WO2022113427A1 - Dispositif optique et système de détection optique - Google Patents

Dispositif optique et système de détection optique Download PDF

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WO2022113427A1
WO2022113427A1 PCT/JP2021/028236 JP2021028236W WO2022113427A1 WO 2022113427 A1 WO2022113427 A1 WO 2022113427A1 JP 2021028236 W JP2021028236 W JP 2021028236W WO 2022113427 A1 WO2022113427 A1 WO 2022113427A1
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optical
mirror
light
waveguide
refractive index
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PCT/JP2021/028236
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English (en)
Japanese (ja)
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享 橋谷
安寿 稲田
和樹 中村
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パナソニックＩｐマネジメント株式会社
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Publication of WO2022113427A1 publication Critical patent/WO2022113427A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/295—Analog deflection from or in an optical waveguide structure]

Definitions

  • This disclosure relates to optical devices and photodetection systems.
  • Patent Document 1 discloses a configuration in which scanning by light can be performed by using a driving device that rotates a mirror.
  • Patent Document 2 discloses an optical phased array having a plurality of nanophotonic antenna elements arranged two-dimensionally. Each antenna element is optically coupled to a variable optical delay line (ie, 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 a phase shifter. This makes it possible to change the amplitude distribution of the far-field radiation pattern.
  • a variable optical delay line ie, a phase shifter
  • Patent Document 3 describes a waveguide provided with an optical waveguide layer in which light is waveguideed inside, a first distributed Bragg reflector formed on the upper surface and the lower surface of the optical waveguide layer, and a waveguide for incidenting light in the waveguide.
  • a light deflection element including a light incident port and a light emitting port formed on the surface of the waveguide for emitting light incident from the light incident port and waveguide in the waveguide is disclosed.
  • One aspect of the present disclosure provides a novel optical device capable of realizing scanning by light with a relatively simple configuration.
  • the optical device includes a first mirror having a first reflecting surface, a second mirror having a second reflecting surface facing the first reflecting surface, the first mirror, and the second mirror. It has at least one optical waveguide region that is located between and propagates light, and a surface that is located between the first mirror and the second mirror and faces the first reflective surface, and has the optical light. It comprises at least one optical input waveguide having a tip that couples light to the wave region within the optical waveguide, the surface and the first reflection of a portion of the optical input waveguide other than the tip. The distance to the surface is larger than the distance between the surface of the tip portion of the optical input waveguide and the first reflecting surface.
  • the present disclosure may be implemented in recording media such as systems, devices, methods, integrated circuits, computer programs or computer readable recording discs, systems, devices, methods, integrated circuits, etc. It may be realized by any combination of 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).
  • the device may be composed of one or more devices. When the device is composed of two or more devices, the two or more devices may be arranged in one device, or may be separately arranged in two or more separated devices.
  • "device" can mean not only one device, but also a system of multiple devices.
  • a one-dimensional scan or a two-dimensional scan using light can be realized with a relatively simple configuration.
  • FIG. 1 is a perspective view schematically showing the configuration of an optical scanning device.
  • FIG. 2 is a diagram schematically showing an example of a cross-sectional structure of one waveguide element and propagating light.
  • FIG. 3A is a diagram showing a cross section of a waveguide array that emits light in a direction perpendicular to the emission plane of the waveguide array.
  • FIG. 3B is a diagram showing a cross section of a waveguide array that emits light in a direction different from the direction perpendicular to the emission plane of the waveguide array.
  • FIG. 4 is a perspective view schematically showing a waveguide array in a three-dimensional space.
  • FIG. 5 is a schematic view of the waveguide array and the phase shifter array as viewed from the normal direction (Z direction) of the light emitting surface.
  • FIG. 6 is a diagram schematically showing an example of an optical device.
  • FIG. 7 is a graph showing the relationship between the emission angle of the emitted light and the thickness of the optical waveguide layer.
  • FIG. 8 is a diagram schematically showing a first example of an optical device according to an embodiment of the present disclosure.
  • FIG. 9 is a diagram schematically showing the structure of the cross section taken along the line AA of FIG.
  • FIG. 10B is a diagram showing the light intensity distribution in the configuration shown in FIG.
  • FIG. 11 is a diagram schematically showing a second example of the optical device according to the present embodiment.
  • FIG. 12 is a diagram schematically showing a third example of the optical device according to the present embodiment.
  • FIG. 13 is a diagram showing a configuration example of an optical scan device in which elements such as an optical turnout, a waveguide array, a phase shifter array, and a light source are integrated on a circuit board.
  • 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 at a distance from the light scan device.
  • FIG. 15 is a block diagram showing a configuration example of a LiDAR system capable of generating a ranging image.
  • all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram is, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (lage scale integration). ) Can be performed by one or more electronic circuits.
  • the LSI or IC may be integrated on one chip, or may be configured by combining a plurality of chips.
  • functional blocks other than the storage element may be integrated on one chip.
  • it is called LSI or IC, but the name changes depending on the degree of integration, and it may be called system LSI, VLSI (very large scale integration), or ULSI (ultra large scale integration).
  • a Field Programmable Gate Array (FPGA) programmed after the LSI is manufactured, or a reconfigurable logic device that can reconfigure the connection relationship inside the LSI or set up the circuit partition inside the LSI can also be used for the same purpose.
  • FPGA Field Programmable Gate Array
  • all or part of the function or operation of a circuit, unit, device, member or part can be executed by software processing.
  • the software is recorded on a non-temporary recording medium such as one or more ROMs, optical discs, hard disk drives, etc., and when the software is run by a processor, the functions identified by the software It is executed by a processor and peripheral devices.
  • the system or device may include one or more non-temporary recording media on which the software is recorded, a processor, and the required hardware device, such as an interface.
  • the present inventor has found that a conventional optical scanning device has a problem that it is difficult to scan a space with light without complicating the configuration of the device.
  • the present inventor paid attention to the above-mentioned problems in the prior art, and examined the configuration for solving these problems.
  • the present inventor has found that the above problem can be solved by using a waveguide element having a pair of facing 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, and emits a part of the light propagating in the optical waveguide layer to the outside.
  • the direction (or emission angle) of the emitted light can be changed by adjusting the refractive index or thickness of the optical waveguide layer or the wavelength of the light input to the optical waveguide layer, as described later. 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 a one-dimensional scan.
  • a two-dimensional scan can be realized. More specifically, by giving an appropriate phase difference to the light supplied to the plurality of waveguide elements and adjusting the phase difference, it is possible to change the direction in which the light emitted from the plurality of waveguide elements strengthens each other. can. Due to the change in the phase difference, the component of the wave vector of the emitted light in the direction intersecting the longitudinal direction of the optical waveguide layer changes. This makes it possible to realize a two-dimensional scan. 2 You can perform a two-dimensional scan. As described above, according to the embodiment of the present disclosure, it is possible to realize a two-dimensional scan by light with a relatively simple configuration.
  • any one of the refractive index, thickness, and wavelength is 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. Means at least one that is done. In order to change the emission direction of light, any one of the refractive index, the thickness, and the wavelength may be controlled independently. Alternatively, any two or all of these three may be controlled to change the light emission direction. In each of the following embodiments, the wavelength of the light input to the optical waveguide layer may be controlled in place of or in addition to the control of the refractive index or the thickness.
  • the above basic principle can be applied not only to applications that emit light but also to applications that receive optical signals.
  • the direction of the receivable light can be changed one-dimensionally.
  • the phase difference of light is changed by a plurality of phase shifters connected to each of a plurality of waveguide elements arranged in one direction, the direction of receivable light can be changed two-dimensionally.
  • the optical scanning device and the optical receiving device can be used as an antenna in an optical detection system such as a LiDAR (Light Detection and Ringing) system. Since the LiDAR system uses short wavelength electromagnetic waves (visible light, infrared rays, or ultraviolet rays) as compared with radar systems using radio waves such as millimeter waves, it is possible to detect the distance distribution of an object with high resolution.
  • a LiDAR system can 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 can be used as one of collision avoidance techniques.
  • an optical scanning device and an optical receiving device may be collectively referred to as an "optical device”.
  • a device used for an optical scanning device or an optical receiving device may also be referred to as an "optical device”.
  • light refers to electromagnetic waves including not only visible light (wavelength of about 400 nm to about 700 nm) but also ultraviolet rays (wavelength of about 10 nm to about 400 nm) and infrared rays (wavelength of about 700 nm to about 1 mm). means.
  • ultraviolet light may be referred to as “ultraviolet light” and infrared light may be referred to as “infrared light”.
  • scanning by light means changing the direction of light.
  • One-dimensional scan means changing the direction of light linearly along a direction that intersects that direction.
  • Tele-dimensional scanning means changing the direction of light two-dimensionally along a plane that intersects the direction.
  • FIG. 1 is a perspective view schematically showing the configuration of the optical scan device 100.
  • the optical scan 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 the 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 the light in the first direction and emit the light in the third direction D3 intersecting the virtual plane parallel to the first and second directions.
  • the first direction (X direction) and the second direction (Y direction) are orthogonal to each other, but they do not have to be orthogonal to each other.
  • a 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.
  • Each of the plurality of 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 mirror 30 and the mirror 40.
  • Each of the mirror 30 and the mirror 40 has a reflective surface intersecting the third direction D3 at the interface with the optical waveguide layer 20.
  • the mirror 30, the mirror 40, and the optical waveguide layer 20 have a shape extending in the first direction (X direction).
  • the first mirrors 30 in the plurality of waveguide elements 10 may be connected to each other.
  • the first mirror 30 in each of the plurality of waveguide elements 10 may be a part of one mirror.
  • the second mirror 40 in each of the plurality of waveguide elements 10 may be a part of one mirror.
  • the optical waveguide layer 20 in each of the plurality of waveguide elements 10 may be a part of one optical waveguide layer. At least, (1) whether each first mirror 30 is separated from the other first mirror 30, (2) whether each second mirror 40 is separated from the other second mirror 40, and (3) each optical waveguide. Since the layer 20 is separated from the other optical waveguide layer 20, a plurality of waveguides can be formed.
  • the reflective surface of the first mirror 30 and the reflective surface of the second mirror 40 face each other almost in parallel.
  • the first mirror 30 has a property of transmitting a part of the light propagating through the optical waveguide layer 20.
  • the first mirror 30 has a higher light transmittance than the second mirror 40 for the light. 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 can be, for example, multilayer mirrors formed by a multilayer film made of a dielectric.
  • the phase of the light input to each waveguide element 10 is controlled, and 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 is synchronized. By changing the wavelengths at the same time, it is possible to realize a two-dimensional scan using light.
  • the present inventor analyzed the operating principle of the waveguide element 10 in order to realize such a two-dimensional scan. Based on the result, we succeeded in realizing a two-dimensional scan by light by driving a plurality of waveguide elements 10 in synchronization.
  • each waveguide element 10 when light is input to each waveguide element 10, light is emitted from the emission surface of each waveguide element 10.
  • the emission surface is located on the opposite side of the reflection surface of the first mirror 30.
  • the direction D3 of the emitted light depends on the refractive index, the thickness, and the wavelength of the light of the optical waveguide layer.
  • at least one of the refractive index, the thickness, and the wavelength of each optical waveguide layer is synchronously controlled so that the light emitted from each waveguide element 10 is in substantially the same direction.
  • the X-direction component of the wave number vector of the light emitted from the plurality of waveguide elements 10 can be changed.
  • the direction D3 of the emitted light can be changed along the direction 101 shown in FIG.
  • the emitted light interferes with each other.
  • the direction in which the light strengthens due to interference can be changed. For example, when a plurality of waveguide elements 10 having the same size are arranged at equal intervals in the Y direction, light having a different phase is input to the plurality of waveguide elements 10 by a fixed amount. By changing the phase difference, the component in the Y direction of the wave vector of the emitted light can be changed.
  • the direction D3 in which the emitted light is strengthened by interference can be changed along the direction 102 shown in FIG. .. This makes it possible to realize a two-dimensional scan using light.
  • FIG. 2 is a diagram schematically showing an example of a cross-sectional structure of one waveguide element 10 and propagating light.
  • the directions perpendicular to the X and Y directions shown in FIG. 1 are defined as the Z direction, and a cross section parallel to the XZ plane of the waveguide element 10 is schematically shown.
  • the first mirror 30 and the second mirror 40 are arranged so as 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 is 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 lower surface (FIG. 2). It propagates in the optical waveguide layer 20 while repeating reflection by the second reflecting surface 40s of the second mirror 40 provided on the lower surface of No. 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 mainly output from the first mirror 30.
  • the light propagation angle means the angle of incidence on the interface between the mirror 30 or the mirror 40 and the optical waveguide layer 20.
  • Light that is incident at an angle closer to perpendicular to the mirror 30 or the mirror 40 can also propagate. That is, light incident on the interface can also propagate at an angle smaller than the critical angle of total reflection. Therefore, the group velocity of light in the propagation direction of light is significantly lower than the speed of light in free space.
  • the waveguide element 10 has the property that the light propagation conditions change significantly with respect to changes in the wavelength of light, the thickness of the optical waveguide layer 20, and the refractive index of the optical waveguide layer 20.
  • a waveguide is referred to as a "reflecting waveguide” or a “slow light waveguide”.
  • the emission angle ⁇ of the light emitted from the waveguide element 10 into the air is expressed by the following equation (1).
  • the emission direction of the light is changed by changing any one of the wavelength ⁇ of the light in the air, the refractive index n w of the optical waveguide layer 20, and the thickness d of the optical waveguide layer 20. Can be done.
  • the emission angle is 0 °.
  • the emission angle changes to about 66 °.
  • the emission angle changes to about 51 °.
  • the emission angle changes to about 30 °. In this way, by changing any one of the wavelength ⁇ of the light, the refractive index n w of the optical waveguide layer 20, and the thickness d of the optical waveguide layer 20, the emission direction of the light can be significantly changed.
  • the optical scan device 100 controls at least one of the wavelength ⁇ of the light input to the optical waveguide layer 20, the refractive index n w of the optical waveguide layer 20, and the thickness d of the optical waveguide layer 20. Controls the emission direction of light.
  • the wavelength ⁇ of light may remain constant during operation without change. In that case, light scanning can be realized with a simpler configuration.
  • the wavelength ⁇ is not particularly limited.
  • the wavelength ⁇ is a wavelength of 400 nm to 1100 nm (that is, visible light to near-infrared light), which provides high detection sensitivity with a photodetector or image sensor that detects light by absorbing light with general silicon (Si). Can be included in the region.
  • the wavelength ⁇ may be included in the wavelength range of near-infrared light from 1260 nm to 1625 nm, which has a relatively low transmission loss in an optical fiber or Si waveguide. Note that these wavelength ranges are 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.
  • the optical scan device 100 may include a first adjusting element that changes at least one of the refractive index, thickness, and wavelength of the optical waveguide layer 20 in each waveguide element 10.
  • the light emission direction can be significantly changed by changing at least one of the refractive index n w , the thickness d, and the wavelength ⁇ of the optical waveguide layer 20. ..
  • the emission angle of the light emitted from the mirror 30 can be changed in the direction along the waveguide element 10.
  • the optical waveguide layer 20 may include a liquid crystal material or an electro-optical material.
  • the optical waveguide layer 20 may be sandwiched by a pair of electrodes. By applying a voltage to the pair of electrodes, the refractive index of the optical waveguide layer 20 can be changed.
  • At least one actuator may be connected to at least one of the mirror 30 and the mirror 40 in order to adjust the thickness of the optical waveguide layer 20.
  • the thickness of the optical waveguide layer 20 can be changed by changing the distance between the mirror 30 and the mirror 40 by at least one actuator. If the optical waveguide layer 20 is formed of a liquid, the thickness of the optical waveguide layer 20 can be easily changed.
  • 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 the light propagating through each waveguide element 10.
  • the phase shift amount is a value based on the phase of the light propagating through the waveguide element 10 at the left end.
  • the waveguide array in this embodiment includes a plurality of waveguide elements 10 arranged at equal intervals.
  • the dashed arc indicates the wavefront of light emitted from each waveguide element 10.
  • the straight line shows the wavefront formed by the interference of light.
  • the arrows indicate the direction of the light emitted from the waveguide array (ie, the direction of the wave vector).
  • the phases of the light propagating in the optical waveguide layer 20 in each waveguide element 10 are the same.
  • the light is emitted in a direction (Z direction) perpendicular to both the arrangement direction (Y direction) of the waveguide element 10 and the direction (X direction) in which the optical waveguide layer 20 extends.
  • FIG. 3B is a diagram showing a cross section of a waveguide array that emits light in a direction different from the direction perpendicular to the emission plane of the waveguide array.
  • the phases of the light propagating in the optical waveguide layer 20 in the plurality of waveguide elements 10 are different by a fixed amount ( ⁇ ) in the arrangement direction.
  • the light is emitted in a direction different from the Z direction.
  • ⁇ the component in the Y direction of the wave vector of light can be changed.
  • the light emission angle ⁇ 0 is expressed by the following equation (2).
  • the direction of the light emitted from the optical scan device 100 is not parallel to the XZ plane or the YZ plane. That is, ⁇ ⁇ 0 ° and ⁇ 0 ⁇ 0 °.
  • FIG. 4 is a perspective view schematically showing a waveguide array in a three-dimensional space.
  • the thick arrow shown in FIG. 4 indicates the direction of the light emitted from the optical scanning device 100.
  • ⁇ is the angle formed by the light emission direction and the YZ plane.
  • ⁇ satisfies equation (1).
  • ⁇ 0 is the angle formed by the light emission direction and the XZ plane.
  • ⁇ 0 satisfies the equation (2).
  • phase shifter that changes the phase of the light may be provided before introducing the light into the waveguide element 10.
  • the optical scan device 100 includes a plurality of phase shifters connected to each of the plurality of waveguide elements 10, and a second adjusting element for adjusting the phase of light propagating through each phase shifter.
  • Each phase shifter includes a waveguide connected directly to or via another waveguide to the optical waveguide layer 20 in the corresponding one of the plurality of waveguide elements 10.
  • the second adjusting element changes the phase difference of the light propagating from the plurality of phase shifters to the plurality of waveguide elements 10, so that the direction of the light emitted from the plurality of waveguide elements 10 (that is, the third).
  • Direction D3 is changed.
  • a plurality of arranged phase shifters are also referred to as "phase shifter arrays”.
  • FIG. 5 is a schematic view of the waveguide array 10A and the phase shifter array 80A as viewed from the normal direction (Z direction) of the light emitting surface.
  • all phase shifters 80 have the same propagation characteristics and all waveguide elements 10 have the same propagation characteristics.
  • Each phase shifter 80 and each waveguide element 10 may have the same length or may have different lengths.
  • the respective phase shift amounts can be adjusted by the drive voltage. Further, by adopting a structure in which the length of each phase shifter 80 is changed in equal steps, it is possible to give a phase shift in equal steps with the same drive voltage.
  • the optical scan device 100 drives an optical turnout 90 that branches and supplies light to a plurality of phase shifters 80, a first drive circuit 70a that drives each waveguide element 10, and each phase shifter 80.
  • a second drive circuit 70b is further provided.
  • the straight arrow in FIG. 5 indicates the input of light.
  • Two-dimensional scanning can be realized by independently controlling the first drive circuit 70a and the second drive circuit 70b provided separately.
  • the first drive circuit 70a functions as one element of the first adjustment element
  • the second drive circuit 70b functions as one element of the second adjustment element.
  • the first drive 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 drive circuit 70b changes the phase of the light propagating inside the optical waveguide layer 20 by changing the refractive index of the optical waveguide layer 20 in each phase shifter 80.
  • the optical turnout 90 may be configured by a waveguide in which light is propagated by total internal reflection, or may be configured by a reflection type waveguide similar to the waveguide element 10.
  • each light may be introduced into the phase shifter 80.
  • a passive phase control structure by adjusting the length of the waveguide leading up to the phase shifter 80 can be used.
  • a phase shifter that has the same function as the phase shifter 80 and can be controlled by an electric signal may be used.
  • the phase may be adjusted before being introduced into the phase shifter 80 so that the light having the same phase is supplied to all the phase shifters 80.
  • the control of each phase shifter 80 by the second drive circuit 70b can be simplified.
  • An optical device having the same configuration as the above-mentioned optical scan device 100 can also be used as an optical receiving device. Details such as the operating principle and operating method of the optical device are disclosed in US Patent Application Publication No. 2018/0224709. The entire disclosure of this document is incorporated herein by reference.
  • the light input to the waveguide element may be, for example, light that has passed through a phase shifter.
  • An optical waveguide may be connected between the phase shifter and the waveguide element.
  • Such an optical waveguide can be, for example, a total internal reflection waveguide that propagates light in one direction by total internal reflection.
  • the optical waveguide may be provided to input light that has passed through the phase shifter to the optical waveguide layer in the waveguide element.
  • an optical device provided with such an optical waveguide will be described.
  • FIG. 6 is a diagram schematically showing an example of the optical device 100.
  • the optical device 100 includes a first structure 100a and a second structure 100b.
  • the first structure 100a includes a first electrode 62a, a first substrate 50a, and a first mirror 30 in this order.
  • the second structure 100b includes a second electrode 62b, a second substrate 50b, and a second mirror 40 in this order.
  • the second structure 100b includes a dielectric layer 51 provided on the mirror 40 and an optical waveguide 11 provided on the dielectric layer 51.
  • the dimension of the optical waveguide 11 in the Y direction is smaller than the dimension of the dielectric layer 51 in the Y direction.
  • the transmittance of the first mirror 30 is higher than that of the second mirror 40.
  • the first substrate 50a and the first electrode 62a have translucency.
  • the first electrode 62a may be, for example, a transparent electrode.
  • the second substrate 50b and the second electrode 62b may or may not have translucency.
  • the first structure 100a and the second structure 100b are fixed to each other so that the reflecting surface 30s of the first mirror 30 and the reflecting surface 40s of the second mirror 40 face each other.
  • the space between the first structure 100a and the second structure 100b is filled with the liquid crystal material 21.
  • the refractive index of the liquid crystal material 21 is lower than the refractive index of the optical waveguide 11 and higher than the refractive index of the dielectric layer 51.
  • the waveguide element 10 shown in FIG. 6 includes a part of the first mirror 30, a part of the second mirror 40, and an optical waveguide layer 20 located between them.
  • the optical waveguide layer 20 in this example is a partial region included in the layer between the first mirror 30 and the second mirror 40. Therefore, in the following description, the optical waveguide layer 20 is referred to as “optical waveguide region 20”.
  • the optical waveguide region 20 is a part of a region filled with the liquid crystal material 21, and extends in the + X direction from a portion surrounding the grating 15 described later provided at the tip portion 11t of the optical waveguide 11.
  • the optical waveguide region 20 propagates light along the X direction.
  • the optical waveguide region 20 includes the liquid crystal material 21, but may also include other dielectric materials such as electro-optical materials whose refractive index can be changed by applying a voltage.
  • the optical waveguide 11 is connected to the optical waveguide region 20.
  • the tip portion 11t of the optical waveguide 11 is in the optical waveguide region 20.
  • the optical waveguide 11 has a surface 11s facing the reflection surface 30s of the first mirror 30.
  • the optical waveguide 11 is supported by the dielectric layer 51.
  • the refractive index of the optical waveguide 11 is higher than the refractive index of the dielectric layer 51 and higher than the refractive index of the liquid crystal material 21. Therefore, light can propagate in the optical waveguide 11 along the X direction by total internal reflection.
  • the optical waveguide 11 is also referred to as an "optical input waveguide".
  • the optical waveguide 11 is provided with a grating 15 at the tip portion 11t.
  • the grating 15 has a structure in which the refractive index changes periodically along the X direction.
  • the grating 15 may include, for example, a plurality of grooves periodically arranged in the X direction. Of the plurality of convex portions formed on the tip portion 11t by the plurality of grooves, the upper surface facing the reflection surface 30s of the first mirror 30 is referred to as "the surface of the tip portion 11t". A part of the light propagating in the optical waveguide 11 is converted into diffracted light by the grating 15.
  • the propagation constant of the diffracted light is a value obtained by shifting the propagation constant of the light propagating through the optical waveguide 11 by the reciprocal lattice portion of the periodic structure formed by the groove of the grating 15, that is, by multiplying the reciprocal of the period by 2 ⁇ . be equivalent to. If the propagation constant of the diffracted light matches the propagation constant of the light propagating in the optical waveguide region 20, the light propagating in the optical waveguide 11 is efficiently coupled to the optical waveguide region 20. Even when these two propagation constants do not completely match, if the difference between these two propagation constants can be reduced, the optical coupling efficiency from the optical waveguide 11 to the optical waveguide region 20 via the grating 15 is improved.
  • the optical coupling efficiency depends on the period, duty ratio, depth, and number of grooves contained in the grating 15. For example, when the wavelength of the light propagating in the optical waveguide 11 in the air is 800 nm or more and 2.0 ⁇ m or less, the groove period is 300 nm or more and 1.7 ⁇ m or less, the duty ratio is 10% or more and 90% or less, and the depth. Can be 5% or more and 100% or less of the thickness of the optical waveguide 11, and the number may be 4 or more and 64 or less.
  • the optical waveguide 11 is not limited to the grating 15, and the tip portion 11t may be provided with an arbitrary configuration for improving the optical coupling efficiency. Such a configuration may be, for example, a tapered structure in which the tip portion 11t narrows toward the optical waveguide region 20.
  • a part of the light propagating in the optical waveguide region 20 is emitted to the outside through the first mirror 30, the first substrate 50a, and the first electrode 62a included in the first structure 100a.
  • the liquid crystal material 21 is located between the first electrode 62a and the second electrode 62b. By applying a voltage between the first electrode 62a and the second electrode 62b, an electric field is generated between these electrodes. By changing the refractive index of the liquid crystal material 21 by the electric field, the emission angle ⁇ of the emitted light can be changed.
  • the first mirror 30, the second mirror 40, the first electrode 62a, the second electrode 62b, the first substrate 50a, and the second substrate 50b extend along the XY plane.
  • a plurality of optical waveguide regions 20 and a plurality of optical waveguides 11 may be arranged along the Y direction between the first mirror 30 and the second mirror 40. Each of the plurality of optical waveguides 11 is connected to the plurality of optical waveguide regions 20.
  • a plurality of optical waveguides 11 may be supported by one dielectric layer 51.
  • a dielectric member having a refractive index lower than that of the optical waveguide region 20 may be provided between two adjacent optical waveguide regions 20.
  • the number of each of the optical waveguide region 20 and the optical waveguide 11 can be any number of 1 or more.
  • the optical waveguide 11 propagates light by total internal reflection, unlike the optical waveguide region 20 which is a slow light waveguide. Therefore, it seems that the portion of the first mirror 30 other than the portion overlapping the optical waveguide region 20 when viewed from the Z direction is not always necessary. The same applies to the first electrode 62a and the first substrate 50a. However, there is an advantage that the warp can be reduced by leaving those parts without removing them.
  • each of the first substrate 50a and the second substrate 50b often has, for example, a convex warp upward or a convex downward.
  • the first mirror 30 and the first electrode 62a may also have the same tendency of warpage as the first substrate 50a.
  • the second mirror 40 and the second electrode 62b may also have the same tendency of warpage as the second substrate 50b.
  • a difference of about 1 ⁇ m may occur in the Z direction between the central portion and the end portion due to the warp.
  • the curvature of the warp at the edges of the substrate is greater than the curvature of the warp at the center of the substrate.
  • the dimension, that is, the thickness of the optical waveguide region 20 in the Z direction becomes non-uniform along the X direction. Due to the non-uniform thickness of the optical waveguide region 20, the optical device 100 may not be able to achieve the designed performance, for example with respect to the emission angle and / or the intensity of the emitted light.
  • the central portion of each of the first substrate 50a and the second substrate 50b which has a small curvature of warp, overlaps the tip portion 11t of the optical waveguide 11 when viewed from the Z direction.
  • the first substrate 50a and the second substrate 50b are arranged therein.
  • the optical waveguide region 20 is located near the central portion of the first substrate 50a and the second substrate 50b, and the end portions of the first substrate 50a and the second substrate 50 are located away from the optical waveguide region 20. Located in. Therefore, the thickness of the optical waveguide region 20 becomes substantially uniform along the X direction.
  • a part of the light propagating in the optical waveguide 11 exudes from the surface 11s of the optical waveguide 11 as an evanescent wave.
  • the evanescent wave reaches the first mirror 30, the evanescent wave leaks to the outside through the first structure 100a. Therefore, a propagation loss of light propagating in the optical waveguide 11 occurs. Since the refractive index of the dielectric layer 51 is lower than that of the liquid crystal material 21, the exudation of the evanescent wave to the dielectric layer 51 is small. Further, since the transmittance of the mirror 40 is lower than that of the mirror 30, it is unlikely that the evanescent wave leaks to the outside through the second structure 100b.
  • mirror spacing By increasing the distance between the first mirror 30 and the second mirror 40 (hereinafter, may be referred to as "mirror spacing"), it is possible to suppress the above-mentioned evanescent wave from reaching the first mirror 30. Therefore, it is possible to reduce the propagation loss of the light propagating in the optical waveguide 11.
  • increasing the mirror spacing i.e., the thickness of the optical waveguide region 20, may raise the following new challenges.
  • FIG. 7 is a graph showing the relationship between the emission angle of the emitted light and the thickness of the optical waveguide region 20.
  • the smallest emission angle is 0 ° and the second smallest emission angle is 51.5 °.
  • the double-headed arrow a shown in FIG. 7 indicates that the difference between these emission angles is 51.5 °.
  • the smallest emission angle is 0 ° and the second smallest emission angle is 41.0 °.
  • the double-headed arrow b shown in FIG. 7 indicates that the difference between these emission angles is 41.0 °.
  • the double-headed arrow b is shorter than the double-headed arrow a, as the thickness of the optical waveguide region 20 increases, the two emitted lights come closer to each other. Therefore, when the reflected light generated by one emitted light is detected for scanning by light, the reflected light generated by the other emitted light may be detected as noise.
  • the present inventor came up with the optical device according to the embodiment of the present disclosure from the above studies.
  • the optical device according to the embodiment of the present disclosure has a structure similar to the structure shown in FIG. 6, but the distance between the surface 11s of the optical waveguide 11 and the reflection surface 30s of the first mirror 30 is not uniform. It is different from the structure shown in.
  • the distance between the surface 11s of the portion other than the tip portion 11t of the optical waveguide 11 and the reflection surface 30s of the first mirror 30 is the surface 11s of the tip portion 11t of the optical waveguide 11 and the first mirror 30. It is larger than the distance from the reflecting surface 30s.
  • the optical device includes a first mirror having a first reflecting surface, a second mirror having a second reflecting surface facing the first reflecting surface, the first mirror, and the second mirror. It has at least one optical waveguide region that is located between the mirrors and propagates light, and a surface that is located between the first mirror and the second mirror and faces the first reflective surface. It comprises at least one optical input waveguide having a tip that couples light to the region within the optical waveguide region. The distance between the surface of the optical input waveguide other than the tip portion and the first reflecting surface is larger than the distance between the surface of the tip portion of the optical input waveguide and the first reflecting surface. .. There is a step between the surface of the first reflective surface facing the tip and the surface of the first reflective surface facing a portion other than the tip.
  • the "distance between the surface of the optical input waveguide other than the tip portion and the first reflecting surface” means the average distance between these two surfaces. The same applies to the "distance between the surface of the tip of the optical input waveguide and the first reflecting surface”.
  • the optical device according to the second item does not overlap the portion of the optical device according to the first item that overlaps the optical waveguide region when the first mirror is viewed from a direction perpendicular to the first reflection surface.
  • the portion has the same thickness.
  • the member supporting the first mirror has a step, the surface of the portion other than the tip of the optical input waveguide and the first reflection can be obtained without removing a part of the first mirror.
  • the distance to the surface can be made larger than the distance between the surface of the tip of the optical input waveguide and the first reflecting surface.
  • the optical device according to the third item is the thickness of the portion of the first mirror that overlaps the optical waveguide region when viewed from a direction perpendicular to the first reflection surface in the optical device according to the first item. Is larger than the thickness of the other part of the first mirror.
  • the distance between the surface of the portion other than the tip portion of the optical input waveguide and the first reflection surface is set to the surface of the tip portion of the optical input waveguide and the first. 1 It can be made larger than the distance to the reflecting surface.
  • the optical device according to the fourth item is provided on the second mirror in the optical device according to any one of the first to third items, and includes a dielectric layer that supports the optical input waveguide.
  • the refractive index of the optical input waveguide is higher than the refractive index of the dielectric layer.
  • the optical device according to the fifth item has the refractive index of the medium between the surface of the optical input waveguide other than the tip portion and the first reflecting surface in the optical device according to the fourth item. It is lower than the refractive index of the optical input waveguide and higher than the refractive index of the dielectric layer.
  • the optical device according to the sixth item is the optical device according to any one of the first to fifth items, wherein the optical input waveguide has a grating having a structure in which the refractive index changes periodically at the tip thereof. Be prepared.
  • the optical coupling efficiency from the optical input waveguide to the optical waveguide region can be improved by grating.
  • the optical device includes a first mirror having a first reflecting surface, a second mirror having a second reflecting surface facing the first reflecting surface, the first mirror, and the second mirror. It has at least one optical waveguide region that is located between the mirrors and propagates light, and a surface that is located between the first mirror and the second mirror and faces the first reflective surface. It comprises at least one optical input waveguide having a tip that couples light to the region within the optical waveguide region.
  • the refractive index of the first medium between the surface of the optical input waveguide other than the tip and the first reflecting surface is the surface of the tip of the optical waveguide and the first. It is lower than the refractive index of the second medium between it and the reflective surface.
  • the refractive index of the first medium between the surface of the optical input waveguide other than the tip portion and the first reflecting surface means the average refractive index between these two surfaces. .. The same applies to "the refractive index of the second medium between the surface of the tip of the optical input waveguide and the first reflecting surface”.
  • the optical device according to the eighth item includes, in the optical device according to the seventh item, a material in which each of the first medium and the second medium can change the refractive index by applying a voltage. ..
  • the refractive index of the first medium and the refractive index of the second medium can be made different.
  • the optical device is a drive for applying a voltage to each of the first electrode pair and the second electrode pair and the first electrode pair and the second electrode pair in the optical device according to the eighth item. It is equipped with a circuit.
  • the first medium and the second medium are made of the same material.
  • the first medium is located between the first electrode pairs and the second medium is located between the second electrode pairs.
  • the drive circuit applies a first voltage to the first electrode pair and applies a second voltage different from the first voltage to the second electrode pair to obtain the refractive index of the first medium. 2 Lower than the refractive index of the medium.
  • this optical device it is possible to suppress that a part of the light propagating in the optical input waveguide reaches the first mirror as an evanescent wave.
  • the optical device according to the tenth item is provided on the second mirror in the optical device according to any one of the seventh to ninth items, and includes a dielectric layer that supports the optical input waveguide.
  • the refractive index of the optical input waveguide is higher than the refractive index of the dielectric layer.
  • the optical device according to the eleventh item is the optical device according to any one of the seventh to tenth items, wherein the optical input waveguide has a grating having a structure in which the refractive index changes periodically. Be prepared.
  • the optical coupling efficiency from the optical input waveguide to the optical waveguide region can be improved by grating.
  • the photodetector system is a photodetector that detects light emitted from the optical device and reflected from an object, and a signal that generates distance distribution data based on the output of the photodetector. It is equipped with a processing circuit.
  • This light detection system can generate a distance image.
  • FIG. 8 is a diagram schematically showing a first example of the optical device 100 according to the embodiment of the present disclosure.
  • the optical device 100 includes a first structure 100a and a second structure 100b.
  • the first structure 100a shown in FIG. 8 is the same as the first structure 100a shown in FIG. 6 except that the first substrate 50a and the first mirror 30 have a two-stage structure forming a step in the X direction. be.
  • the first substrate 50a shown in FIG. 8 is manufactured by removing a part of the first substrate 50a shown in FIG.
  • the first mirror 30 has a two-stage structure similar to the first substrate 50a.
  • the step overlaps with a portion other than the tip portion 11t of the optical waveguide 11 when viewed from the Z direction. With such a configuration, it is possible to suppress the light coupled from the optical waveguide 11 to the optical waveguide region 20 via the grating 15 to be reflected by the step.
  • the step between the first substrate 50a and the first mirror 30 may be, for example, 0.05 ⁇ m or more and 0.5 ⁇ m or less.
  • the step may be 0.1 ⁇ m or more and 0.3 ⁇ m or less in a certain example.
  • the warp in the central portion of the first substrate 50a is sufficiently small as compared with the step.
  • the second structure 100b shown in FIG. 8 is the same as the second structure 100b shown in FIG. In the example shown in FIG. 8, the second mirror 40 has a flat structure unlike the first mirror 30.
  • the space between the first structure 100a and the second structure 100b is filled with the liquid crystal material 21 as in the example shown in FIG.
  • a medium such as the liquid crystal material 21 that fills the space is also referred to as an "intermediate medium".
  • the intermediate medium may be made of not the liquid crystal material 21 but another kind of dielectric material whose refractive index can be changed by applying a voltage, for example, an electro-optical material.
  • the optical device 100 includes a light emitting unit 100E that emits light to the outside and an optical input unit 100I connected to the light emitting unit 100E.
  • the light emitting unit 100E is included in each of the first mirror 30, the first substrate 50a, the first electrode 62a, the second mirror 40, the second substrate 50b, the second electrode 62b, the dielectric layer 51, and the optical waveguide 11.
  • a portion overlapping the optical waveguide region 20 when viewed from the Z direction and the optical waveguide region 20 are included.
  • the portion of the dielectric layer 51 that overlaps the optical waveguide region 20 when viewed from the Z direction is the tip end portion of the dielectric layer 51 and is inside the optical waveguide region 20.
  • the optical input unit 100I is included in each of the first mirror 30, the first substrate 50a, the first electrode 62a, the second mirror 40, the second substrate 50b, the second electrode 62b, the dielectric layer 51, and the optical waveguide 11. It includes a portion that does not overlap the optical waveguide region 20 when viewed from the Z direction, and a region between the first structure 100a and the second structure 100b other than the optical waveguide region 20.
  • the thickness of the first mirror 30 in the light emitting unit 100E is equal to the thickness of the first mirror 30 in the light input unit 100I.
  • the first mirror 30 has the same thickness in the light emitting unit 100E and the light input unit 100I.
  • the same thickness does not mean that the thicknesses are exactly the same, but means that the difference in thickness is 5% or less of the thickness of the first mirror 30.
  • the distance between the first mirror 30 and the second mirror 40 in the optical input unit 100I is more than the distance between the first mirror 30 and the second mirror 40 in the light emitting unit 100E. Only big. Therefore, the distance between the surface 11s of the optical waveguide 11 in the optical input unit 100I and the reflection surface 30s of the first mirror 30 is the distance between the surface 11s of the optical waveguide 11 and the reflection surface 30s of the first mirror 30 in the light emission unit 100E. It is larger by the amount of the step.
  • the refractive index of the intermediate medium that is, the liquid crystal material between the surface 11s of the optical waveguide 11 and the reflective surface 30s of the first mirror 30 in the optical input unit 100I is lower than the refractive index of the optical waveguide 11 and the dielectric layer. It is higher than the refractive index of 51.
  • the surface 11s of the optical waveguide 11 in the optical input unit 100I means the surface 11s of a portion other than the tip portion 11t of the optical waveguide 11.
  • the surface 11s of the optical waveguide 11 in the light emitting unit 100E means the surface 11s of the tip portion 11t of the optical waveguide 11.
  • the “distance between the surface 11s of the optical waveguide 11 and the reflecting surface 30s of the first mirror 30 in the optical input unit 100I” means the average distance between these two surfaces. The same applies to the "distance between the surface 11s of the optical waveguide 11 in the light emitting unit 100E and the reflecting surface 30s of the first mirror 30".
  • the distance between the surface 11s of the optical waveguide 11 and the reflecting surface 30s of the first mirror 30 in the optical input unit 100I is larger than that in the example shown in FIG. With such a configuration, it is possible to prevent a part of the light propagating in the optical waveguide 11 from reaching the mirror 30 as an evanescent wave. As a result, it is possible to suppress the evanescent wave from leaking to the outside through the first structure 100a.
  • the thickness of the optical waveguide region 20 in the light emitting unit 100E does not increase as compared with the example shown in FIG. From the above, in the example shown in FIG. 8, it is possible to reduce the propagation loss of the light propagating in the optical waveguide 11 without bringing the two emitted lights emitted from the optical device 100 close to each other.
  • the distance between the surface 11s of the optical waveguide 11 in the optical input unit 100I and the reflection surface 30s of the first mirror 30 affects the propagation loss of light propagating in the optical waveguide 11. The impact will be explained based on numerical calculations.
  • FIG. 9 is a diagram schematically showing the structure of the cross section taken along the line AA of FIG.
  • the first electrode 62a, the first substrate 50a, the second electrode 62b, and the second substrate 50b are not shown. Since these components are not directly related to the propagation loss of the light propagating in the optical waveguide 11, they are not considered in the numerical calculation.
  • the distance between the surface 11s of the optical waveguide 11 and the reflection surface 30s of the first mirror 30 is d 1
  • the thickness of the optical waveguide 11 is d w1
  • the width of the optical waveguide 11 is w w1
  • the dielectric material Let the thickness of the layer 51 be dsub .
  • the refractive index of the optical waveguide 11 is n w1
  • the refractive index of the intermediate medium between the first structure 100a and the second structure 100b is n 1
  • the intensity I of the evanescent wave exuding from the surface 11s of the optical waveguide 11 is expressed by the following equation (3).
  • d 0 is the exudation distance of the evanescent wave, and is expressed by the following equation (4).
  • ⁇ is the wavelength of light propagating in the optical waveguide 11 in the air.
  • ⁇ in is the angle of incidence on the interface when light propagating in the optical waveguide 11 along the X direction is incident on the interface between the optical waveguide 11 and the intermediate medium and is totally reflected.
  • the intensity of the evanescent wave decreases exponentially as the distance from the surface 11s of the optical waveguide 11 increases. Therefore, by increasing the distance d1 shown in FIG. 9, a part of the light propagating in the optical waveguide 11 becomes difficult to reach the first mirror 30 as an evanescent wave, and the light propagating in the optical waveguide 11 is propagated. The loss can be reduced. If the distance d 1 shown in FIG. 9 is larger than the distance d 0 , the propagation loss of the light propagating in the optical waveguide 11 can be almost ignored.
  • the mirrors 30 and 40 have a laminated structure in which a plurality of high refractive index layers and a plurality of low refractive index layers are alternately laminated.
  • the refractive index of the high refractive index layer is 2.36, and the thickness of the high refractive index layer is 107 nm.
  • the refractive index of the low refractive index layer is 1.47, and the thickness of the low refractive index layer is 172 nm.
  • the total number of layers of the high refractive index layer and the low refractive index layer in the mirror 30 is 15.
  • the total number of layers of the high-refractive index layer and the low-refractive index layer in the mirror 40 was 21, and Femsim of Synopsys was used for the calculation of the light intensity distribution. In the examples shown in FIGS. 10A and 10B, black indicates zero light intensity and white indicates high light intensity.
  • the first substrate 50a does not have to have a two-stage structure.
  • the first substrate 50a may have no step, and only the first mirror 30 may have a step.
  • an example of such an optical device 100 will be described with reference to FIG.
  • FIG. 11 is a diagram schematically showing a second example of the optical device 100 according to the present embodiment.
  • the example shown in FIG. 11 differs from the example shown in FIG. 8 in that the first substrate 50a has a flat structure, and the first mirror 30 has a two-stage structure by being partially removed.
  • the thickness of the first mirror 30 in the light emitting unit 100E is larger than the thickness of the first mirror 30 in the light input unit 100I.
  • the distance between the surface 11s of the optical waveguide 11 in the optical input unit 100I and the reflection surface 30s of the first mirror 30 is the reflection of the surface 11s of the optical waveguide 11 and the first mirror 30 in the light emission unit 100E.
  • the distance between the first mirror 30 and the second mirror 40 decreases discontinuously.
  • the mirror spacing does not have to decrease discontinuously and may decrease continuously.
  • the first mirror 30 has a two-stage structure. However, if the refractive index of the intermediate medium in the light input unit 100I is lower than the refractive index of the intermediate medium in the light emission unit 100E, the first mirror 30 does not need to have a two-stage structure.
  • an example of such an optical device will be described with reference to FIG.
  • FIG. 12 is a diagram schematically showing a third example of the optical device 100 according to the present embodiment.
  • the example shown in FIG. 12 differs from the example shown in FIG. 8 in that the substrate 50a and the mirror 30 in the first structure 100a have a flat structure, and the electrodes 62a in the first structure 100a have two electrodes 62c. And at the point where it is divided into 62d.
  • the light input unit 100I includes an electrode 62c
  • the light emission unit 100E includes an electrode 62d.
  • the intermediate medium in the optical input unit 100I is located between the electrode 62c and a part of the electrode 62b.
  • the intermediate medium in the light emitting unit 100E is located between the electrode 62d and the other portion of the electrode 62b.
  • the electrode 62c and the portion of the electrode 62b on the optical input portion 100I side are referred to as a "first electrode pair", and the voltage applied to the first electrode pair is referred to as a "first voltage”.
  • the electrode 62d and the portion of the electrode 62b on the light emitting portion 100E side are referred to as a "second electrode pair", and the voltage applied to the second electrode pair is referred to as a "second voltage”.
  • the portion of the intermediate medium located between the first electrode pairs is referred to as "first medium”, and the portion of the intermediate medium located between the second electrode pairs is also referred to as "second medium”.
  • the optical device 100 shown in FIG. 12 includes a drive circuit similar to that of the first drive circuit 70a shown in FIG.
  • the drive circuit applies a first voltage to the first electrode pair and a second voltage to the second electrode pair.
  • different voltages can be applied to the intermediate medium (that is, the first medium) in the light emitting unit 100E and the intermediate medium (that is, the second medium) in the light input unit 100I.
  • the intermediate medium in the light input unit 100I and the light emission unit 100E can be formed from, for example, the same liquid crystal material 21.
  • the difference in refractive index between the two can be, for example, 0.05 or more and 0.25 or less.
  • the refractive index of the intermediate medium between the surface 11s of the optical waveguide 11 in the optical input unit 100I and the reflection surface 30s of the first mirror 30 is the surface 11s and the first surface of the optical waveguide 11 in the light emitting unit 100E. It may be lower than the refractive index of the intermediate medium between the mirror 30 and the reflecting surface 30s.
  • the “refractive index of the intermediate medium between the surface 11s of the optical waveguide 11 and the reflecting surface 30s of the first mirror 30 in the optical input unit 100I” means the average refractive index between these two surfaces. The same applies to "the refractive index of the intermediate medium between the surface 11s of the optical waveguide 11 in the light emitting unit 100E and the reflecting surface 30s of the first mirror 30".
  • the distance d 0 of the evanescent wave represented by the equation (4) can be reduced. This is because the refractive index n 1 in the equation (4) decreases. Therefore, even if the distance between the surface 11s of the optical waveguide 11 and the reflection surface 30s of the first mirror 30 in the light emitting unit 100E and the optical input unit 100I is equal, a part of the light propagating in the optical waveguide 11 is used as an evanescent wave. It is possible to suppress reaching the mirror 30. Also in the example shown in FIG. 12, it is possible to reduce the propagation loss of the light propagating in the optical waveguide 11 without bringing the two emitted lights emitted from the optical device 100 close to each other.
  • one optical waveguide 11 is connected to one optical waveguide region 20, but the optical device of the present disclosure is not limited to such a configuration.
  • a plurality of optical waveguides 11 arranged along the Y direction may be connected to one optical waveguide region extending in a plane along the XY plane between the first mirror 30 and the second mirror 40.
  • Light propagating through the plurality of optical waveguides 11 is coupled to one optical waveguide region.
  • the combined light interferes within the optical waveguide region to form an optical beam.
  • the light beam formed in the optical waveguide region is emitted to the outside via the first structure 100a. Even in this case, the X-direction component and the Y-direction component of the wave vector of the emitted light can be changed.
  • FIG. 13 is a diagram showing a configuration example of an optical scan device 100 in which elements such as an optical turnout 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 scan device 100 also includes embodiments 1 and 2, as well as an optical device according to a modification.
  • the light source 130 can 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 having a wavelength of ⁇ in free space.
  • the optical turnout 90 branches the light from the light source 130 and introduces it into the waveguide in the plurality of phase shifters.
  • an electrode 62A and a plurality of 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 from each of the plurality of electrodes 62B to the plurality of phase shifters 80 in the phase shifter array 80A.
  • the electrode 62A and the plurality of electrodes 62B may be connected to a control circuit (not shown) that generates the above control signal.
  • the control circuit may be provided on the chip shown in FIG. 13 or may be provided on another chip in the optical scan device 100.
  • all the components shown in FIG. 13 can be integrated on a chip having a size of about 2 mm ⁇ 1 mm.
  • FIG. 14 is a schematic diagram showing a state in which a light beam such as a laser is irradiated far from the optical scan device 100 to perform a two-dimensional scan.
  • the two-dimensional scan is performed by moving the beam spot 310 horizontally and vertically.
  • a known TOF (Time Of Flight) method a two-dimensional distance measurement image can be acquired.
  • 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 to obtain a distance.
  • FIG. 15 is a block diagram showing a configuration example of a LiDAR system 300, which is an example of a photodetection system capable of generating such a ranging image.
  • the LiDAR system 300 includes an optical scan device 100, a photodetector 400, a signal processing circuit 600, and a control circuit 500.
  • the photodetector 400 detects the light emitted from the optical scan device 100 and reflected from the object.
  • the photodetector 400 may be, for example, an image sensor sensitive to the wavelength ⁇ of light emitted from the optical scan device 100, or a photodetector including a light receiving element such as a photodiode.
  • the photodetector 400 outputs an electric signal according to the amount of received light.
  • the signal processing circuit 600 calculates the distance to the object based on the electric signal output from the photodetector 400, and generates the distance distribution data.
  • the distance distribution data is data showing a two-dimensional distribution of distance (that is, a distance measurement image).
  • the control circuit 500 is a processor that controls the optical scan device 100, the photodetector 400, and the signal processing circuit 600.
  • the control circuit 500 controls the timing of irradiation of the light beam from the optical scan 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.
  • the frame rate for acquiring a distance measurement image can be selected from, for example, 60 fps, 50 fps, 30 fps, 25 fps, 24 fps, etc., which are commonly used in moving images. Further, considering the application to an in-vehicle system, the higher the frame rate, the higher the frequency of acquiring the distance measurement image, and the more accurately the obstacle can be detected. For example, when traveling at 60 km / h, an image can be acquired every time the car moves about 28 cm at a frame rate of 60 fps. 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.
  • the time required to acquire one ranging image depends on the speed of the beam scan. For example, in order to acquire an image having a resolution of 100 ⁇ 100 at 60 fps, it is necessary to perform a beam scan at 1.67 ⁇ s or less for each point.
  • the control circuit 500 controls the emission of the light beam by the optical scan device 100 and the signal storage / reading by the photodetector 400 at an operating speed of 600 kHz.
  • the optical scanning device or the optical device in each of the above-described embodiments of the present disclosure has almost the same configuration and can also be used as an optical receiving device.
  • the optical receiving device includes the same waveguide array 10A as the optical scanning device, and a first adjusting 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 the light transmitted through the first mirror 30 in the second direction.
  • Receivable light captured in each optical waveguide layer 20 by the first adjusting element changing at least one of the refractive index and thickness of the optical waveguide layer 20 in each waveguide element 10 and the wavelength of light.
  • the second adjusting element for changing the phase difference between the two is provided, the direction of the receivable light can be changed two-dimensionally.
  • an optical receiving device in which the light source 130 in the optical scanning device 100 shown in FIG. 13 is replaced with a receiving circuit can be configured.
  • the light is sent to the optical turnout 90 through the phase shifter array 80A, and finally collected at one place and sent to the receiving circuit.
  • the sensitivity of the optical receiving device can be adjusted by the adjusting 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 vector (thick arrow in the figure) are opposite.
  • the incident light has an optical component in the direction in which the waveguide element 10 extends (X direction in the figure) and an optical component in the arrangement direction of the waveguide elements 10 (Y direction in the figure).
  • the sensitivity of the optical component in the X direction can be adjusted by the adjusting element incorporated in the waveguide array 10A.
  • the sensitivity of the optical component in the arrangement direction of the waveguide element 10 can be adjusted by the adjusting element incorporated in the phase shifter array 80A. From the phase difference ⁇ of the light when the sensitivity of the optical receiving device is maximized, the refractive index nw and the thickness d of the optical waveguide layer 20, ⁇ and ⁇ 0 shown in FIG. 4 can be found. Thereby, the incident direction of the light can be specified.
  • the optical scanning device and the optical receiving device according to the embodiment of the present disclosure can be used for applications such as a rider system mounted on a vehicle such as an automobile, a UAV, or an AGV.
  • Waveguide element optical waveguide 11 optical waveguide 10A waveguide array 15 grating 20 optical waveguide layer, optical waveguide region 20L optical 21 liquid crystal material 30 first mirror 40 second mirror 50a first substrate 50b second substrate 51 dielectric layer 62a 1st electrode 62b 2nd electrode 62c 3rd electrode 62d 4th electrode 70a Drive circuit of waveguide array 70b Drive circuit of phase shifter array 80 Phase shifter 80A Phase shifter array 90 Optical brancher 100 Optical device 100a 1st structure 100b 2nd structure Body 101, 102 Direction 130 Light source 310 Beam spot 400 Photodetector 500 Control circuit 600 Signal processing circuit

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

L'invention concerne un dispositif optique comprenant : un premier miroir ayant une première surface réfléchissante ; un second miroir ayant une seconde surface réfléchissante faisant face à la première surface réfléchissante ; au moins une région de guide d'ondes optique qui est positionnée entre le premier miroir et le second miroir et propage de la lumière ; et au moins un guide d'ondes d'entrée de lumière qui est positionné entre le premier miroir et le second miroir et a une surface faisant face à la première surface réfléchissante, et dans lequel une section d'extrémité avant qui couple la lumière à la région de guide d'ondes optique se trouve à l'intérieur de la région de guide d'ondes optique. La distance entre la première surface réfléchissante et la surface d'une partie autre que la section d'extrémité avant dans le guide d'ondes d'entrée de lumière est supérieure à la distance entre la première surface réfléchissante et la surface de la section d'extrémité avant dans le guide d'ondes d'entrée de lumière.
PCT/JP2021/028236 2020-11-24 2021-07-30 Dispositif optique et système de détection optique WO2022113427A1 (fr)

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Citations (6)

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Publication number Priority date Publication date Assignee Title
WO2017106880A1 (fr) * 2015-12-17 2017-06-22 Finisar Corporation Systèmes couplés en surface
WO2019130721A1 (fr) * 2017-12-28 2019-07-04 パナソニックＩｐマネジメント株式会社 Dispositif optique
WO2019187681A1 (fr) * 2018-03-27 2019-10-03 パナソニックＩｐマネジメント株式会社 Dispositif optique et système de détection de lumière
WO2019187777A1 (fr) * 2018-03-27 2019-10-03 パナソニックＩｐマネジメント株式会社 Dispositif optique et système de détection optique
JP2019174538A (ja) * 2018-03-27 2019-10-10 パナソニックＩｐマネジメント株式会社 光デバイス
WO2019224341A1 (fr) * 2018-05-24 2019-11-28 Robert Bosch Gmbh Dispositif de déflexion de faisceau pour influencer un angle d'un faisceau lumineux sortant du dispositif de déflexion de faisceau et procédé pour faire fonctionner un dispositif de déflexion de faisceau

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017106880A1 (fr) * 2015-12-17 2017-06-22 Finisar Corporation Systèmes couplés en surface
WO2019130721A1 (fr) * 2017-12-28 2019-07-04 パナソニックＩｐマネジメント株式会社 Dispositif optique
WO2019187681A1 (fr) * 2018-03-27 2019-10-03 パナソニックＩｐマネジメント株式会社 Dispositif optique et système de détection de lumière
WO2019187777A1 (fr) * 2018-03-27 2019-10-03 パナソニックＩｐマネジメント株式会社 Dispositif optique et système de détection optique
JP2019174538A (ja) * 2018-03-27 2019-10-10 パナソニックＩｐマネジメント株式会社 光デバイス
WO2019224341A1 (fr) * 2018-05-24 2019-11-28 Robert Bosch Gmbh Dispositif de déflexion de faisceau pour influencer un angle d'un faisceau lumineux sortant du dispositif de déflexion de faisceau et procédé pour faire fonctionner un dispositif de déflexion de faisceau

Non-Patent Citations (1)

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Title
GU, X. ET AL.: "Experimental demonstration of thermal beam steering on a Bragg reflector waveguide", IEICE GENERAL CONFERENCE; OKAYAMA, JAPAN; MARCH 20-23, 2012, vol. 1, no. 1, 20 March 2012 (2012-03-20) - 23 March 2012 (2012-03-23), JP, pages 223, XP009537112 *

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