Optical Devices and Optical Detection Systems

Abstract

This optical device comprises: a first structure having a first surface; a second structure having a second surface that faces the first surface; one or more optical waveguide regions including a liquid crystal material, the optical waveguide regions being positioned between the first surface of the first structure and the second surface of the second structure; and a first alignment film that is a rubbing alignment film for aligning the liquid crystal material, the first alignment film being provided on the first surface. Either (A) the second surface contacts the liquid crystal material without the interposition of any alignment film, or (B) a second alignment film for aligning the liquid crystal material is furthermore provided, the second alignment film being an alignment film other than a rubbing alignment film, and being provided on the second surface.

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 [Patent Document 4] JP 2001-100214 A Summary of the Invention [Problem to be solved by the invention]

[0007] One aspect of the present disclosure provides an optical device with a relatively simple configuration and low optical loss. [Means for solving the problem]

[0008] An optical device according to one embodiment of the present disclosure comprises a first structure having a first surface, a second structure having a second surface opposite to the first surface, one or more optical waveguide regions located between the first surface of the first structure and the second surface of the second structure and containing a liquid crystal material, and a first alignment film which is a rubbing alignment film provided on the first surface and aligns the liquid crystal material, wherein (A) the second surface contacts the liquid crystal material without any alignment film therebetween, or (B) the optical device further comprises a second alignment film which is an alignment film other than a rubbing alignment film provided on the second surface and aligns the liquid crystal material.

[0009] A comprehensive or specific aspect of the present disclosure may be realized in a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable recording disk, or may be realized in any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. The computer-readable recording medium may include a non-volatile recording medium such as a CD-ROM (Compact Disc-Read Only Memory). An apparatus may be composed of one or more devices. When an apparatus is composed of two or more devices, the two or more devices may be arranged in one device, or may be arranged separately in two or more separate devices. In this specification and the claims, "apparatus" may mean not only one device, but also a system consisting of multiple devices. Effect of the Invention

[0010] According to one aspect of the present disclosure, an optical device with low optical loss can be realized with a relatively simple configuration. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view illustrating a schematic configuration of an optical scanning device. [Diagram 2] FIG. 2 is a diagram illustrating an example of a cross-sectional structure of one waveguide element and propagating light. [Figure 3A] 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. [Figure 3B] 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. [Figure 4] FIG. 4 is a perspective view that illustrates a waveguide array in a three-dimensional space. [Diagram 5] FIG. 5 is a schematic diagram of the waveguide array and the phase shifter array as viewed from the normal direction (Z direction) of the light emission surface. [Figure 6A] FIG. 6A is a plan view diagrammatically illustrating an example of an optical device according to the first embodiment of the present disclosure. [Figure 6B] FIG. 6B is a diagram showing a state in which the upper components are removed from FIG. 6A. [Figure 7A] FIG. 7A is a cross-sectional view taken along line VIIA-VIIA in FIG. 6A. [Figure 7B] FIG. 7B is a cross-sectional view taken along line VIIB-VIIB in FIG. 6A. [Figure 7C] FIG. 7C is a cross-sectional view taken along line VIIC-VIIC in FIG. 6A. [Figure 8A] FIG. 8A is a cross-sectional view illustrating a schematic example of an optical device according to a second embodiment of the present disclosure. [Figure 8B] FIG. 8B is a cross-sectional view illustrating a schematic example of an optical device according to the second embodiment of the present disclosure. [Figure 8C] FIG. 8C is a cross-sectional view illustrating a schematic example of an optical device according to the second embodiment of the present disclosure. [Figure 9A] FIG. 9A is a diagram illustrating the second alignment film in the second embodiment. [Figure 9B] FIG. 9B is a diagram illustrating the second alignment film in the second embodiment. [Figure 9C] FIG. 9C is a diagram illustrating the second alignment film in the second embodiment. [Figure 9D] FIG. 9D is a diagram illustrating the second alignment film in the second embodiment. [Figure 9E] FIG. 9E is a diagram illustrating the second alignment film in the second embodiment. [Figure 10A] FIG. 10A is a diagram illustrating a schematic view of how light is emitted from the optical device according to the first embodiment. [Figure 10B] FIG. 10B is a diagram illustrating a schematic view of how light is emitted from the optical device according to the second embodiment. [Figure 11A] FIG. 11A is a plan view diagrammatically illustrating an example of an optical device according to a modified example of the second embodiment of the present disclosure. [Figure 11B] FIG. 11B is a diagram showing a state in which the upper components are removed from FIG. 11A. [Figure 12A] FIG. 12A is a cross-sectional view taken along line XIIA-XIIA in FIG. 11A. [Figure 12B] FIG. 12B is a cross-sectional view taken along line XIIB-XIIB in FIG. 11A. [Figure 12C] FIG. 12C is a cross-sectional view taken along line XIIC-XIIC in FIG. 11A. [Figure 13] FIG. 13 is a diagram showing a configuration example of an optical scanning device in which elements such as an optical branching unit, a waveguide array, a phase shifter array, and a light source are integrated on a circuit board. [Figure 14] FIG. 14 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. [Figure 15] FIG. 15 is a block diagram showing an example of the configuration of a LiDAR system capable of generating a distance measurement image. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection forms of the components, steps, and the order of steps shown in the following embodiments are examples and are not intended to limit the technology of the present disclosure. Among the components in the following embodiments, components that are not described in the independent claims showing the highest concept are described as optional components. Each figure is a schematic diagram and is not necessarily illustrated strictly. Furthermore, in each figure, substantially the same or similar components are given the same reference numerals. Duplicate descriptions may be omitted or simplified.

[0013] (Findings on which this disclosure is based) Before describing the embodiments of the present disclosure, the findings on which the present disclosure is based will be described.

[0014] The present inventor has found that a problem with conventional optical scanning devices is that it is difficult to scan a space with light without complicating the configuration of the device.

[0015] 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.

[0016] 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.

[0017] The present inventor has focused on the above problems in the conventional technology and has studied a configuration for solving these problems. The present inventor has found that the above problems can be solved by using a waveguide element having a pair of opposing mirrors and an optical waveguide layer sandwiched between the mirrors. One of the pair of mirrors in the waveguide element has a higher light transmittance than the other mirror, and emits a part of the light propagating through the optical waveguide layer to the outside. As described below, 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. 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 also 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, according to the embodiment of the present disclosure, 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 alone. Alternatively, any two or all of these three may be controlled to change the output direction of light. In each of the following embodiments, 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] 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".

[0022] An example of the basic configuration of an optical device and its operating principle will be described below.

[0023] <Basic configuration example of an optical scanning device> The configuration of an optical scanning device that performs two-dimensional scanning will be described below as an example. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to make it easier for those skilled in the art to understand.

[0024] 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). In this specification, ultraviolet light may be referred to as "ultraviolet light" and infrared light may be referred to as "infrared light."

[0025] 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.

[0026] FIG. 1 is a perspective view showing a schematic configuration of an optical scanning device 100. The optical scanning device 100 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 and emit 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.

[0027] The orientation of the structures shown in the drawings of this application is set in consideration of the ease of understanding of the description, and does not limit the orientation when the present embodiment is actually implemented. Furthermore, the shape and size of the whole or part of the structures shown in the drawings do not limit the actual shape and size.

[0028] Each of the multiple waveguide elements 10 has a first mirror 30 and a second mirror 40 facing each other, and an optical waveguide layer 20 located between the mirrors 30 and 40. Each of the mirrors 30 and 40 has a reflective surface that intersects with the third direction D3 at the interface with the optical waveguide layer 20. The mirrors 30 and 40 and the optical waveguide layer 20 have a shape extending in the first direction (X direction).

[0029] 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. The term "separately configured" includes not only being physically arranged with a space between them, but also being separated by a material having a different refractive index between them.

[0030] 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").

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The operating principle of the optical scanning device 100 will now be described.

[0036] <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 propagating light. In FIG. 2, a direction perpendicular to the X direction and the Y direction shown in FIG. 1 is set 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 first mirror 30 and a second mirror 40 are arranged to sandwich the optical waveguide layer 20. The first mirror 30 has a first reflecting surface 30s. The second mirror 40 has a second reflecting surface 40s facing the first reflecting surface 30s. The light 20L 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 reflecting surface 30s of the first mirror 30 provided on the upper surface (upper surface in FIG. 2) of the optical waveguide layer 20 and the second reflecting surface 40s of the second mirror 40 provided on the lower surface (lower surface in FIG. 2). The light transmittance of the first mirror 30 is higher than the light transmittance of the second mirror 40. Therefore, a part of the light can be output mainly from the first mirror 30.

[0037] In a general waveguide such as an optical fiber, light propagates along the waveguide while repeating total reflection. In contrast, in the waveguide element 10 of this 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."

[0038] The emission angle θ of light emitted from the waveguide element 10 into the air is expressed by the following formula (1).

number

[0039] 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.

[0040] 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.

[0041] Therefore, the optical scanning device 100 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 (i.e., visible light to near infrared light) in which a high detection sensitivity is 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.

[0042] To change the direction of the output light, the optical scanning device 100 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 .

[0043] 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.

[0044] 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.

[0045] 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.

[0046] <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.

[0047] 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 straight line indicates the wavefront formed by the interference of light. The arrow indicates the direction of light emitted from the waveguide array (i.e., the direction of the wave vector). In the example of FIG. 3A, the phase of light propagating through the optical waveguide layer 20 in each waveguide element 10 is the same. In this case, the light is emitted in a direction (Z direction) perpendicular to both the arrangement direction (Y direction) of the waveguide elements 10 and the extension direction (X direction) of the optical waveguide layer 20.

[0048] 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 the multiple waveguide elements 10 differs by a certain 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 wave vector of the light can be changed. If the center-to-center distance between two adjacent waveguide elements 10 is p, the light emission angle α0 is expressed by the following formula (2).

number

[0049] In the example shown in FIG. 2, the direction of light emission is parallel to the XZ plane. That is, α0=0°. In the example shown in FIG. 3A and FIG. 3B, the direction of light emitted from the optical scanning device 100 is parallel to the YZ plane. That is, θ=0°. However, in general, the direction of light emitted from the optical scanning device 100 is not parallel to either the XZ plane or the YZ plane. That is, θ≠0° and α0≠0°.

[0050] 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 100. θ is the angle between the light emission direction and the YZ plane. θ satisfies formula (1). α0 is the angle between the light emission direction and the XZ plane. α0 satisfies formula (2).

[0051] <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 100 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 are also referred to as a "phase shifter array" in the same manner as the waveguide array.

[0052] 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. Also, by making the length of each phase shifter 80 change in equal steps, it is possible to give equal-step phase shifts with the same driving voltage. Furthermore, this optical scanning device 100 further includes an optical branching unit 90 that branches and supplies light to a plurality of phase shifters 80, a first driving circuit 70a that drives each waveguide element 10, and a second driving circuit 70b 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 and second driving circuits 70a and 70b, which are provided separately. In this example, the first driving circuit 70a functions as one element of the first adjustment element, and the second driving circuit 70b functions as one element of the second adjustment element.

[0053] The first driving circuit 70a 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 70b changes the phase of light propagating inside the waveguide 20 by changing the refractive index of the waveguide 20 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.

[0054] 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 70b can be simplified.

[0055] An optical device having a configuration similar to that of the optical scanning device 100 described above can also be used as an optical receiving device. Details of the operation principle and operation method of the optical device are disclosed in U.S. Patent Application Publication No. 2018 / 0224709. The entire disclosure of this document is incorporated herein by reference.

[0056] <Liquid crystal alignment film> When the optical waveguide layer 20 contains a liquid crystal material, the reflecting surface 30s of the mirror 30 and the reflecting surface 40s of the mirror 40 may be provided with an alignment film that aligns the long axis of the liquid crystal molecules in the liquid crystal material in a specific direction. The alignment film may be formed of a material that can realize a relatively high alignment control force, such as polyimide. The alignment direction of the alignment film may be determined, for example, by rubbing. An alignment film formed by rubbing a material such as polyimide is thick and has an uneven thickness. When light is incident on such an alignment film, absorption and scattering of the light occur. As shown in FIG. 2, when light is multiple-reflected and propagates in the optical waveguide layer 20 along the X direction, the light is absorbed and scattered many times by the upper and lower alignment films. As a result, a non-negligible light loss may occur in the optical waveguide layer 20. According to the inventor's study, this light loss is about 50%.

[0057] In order to solve the above problems, the inventors have come up with the configuration of the embodiment of the present disclosure described below. An optical device according to an embodiment of the present disclosure can be fabricated by combining a first structure including the above-mentioned first mirror and the like with a second structure including the above-mentioned second mirror and the like. A region corresponding to the above-mentioned optical waveguide layer is formed between the surface of the first structure (hereinafter also referred to as the "first surface") and the surface of the second structure (hereinafter also referred to as the "second surface"). This region is referred to as the "optical waveguide region". The optical waveguide region may be formed of, for example, a liquid crystal material. The optical waveguide region may contain a material other than the liquid crystal material. In an embodiment, a first alignment film is provided on the first surface, in which the alignment direction of the liquid crystal material is determined by rubbing, while no alignment film is provided on the second surface. Therefore, the loss of propagating light can be suppressed compared to a configuration in which an alignment film that causes a non-negligible light loss is provided on both the first surface and the second surface. In another embodiment, the first surface is provided with a first alignment film whose alignment direction is determined by rubbing, while the second surface is provided with a second alignment film whose alignment direction is determined without rubbing. The second alignment film may be an alignment film bonded to the second surface via, for example, a siloxane bond between silicon (Si) and oxygen (O) (see, for example, Patent Document 4). The alignment direction of the second alignment film may be determined, for example, by irradiation with polarized light. The light loss caused by the second alignment film is negligibly small. Therefore, compared with a configuration in which the rubbing alignment film is provided on both the first surface and the second surface, the loss of propagating light can be suppressed. The addition of the second alignment film in addition to the first alignment film can make the alignment direction of the liquid crystal material more uniform. Below, an optical device and a light detection system according to an embodiment of the present disclosure will be briefly described.

[0058] The optical device according to the first item includes a first structure having a first surface, a second structure having a second surface facing the first surface, one or more optical waveguide regions containing a liquid crystal material and located between the first surface of the first structure and the second surface of the second structure, and a first alignment film that is a rubbing alignment film that is provided on the first surface and aligns the liquid crystal material. (A) The second surface contacts the liquid crystal material without any alignment film. Or (B) The optical device further includes a second alignment film that is provided on the second surface and is an alignment film other than a rubbing alignment film and aligns the liquid crystal material.

[0059] In this optical device, the loss of light propagating through the optical waveguide region can be suppressed.

[0060] An optical device according to a second aspect is the optical device according to the first aspect, wherein the second alignment film is a photo-alignment film formed by irradiation with polarized light.

[0061] In this optical device, the alignment direction of the alignment film can be determined without rubbing.

[0062] An optical device according to a third item is the optical device according to the first or second item, wherein the second alignment film is a film including a material bonded to the second surface via a siloxane bond.

[0063] In this optical device, the adhesion and coverage of the second alignment film can be improved by siloxane bonds.

[0064] An optical device according to a fourth aspect is the optical device according to the third aspect, wherein the film is a monolayer.

[0065] In this optical device, the loss of light in the monolayer can be substantially ignored.

[0066] An optical device according to a fifth aspect of the present invention is an optical device according to any one of the first to fourth aspects, wherein the second surface has one or more recesses having a depth of 1 μm or more and 10 μm or less, and the liquid crystal material covers the one or more recesses.

[0067] In this optical device, even if the recess has a depth of 1 μm or more and 10 μm or less, the liquid crystal material can be aligned by the first alignment film.

[0068] An optical device according to a sixth aspect is the optical device according to the fifth aspect, wherein the one or more recesses are a plurality of recesses, and the one or more optical waveguide regions are a plurality of optical waveguide regions, each of which covers a corresponding one of the recesses.

[0069] In this optical device, light can be propagated through a plurality of optical waveguide regions.

[0070] The optical device according to the seventh aspect is the optical device according to any one of the first to sixth aspects, wherein the first surface is a flat surface or an undulating surface having a height difference of less than 1 μm, and the liquid crystal material covers the flat surface or the undulating surface.

[0071] In this optical device, an alignment film whose alignment direction is defined by rubbing can be provided on the first surface having few irregularities.

[0072] An optical device according to an eighth item is an optical device according to any one of the first to seventh items, wherein the first structure includes a first mirror having the first surface, and the second structure includes a second mirror having the second surface.

[0073] In this optical device, light can be propagated to the optical waveguide region by reflection from the first and second mirrors regardless of the critical angle of total reflection.

[0074] An optical device according to a ninth aspect is the optical device according to the eighth aspect, wherein the first mirror and the second mirror are both formed of a dielectric multilayer film.

[0075] In this optical device, the mirror does not contain metal and is made of a dielectric multilayer film, allowing light to be reflected with virtually no loss.

[0076] An optical device according to a tenth aspect is the optical device according to the ninth aspect, wherein the first mirror has a higher light transmittance than the second mirror.

[0077] In this optical device, the light propagating through the optical waveguide region can be emitted to the outside via the first mirror.

[0078] An optical device according to an eleventh aspect is the optical device according to the tenth aspect, wherein the first structure includes a first electrode, and the second structure includes a second electrode facing the first electrode. The one or more optical waveguide regions are located between the first electrode and the second electrode. By changing a voltage applied to the first electrode and the second electrode, a direction of light emitted from the one or more optical waveguide regions through the first structure, or an incident direction of light taken into the one or more optical waveguide regions through the first structure changes.

[0079] In this optical device, by applying a voltage between the first electrode and the second electrode, it is possible to emit light toward an external object located at a specific location and receive light reflected from the object.

[0080] An optical device according to a twelfth item is the optical device according to the first item, further comprising a plurality of phase shifters connected to the one or more optical waveguide regions directly or via other waveguides.

[0081] In this optical device, multiple phase shifters, whether one or more unidirectional optical guiding regions or a single planar optical guiding region, can change the direction of light exiting the optical device or the direction of light entering the optical device.

[0082] An optical device according to a thirteenth aspect is the optical device according to the first aspect, wherein the one or more optical waveguide regions are a plurality of optical waveguide regions, and the optical device further includes a plurality of phase shifters each connected to the plurality of optical waveguide regions directly or via another waveguide.

[0083] In this optical device, the direction of light emitted from the optical device or the direction of light incident on the optical device can be changed by a plurality of phase shifters respectively connected to a plurality of optical waveguides.

[0084] An optical detection system according to a fourteenth item includes an optical device according to any one of the first to thirteenth 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.

[0085] This light detection system is capable of producing a range image.

[0086] 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.

[0087] 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.

[0088] (Embodiment 1) Hereinafter, the optical device according to the first embodiment of the present disclosure will be described with reference to Fig. 6A to Fig. 7C. Fig. 6A is a plan view that shows a schematic configuration of the optical device 100A according to the first embodiment of the present disclosure. Fig. 6B is a view showing a state in which the upper components are removed from Fig. 6A. Figs. 7A, 7B, and 7C are cross-sectional views taken along lines VIIA-VIIA, VIIB-VIIB, and VIIC-VIIC, respectively, of Fig. 6A.

[0089] As shown in FIG. 7A to FIG. 7C, the optical device 100A includes an upper structure 100a, a lower structure 100b, a plurality of optical waveguide regions 20, and an alignment film 22. The optical device 100A can be fabricated, for example, by a process of bonding the upper structure 100a and the lower structure 100b together and injecting a liquid crystal material into the space between them. A part of the space into which the liquid crystal material is injected is the optical waveguide region 20. In this specification, the side where the upper structure 100a is located is referred to as "upper", and the side where the lower structure 100b is located is referred to as "lower". The terms "upper", "lower", "upper", and "lower" do not limit the orientation of the optical device 100A during use, and the optical device 100A may be oriented in any direction.

[0090] In this specification, the upper structure 100a is also referred to as the "first structure 100a," and the lower structure 100b is also referred to as the "second structure 100b." Of the surface of the upper structure 100a, a portion facing the lower structure 100b is referred to as the "first surface." Of the surface of the lower structure 100b, a portion facing the upper structure 100a is referred to as the "second surface." The first surface and the second surface face each other. In the following description, the first surface of the first structure 100a is also referred to as the "lower surface," and the second surface of the second structure 100b is also referred to as the "upper surface."

[0091] The upper structure 100a in this embodiment includes a substrate 50a, an electrode 62a, and a mirror 30. The electrode 62a, the mirror 30, and an alignment film 22 are provided on the substrate 50a in this order.

[0092] The lower structure 100b in this embodiment includes a substrate 50b, an electrode 62b, a mirror 40, a dielectric layer 51, a plurality of partition walls 73, a sealing member 79, and a plurality of optical waveguides 11. An electrode 62b is provided on the substrate 50b. A mirror 40 is provided on the electrode 62b. A reflecting surface 40s of the mirror 40 faces a reflecting surface 30s of the mirror 30. A dielectric layer 51 is provided on the mirror 40. A plurality of partition walls 73, a sealing member 79, and a plurality of optical waveguides 11 are provided on the dielectric layer 51.

[0093] In this embodiment, the multiple optical waveguide regions 20 are located between the reflecting surface 30s of the mirror 30 and the reflecting surface 40s of the mirror 40. In the example shown in FIG. 7C, six optical waveguide regions 20 arranged along the Y direction are formed between multiple partition walls 73. The number of optical waveguide regions 20 is not limited to six, and may be any number equal to or greater than one. The optical waveguide regions 20, a portion of the mirror 30 that overlaps with the optical waveguide region 20 when viewed from the Z direction, and a portion of the mirror 40 that overlaps with the optical waveguide region 20 when viewed from the Z direction form an optical waveguide. The optical waveguide functions as the slow light waveguide described above.

[0094] The alignment film 22 in this embodiment is provided on the reflecting surface 30s of the mirror 30 in the upper structure 100a before the upper structure 100a and the lower structure 100b are bonded together.

[0095] The configuration of the optical device 100A according to this embodiment will be described in detail below.

[0096] Of the substrates 50a and 50b, the substrate on the side from which light is emitted has light-transmitting properties. Both the substrates 50a and 50b may have light-transmitting properties. Similarly, of the electrodes 62a and 62b, the electrode on the side from which light is emitted has light-transmitting properties. Both the electrodes 62a and 62b may have light-transmitting properties. At least one of the electrodes 62a and 62b may be formed of, for example, a transparent electrode. In the example shown in FIG. 6A to FIG. 7C, light is emitted from the optical waveguide 10 through the electrode 62a and the substrate 50a in the upper structure 100a.

[0097] A plurality of partition walls 73 are provided on the dielectric layer 51. The plurality of partition walls 73 are aligned in the Y direction. Each of the plurality of partition walls 73 has a structure extending along the X direction. A portion of the dielectric layer 51 located between the plurality of partition walls 73 when viewed from the Z direction is removed. As a result, a plurality of portions of the reflecting surface 40s of the mirror 40 are exposed. The plurality of exposed portions are aligned in the Y direction. Each of the plurality of exposed portions has a shape extending along the X direction. As shown in FIG. 7C, the portion of the dielectric layer 51 that has not been removed and the partition wall 73 directly above it form a convex portion extending along the X direction. Therefore, a plurality of convex portions aligned in the Y direction are formed on the mirror 40. A plurality of concave portions are formed between the plurality of convex portions. The concave portions also have a structure extending along the X direction. The depth of each concave portion, i.e., the height of the convex portions on both sides of each concave portion, can be, for example, 1 μm or more and 10 μm or less. Here, the depth of the concave portion and the height of the convex portion mean the respective dimensions measured along the Z direction in the figure. In this embodiment, a plurality of recesses are formed by the dielectric layer 51 and the plurality of partition walls 73, and these recesses define a plurality of optical waveguide regions 20. When the number of recesses is one, a single optical waveguide region 20 is formed within the recess.

[0098] The optical waveguide regions 20 are defined in a region where the recesses are located when viewed from the Z direction. The optical waveguide region 20 is surrounded by the reflecting surface 30s of the mirror 30, the reflecting surface 40s of the mirror 40, and two adjacent protrusions. The optical waveguide region 20 includes a dielectric member 21. In this embodiment, the dielectric member 21 is made of a liquid crystal material.

[0099] The refractive index of the optical waveguide region 20 is higher than the refractive index of the partition wall 73 and the dielectric layer 51. The light propagating in the optical waveguide region 20 does not leak to the convex portions located on both sides of the optical waveguide region 20. This is because the light propagating in the optical waveguide region 20 is totally reflected at the interface between the optical waveguide region 20 and the convex portions. The region where the convex portions exist can be called a "non-waveguide region". A plurality of optical waveguide regions 20 and a plurality of non-waveguide regions are alternately arranged in the Y direction between the mirror 30 and the mirror 40. This configuration corresponds to a plurality of optical waveguides 10 arranged in the Y direction. The mirror 30 is located between the region where the plurality of optical waveguide regions 20 and a plurality of non-waveguide regions are alternately arranged in the Y direction and the substrate 50a. The mirror 40 is located between the region where the plurality of optical waveguide regions 20 and a plurality of non-waveguide regions are alternately arranged in the Y direction and the substrate 50b.

[0100] The electrodes 62a and 62b face each other and indirectly sandwich the dielectric member 21. "Indirectly sandwiched" means sandwiched via another member. In this embodiment, the mirror 30, the alignment film 22, and the mirror 40 are disposed between the electrodes 62a and 62b. The positional relationship between the electrode 62a and the mirror 30 may be reversed. In that case, the alignment film 22 may be formed on the surface of the electrode 62a. Similarly, the positional relationship between the electrode 62b and the mirror 40 may be reversed. The refractive index of the dielectric member 21 can be adjusted by adjusting the voltage applied to the electrodes 62a and 62b. The emission angle of the light emitted to the outside from the optical waveguide 10 changes by changing the voltage.

[0101] The seal member 79 fixes the gap between the upper structure 100a and the lower structure 100b. As shown in FIG. 6B, the seal member 79 surrounds the multiple optical waveguides 10 and the multiple partition walls 73 when viewed from the Z direction. The seal member 79 includes a portion extending along the Y direction and a portion extending along the X direction from both sides of the portion. The seal member 79 is disposed on the dielectric layer 51, and the portion extending along the Y direction is provided so as to straddle the multiple optical waveguides 11. The upper surface of the seal member 79 is parallel to the XY plane. The size in the Z direction of the portion of the seal member 79 located directly above the dielectric layer 51 is equal to or larger than the total thickness (i.e., the dimension in the Z direction) of the partition walls 73, the mirror 30, and the alignment film 22. The seal member 79 may be formed of, for example, an ultraviolet curing resin or a thermosetting resin. The material of the sealing member 79 does not need to be an ultraviolet curing resin or a thermosetting resin as long as it is a material that can maintain the gap between the substrates 50a and 50b for a long period of time. The liquid crystal material that constitutes the dielectric member 21 can be injected into the space surrounded by the sealing member 79 by, for example, vacuum injection. By injecting the liquid crystal material into the space, it is possible to prevent vacuum leakage when injecting the liquid crystal material.

[0102] The optical waveguides 11 are connected to the optical waveguide regions 20, respectively. Light is supplied from the optical waveguides 11 to the optical waveguide regions 20. In the examples shown in FIG. 6A to FIG. 7C, the optical waveguides 11 are located on the dielectric layer 51. The dielectric layer 51 is located between the substrate 50b and the optical waveguides 11. By adjusting the size of the dielectric layer 51 in the Z direction, the light propagating through the optical waveguides 11 can be efficiently coupled to the optical waveguides 10. The size of the dielectric layer 51 in the Z direction can be adjusted, for example, so that the optical waveguides 11 are located near the center of the optical waveguide regions 20 in the Z direction. The optical waveguides 11 are waveguides that propagate light by total reflection. Therefore, the refractive index of the optical waveguides 11 is higher than the refractive index of the dielectric layer 51. The optical waveguides 11 may be slow light waveguides.

[0103] Each of the optical waveguides 11 includes a portion located between two adjacent partitions of the partitions 73. As shown in FIG. 6B and FIG. 7A, each of the optical waveguides 11 may include a grating 15 having a periodic structure along the X direction in the portion. The propagation constant of the optical waveguide 11 is different from that of the optical waveguide 10. The grating 15 shifts the propagation constant of the optical waveguide 11 by the reciprocal lattice of the periodic structure. The reciprocal lattice of the periodic structure is a value obtained by multiplying the reciprocal of the period by 2π. If the propagation constant of the optical waveguide 11 shifted by the reciprocal lattice matches the propagation constant of the optical waveguide 10, the light propagating through the optical waveguide 11 is efficiently coupled to the optical waveguide 10.

[0104] After upper structure 100a and lower structure 100b are bonded together, liquid crystal material is injected through injection opening 79o shown in Fig. 6B. After the liquid crystal material is injected, injection opening 79o is closed with the same material as sealing member 79. The area sealed in this manner is entirely filled with liquid crystal material.

[0105] The alignment film 22 is a rubbing alignment film whose alignment direction is determined by rubbing. In rubbing, the alignment film is rubbed in a predetermined direction with a roll wrapped with nylon cloth, thereby determining the alignment direction of the alignment film. The alignment film 22 is provided on the reflecting surface 30s of the mirror 30 included in the lower surface of the upper structure 100a. The upper surface of the lower structure 100b is in contact with the dielectric member 21 without any alignment film. The reflecting surface 30s of the mirror 30 is a flat surface or an uneven surface having a height difference of less than 1 μm. The dielectric member 21 covers the flat surface or the uneven surface. With an alignment film provided on such a surface, the alignment direction can be uniformly determined by rubbing. The rubbing alignment film has a higher alignment control power than the photoalignment film described later. Therefore, the liquid crystal material can be effectively aligned just by providing the rubbing alignment film on the reflecting surface 30s of the mirror 30.

[0106] In the optical device 100A according to this embodiment, the alignment film 22 is provided on the reflecting surface 30s of the mirror 30, but not on the reflecting surface 40s of the mirror 40. Therefore, even if light propagates through the optical waveguide 10 while being multiple-reflected by the reflecting surfaces 30s and 40s, the loss of propagating light can be reduced to about half compared to a configuration in which rubbed alignment films are provided on the upper and lower reflecting surfaces.

[0107] Specific examples of materials and sizes of components used in fabricating the optical device 100A according to this embodiment will be described below. Hereinafter, the size in the Z direction will also be referred to as "thickness."

[0108] First, specific examples of materials and sizes of the components of the upper structure 100a will be described.

[0109] The substrate 50a may be formed of, for example, a SiO2 layer. The sizes of the substrate 50b in the X and Y directions may be, for example, 8 mm and 20 mm, respectively, and the thickness of the substrate 50a may be, for example, 0.7 mm.

[0110] The electrode 62a may be formed, for example, from an ITO sputtered layer, and may have a thickness of, for example, 50 nm.

[0111] The mirror 30 may be a multilayer reflective film. The multilayer reflective film may be formed by alternately depositing and stacking Nb2O5 layers and SiO2 layers. The Nb2O5 layer has a refractive index n=2.282. The thickness of the Nb2O5 layer may be, for example, about 100 nm. The SiO2 layer has a refractive index n=1.468. The thickness of the SiO2 layer may be, for example, about 200 nm. The mirror 30 has, for example, seven Nb2O5 layers and six SiO2 layers, for a total of 13 layers. The thickness of the mirror 30 may be, for example, 1.9 μm.

[0112] Next, examples of materials and sizes of the components of the lower structure 100b will be described.

[0113] The substrate 50b may be formed of, for example, a SiO2 layer. The size of the substrate 50b in the X-direction and the Y-direction may both be, for example, 15 mm. The thickness of the substrate 50b may be, for example, 0.7 mm.

[0114] The electrode 62b may be formed, for example, from an ITO sputtered layer, and may have a thickness of, for example, 50 nm.

[0115] The mirror 40 may be a multilayer reflective film. The multilayer reflective film may be formed by alternately depositing and stacking, for example, Nb2O5 layers and SiO2 layers. The Nb2O5 layer has a refractive index n=2.282. The thickness of the Nb2O5 layer may be, for example, about 100 nm. The SiO2 layer has a refractive index n=1.468. The thickness of the SiO2 layer may be, for example, about 200 nm. The mirror 40 has, for example, 31 Nb2O5 layers and 30 SiO2 layers, for a total of 61 layers. The thickness of the mirror 40 may be, for example, 9.1 μm.

[0116] The dielectric layer 51 may be formed of, for example, a SiO2 vapor-deposited layer. The SiO2 vapor-deposited layer has a refractive index n=1.468. The thickness of the SiO2 vapor-deposited layer may be, for example, about 1.0 μm.

[0117] The optical waveguide 11 may be formed, for example, from a Nb2O5 vapor deposition layer. The Nb2O5 vapor deposition layer has a refractive index n=2.282. The thickness of the Nb2O5 vapor deposition layer may be, for example, about 300 nm. The optical waveguide 11 may have a grating 15 and a grating 13 formed therein. The grating 15 may have, for example, a duty ratio of 1:1 and a pitch of 640 nm. The grating 13 may have, for example, a duty ratio of 1:1 and a pitch of 680 nm. The grating 15 and the grating 13 may be formed by patterning using a photolithography method. The size of the optical waveguide 11 in the Y direction may be, for example, 10 μm.

[0118] The partition wall 73 may be formed of a SiO2 deposition layer. The SiO2 deposition layer has a refractive index n=1.468. The thickness of the SiO2 deposition layer may be, for example, 1.0 μm. The size of the partition wall 73 in the Y direction may be, for example, 50 μm.

[0119] In the optical waveguide region 20, a portion of the dielectric layer 51 may be removed by patterning using, for example, a photolithography method. The thickness of the optical waveguide region 20 may be, for example, 2.0 μm. The size of the optical waveguide region 20 in the Y direction may be, for example, 10 μm.

[0120] The dielectric member 21 may be made of, for example, 5CB liquid crystal. The alignment film 22 may be made of, for example, polyimide. The thickness of the polyimide alignment film may be, for example, about 80 nm, and the thickness variation may be 0 nm or more and 150 nm or less. The polyimide alignment film is thick and the thickness is non-uniform. When light is incident on such a polyimide alignment film, absorption and scattering of the light occurs. The polyimide alignment film may be formed by applying an alignment material of a polyimide solution to the reflecting surface 30s of the mirror 30, and drying and hardening the applied material. Depending on the formation method, the polyimide alignment film may also be provided on the surface of the upper structure 100a other than the reflecting surface 30s of the mirror 30. Since the polyimide alignment film functions as an insulator, at least a part of the electrode 62a is exposed for electrical conduction without being covered by the polyimide alignment film.

[0121] For example, an ultraviolet curing adhesive 3026E manufactured by ThreeBond may be used for the seal member 79. In one example, the wavelength is 365 nm and the energy density is 100 mJ / cm 2 The seal member 79 is cured by irradiation with ultraviolet light, and the upper structure 100a and the lower structure 100b, on which the alignment film 22 is provided, are bonded together. Through this bonding, the optical device 100A according to this embodiment is obtained.

[0122] The substrates 50a and 50b may be made of a material other than SiO2. The substrates 50a and 50b may be, for example, inorganic substrates such as glass or sapphire, or resin substrates such as acrylic or polycarbonate. These inorganic substrates and resin substrates have light transmissivity and can be used as the substrates 50a and 50b.

[0123] The reflectance of the mirror 30 from which light is emitted is, for example, 99.9%, and the reflectance of the mirror 40 from which light is not emitted is, for example, 99.99%. This condition can be realized by adjusting the number of layers in the multilayer reflective film. As a combination of two layers in the multilayer reflective film, for example, one layer has a refractive index of 2 or more, and the other layer has a refractive index of less than 2. If the difference between the two refractive indices is large, a high reflectance can be obtained. The layer with a refractive index of 2 or more is, for example, SiN x , AlN x , TiO x , ZrO x (1.7≦x≦2.0), NbO y , and TaO y (2.2≦y≦2.5). The layer having a refractive index of less than 2 is, for example, SiO x and AlO x The present invention is formed from at least one selected from the group consisting of:

[0124] The refractive index of the dielectric layer 51 may be, for example, less than 2. The refractive index of each optical waveguide 11 may be, for example, greater than or equal to 2. If the difference between the two refractive indices is sufficiently large, the evanescent light leaking from each optical waveguide 11 into the dielectric layer 51 can be reduced.

[0125] (Embodiment 2) Next, an optical device according to embodiment 2 of the present disclosure will be described with reference to Figs. 8A to 8C. The optical device of this embodiment differs from the optical device of embodiment 1 in that an alignment film is provided not only on the surface of the first structure 100a but also on the surface of the second structure 100b. However, unlike the alignment film provided on the surface of the first structure 100a, the alignment film provided on the surface of the second structure 100b is formed by a method other than rubbing. Hereinafter, the optical device of this embodiment will be described, focusing on the differences from embodiment 1.

[0126] 8A to 8C are cross-sectional views that are schematic diagrams of an example of an optical device 100B according to this embodiment. FIG. 8A to FIG. 8C correspond to FIG. 7A to FIG. 7C, respectively. That is, FIG. 8A to FIG. 8C are cross-sectional views along the lines VIIA-VIIA, VIIB-VIIB, and VIIC-VIIC in FIG. 6A, respectively. The structure of the optical device 100B seen from the Z direction is the same as that shown in FIG. 6A, except that an alignment film is also provided on the surface of the lower structure 100b. In the example shown in FIG. 8A to FIG. 8C, the upper structure 100a includes a first alignment film 22a having the same structure as the alignment film 22 described above. On the other hand, the lower structure 100b includes a second alignment film 22b formed by a method other than rubbing. The second alignment film 22b is provided on the upper surface, the lower surface, and the side surface of the lower structure 100b. More specifically, the second alignment film 22b is provided on the surfaces of the substrate 50b, the mirror 40, the dielectric layer 51, the partition wall 73, the sealing member 79, and the optical waveguide 11 that would be exposed if the second alignment film 22b were not present.

[0127] The second alignment film 22b in this embodiment is an alignment film other than a rubbed alignment film. The alignment film 22b may be, for example, a photo-alignment film in which the alignment direction is determined by irradiation with polarized light. The second alignment film 22b may be, for example, a film bonded to the surface of the second structure 100b via a siloxane bond, more specifically, a monomolecular alignment film. The siloxane bond improves the adhesion and coverage of the monomolecular film. The monomolecular alignment film can be produced at low cost. In the example shown in FIG. 8A to FIG. 8C, for the convenience of producing the optical device 100B, the second alignment film 22b is also provided on the surface of the lower structure 100b other than the reflecting surface 40s of the mirror 40. However, the second alignment film 22b does not necessarily have to be provided on the surface of the lower structure 100b other than the reflecting surface 40s of the mirror 40.

[0128] As described above, the upper surface of the lower structure 100b has a plurality of recesses having a depth of 1 μm or more and 10 μm or less. The dielectric member 21 covers the plurality of recesses. It is not easy to form a rubbing alignment film that aligns the liquid crystal material in a specific direction on the surface of the second structure 100b having such a plurality of recesses. The protrusions located on both sides of each recess may hinder rubbing, causing unevenness in the alignment direction. Furthermore, the protrusions may be destroyed by rubbing, which may impair the function of the optical waveguide region 20 as a waveguide. In contrast, when the second alignment film 22b is formed by irradiating polarized light, the alignment film 22b that aligns the liquid crystal material in a specific direction can be easily formed. It is desirable that the protrusions do not have a shape that blocks the irradiation of polarized light to the alignment film. Such a shape may be, for example, an inverse tapered shape that becomes wider as it moves away from the reflecting surface 40s of the mirror 40.

[0129] The monomolecular alignment film has a thin and uniform thickness compared to the polyimide alignment film. The thickness of the monomolecular alignment film is about 2 nm, which is the molecular size. Even if light is incident on such a monomolecular alignment film, the light is hardly absorbed or scattered. Therefore, even if the light is multiple-reflected and propagates in the optical waveguide region 20 along the X direction as shown in FIG. 2, the light is hardly absorbed or scattered by the monomolecular alignment film. As a result, the loss of propagating light can be suppressed.

[0130] Since the second alignment film 22b is thin and does not function as an insulating film, there is no problem if the second alignment film 22b provided on the surfaces other than the reflecting surface 40s of the mirror 40 is left. Therefore, in the production of the optical device 100B, the step of removing the second alignment film 22b can be omitted. Depending on the application, the alignment film 22 provided on the surfaces other than the reflecting surface 40s of the mirror 40 may be removed.

[0131] Next, specific examples of materials for the second alignment film 22b and methods for providing the second alignment film 22b will be described with reference to Figures 9A to 9E. Figures 9A to 9E are diagrams for explaining examples of the second alignment film 22b in the second embodiment.

[0132] Fig. 9A shows a schematic diagram of a state in which the lower structure 100b is immersed in a solution 23 containing at least a silane-based compound. As shown in Fig. 9A, the solution 23 containing at least a silane-based compound is brought into contact with the lower structure 100b, and the silane-based compound is chemically adsorbed to form a film bonded via siloxane bonds. In the molecule 23m shown in Fig. 9A, the elliptical portion 23m1 represents a siloxane bond, the thin and long portion 23m2 represents a carbon-hydrogen bond, and the thick and short portion 23m3 represents a bond other than those.

[0133] 9B, the excess silane compound that is not chemically adsorbed is dissolved and removed in a cleaning solution 24, and the film becomes a monomolecular film 22b0 bonded via siloxane bonds. This monomolecular film 22b0 functions as the second alignment film 22b described above.

[0134] The orientation direction of the monolayer 22b0 is determined as follows. The monolayer 22b0 can be oriented by draining off the cleaning solution 24, as shown in Fig. 9B. The upward arrow indicates the direction in which the lower structure 100b is pulled up, and the downward arrow indicates the orientation direction.

[0135] Alternatively, when the monolayer 22b0 bonded via siloxane bonds has a photosensitive group, as shown in FIG. 9C, the monolayer 22b0 is irradiated with polarized light 26p obtained by passing unpolarized ultraviolet light 26 through a polarizer 25, thereby crosslinking or polymerizing the photosensitive group as shown in FIG. 9D. The thick lines in FIG. 9D represent crosslinking. As a result of irradiation with polarized light 26p, the monolayer 22b0 becomes a monolayer alignment film having uniform alignment anisotropy with respect to the liquid crystal. It is to be noted that a monolayer alignment film exhibiting alignment anisotropy can also be obtained by rubbing the surface of the monolayer bonded via siloxane bonds.

[0136] Whether the alignment film has been subjected to the alignment treatment by draining or polarized light irradiation or by rubbing can be determined by whether the alignment film has scratches. Draining or polarized light irradiation does not scratch the alignment film. On the other hand, rubbing does scratch the alignment film.

[0137] As shown in FIG. 9E, the liquid crystal material 21 composed of rod-shaped molecules is aligned in a specific direction by the monomolecular alignment film 22b0.

[0138] The solution 23 containing the silane-based compound is a solution in which the silane-based compound is dissolved in a solvent. A part of the silane-based compound may be undissolved. A typical example of such a solution is a supersaturated solution.

[0139] The following (1) to (5) are specific examples of silane compounds that can be used in the above-mentioned method for producing the second alignment film 22b. (1)SiY p Cl 3-p (2)CH3-(CH2) r SiY q Cl 3-q (3) CH3 (CH2) s O(CH2) t SiY q Cl 3-q (4) CH3 (CH2) u -Si(CH3)2(CH2) v -SiYq Cl 3-q (5)CF3COO(CH2) w SiY q Cl 3-q

[0140] Here, p is an integer from 0 to 3, q ​​is an integer from 0 to 2, r is an integer from 1 to 25, s is an integer from 0 to 12, t is an integer from 1 to 20, u is an integer from 0 to 12, v is an integer from 1 to 20, and w is an integer from 1 to 25. Y represents one selected from the group consisting of hydrogen, an alkyl group, an alkoxyl group, a fluorine-containing alkyl group, and a fluorine-containing alkoxy group.

[0141] Further, specific examples of trichlorosilane-based compounds are given below in (6) to (14). (6)CF3(CH2)9SiCl3 (7)CH3(CH2)9OSiCl3 (8)CH3(CH2)9Si(CH3)2(CH2) 10 SiCl3 (9)CH3COO(CH2) 15 SiCl3 (10)CF3(CF2)7-(CH2)2-SiCl3 (11)CF3(CF2)7-C6H4-SiCl3 (12)C6H5-CH=CH-CO-O-(CH2)6-O-SiCl3 (13)C6H5-CO-CH=CH-C6H4-O-(CH2)6-O-SiCl3 (14)C6H5-CH=CH-CO-C6H4-O-(CH2)6-O-SiCl3

[0142] Compound (12) has a photosensitive cinnamoyl group. Compounds (13) and (14) also have a photosensitive chalconyl group. The photosensitive group is polymerized by irradiation with ultraviolet light. Furthermore, instead of the above chlorosilane-based compounds, isocyanate-based silane compounds in which the chlorosilyl group is replaced with an isocyanate group, or alkoxy-based silane compounds in which the chlorosilyl group is replaced with an alkoxy group may be used.

[0143] For example, instead of the chlorosilane (6), the following isocyanate-based silane compound (15) or alkoxy-based silane compound (16) can be used. (15)CH3(CH2)9Si(OC2H5)3 (16)CH3(CH2)9Si(NCO)3

[0144] When an isocyanate-based silane compound or an alkoxy-based silane compound is used, hydrochloric acid is not generated during chemical bonding, which has the advantage that the equipment is not damaged and the work is easy.

[0145] Next, a process for forming a thin film on the surface of a substrate using a silane compound, as well as examples of a solvent and a substrate used in the process, will be described.

[0146] The following chemical formula (1) shows the reaction steps when a silane compound, CF3-(CF2)7-(CH2)2-SiCl3 shown as compound (10), is brought into contact with a glass substrate. [ka]

[0147] The first dehydrochlorination reaction shown in chemical formula (1) is a chemical adsorption reaction. When a silane compound solution is brought into contact with a glass substrate having OH groups, a dehydrochlorination reaction occurs. This reaction causes one end of the silane compound molecule to chemically bond to the OH group on the substrate surface. This reaction is a reaction between the SiCl group of the silane compound and the OH group. If the silane compound solution contains a lot of water, the reaction with the substrate is inhibited. Therefore, to ensure that the reaction proceeds smoothly, it is desirable to use a non-aqueous solvent that does not contain active hydrogen such as OH groups, and to carry out the reaction in an atmosphere with low humidity. Details of the humidity conditions will be described later. After that, through H2O hydrolysis and drying / dehydration, a film bonded via siloxane bonds is formed on the surface of the glass substrate.

[0148] Examples of the solvent for the silane compound that can be used in this embodiment include at least one selected from the group consisting of water-free hydrocarbon solvents, fluorocarbon solvents, and silicone solvents. Examples of the petroleum solvent that can be used in this embodiment include at least one selected from the group consisting of petroleum naphtha, solvent naphtha, petroleum ether, petroleum benzine, isoparaffin, normal paraffin, decalin, industrial gasoline, kerosene, ligroin, dimethyl millicorn, phenyl silicone, alkyl modified silicone, and polyester silicone. Examples of the fluorocarbon solvent that can be used in this embodiment include at least one selected from the group consisting of fluorocarbon solvents, Fluorinert (a product of 3M Co., Ltd.), and Afluid (a product of Asahi Glass Co., Ltd.). These solvents may be used alone or in combination of two or more compatible solvents.

[0149] In particular, silicone has only a small amount of moisture and is not easily hygroscopic. Furthermore, silicone acts to solvate with chlorosilane compounds and prevent the chlorosilane compounds from coming into direct contact with moisture. Therefore, when a solution consisting of a chlorosilane compound and silicone is brought into contact with the underlayer, the chlorosilane compounds can be chemically adsorbed to the OH groups exposed on the underlayer while preventing adverse effects of moisture in the surrounding atmosphere.

[0150] Considering the provision of the second alignment film 22b, the optical waveguide 11, the mirrors 30 and 40, the dielectric layer 51, and the partition wall 73 in the optical device 100B may be made of, for example, the following materials. x , AlN x , TiO x , ZrO x , NbO y , and TaO y Among the materials, the material having a refractive index of less than 2 is SiO x and AlO xThe material is at least one selected from the group consisting of: The material can secure a large number of OH groups, which are adsorption sites for silane compounds. Therefore, an alignment film having excellent alignment properties can be formed on the surface of the material.

[0151] On the other hand, the electrode 62b in the optical device 100B may be made of at least one conductive material selected from the group consisting of ITO and Al. The seal member 79 in the optical device 100B may be made of a polymer material such as an acrylic or silicone material. These conductive and polymer materials have few OH groups, which are adsorption sites for silane compounds. For this reason, when an alignment film is also formed on the surface of these materials, the surface is subjected to a hydrophilic treatment that generates or increases OH groups. As the hydrophilic treatment, a SiO2 film or SiN x It is effective to provide a film or to generate OH groups on the surface by UV-O3 treatment.

[0152] Examples of the cleaning method in this embodiment include immersion and steam cleaning. In particular, steam cleaning can strongly remove excess silane compounds that are not chemically adsorbed on the entire surface of the lower structure 100b by the penetration force of steam. Examples of cleaning solvents that can be used in this embodiment include at least one selected from the group consisting of water-free hydrocarbon solvents, fluorocarbon solvents, and silicone solvents. Examples of petroleum-based cleaning solvents that can be used in this embodiment include at least one selected from the group consisting of petroleum naphtha, solvent naphtha, petroleum ether, petroleum benzine, isoparaffin, normal paraffin, decalin, industrial gasoline, kerosene, ligroin, dimethyl millicorn, phenyl silicone, alkyl-modified silicone, and polyester silicone. Examples of fluorocarbon-based solvents that can be used in this embodiment include at least one selected from the group consisting of fluorocarbon solvents, Fluorinert (a product of 3M Co., Ltd.), and Afluid (a product of Asahi Glass Co., Ltd.). These solvents and solvents may be used alone or in combination of two or more compatible types.

[0153] As an orientation method by draining, there is a method in which the surface of the lower structure 100b is held in the vertical direction and the cleaning liquid is drained off, as shown in FIG. 9B. This allows the cleaning liquid to be drained only in the vertical direction. In particular, when a cleaning liquid with a boiling point of 200° C. or less is drained off, the method has excellent drying properties after draining. Furthermore, chloroform is excellent at removing chlorosilane polymers generated by the reaction between chlorosilane and water.

[0154] As an orientation method by liquid drainage, there is a method in which the cleaning liquid is drained by blowing gas onto the surface of the lower structure 100b. This allows the cleaning liquid to be drained in a short time only in the direction in which the gas is blown. In particular, when a cleaning liquid with a boiling point of 150°C or higher is drained, the cleaning liquid does not evaporate even when the gas is blown. Furthermore, N-methyl-2-pyrrolidinone is excellent at removing chlorosilane polymers generated by the reaction between chlorosilane and water.

[0155] In the alignment by irradiation with polarized light applicable to this embodiment, the polarized ultraviolet light to be irradiated may have a wavelength distribution of, for example, 300 nm to 400 nm. The irradiation amount is, for example, about 50 mJ / cm at 365 nm. 2 More than about 2000mJ / cm 2 In particular, 1000 mJ / cm 2 At doses of 100 mJ / cm2 or more, the alignment of the liquid crystal material tends to be homogeneous. Conversely, at doses of less than 100 mJ / cm2, the alignment of the liquid crystal material tends to be pretilt.

[0156] (Example) Next, the effect of reducing the deviation in the alignment direction of the liquid crystal material contained in the dielectric member 21 in the first and second embodiments will be described. The deviation in the alignment direction of the liquid crystal material can be known by measuring the retardation of the liquid crystal cell. Due to optical anisotropy, the liquid crystal material has a fast axis along which the phase of light advances and a slow axis along which the phase of light delays. The deviation in the alignment direction of the liquid crystal material is determined by the angle between the direction of the alignment treatment and the slow axis direction of the liquid crystal material. As a comparative example, in a configuration in which a monomolecular alignment film having siloxane bonds is provided on the reflecting surface 30s of the mirror 30 and no alignment film is provided on the upper surface of the lower structure 100b, the alignment direction of the liquid crystal material is deviated by 0.5 degrees from the desired direction. In contrast, in the optical device 100A according to the first embodiment, the alignment film 22, which is a polyimide alignment film (i.e., a rubbing alignment film), reduces the deviation in the alignment direction of the liquid crystal material to 0.1 degrees. This is because the polyimide alignment film has a higher alignment regulating force than the monomolecular alignment film. In the optical device 100B according to the second embodiment, the deviation in the alignment direction of the liquid crystal material was reduced to 0.05 degrees by the first alignment film 22a, which is a polyimide alignment film, and the second alignment film 22b, which is a photo-alignment film. It was confirmed that the alignment direction of the liquid crystal material 21 can be more uniformly aligned by adding a photo-alignment film in addition to the polyimide alignment film.

[0157] Next, with reference to Figs. 10A and 10B, the effect of improving the loss of light emitted from the optical device 100A according to the first embodiment and the optical device 100B according to the second embodiment will be described. Fig. 10A is a diagram showing a schematic diagram of the manner in which light is emitted from the optical device 100A according to the first embodiment. Fig. 10B is a diagram showing a schematic diagram of the manner in which light is emitted from the optical device 100B according to the second embodiment. In the example shown in Figs. 10A and 10B, the intensity of light emitted from the optical device 100A and the optical device 100B was measured by a photodetector (not shown) fixed in the direction of an emission angle θ = 60°. In this measurement, a 589 nm laser light was input to each optical waveguide 11 via the grating 13. The loss of the emitted light was calculated based on the intensity of light emitted from a configuration without an alignment film.

[0158] In a comparative example, in a configuration in which a polyimide alignment film was provided on the reflecting surface 30s of the mirror 30 and the upper surface of the lower structure 100b, the loss of emitted light was about 50%. In contrast, in the example shown in Fig. 10A, the loss of emitted light was reduced to about 25%. In the example shown in Fig. 10B, the loss of emitted light was also about 25%.

[0159] Polyimide alignment films are often used in liquid crystal displays. In liquid crystal displays, light passes through the alignment films on the top and bottom substrates only once. Therefore, even if the polyimide alignment film is thick and non-uniform in thickness, light loss due to absorption and scattering in the alignment film is not a significant problem with a single pass.

[0160] On the other hand, in the optical device 100A according to the first embodiment and the optical device 100B according to the second embodiment, as described above, the light propagates through the optical waveguide region 20 while being multiple-reflected by the reflecting surface 30s of the mirror 30 and the reflecting surface 40s of the mirror 40. Therefore, in a configuration in which both are provided with a polyimide alignment film, the light loss due to absorption and scattering in the alignment film cannot be ignored. To solve this problem, the optical device 100A according to the first embodiment and the optical device 100B according to the second embodiment adopt a structure in which a polyimide alignment film is provided on the reflecting surface 30s of the mirror 30 and a polyimide alignment film is not provided on the upper surface of the lower structure 100b. With such a structure, the light loss can be reduced to about half. In particular, in the optical device 100B according to the second embodiment, the second alignment film 22b, which is an optical alignment film, can more uniformly align the alignment direction of the liquid crystal material 21 without substantially causing light loss in the second alignment film 22b.

[0161] (Modification) In the optical device 100A according to the first embodiment and the optical device 100B according to the second embodiment, a plurality of optical waveguide regions 20 arranged in the Y direction are provided. However, providing a plurality of optical waveguide regions 20 is not an essential requirement, and one optical waveguide region 20 may be provided. Such an optical waveguide region 20 may be, for example, one planar optical waveguide. Below, a modified example of the optical device 100B according to the second embodiment will be described with reference to Figs. 11A to 12C. The modified example described below can also be applied to the optical device 100A according to the first embodiment. The only difference between the optical device 100B according to the second embodiment and the optical device 100A according to the first embodiment is the presence or absence of the second alignment film 22b. Fig. 11A is a diagram that illustrates an example of an optical device 110 according to this modified example when viewed from the Z direction. However, in Fig. 11A, the second alignment film 22b is omitted. Fig. 11B is a diagram illustrating a state in which the upper structure 100a is removed from the structure shown in Fig. 11A. 12A, 12B, and 12C are cross-sectional views taken along lines XIIA-XIIA, XIIB-XIIB, and XIIC-XIIC, respectively, of FIG. 11A.

[0162] The upper structure 110a in this modification has the same structure as the upper structure 100a in the second embodiment. In contrast, the lower structure 110b in this modification is different from the lower structure 100b in the second embodiment in that, as shown in FIG. 11B, two partition walls 73 are arranged on both sides of one optical waveguide region 20. As shown in FIGS. 12A to 12C, the lower structure 100b has a relatively wide recess. With this structure, the reflecting surface 40s of the mirror 40 is exposed over a relatively wide range extending along the X direction and the Y direction. As shown in FIG. 12C, the recess is located between two protruding portions extending in the X direction. In this example, a planar optical waveguide is formed by the reflecting surface 30s of the mirror 30, the reflecting surface 40s of the mirror 40, and one optical waveguide region 20 extending along the X direction and the Y direction located between them. The optical waveguide region 20 is surrounded by two convex portions formed by the reflecting surface 30s of the mirror 30, the reflecting surface 40s of the mirror 40, and the partition wall 73. The optical waveguide region 20 is filled with a dielectric member 21 containing a liquid crystal material.

[0163] 11B, the multiple optical waveguides 11 are connected to an optical waveguide region 20 in the planar optical waveguide 10. Light propagating through the multiple optical waveguides 11 is coupled to the optical waveguide region 20. The coupled light interferes in the optical waveguide region 20 to form a light beam. The light beam formed in the optical waveguide region 20 is emitted to the outside via the mirror 30, the electrode 62a, and the substrate 50a. The optical device 110 according to the modified example can also change the X-direction component and the Y-direction component of the wave vector of the emitted light.

[0164] In this example, when the second alignment film 22b is formed by rubbing, good alignment performance cannot be achieved, especially at the step portion, due to the influence of the step portion at the edge of the recess. To solve this problem, the second alignment film 22b is formed by a method other than rubbing, such as irradiation with polarized light. This makes it possible to form the second alignment film 22b with good alignment performance even at the step portion.

[0165] In the first and second embodiments, the examples, and the modified examples, the optical waveguide 10 is a slow-light waveguide. However, the optical waveguide 10 does not need to be a slow-light waveguide. The optical waveguide 10 may be, for example, an optical waveguide that does not include the mirror 30 and the mirror 40 and propagates light in the optical waveguide region 20 by total reflection at the surfaces of the substrates 50a and 50b. The light propagating in the optical waveguide may be emitted to the outside, for example, from the end of the optical waveguide 10, rather than via the substrate 50a or the substrate 50b.

[0166] In the first and second embodiments, examples, and modified examples, the alignment films 22, 22a, and 22b are functional films that align the liquid crystal material contained in the dielectric member 21 in a specific direction. Instead of or in addition to these alignment films, various functional films may be provided according to other purposes or applications. For example, a functional film having at least one of the properties of heat resistance, scratch resistance, adhesiveness, translucency, light blocking, flexibility, rigidity, conductivity, and insulation may be provided. The dielectric member 21 is not limited to a liquid crystal material, and may include a material suitable for the performance of the functional film.

[0167] (Application example) <Application to optical scanning devices> FIG. 13 is a diagram showing a configuration example of an optical scanning device 100 in which elements such as an optical splitter 90, a waveguide array 10A, a phase shifter array 80A, and a light source 130 are integrated on a circuit board (for example, a chip). The optical scanning device 100 includes the optical devices according to the first and second embodiments and modified examples. 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 multiple phase shifters. In the example shown in FIG. 13, an electrode 62A and multiple electrodes 62B are provided on the chip. A control signal is supplied to the waveguide array 10A from the electrode 62A. A control signal is sent to each of the multiple phase shifters 80 in the phase shifter array 80A from the multiple electrodes 62B. The electrode 62A and the multiple 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. 13, or may be provided on another chip in the optical scanning device 100.

[0168] By integrating all the components on a chip as shown in Fig. 13, wide-range optical scanning can be achieved with a small device. For example, all the components shown in Fig. 13 can be integrated on a chip of about 2 mm × 1 mm.

[0169] 14 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 flight time of light by irradiating a laser and observing the reflected light from an object, thereby determining the distance.

[0170] FIG. 15 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 indicating 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.

[0171] 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.

[0172] 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.

[0173] <Application to optical receiving device> The optical scanning device or the optical 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 waveguide array 10A as the optical scanning device, and a first adjustment element that adjusts the direction of receivable light. Each first mirror 30 of the waveguide array 10A transmits light incident on the opposite side of the first reflecting surface from the third direction. Each optical waveguide layer 20 of the waveguide array 10A propagates light transmitted through the first mirror 30 in the second direction. The first adjustment element changes at least one of the refractive index and thickness of the optical waveguide layer 20 in each waveguide element 10, and the wavelength of light, thereby changing the direction of receivable light taken into each optical waveguide layer 20. Furthermore, when the optical receiving device includes a plurality of phase shifters 80, or 80a and 80b, identical to those in the optical scanning device, and a second adjustment element that changes the phase difference between the light output from the plurality of waveguide elements 10 after passing through the plurality of phase shifters 80, or 80a and 80b, the direction of the receivable light can be changed two-dimensionally.

[0174] For example, an optical receiving device can be constructed by replacing the light source 130 in the optical scanning device 100 shown in FIG. 13 with a receiving circuit. When light of wavelength λ is incident on the waveguide array 10A, 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 waveguide array and the phase shifter array 80A. In the optical receiving device, for example, in FIG. 4, the directions of the wave vectors (thick arrows 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 arrangement direction of the waveguide element 10 (Y direction in the figure). The sensitivity of the light component in the X direction can be adjusted by an adjustment element incorporated in the waveguide array 10A. On the other hand, the sensitivity of the optical component in the arrangement direction of the waveguide element 10 can be adjusted by an adjustment element incorporated in the phase shifter array 80A. θ and α0 shown in Fig. 4 can be determined from the optical phase difference Δφ when the sensitivity of the optical receiving device is maximized, and the refractive index nw and thickness d of the optical waveguide layer 20. This makes it possible to identify the incident direction of the light. [Industrial Applicability]

[0175] 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]

[0176] 10. Waveguide elements, optical waveguides 11 Optical waveguide 10A Waveguide Array 13 Grating 15 Grating 20 Optical waveguide layer 20L light 21 Dielectric materials 22 membrane 22a First alignment film 22b Second alignment film 22b0 monolayer, monolayer orientation 23m molecule 30 Mirror No. 1 40 2nd Mirror 50a, 50b Substrate 51 Dielectric layer 62a, 62b electrode 70a Waveguide array drive circuit 70b Phase shifter array driver circuit 73 Multiple bulkheads 80 Phase Shifter 80A Phase Shifter Array 90 Optical splitter 100, 100A, 100B 、 110 Optical Devices 100a, 110a Upper structure 100b, 110b substructure 101, 102 direction 130 light source 310 Beam Spot 400 Photodetector 500 Control circuit 600 Signal Processing Circuit

Claims

1. a first structure having a first surface; a second structure having a second surface opposite the first surface; one or more optical guiding regions located between the first surface of the first structure and the second surface of the second structure, the optical guiding regions comprising a liquid crystal material; a first alignment film that is a rubbing alignment film provided on the first surface and that aligns the liquid crystal material; a second alignment film provided on the second surface and formed by irradiation with polarized light; Equipped with Optical devices.

2. the second alignment film is a film including a material bonded to the second surface via a siloxane bond; 10. The optical device of claim 1 .

3. The film is a monolayer.

3. The optical device according to claim 2.

4. the second surface has one or more recesses having a depth of at least 1 μm and not more than 10 μm; the liquid crystal material covers the one or more recesses.

4. An optical device according to claim 1.

5. the one or more recesses is a plurality of recesses; the one or more optical waveguide regions are a plurality of optical waveguide regions, each of the plurality of optical waveguide regions covering a respective one of the plurality of recesses; 5. The optical device according to claim 4.

6. The first surface is a flat surface or an undulating surface having a height difference of less than 1 μm; the liquid crystal material covers the flat surface or the contoured surface; 6. An optical device according to claim 1.

7. the first structure includes a first mirror having the first surface; the second structure includes a second mirror having the second surface; 7. An optical device according to claim 1.

8. the first mirror and the second mirror are both formed of a dielectric multilayer film; 8. The optical device according to claim 7.

9. The first mirror has a higher light transmittance than the second mirror.

9. The optical device according to claim 8.

10. the first structure includes a first electrode; the second structure includes a second electrode facing the first electrode, the one or more optical guiding regions are located between the first electrode and the second electrode; a direction of light emitted from the one or more optical waveguide regions through the first structure, or an incident direction of light taken into the one or more optical waveguide regions through the first structure, is changed by changing a voltage applied to the first electrode and the second electrode; 10. The optical device of claim 9.

11. a plurality of phase shifters coupled to the one or more optical waveguide regions, either directly or through other waveguides; 10. The optical device of claim 1 .

12. the one or more optical guiding regions are a plurality of optical guiding regions; The optical waveguide further includes a plurality of phase shifters respectively connected to the plurality of optical waveguide regions directly or via other waveguides.

10. The optical device of claim 1 .

13. An optical device according to any one of claims 1 to 12; 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.

Images