG. 14A is a cross-sectional view taken along the XZ plane, which diagrammatically illustrates an example of an optical device according to the second embodiment. FIG. 14B is a cross-sectional view in the XY plane that typically illustrates an example of the optical device according to the second embodiment. [Figure 15] Figure 15 shows the same as Figure 14 A and Figure 14B 1 is a diagram showing a schematic view of a state in which a light beam is emitted from an optical device. FIG. 16A is a diagram showing the intensity distribution in the XY plane of light propagating between two mirrors. FIG. 16B is a diagram showing the intensity distribution in the XZ plane of the light propagating between the two mirrors. FIG. 17A is a diagram illustrating a first example of a configuration for driving a planar optical waveguide. FIG. 17B is a diagram illustrating a second example of the configuration for driving the planar optical waveguide. FIG. 18 is a diagram showing a configuration example of an optical scanning device in which elements are integrated on a circuit board. FIG. 19 is a schematic diagram showing a state in which a two-dimensional scan is performed by irradiating a light beam such as a laser from an optical scanning device at a distance. FIG. 20 is a block diagram showing a configuration example of a LiDAR system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Before describing the embodiments of the present disclosure, the findings on which the present disclosure is based will be described.

[0013] The present inventor has found that a problem with conventional optical scanning devices is that it is not easy to scan space with light without complicating the configuration of the device.

[0014] For example, the technology disclosed in Patent Document 1 requires a drive device for rotating the mirror, which makes the device configuration complicated and poses the problem of not being robust against vibration.

[0015] In the optical phased array described in Patent Document 2, it is necessary to branch light and introduce it into a plurality of column waveguides and a plurality of row waveguides, and guide the light to a plurality of antenna elements arranged two-dimensionally. This makes the wiring of the waveguide for guiding the light very complicated. In addition, the range of the two-dimensional scan cannot be enlarged. Furthermore, in order to change the amplitude distribution of the emitted light in the far field two-dimensionally, it is necessary to connect a phase shifter to each of the two-dimensionally arranged antenna elements and attach wiring for phase control to the phase shifter. This changes the phase of the light incident on the two-dimensionally arranged antenna elements by different amounts. This makes the configuration of the elements very complicated.

[0016] The present inventors have focused on the above problems in the conventional technology and have studied configurations for solving these problems. In the following, for comparison with the embodiments of the present disclosure, a configuration that the present inventors studied before conceiving the embodiments of the present disclosure will be described. The configuration includes a waveguide element having a pair of opposing mirrors and an optical waveguide layer sandwiched between the mirrors.

[0017] One of the pair of mirrors in the waveguide element has a higher optical transmittance than the other, and emits a part of the light propagating through the optical waveguide layer to the outside. The direction (or emission angle) of the emitted light can be changed by adjusting the refractive index or thickness of the optical waveguide layer, or the wavelength of the light input to the optical waveguide layer, as described below. More specifically, by changing the refractive index, thickness, or wavelength, the component of the wave vector of the emitted light in the direction along the longitudinal direction of the optical waveguide layer can be changed. This realizes one-dimensional scanning.

[0018] Furthermore, when an array of multiple waveguide elements is used, two-dimensional scanning can be realized. More specifically, by providing an appropriate phase difference to the light supplied to the multiple waveguide elements and adjusting the phase difference, the direction in which the light emitted from the multiple waveguide elements reinforce each other can be changed. The change in phase difference changes the component of the wave vector of the emitted light in the direction intersecting the direction along the longitudinal direction of the optical waveguide layer. This allows two-dimensional scanning to be realized. Note that even when performing two-dimensional scanning, it is not necessary to change the refractive index, thickness, or wavelength of the multiple optical waveguide layers by different amounts. That is, two-dimensional scanning can be performed by providing an appropriate phase difference to the light supplied to the multiple optical waveguide layers and synchronously changing at least one of the refractive index, thickness, and wavelength of the multiple optical waveguide layers by the same amount. In this way, two-dimensional scanning by light can be realized with a relatively simple configuration.

[0019] In this specification, "at least one of the refractive index, thickness, and wavelength" means 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. In order to change the output direction of light, any one of the refractive index, thickness, and wavelength may be controlled independently. Alternatively, any two or all of these three may be controlled to change the output direction of light. Instead of or in addition to controlling the refractive index or thickness, the wavelength of light input to the optical waveguide layer may be controlled.

[0020] The above basic principles can be applied not only to applications for emitting light, but also to applications for receiving optical signals. By changing at least one of the refractive index, thickness, and wavelength, the direction of the light that can be received can be changed one-dimensionally. Furthermore, by changing the phase difference of light using multiple phase shifters connected to multiple waveguide elements arranged in one direction, the direction of the light that can be received can be changed two-dimensionally.

[0021] In this disclosure, "scanning" with light means changing the direction of light. "One-dimensional scanning" means changing the direction of light linearly along a direction intersecting the direction. "Two-dimensional scanning" means changing the direction of light two-dimensionally along a plane intersecting the direction.

[0022] <Example of optical scanning device configuration> First, as an example, the configuration of an optical scanning device that performs two-dimensional scanning, which was previously examined by the present inventor, will be described.

[0023] FIG. 1 is a perspective view showing a schematic configuration of an optical scanning device 98 previously examined by the present inventor. The optical scanning device 98 includes a waveguide array including a plurality of waveguide elements 10. Each of the plurality of waveguide elements 10 has a shape extending in a first direction (X direction in FIG. 1). The plurality of waveguide elements 10 are regularly arranged in a second direction (Y direction in FIG. 1) intersecting the first direction. The plurality of waveguide elements 10 propagate light in the first direction, while emitting light in a third direction D3 intersecting a virtual plane parallel to the first and second directions. In this embodiment, the first direction (X direction) and the second direction (Y direction) are orthogonal to each other, but they do not necessarily have to be orthogonal to each other. In this embodiment, the plurality of waveguide elements 10 are arranged at equal intervals in the Y direction, but they do not necessarily have to be arranged at equal intervals.

[0024] For reference, mutually orthogonal X-axis, Y-axis, and Z-axis are shown diagrammatically. In this specification, the direction of the arrow of the axis is the + direction, and the opposite direction is the - direction. Note that the orientation of the structures shown in the drawings of this application is set in consideration of the ease of explanation, and does not limit the orientation when the embodiment of the present disclosure is actually implemented. In addition, the shape and size of the whole or part of the structure shown in the drawings do not limit the actual shape and size.

[0025] 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 mirror 30 and the mirror 40. Each of the mirror 30 and the mirror 40 has a reflective surface that intersects with the third direction D3 at the interface with the optical waveguide layer 20. The mirror 30 and the mirror 40, and the optical waveguide layer 20 have a shape that extends in the first direction (X direction).

[0026] As described later, the first mirrors 30 of the waveguide elements 10 may be portions of a mirror that is integrally formed. The second mirrors 40 of the waveguide elements 10 may be portions of a mirror that is integrally formed. The optical waveguide layers 20 of the waveguide elements 10 may be portions of an optical waveguide layer that is integrally formed. A plurality of waveguides can be formed by at least (1) configuring each first mirror 30 separately from the other first mirrors 30, (2) configuring each second mirror 40 separately from the other second mirrors 40, or (3) configuring each optical waveguide layer 20 separately from the other optical waveguide layers 20. "Configured separately" includes not only providing a physical space but also sandwiching a material with a different refractive index between them to separate them.

[0027] The reflecting surface of the first mirror 30 and the reflecting surface of the second mirror 40 face each other substantially parallel to each other. Of the two mirrors 30 and 40, at least the first mirror 30 has a property of transmitting a part of the light propagating through the optical waveguide layer 20. In other words, the first mirror 30 has a higher optical transmittance for the light than the second mirror 40. Therefore, a part of the light propagating through the optical waveguide layer 20 is emitted to the outside from the first mirror 30. Such mirrors 30 and 40 may be multilayer film mirrors formed, for example, by a multilayer film made of a dielectric material (sometimes referred to as a "multilayer reflective film").

[0028] By controlling the phase of the light input to each waveguide element 10 and further synchronously changing the refractive index or thickness of the optical waveguide layer 20 in these waveguide elements 10, or the wavelength of the light input to the optical waveguide layer 20, two-dimensional scanning by light can be realized.

[0029] In order to realize such two-dimensional scanning, the present inventor analyzed the operating principle of the waveguide element 10. Based on the results, the inventor succeeded in realizing two-dimensional scanning by light by synchronously driving a plurality of waveguide elements 10.

[0030] As shown in FIG. 1, when light is input to each waveguide element 10, the light is output from the output surface of each waveguide element 10. The output surface is located on the opposite side to the reflecting surface of the first mirror 30. The direction D3 of the output light depends on the refractive index, thickness, and wavelength of the optical waveguide layer. In this embodiment, at least one of the refractive index, thickness, and wavelength of each optical waveguide layer is synchronously controlled so that the light output from each waveguide element 10 is in approximately the same direction. This makes it possible to change the X-direction component of the wave vector of the light output from the multiple waveguide elements 10. In other words, the direction D3 of the output light can be changed along the direction 101 shown in FIG. 1.

[0031] Furthermore, since the light beams emitted from the multiple waveguide elements 10 are directed in the same direction, the emitted light beams interfere with each other. By controlling the phase of the light beams emitted from each waveguide element 10, the direction in which the light beams reinforce each other by 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 beams having phases different from each other by a certain amount are input to the multiple waveguide elements 10. By changing the phase difference, the Y-directional component of the wave vector of the emitted light beams can be changed. In other words, by changing the phase difference of the light beams introduced into the multiple waveguide elements 10, the direction D3 in which the emitted light beams reinforce each other by interference can be changed along the direction 102 shown in FIG. 1. This makes it possible to realize two-dimensional scanning by light.

[0032] The operating principle of the optical scanning device 98 will now be described.

[0033] <Operation principle of waveguide elements> FIG. 2 is a diagram showing an example of a cross-sectional structure of one waveguide element 10 and a light propagating therethrough. In FIG. 2, the direction perpendicular to the X and Y directions shown in FIG. 1 is taken as the Z direction, and a cross section parallel to the XZ plane of the waveguide element 10 is shown. In the 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 propagates through the optical waveguide layer 20 while being repeatedly reflected by the first mirror 30 provided on the upper surface (upper surface in FIG. 2) of the optical waveguide layer 20 and the second mirror 40 provided on the lower surface (lower surface in FIG. 2). The optical transmittance of the first mirror 30 is higher than that of the second mirror 40. Therefore, a part of the light can be output mainly from the first mirror 30. Depending on the application, the transmittance of the first mirror and the transmittance of the second mirror may be adjusted so that light is emitted from the second mirror 40 instead of the first mirror 30, or light may be emitted from both the first mirror 30 and the second mirror 40.

[0034] In a waveguide such as a normal optical fiber, light propagates along the waveguide while repeating total reflection. In contrast, in the waveguide element 10 of the present embodiment, light propagates while repeating reflection by the mirrors 30 and 40 arranged above and below the optical waveguide layer 20. Therefore, there is no restriction on the propagation angle of light. Here, the propagation angle of light means the angle of incidence at the interface between the mirror 30 or 40 and the optical waveguide layer 20. Light incident at an angle closer to a right angle to the mirror 30 or 40 can also propagate. In other words, light incident at an angle smaller than the critical angle of total reflection can also propagate. Therefore, the group velocity of light in the propagation direction of light is significantly reduced compared to the speed of light in free space. As a result, the waveguide element 10 has the property that the propagation conditions of light change 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. Such a waveguide is called a "reflective waveguide" or a "slow light waveguide."

[0035] The emission angle θ of light emitted from the waveguide element 10 into the air is expressed by the following formula (1).

number

[0036] As can be seen from formula (1), the wavelength of light in air, λ, the refractive index of the optical waveguide layer 20, n w and the thickness d of the optical waveguide layer 20, the outgoing direction of light can be changed.

[0037] For example, n w When = 2, d = 387 nm, λ = 1550 nm, and m = 1, the emission angle is 0°. From this state, the refractive index is n w = 2.2, the output angle changes to approximately 66°. On the other hand, if the thickness is changed to d = 420 nm without changing the refractive index, the output angle changes to approximately 51°. If the wavelength is changed to λ = 1500 nm without changing either the refractive index or the thickness, the output angle changes to approximately 30°. In this way, when the wavelength λ of light and the refractive index n of the optical waveguide layer 20 are w By changing either the thickness d of the optical waveguide layer 20 or the thickness d of the optical waveguide layer 20, the light emission direction can be changed significantly.

[0038] Therefore, the optical scanning device 98 in the embodiment of the present disclosure is configured such that the wavelength λ of the light input to the optical waveguide layer 20 and the refractive index n w, and the thickness d of the optical waveguide layer 20, thereby controlling the light emission direction. The wavelength λ of the light may be kept constant without being changed during operation. In that case, the light scanning can be realized with a simpler configuration. The wavelength λ is not particularly limited. For example, the wavelength λ may be included in the wavelength range of 400 nm to 1100 nm (visible light to near infrared light) in which a high detection sensitivity can be obtained in a photodetector or image sensor that detects light by absorbing light with general silicon (Si). In another example, the wavelength λ may be included in the wavelength range of near infrared light from 1260 nm to 1625 nm in which the transmission loss is relatively small in an optical fiber or a Si waveguide. Note that these wavelength ranges are only examples. The wavelength range of the light used is not limited to the wavelength range of visible light or infrared light, and may be, for example, the wavelength range of ultraviolet light.

[0039] To change the direction of the output light, the optical scanning device 98 may include a first adjusting element that changes at least one of the refractive index, thickness, and wavelength of the optical waveguiding layer 20 in each waveguide element 10 .

[0040] As described above, by using the waveguide element 10, the refractive index n w By changing at least one of the thickness d and wavelength λ, the emission direction of the light can be changed significantly. This allows the emission angle of the light emitted from the mirror 30 to be changed in a direction along the waveguide element 10. By using at least one waveguide element 10, such one-dimensional scanning can be realized.

[0041] The optical waveguide layer 20 may include a liquid crystal material or an electro-optic material to adjust the refractive index of at least a portion of the optical waveguide layer 20. The optical waveguide layer 20 may be sandwiched between a pair of electrodes. The refractive index of the optical waveguide layer 20 can be changed by applying a voltage to the pair of electrodes.

[0042] In order to adjust the thickness of the optical waveguide layer 20, for example, at least one actuator may be connected to at least one of the first mirror 30 and the second mirror 40. The thickness of the optical waveguide layer 20 can be changed by changing the distance between the first mirror 30 and the second mirror 40 by the at least one actuator. If the optical waveguide layer 20 is formed from a liquid, the thickness of the optical waveguide layer 20 can be easily changed.

[0043] <Operation principle of 2D scanning> In a waveguide array in which a plurality of waveguide elements 10 are arranged in one direction, the emission direction of the light changes due to interference of the light emitted from each waveguide element 10. The emission direction of the light can be changed by adjusting the phase of the light supplied to each waveguide element 10. The principle behind this is explained below.

[0044] FIG. 3A is a diagram showing a cross section of a waveguide array that emits light in a direction perpendicular to the emission surface of the waveguide array. FIG. 3A also shows the phase shift amount of light propagating through each waveguide element 10. Here, the phase shift amount is a value based on the phase of light propagating through the leftmost waveguide element 10. The waveguide array in this embodiment includes a plurality of waveguide elements 10 arranged at equal intervals. In FIG. 3A, the dashed arc indicates the wavefront of light emitted from each waveguide element 10. The solid line indicates the wavefront formed by the interference of light. The closed solid curve indicates the intensity distribution of the interfered light. The interfered light includes a central main lobe and side lobes on both sides of the central main lobe. The main lobe corresponds to the zeroth order diffracted light. Although not shown in FIG. 3A, the interfered light may also include grating lobes corresponding to higher order diffracted light. The arrow indicates the direction of the zeroth order diffracted light emitted from the waveguide array. 3A, the phases of the light propagating through the optical waveguide layer 20 in each waveguide element 10 are all equal. In this case, the light is emitted in a direction (Z direction) perpendicular to both the arrangement direction of the waveguide elements 10 (Y direction) and the extension direction of the optical waveguide layer 20 (X direction).

[0045] FIG. 3B is a diagram showing a cross section of a waveguide array that emits light in a direction different from the direction perpendicular to the emission surface of the waveguide array. In the example shown in FIG. 3B, the phase of light propagating through the optical waveguide layer 20 in multiple waveguide elements 10 differs by a fixed amount (Δφ) in the arrangement direction. 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 direction can be changed. If the center-to-center distance between two adjacent waveguide elements 10 is p, then the light emission angle α 0 is expressed by the following equation (2).

number

[0046] In the example shown in FIG. 2, the light emission direction is parallel to the XZ plane. That is, α 0 3A and 3B, the direction of the light emitted from the optical scanning device 98 is parallel to the YZ plane. That is, θ=0°. However, in general, the direction of the light emitted from the optical scanning device 98 is not parallel to either the XZ plane or the YZ plane. That is, θ≠0° and α 0 ≠0°.

[0047] FIG. 4 is a perspective view showing a schematic diagram of a waveguide array in a three-dimensional space. The thick arrows shown in FIG. 4 indicate the direction of light emitted from the optical scanning device 98. θ is the angle between the light emission direction and the YZ plane. θ satisfies the formula (1). α 0 is the angle between the light emission direction and the XZ plane. α 0 satisfies equation (2).

[0048] <Phase control of light introduced into a waveguide array> In order to control the phase of the light emitted from each of the waveguide elements 10, for example, a phase shifter that changes the phase of the light may be provided before the light is introduced into the waveguide element 10. The optical scanning device 98 in this embodiment includes a plurality of phase shifters connected to each of the plurality of waveguide elements 10, and a second adjustment element that adjusts the phase of the light propagating through each phase shifter. Each phase shifter includes a waveguide that is connected directly to the optical waveguide layer 20 in the corresponding one of the plurality of waveguide elements 10 or via another waveguide. The second adjustment element changes the direction of the light emitted from the plurality of waveguide elements 10 (i.e., the third direction D3) by changing the difference in the phase of the light propagating from the plurality of phase shifters to the plurality of waveguide elements 10. In the following description, the plurality of arranged phase shifters may be referred to as a "phase shifter array" in the same manner as the waveguide array.

[0049] FIG. 5 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 emission surface. In the example shown in FIG. 5, all the phase shifters 80 have the same propagation characteristics, and all the waveguide elements 10 have the same propagation characteristics. Each phase shifter 80 and each waveguide element 10 may have the same length or different lengths. When the lengths of the phase shifters 80 are equal, for example, the amount of phase shift of each can be adjusted by the driving voltage. In addition, by making the length of each phase shifter 80 into a structure in which it is changed in equal steps, it is also possible to give equal-step phase shifts with the same driving voltage. Furthermore, this optical scanning device 98 further includes an optical branching device 90 that branches and supplies light to a plurality of phase shifters 80, a first driving circuit 110 that drives each waveguide element 10, and a second driving circuit 120 that drives each phase shifter 80. The straight arrow in FIG. 5 indicates the input of light. Two-dimensional scanning can be realized by independently controlling the first driving circuit 110 and the second driving circuit 120. In this example, the first driving circuit 110 functions as one element of a first adjustment element, and the second driving circuit 120 functions as one element of a second adjustment element.

[0050] 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 the thickness of the optical waveguide layer 20 in each waveguide element 10. The second driving circuit 120 changes the phase of light propagating inside the waveguide by changing the refractive index of the waveguide in each phase shifter 80. The optical splitter 90 may be configured with a waveguide in which light propagates by total reflection, or may be configured with a reflective waveguide similar to the waveguide element 10.

[0051] In addition, each light may be introduced into the phase shifter 80 after controlling the phase of each light branched by the optical branching device 90. For this phase control, for example, a passive phase control structure by adjusting the length of the waveguide leading to the phase shifter 80 may be used. Alternatively, a phase shifter that has a function similar to that of the phase shifter 80 and can be controlled by an electric signal may be used. By such a method, for example, the phase may be adjusted before being introduced into the phase shifter 80 so that light of equal phase is supplied to all the phase shifters 80. By such adjustment, the control of each phase shifter 80 by the second driving circuit 120 can be simplified.

[0052] An optical device having a configuration similar to the optical scanning device 98 described above can also be used as an optical receiving device. Details of the optical device, such as the operating principle and the operating method, are disclosed in U.S. Patent Application Publication No. 2018 / 0224709, the entire disclosure of which is incorporated herein by reference.

[0053] The optical device 98 described above includes a plurality of waveguide elements 10. The inventors further investigated the configuration of a simpler optical device for performing two-dimensional scanning and found that a plurality of waveguide elements 10 is not necessarily required for two-dimensional scanning. As described below, the optical device in the present disclosure includes a plurality of optical waveguides and a planar waveguide directly or indirectly connected to the plurality of optical waveguides. The planar waveguide includes an optical waveguide layer 20, a mirror 30, and a mirror 40. Even with such a simple configuration, two-dimensional scanning can be realized.

[0054] The optical scanning device and the optical receiving device according to the embodiment of the present disclosure may be used as an antenna in an optical detection system such as a LiDAR (Light Detection and Ranging) system. Compared with a radar system using radio waves such as millimeter waves, the LiDAR system uses electromagnetic waves with short wavelengths (visible light, infrared light, or ultraviolet light), and therefore can detect the distance distribution of an object with high resolution. Such a LiDAR system may be mounted on a moving body such as an automobile, a UAV (Unmanned Aerial Vehicle, so-called drone), or an AGV (Automated Guided Vehicle), and may be used as one of collision avoidance technologies. In this specification, the optical scanning device and the optical receiving device may be collectively referred to as an "optical device". In addition, a device used in the optical scanning device or the optical receiving device may also be referred to as an "optical device".

[0055] The optical device according to the first aspect includes a plurality of optical waveguides each extending in a first direction and arranged in a second direction intersecting the first direction, and a planar optical waveguide directly or indirectly connected to the plurality of optical waveguides. The plurality of optical waveguides propagate light along the first direction. The planar optical waveguide includes a first mirror and a second mirror facing each other and extending along the first direction and the second direction, and an optical waveguide layer located between the first mirror and the second mirror.

[0056] In this optical device, light propagating through a plurality of optical waveguides is made to interfere within an optical waveguide layer in a planar waveguide, thereby making it possible to realize optical scanning with a relatively simple configuration.

[0057] The optical device according to the second item is the optical device according to the first item, further comprising at least one of an electrode that changes the refractive index of the optical waveguide layer and an actuator that changes the thickness of the optical waveguide layer.

[0058] In this optical device, the direction of light emitted from the optical waveguide layer to the outside via the first mirror and / or the second mirror can be changed by changing at least one of the refractive index and the thickness of the optical waveguide layer.

[0059] The optical device according to the third aspect is the optical device according to the first or second aspect, further comprising another optical waveguide provided between the plurality of optical waveguides and the planar optical waveguide, the plurality of optical waveguides branching off from the other optical waveguide.

[0060] In this optical device, light propagates through a plurality of optical waveguides, and the light that has interfered in the other optical waveguides can be propagated through the planar optical waveguide.

[0061] The optical device according to a fourth aspect is the optical device according to the first or second aspect, wherein the optical waveguide layer in the planar optical waveguide includes an optical coupling portion containing end portions of the plurality of optical waveguides, and an optical waveguide portion adjacent to the optical coupling portion, and the end portions of the plurality of optical waveguides include one or more gratings.

[0062] In this optical device, light propagating through a plurality of optical waveguides can be efficiently propagated to the optical waveguide layer in the planar optical waveguide.

[0063] The optical device according to the fifth aspect is the optical device according to the third aspect, wherein the optical waveguide layer in the planar optical waveguide includes an optical coupling portion containing a tip portion of the other optical waveguide, and an optical waveguide portion adjacent to the optical coupling portion, and the tip portion of the other optical waveguide includes one or more gratings.

[0064] In this optical device, light that propagates through a plurality of optical waveguides and interferes in other optical waveguides can be efficiently propagated to the optical waveguide layer in the planar optical waveguide.

[0065] An optical device according to a sixth item is the optical device according to the fourth or fifth item, wherein the refractive index and / or thickness of the optical coupling portion and the refractive index and / or thickness of the optical waveguide portion of the optical waveguide layer can be adjusted separately.

[0066] In this optical device, the direction of light emitted from the first mirror and / or the second mirror can be changed while efficient optical coupling from the multiple optical waveguides 11 to the optical waveguide layer 20 is maintained.

[0067] An optical device according to a seventh item is the optical device according to any one of the first to sixth items, wherein the plurality of optical waveguides are arranged at equal intervals in the second direction.

[0068] In this optical device, when the phase of light propagating through the multiple optical waveguides is changed by a constant amount along the second direction, the direction of the light emitted from the first mirror and / or the second mirror can be changed.

[0069] An optical device according to an eighth aspect is the optical device according to any one of the first to sixth aspects, wherein the plurality of optical waveguides include a first optical waveguide, a second optical waveguide, and a third optical waveguide that are continuously arranged in this order in the second direction, and a center-to-center distance between the first optical waveguide and the second optical waveguide is different from a center-to-center distance between the second optical waveguide and the third optical waveguide.

[0070] In this optical device, the occurrence of side lobes and grating lobes caused by optical interference in the optical waveguide layer can be suppressed.

[0071] An optical device according to a ninth item is the optical device according to any one of the first to eighth items, further comprising a phase shifter that changes a phase difference of the light propagating through each of the plurality of optical waveguides.

[0072] In this optical device, the direction of light emitted from the first mirror and / or the second mirror can be changed by the phase shifter.

[0073] An optical detection system according to a tenth item includes an optical device according to any one of the first to ninth items, an optical detector that detects light emitted from the optical device and reflected from an object, and a signal processing circuit that generates distance distribution data based on the output of the optical detector.

[0074] This light detection system is capable of producing a range image of an object.

[0075] In the present disclosure, all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram may be implemented by one or more electronic circuits including, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (large scale integration). The LSI or IC may be integrated into one chip, or may be configured by combining multiple chips. For example, functional blocks other than memory elements may be integrated into one chip. Here, although it is called an LSI or an IC, the name may change depending on the degree of integration, and it may be called a system LSI, a VLSI (very large scale integration), or an ULSI (ultra large scale integration). A Field Programmable Gate Array (FPGA), which is programmed after the manufacture of the LSI, or a reconfigurable logic device, which can reconfigure the junction relationship inside the LSI or set up the circuit partition inside the LSI, can also be used for the same purpose.

[0076] Furthermore, all or part of the functions or operations of a circuit, unit, device, member, or section can be executed by software processing. In this case, the software is recorded in one or more non-transitory recording media such as ROMs, optical disks, hard disk drives, etc., and when the software is executed by a processor, the functions specified in the software are executed by the processor and peripheral devices. The system or device may include one or more non-transitory recording media on which the software is recorded, a processor, and necessary hardware devices, such as interfaces.

[0077] In this disclosure, "light" refers to electromagnetic waves including not only visible light (wavelength of about 400 nm to about 700 nm), but also ultraviolet light (wavelength of about 10 nm to about 400 nm) and infrared light (wavelength of about 700 nm to about 1 mm).

[0078] Hereinafter, more specific embodiments of the present disclosure will be described. However, more detailed explanations than necessary may be omitted. For example, detailed explanations of already well-known matters and overlapping explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the inventors provide the accompanying drawings and the following explanation so that those skilled in the art can fully understand the present disclosure, and do not intend to limit the subject matter described in the claims by them. In the following description, the same reference numerals are used for identical or similar components.

[0079] (Embodiment 1) Before describing the first embodiment of the present disclosure, a comparative example will be described with reference to FIGS. 6A to 8C.

[0080] Fig. 6A is a perspective view showing a comparative optical device 99. In Fig. 6A, the left and right components are shown in a separated state, but these components are typically in contact with each other. The comparative optical device 99 corresponds to the configuration of Fig. 1 in which a plurality of waveguide elements 10 are arranged, as described below.

[0081] In the example shown in FIG. 6A, the optical device 99 in the comparative example includes a plurality of optical waveguides 11 arranged in the Y direction, a mirror 30, a mirror 40, and an optical waveguide layer 20 located between these mirrors. The optical waveguide layer 20 includes a first member 24a and a plurality of second members 24b each extending in the X direction and arranged in the Y direction. Two side surfaces and an upper surface of the second member 24b are in contact with the first member 24a. The lower surface of the second member 24b is in contact with the mirror 40. The plurality of optical waveguides 11 are provided on a substrate 41. The refractive index of the optical waveguide 11 is greater than the refractive index of its surroundings. The surroundings include a medium in contact with the two side surfaces and the upper surface of the optical waveguide 11, and the substrate 41 in contact with the lower surface of the optical waveguide 11. The optical waveguide 11 propagates light along the X direction by total reflection. The plurality of optical waveguides 11 may branch off from other optical waveguides.

[0082] FIG. 6B is a perspective view that shows a schematic configuration on the right side of FIG. 6A. However, the arrangement direction is different. As shown in FIG. 6B, there are a plurality of waveguide portions 26a and a plurality of non-waveguide portions 26b that are alternately arranged in the Y direction between the mirror 30 and the mirror 40. The plurality of waveguide portions 26a and the plurality of non-waveguide portions 26b extend along the X direction. The waveguide portion 26a is located between two non-waveguide portions 26b. The waveguide portion 26a includes a first member 24a. The non-waveguide portion 26b includes a first member 24a and a second member 24b. The first member 24a exists in both the waveguide portion 26a and the non-waveguide portion 26b. In the optical device 99 in the comparative example, the refractive index n of the first member 24a is 1.0 μm. 1 is the refractive index n 2In this case, the refractive index of the waveguide portion 26a is higher than the average refractive index of the non-waveguiding portion 26b. Thus, light propagates along the X direction in the waveguide portion 26a by total reflection in the Y direction. The first member 24a may be formed of, for example, a liquid crystal material or an electro-optical material, and the second member 24b may be formed of, for example, a dielectric material such as glass. The refractive index of the liquid crystal material may be changed by application of an external voltage.

[0083] 6B, a configuration including waveguide portion 26a, a portion of mirror 30 directly above waveguide portion 26a, and a portion of mirror 40 directly below waveguide portion 26a corresponds to the above-mentioned waveguide element 10. In other words, a plurality of waveguide elements 10 are arranged in the Y direction.

[0084] In an optical device 99 of the comparative example, an end face of the optical waveguide 11 parallel to the YZ plane and an end face of the waveguide portion 26a in the optical waveguide layer 20 parallel to the YZ plane are connected.

[0085] 7 is a diagram showing a schematic diagram of light being emitted from the optical device 99 of FIG. 6A. For simplicity, the mirrors 30 and 40 are omitted. The optical waveguides 11 and the optical waveguide layer 20 are shown in a plan view, while the light emitted to the outside is shown in a perspective view. The black and white shading represents the intensity of the light. Black represents high intensity, and white represents low intensity.

[0086] In the example shown in Fig. 7, light propagating from the multiple optical waveguides 11 through the multiple waveguide sections 26a in the optical waveguide layer 20 along the X direction is emitted to the outside from the mirror 30. By emitting the light to the outside, the shading representing the light intensity in the waveguide section 26a becomes thinner along the +X direction. The light emitted to the outside from the multiple waveguide sections 26a via the mirror 30 interferes to form a light beam propagating in a specific direction, as shown in Figs. 3A and 3B. The light beam can change in the direction represented by the double arrow, as shown in Fig. 7.

[0087] 8A to 8C are diagrams showing an example of the intensity distribution of light propagating between the mirror 30 and the mirror 40 and an example of the intensity distribution of light emitted far away in a comparative example. The left diagram of each diagram shows the intensity distribution in the XY plane of the light propagating between the mirror 30 and the mirror 40. The left side of the left diagram corresponds to the connection part between the multiple optical waveguides 11 and the optical waveguide layer 20. The right diagram of each diagram shows the intensity distribution of light emitted far away. Synopsys' ModePROP was used to calculate the intensity distribution of the light shown in the left diagram and the right diagram. The far-field pattern, which is the intensity distribution of the light emitted far away, was calculated by Fourier transforming the intensity distribution of the light on the light emission surface of the mirror 30. In the example shown in FIG. 8A to FIG. 8C, the distance between the mirror 30 and the mirror 40 is 2.13 μm. The width of the second member 24b is 2 μm, and the height is 0.9 μm. The width of the waveguide portion 26a is 3 μm, and the width of the non-waveguiding portion 26b is equal to the width of the second member 24b.

[0088] In the example shown in FIG. 8A, the refractive index of the first member 24a is n 1 = 1.68, and the refractive index of the second member 24b is n 2 =1.46. As shown in the left diagram of FIG. 8A, light propagates through the waveguide portion 26a along the X direction. The phases of the light propagating through the multiple waveguide portions 26a are all equal. As shown in the right diagram of FIG. 8A, the far-field pattern shows zeroth-order diffracted light at the center and ±1st-order diffracted light on either side of it. In the example shown in the right diagram of FIG. 8A, the emission angle θ of the light emitted from the mirror 30 is equal to or greater than 45 degrees and equal to or less than 50 degrees. This emission angle θ is relatively large. The emission angle α of the zeroth-order diffracted light 0 is 0 degrees.

[0089] In the example shown in Fig. 8B, unlike the example shown in Fig. 8A, the phase of the light propagating through the multiple optical waveguides 11 is shifted by Δφ=π along the +Y direction. The left diagram of Fig. 8B is almost the same as the left diagram of Fig. 8A. In the right diagram of Fig. 8B, the far-field pattern is shifted by Δφ=π in increments of Δφ=π increments in comparison with the right diagram of Fig. 8A. 0This means that the Y-direction component of the direction of the light emitted from the mirror 30 changes due to the difference in the phase of the input light. In the example shown on the right side of FIG. 8B, the emission angle α of the zeroth-order diffracted light 0 is 6 degrees. The ±1st order diffracted lights change in a similar manner. In addition, new higher order diffracted lights appear.

[0090] In the example shown in FIG. 8C, unlike the example shown in FIG. 8B, the refractive index of the first member 24a is n 1 = 1.52. The left diagram of FIG. 8C differs from the left diagrams of FIG. 8A and FIG. 8B in that the light intensity is lower along the +X direction. In the right diagram of FIG. 8C, the far-field pattern changes in the direction in which the emission angle θ decreases compared to the right diagram of FIG. 8B. This means that the refractive index of the optical waveguide layer 20 changes, and the component in the X direction of the direction of the light emitted from the mirror 30 changes. In the example shown in the right diagram of FIG. 8C, the emission angle θ of the light emitted from the mirror 30 is 15 degrees or more and 20 degrees or less. This emission angle θ is relatively small.

[0091] Next, an optical device according to an embodiment of the present disclosure will be described with reference to Figures 9A to 11C. According to the optical device according to the present embodiment, it is possible to realize two-dimensional scanning with a simpler configuration than the optical device 99 according to the comparative example. In the following, the same description as that of the comparative example may be omitted.

[0092] 9A is a schematic diagram of an optical device 100 according to a first embodiment of the present disclosure. In the example shown in FIG. 9A, the optical device 100 includes a plurality of optical waveguides 11 and a single planar optical waveguide 50 to which the plurality of optical waveguides 11 are directly connected. The planar optical waveguide 50 includes a mirror 30 and a mirror 40 extending along the X direction and the Y direction, and an optical waveguide layer 20 located between these mirrors. The optical device 100 according to the first embodiment of the present disclosure differs from the optical device 99 according to the comparative example in that the optical waveguide layer 20 does not include a plurality of second members 24b aligned in the Y direction.

[0093] FIG. 9B is a perspective view showing the planar optical waveguide 50 of FIG. 9A. However, the arrangement direction is different. As shown in FIG. 9B, the optical waveguide layer 20 is uniform in any direction parallel to the XY plane. In one example, the optical waveguide layer 20 may include, for example, a liquid crystal material or an electro-optical material. The refractive index of the liquid crystal material or the electro-optical material may be changed by the application of an external voltage. In another example, the optical waveguide layer 20 may include, for example, a deformable liquid or gas. The thickness of the optical waveguide layer 20 may be changed by changing the distance between the mirror 30 and the mirror 40. By changing the refractive index and / or thickness of the optical waveguide layer 20, the component parallel to the X direction of the direction of the light propagating through the optical waveguide layer 20 and output through the mirror 30 can be changed. The first driving circuit 110 described above can drive the planar optical waveguide 50 to change the refractive index and / or thickness of the optical waveguide layer 20. A specific configuration for driving the planar optical waveguide 50 will be described later.

[0094] A phase shifter array 80A may be connected to the multiple optical waveguides 11. The phase shifter array 80A can shift the phase of light propagating through the multiple optical waveguides 11 by a fixed amount along the Y direction. As a result, it is possible to change the component parallel to the Y direction among the directions of light propagating through the optical waveguide layer 20 and output from the mirror 30. The multiple optical waveguides 11 themselves may function as the phase shifter array 80A. The second driving circuit 120 described above can drive the phase shifter array 80A to perform the above-mentioned phase shift.

[0095] Fig. 10 is a diagram showing a schematic view of the light emitted from the optical device 100 of Fig. 9A. Unlike the example shown in Fig. 7, the light input from the multiple optical waveguides 11 and propagating in the optical waveguide layer 20 interferes in the optical waveguide layer 20 to form light beams 22b. The dashed curves, solid lines, and closed solid curves are as described with reference to Figs. 3A and 3B. These light beams 22b are emitted to the outside from the mirror 30 and propagate in a specific direction.

[0096] 11A to 11C are diagrams showing an example of the intensity distribution of light propagating between the mirror 30 and the mirror 40 and an example of the intensity distribution of light emitted to a distant location in the first embodiment. The left and right diagrams and the calculation method are as described above. In the example shown in Fig. 11A to 11C, the thickness of the optical waveguide layer 20 is 2.13 μm.

[0097] In the example shown in FIG. 11A, the refractive index of the optical waveguide layer 20 is n 1 = 1.68. As shown in the left diagram of FIG. 11A, a light beam is formed in the optical waveguide layer 20 along the +X direction. The intensity of the light beam is high near Y=0, which corresponds to the center of the middle optical waveguide among the multiple optical waveguides 11. Side lobes are formed around the main lobe. The light beam propagates in the optical waveguide layer 20 along the X direction. The far-field pattern shown in the right diagram of FIG. 11A is similar to the field pattern shown in the right diagram of FIG. 8A. However, as shown in the right diagram of FIG. 11A, the intensity of the ±1st order diffracted light is low.

[0098] In the example shown in FIG. 11B, unlike the example shown in FIG. 11A, the phase of the light propagating through the multiple optical waveguides is shifted by π along the +Y direction. In the left diagram of FIG. 11B, the light beam has high intensity in two directions compared to the left diagram of FIG. 11A. One direction includes a component in the +X direction and a component in the +Y direction, and the other direction includes a component in the +X direction and a component in the −Y direction. B As shown in the right diagram of FIG. 11B, the far-field pattern also has high intensity in two directions. This means that the Y-direction component of the light exiting from mirror 30 changes due to the different phase of the input light. The far-field pattern shown in the right diagram of FIG. 11B is similar to the field pattern shown in the right diagram of FIG. 8B.

[0099] In the example shown in FIG. 11C, unlike the example shown in FIG. 11B, the refractive index of the optical waveguide layer 20 is n 1 = 1.52. The left diagram in FIG. 11C is BIn the right diagram of Fig. 11C, the light beam is shifted in the -X direction compared to the left diagram of Fig. 11B. In the right diagram of Fig. 11C, the far-field pattern changes in the direction in which the output angle θ decreases compared to the right diagram of Fig. 11B. The far-field pattern shown in the right diagram of Fig. 11C is similar to the field pattern shown in the right diagram of Fig. 8C.

[0100] As described above, it has become clear that the optical device 100 in the first embodiment can also realize two-dimensional scanning, similar to the optical device 99 in the comparative example. According to the optical device 100 in the first embodiment, since a plurality of waveguide elements 10 is not required, the fabrication can be facilitated.

[0101] Next, crosstalk occurring between light propagating through the multiple optical waveguides 11 will be described. In the example shown in FIG. 9A, the multiple optical waveguides 11 are periodically arranged at equal intervals along the Y direction. When light propagates through the optical waveguides 11 along the X direction, evanescent light seeps out from the optical waveguides 11 in the Y direction. If the center-to-center distance between two adjacent optical waveguides is short, the evanescent light that seeps out from the optical waveguide may move to the adjacent optical waveguide. As a result, the light propagating through the multiple optical waveguides 11 may enter the optical waveguide layer 20 without a phase difference.

[0102] FIG. 12 is a diagram showing the period dependency of the crosstalk rate occurring between a plurality of optical waveguides 11 each having a length of 100 μm. The optical waveguide 11 has a refractive index of 2.0, and the substrate 41 has a refractive index of 1.46. The optical waveguide 11 has a width of 600 nm and a height of 300 nm. As shown in FIG. 12, as the period between the plurality of optical waveguides 11 increases, the crosstalk rate decreases while oscillating. If the period is 1.3 μm or more, the crosstalk rate can be suppressed to a few percent or less.

[0103] Next, a first modified example and a second modified example of the optical device 100 in the first embodiment will be described with reference to Figures 13A and 13B. Descriptions that overlap with the first embodiment may be omitted.

[0104] FIG. 13A is a diagram showing a first modified example of the optical device 100 in the first embodiment. In the first modified example, unlike the first embodiment, the multiple optical waveguides 11 are not arranged at equal intervals along the Y direction. In the example shown in FIG. 13A, five optical waveguides 11 are arranged in the +Y direction in the order of "first optical waveguide 11" and "second optical waveguide 12". 1 " to "5th optical waveguide 11 5 The first optical waveguide 11 1 and the second optical waveguide 11 2 First center distance d 1 The second optical waveguide 11 2 and the third optical waveguide 11 3 Second center distance d 2 The third optical waveguide 11 3 and the fourth optical waveguide 11 4 Third center distance d 3 The second optical waveguide 11 2 and the third optical waveguide 11 3 Second center distance d 2 The fourth optical waveguide 11 4 and the fifth optical waveguide 11 5 The fourth center distance d 4 The first optical waveguide 11 1 and the second optical waveguide 11 2 First center distance d 1 That is, d 2 =d 3 >d 1 =d 4 The distances between the optical waveguides 11 do not have to be equal, and some of the distances may be different. 1 From the fourth center distance d 4 By appropriately designing, it is possible to suppress the occurrence of side lobes and grating lobes in the light beam 22b. As a result, it is possible to suppress the occurrence of side lobes and grating lobes in the light output from the mirror 30.

[0105] FIG. 13B is a diagram showing a second modified example of the optical device 100 in the first embodiment. In the second modified example, unlike the first embodiment, a plurality of optical waveguides 11, an optical waveguide layer 20, and one or more elastic spacers 72 are provided on the mirror 40. The one or more elastic spacers 72 are located around the tip portions of the plurality of optical waveguides 11 and around the optical waveguide layer 20. The shape of the one or more elastic spacers 72 may be one continuous curve. The size of the elastic spacer 72 in the Z direction is larger than the size of the optical waveguide 11 in the Z direction and larger than the size of the optical waveguide layer 20 in the Z direction. The optical device 100 in the second modified example is fabricated by attaching the mirror 30 and the mirror 40 so that at least a part of the elastic spacer 72 and the optical waveguide layer 20 are located between the mirrors.

[0106] If the multiple elastic spacers 72 were not present, the mirror 30 may first come into contact with a part of a component provided on the mirror 40 during attachment. In this case, the contacted part may become a fulcrum and the mirror 30 may tilt relative to the mirror 40. As a result, the intensity of the light emitted from the mirror 30 may decrease.

[0107] In contrast, when multiple elastic spacers 72 are present, the mirror 30 first comes into contact with the elastic spacers 72. Since the elastic spacers 72 are compressed, the mirror 40 and the mirror 30 can be bonded together so that the gap between the mirror 30 and the mirror 40 is uniform. As a result, a decrease in the intensity of the light emitted from the mirror 30 can be suppressed.

[0108] (Embodiment 2) Next, an example of an optical device according to the second embodiment of the present disclosure will be described with reference to FIGS. 14A to 16B.

[0109] 14A and 14B are cross-sectional views in the XZ plane and the XY plane, respectively, which are schematic diagrams illustrating an example of the optical device 100 in the second embodiment. In the example illustrated in FIG. 14A and FIG. 14B, another planar optical waveguide 12 is located between a plurality of optical waveguides 11 and a planar optical waveguide 50. In other words, the planar optical waveguide 50 is indirectly connected to the plurality of optical waveguides 11 via the planar optical waveguide 12. The plurality of optical waveguides 11 branch off from the planar optical waveguide 12.

[0110] The mirror 40 is also located below the multiple optical waveguides 11 and the planar optical waveguide 12. The multiple optical waveguides 11 and the planar optical waveguide 12 are disposed on the mirror 40 via the clad 51. The refractive index of the optical waveguide 11 is higher than that of the clad 51. The refractive index of the planar optical waveguide 12 is higher than that of the clad 51. The multiple optical waveguides 11 are arranged along the Y direction. The clad 51 has a structure parallel to the XY plane. The portion of the clad 51 where the multiple optical waveguides 11 and the planar optical waveguide 12 are not located above may be removed. The optical waveguide layer 20 and the mirror 30 located above the planar optical waveguide 12 are not necessarily required.

[0111] The optical waveguide layer 20 includes an optical coupling portion 20c that includes a tip portion of the planar optical waveguide 12, and an optical waveguide portion 20g that is adjacent to the optical coupling portion 20c. The tip portion of the planar optical waveguide 12 is located between the mirror 30 and the mirror 40. Light propagating through the planar optical waveguide 12 from the multiple optical waveguides 11 is coupled to the optical waveguide portion 20g via the optical coupling portion 20c.

[0112] A grating 15 is provided at the tip portion of the planar optical waveguide 12. The grating 15 includes a plurality of recesses and / or protrusions, the number of which is 4 to 64. By appropriately designing the period of the grating 15, it is possible to compensate for the difference between the propagation constant of the light propagating through the planar optical waveguide 12 and the propagation constant of the light propagating through the optical waveguide layer 20. This compensation allows efficient coupling of light from the planar optical waveguide 12 to the optical waveguide layer 20.

[0113] Figure 15 is a cross-sectional view of Figure 14. A and Figure 14B 1 is a schematic diagram showing a state in which a light beam is emitted from the optical device 100. Light propagating through the multiple optical waveguides 11 along the X direction interferes in the planar optical waveguide 12 to form a light beam 22b. The light beam 22b is emitted to the outside from the optical waveguide portion 20g in the optical waveguide layer 20 via the mirror 30 and propagates in a specific direction.

[0114] 16A and 16B are diagrams showing the intensity distribution in the XY plane and the XZ plane of the light propagating between the mirror 30 and the mirror 40, respectively. The calculation method is as described above. In the example shown in FIG. 16A and FIG. 16B, the optical waveguide 11 has a refractive index of 2.115, a width of 600 nm, a number of waveguides of 4, and a period of 1.8 μm. The cladding 51 has a refractive index of 1.46. The planar optical waveguide 12 has a refractive index of 2.115. The optical waveguide layer 20 has a refractive index of 1.61, and a thickness of 2.13 μm. The phases of the light propagating through the multiple optical waveguides 11 are all equal.

[0115] As shown in Fig. 16A, a light beam is formed in planar optical waveguide 12. As shown in Fig. 16B, the light beam formed in planar optical waveguide 12 propagates through grating 15 in optical waveguide portion 20g.

[0116] 14A, the refractive index and / or thickness of the optical coupling portion 20c and the refractive index and / or thickness of the optical waveguide portion 20g may be adjusted separately in the optical waveguide layer 20. By adjusting the refractive index and / or thickness separately, the direction of the light emitted from the mirror 30 can be changed while maintaining efficient optical coupling from the optical waveguide 11 to the optical waveguide layer 20.

[0117] Instead of the second embodiment, in the first embodiment, the optical waveguide layer 20 in the planar optical waveguide 50 may include an optical coupling portion that includes the tip portions of the optical waveguides 11, and an optical guiding portion adjacent to the optical coupling portion. The tip portions of the optical waveguides 11 may include one or more gratings. With this configuration, light can be efficiently coupled from the optical waveguides 11 to the optical waveguide layer 20.

[0118] The first and second modifications in the first embodiment can also be applied to the second embodiment.

[0119] (Configuration for Driving Planar Optical Waveguide 50) Next, a configuration for driving the planar optical waveguide 50 will be described with reference to FIGS. 17A and 17B.

[0120] FIG. 17A is a diagram showing a first example for driving the planar optical waveguide 50. In the example shown in FIG. 17A, the planar optical waveguide 50 further includes a first electrode 62a arranged between the optical waveguide layer 20 and the mirror 30, and a second electrode 62b arranged between the optical waveguide layer 20 and the mirror 40. The first electrode 62a may be, for example, a transparent electrode. Light propagating in the optical waveguide layer 20 is emitted to the outside through the first electrode 62a and the mirror 30. The second electrode 62b may be, for example, a transparent electrode, or an electrode made of a metal. The optical waveguide layer 20 may include, for example, a liquid crystal material or an electro-optical material. The optical waveguide layer 20 is located between a pair of electrodes including the first electrode 62a and the second electrode 62b. The first driving circuit described above applies a voltage to the pair of electrodes to change the refractive index of the optical waveguide layer 20.

[0121] FIG. 17B is a diagram showing a schematic diagram of a second example of the planar optical waveguide 50. In the example shown in FIG. 17B, the planar optical waveguide 50 further includes a pair of actuators 70 supporting the mirror 30. The pair of actuators 70 may support the mirror 40 instead of the mirror 30, or may support the mirror 30 and the mirror 40. The optical waveguide layer 20 may include, for example, a deformable liquid or gas. For example, electrostatic force, electromagnetic induction, a piezoelectric material, a shape memory alloy, or heat may be used for the pair of actuators 70. The pair of actuators 70 change the thickness of the optical waveguide layer 20 by changing the distance between the mirror 30 and the mirror 40. The first driving circuit described above applies a voltage to the pair of actuators 70 including, for example, a piezoelectric material to change the thickness of the optical waveguide layer 20.

[0122] By changing the refractive index and / or thickness of the optical waveguide layer 20 as described above, it is possible to change the component of the direction of the light emitted from the mirror 30 that is parallel to the X direction.

[0123] (Application example) FIG. 18 is a diagram showing a configuration example of an optical scanning device 100 in which elements such as a planar optical waveguide 50, a plurality of optical waveguides 11, an optical splitter 90, a phase shifter array 80A, and a light source 130 are integrated on a circuit board (for example, a chip). The light source 130 may be, for example, a light emitting element such as a semiconductor laser. The light source 130 in this example emits light of a single wavelength, which has a wavelength λ in free space. The optical splitter 90 splits the light from the light source 130 and introduces it into the waveguides in the plurality of phase shifters. In the example shown in FIG. 18, an electrode 62A and a plurality of electrodes 62B are provided on the chip. A control signal is supplied to the planar optical waveguide 50 from the electrode 62A. A control signal is sent from the plurality of electrodes 62B to the plurality of phase shifters 80 in the phase shifter array 80A. The electrode 62A and the plurality of electrodes 62B may be connected to a control circuit (not shown) that generates the above control signal. The control circuit may be provided on the chip shown in FIG. 18, or may be provided on another chip in the optical scanning device 100.

[0124] By integrating all the components on a chip as shown in Figure 18, wide-range optical scanning can be achieved with a small device. For example, all the components can be integrated on a chip of about 2 mm × 1 mm.

[0125] 19 is a schematic diagram showing a state in which a two-dimensional scan is performed by irradiating a light beam such as a laser from the optical scanning device 100 to a distant object. The two-dimensional scan is performed by moving a beam spot 310 in the horizontal and vertical directions. For example, by combining with a known TOF (Time Of Flight) method, a two-dimensional distance measurement image can be obtained. The TOF method is a method of calculating the time of flight of light by irradiating a laser and observing the reflected light from an object, thereby determining the distance.

[0126] FIG. 20 is a block diagram showing a configuration example of a LiDAR system 300, which is an example of a light detection system capable of generating such a distance measurement image. The LiDAR system 300 includes an optical scanning device 100, an optical detector 400, a signal processing circuit 600, and a control circuit 500. The optical detector 400 detects light emitted from the optical scanning device 100 and reflected from an object. The optical detector 400 may be, for example, an image sensor having sensitivity to the wavelength λ of light emitted from the optical scanning device 100, or a photodetector including a light receiving element such as a photodiode. The optical detector 400 outputs an electrical signal according 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 optical detector 400, and generates distance distribution data. The distance distribution data is data showing a two-dimensional distribution of distances (i.e., a distance measurement image). The control circuit 500 is a processor that controls the optical scanning device 100, the optical detector 400, and the signal processing circuit 600. The control circuit 500 controls the timing of irradiation of the light beam from the optical scanning device 100 and the timing of exposure and signal readout of the photodetector 400, and instructs the signal processing circuit 600 to generate a distance measurement image.

[0127] In 2D scanning, the frame rate for acquiring distance measurement images can be selected from 60 fps, 50 fps, 30 fps, 25 fps, 24 fps, etc., which are commonly used for videos. In addition, when considering application to in-vehicle systems, the higher the frame rate, the more frequently distance measurement images are acquired, and the more accurate obstacle detection is possible. For example, when driving at 60 km / h, at a frame rate of 60 fps, an image can be acquired every time the car moves about 28 cm. At a frame rate of 120 fps, an image can be acquired every time the car moves about 14 cm. At a frame rate of 180 fps, an image can be acquired every time the car moves about 9.3 cm.

[0128] The time required to acquire one distance measurement image depends on the speed of beam scanning. For example, to acquire an image with a resolution of 100 x 100 at 60 fps, beam scanning must be performed in 1.67 μs or less per point. In this case, the control circuit 500 controls the emission of the light beam by the optical scanning device 100 and the signal accumulation and readout by the photodetector 400 at an operating speed of 600 kHz.

[0129] <Application to optical receiving device> The optical scanning device in each of the above-mentioned embodiments of the present disclosure can also be used as an optical receiving device with almost the same configuration. The optical receiving device includes the same planar optical waveguide 50 and multiple optical waveguides 11 as the optical scanning device, and a first adjustment element that adjusts the direction of receivable light. The first mirror 30 transmits light incident on the opposite side of the first reflecting surface from the third direction. The optical waveguide layer 20 propagates the light that has passed through the first mirror 30 in the second direction. The first adjustment element can change the direction of receivable light by changing at least one of the refractive index and thickness of the optical waveguide layer 20 and the wavelength of light. Furthermore, when the optical receiving device includes multiple phase shifters 80 that are the same as the optical scanning device, and a second adjustment element that changes the phase difference of the light outputted through the phase shifters 80, the direction of receivable light can be changed two-dimensionally.

[0130] For example, an optical receiving device can be constructed by replacing the light source 130 in the optical scanning device 100 shown in Fig. 18 with a receiving circuit. When light with a wavelength λ enters the planar optical waveguide 50, the light is sent to the optical splitter 90 through the phase shifter array 80A, and is finally collected at one point and sent to the receiving circuit. The intensity of the light collected at one 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 separately incorporated in the planar optical waveguide 50 and the phase shifter array 80A.

[0131] The above-described embodiments can be combined as appropriate. [Industrial Applicability]

[0132] The optical scanning device and the optical receiving device according to the embodiments of the present disclosure can be used in applications such as lidar systems mounted on vehicles such as automobiles, UAVs, and AGVs. [Explanation of symbols]

[0133] 10 Waveguide elements 10A Waveguide Array 11 Optical waveguide 12 Other planar optical waveguides 15 Grating 20 Optical waveguide layer 20c Optical coupling part 20g optical waveguide part 22 light 22b Light beam 24a First member 24b Second member 26a Waveguide section 26b Non-guiding part 30 Mirror No. 1 40 2nd Mirror 41 Substrate 50 Planar optical waveguide 51 Clad 62a, 62b, 62A, 62B electrode 70 Pair of Actuators 72 Elastic spacer 80 Phase Shifter 80A Phase Shifter Array 90 Optical splitter 99 Optical Devices 100 Optical Scanning Device 101, 102 direction 110 First drive circuit 120 Second drive circuit 130 Light source 300 LiDAR System 310 Beam Spot 400 Photodetector 500 Control circuit 600 Signal Processing Circuit

Claims

1. a plurality of optical waveguides each extending in a first direction and arranged in a second direction intersecting the first direction, each optical waveguide propagating light of the same wavelength along the first direction; a planar optical waveguide connected directly or indirectly to the plurality of optical waveguides; a phase shifter that changes a phase of the light propagating through each of the plurality of optical waveguides; Equipped with The planar optical waveguide comprises: a first mirror and a second mirror facing each other and extending along the first direction and the second direction; an optical waveguide layer located between the first mirror and the second mirror; Equipped with the light propagating through each of the plurality of optical waveguides interferes within the optical waveguide layer in the planar optical waveguide to form a light beam; Optical devices.

2. and further comprising at least one of an electrode that changes the refractive index of the optical waveguide layer and an actuator that changes the thickness of the optical waveguide layer.

10. The optical device of claim 1 .

3. Further comprising another optical waveguide provided between the plurality of optical waveguides and the planar optical waveguide, The plurality of optical waveguides are branched off from the other optical waveguide.

3. An optical device according to claim 1 or 2.

4. the optical waveguide layer in the planar optical waveguide includes an optical coupling portion including tip portions of the optical waveguides, and an optical waveguide portion adjacent to the optical coupling portion, the tip portions of the plurality of optical waveguides include one or more gratings; 3. An optical device according to claim 1 or 2.

5. the optical waveguide layer in the planar optical waveguide includes an optical coupling portion including a tip portion of the other optical waveguide, and an optical waveguide portion adjacent to the optical coupling portion, The tip portion of the other optical waveguide includes one or more gratings.

4. The optical device according to claim 3.

6. In the optical waveguide layer, the refractive index and / or thickness of the optical coupling portion and the refractive index and / or thickness of the optical waveguide portion can be adjusted separately.

6. An optical device according to claim 4 or 5.

7. The plurality of optical waveguides are arranged at equal intervals in the second direction.

7. An optical device according to claim 1.

8. the plurality of optical waveguides include a first optical waveguide, a second optical waveguide, and a third optical waveguide that are continuously arranged in this order in the second direction; a center-to-center distance between the first optical waveguide and the second optical waveguide is different from a center-to-center distance between the second optical waveguide and the third optical waveguide; 7. An optical device according to claim 1.

9. The planar optical waveguide to which the plurality of optical waveguides are connected is single.

9. An optical device according to claim 1.

10. each of at least two of the plurality of optical waveguides inputs the light into the planar optical waveguide; 10. An optical device according to claim 1.

11. An optical device according to any one of claims 1 to 10; a photodetector that detects light emitted from the optical device and reflected from an object; a signal processing circuit for generating distance distribution data based on an output of the photodetector; Equipped with Optical detection system.

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