JP6711025B2 - Grating coupler, grating coupler array, imaging optical system, optical scanner, and laser radar device - Google Patents

Description

The present invention relates to a grating coupler, a grating coupler array, an image forming optical system, an optical scanner, and a laser radar device.

The grating coupler is an element that radiates light propagating through the waveguide to the outside, or an element that receives light input from the outside and couples the light into the waveguide. As a grating coupler having such a function, the one disclosed in Non-Patent Document 1 is known. FIG. 10A shows a conceptual diagram of the grating coupler 80 disclosed in Non-Patent Document 1.

As shown in FIG. 10A, the grating coupler 80 includes an introduction waveguide 86, an adiabatic taper portion 84 connected to the introduction waveguide 86, and a diffraction grating portion 82. In the grating coupler 80, the light that has propagated through the introduction waveguide 86 propagates through the tapered portion 84 and is then emitted from the diffraction grating portion 82. On the other hand, the light incident on the diffraction grating section 82 propagates through the tapered section 84 and is coupled to the introduction waveguide 86. Hereinafter, a grating coupler having a structure like the grating coupler 80 shown in FIG. 10A will be referred to as a “tapered grating coupler”.

On the other hand, as another example of the grating coupler, one disclosed in Non-Patent Document 2 is known. FIG. 10B shows a conceptual diagram of the grating coupler 90 disclosed in Non-Patent Document 2. As shown in FIG. 10B, the grating coupler 90 includes an introduction waveguide 96, a condensing unit 94, and a diffraction grating unit 92. In the grating coupler 90, the diffraction grating section 92 is configured to exhibit a lens effect having a focal point at the connection point between the condensing section 94 and the introduction waveguide 96.

Similarly to the grating coupler 80, in the grating coupler 90, the light that has propagated through the introduction waveguide 96 propagates through the condensing unit 94 and then is emitted from the diffraction grating unit 92. On the other hand, the light that has entered the diffraction grating section 92 propagates through the condensing section 94 and is coupled to the introduction waveguide 96. Hereinafter, a grating coupler having a structure like the grating coupler 90 shown in FIG. 10B will be referred to as a “condensing grating coupler”.

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL.24, No.24, DECEMBER 15, 2012 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL.19, No.23, DECEMBER 1, 2007

By the way, in a device using an optical array antenna such as a laser radar device, a grating coupler arrayed in a light projecting section or a light receiving section, that is, a grating coupler array may be used. At that time, from the viewpoint of miniaturization of the laser radar device, the grating coupler array is required to have a high integration density.

However, in the above-mentioned taper type grating coupler, since it is necessary to change the propagation mode "adiabatically" so that the taper portion 84 does not disturb the propagation mode of the propagating light, the length of the taper portion 84 is extremely large. There is a problem that it becomes long and it is difficult to miniaturize.

On the other hand, in the above-mentioned condensing grating coupler, due to its structure, the entire size is larger than the effective equal light receiving area (effective aperture) of the diffraction grating section 92, and it is difficult to reduce the size. There was a problem.

On the other hand, when the grating coupler is integrated by the optical waveguide technology and the grating coupler array is to be realized as an optical integrated circuit, the minimum bending radius when connecting the waveguides and performing the waveguide wiring in the conventional grating coupler. However, there is a problem that another optical element cannot be arranged in a portion that secures the minimum bending radius. In other words, the grating coupler according to the conventional technique has a problem that the effective aperture is small in spite of the large overall size and it is difficult to increase the integration density.

Further, in an optical array antenna such as a laser radar device, there is a configuration using an image forming optical system as a configuration of a light projecting unit and a light receiving unit. In the configuration of the light projecting unit and the light receiving unit using the image forming optical system, it is desirable that the grating couplers be arranged in an array with a high occupancy ratio of the effective apertures without a gap. However, it is difficult to form an array in this manner with the above-mentioned conventional grating coupler.

The above problem will be described in more detail with reference to FIG. FIG. 11A is a diagram showing a photodetector 900 using a grating coupler array according to the related art, and FIG. 11B is a diagram conceptually showing an output side grating coupler 902. (C) is a figure which shows notionally each grating coupler 904 by the side of incidence. The light receiver 900 includes a grating coupler array 910 in which the grating couplers 904 are arranged in an array, and a lens 912.

As shown in FIG. 11B, in the grating coupler 902 on the emission side, the area occupied by the light projecting region 906 is smaller than the area of the entire diffraction grating portion, and the diffraction grating portion cannot be used effectively. The same applies to the grating coupler 904 on the incident side, and the ratio of the area of the light receiving region 908 to the entire diffraction grating portion is small. For example, when the light receiver 900 is configured using such a grating coupler according to the related art, the point image of the object O formed by the light receiving region 908 upon incidence of the received light Pr in the light receiver 900 is as shown in FIG. As shown in FIG. 11(a), the density becomes low.

The present invention has been made in view of the above problems, and when arranged in an array, it is possible to increase the integration density and facilitate mutual connection, a grating coupler, a grating coupler array, and an imaging device. An object is to provide an optical system, an optical scanner, and a laser radar device.

In order to achieve the above object, the grating coupler according to claim 1 is configured such that an introduction waveguide for introducing light and an end portion having a predetermined width are connected to one end of the introduction waveguide, and A spot size conversion part that expands from both ends in a substantially fan shape and that expands the spot size of light propagating in the introduction waveguide, and the spot around the connection part between the introduction waveguide and the spot size conversion part A diffraction grating portion formed of a plurality of arcuate concavo-convex portions formed concentrically along the arc portion of the size conversion portion, and the introduction waveguide, the spot size conversion portion, and the diffraction grating portion in an optical integrated circuit Integrated, the overall shape of the optical integrated circuit by exhibiting a substantially rectangular shape by gradually increasing after gradually increasing the length of the arc , the introduction waveguide is arranged at one apex of the substantially rectangular shape, The shape is symmetrical with respect to a line segment that connects the one apex and the apex on the diagonal of the one apex .

The invention according to claim 2 is the invention according to claim 1, wherein the introduction waveguide has a width in plan view of the introduction waveguide near a connection point with the spot size conversion portion. It has a taper portion which is enlarged in a taper shape in the traveling direction of propagation light in the waveguide.

In the invention according to claim 3, in the invention according to claim 2, the end portion of the spot size conversion portion is in a direction opposite to the traveling direction in the vicinity of a connection point with the introduction waveguide. It is folded back and formed into a flare shape.

In order to achieve the above object, the grating coupler array according to claim 4 has a waveguide extending in a predetermined direction, a plurality of directional couplers provided along the waveguide, and the plurality of directions. The grating according to any one of claims 1 to 3, wherein the introduction waveguide is connected to a sex coupler, and a plurality of the substantially rectangular-shaped sides are arranged to face each other in the predetermined direction. It includes a coupler.

In order to achieve the above object, the imaging optical system according to claim 5 includes the grating coupler array according to claim 4 and a lens corresponding to each of the plurality of grating couplers forming the grating coupler array. And a lens array provided therein.

In order to achieve the above object, the optical scanner according to claim 6 is a light source, and the imaging optical system according to claim 5, wherein one end of the waveguide of the grating coupler array is connected to the light source. A plurality of optical switches connected to each of the plurality of grating couplers forming the grating coupler array.

In order to achieve the above object, the grating coupler array according to claim 7 has a waveguide extending in a predetermined direction, a plurality of directional couplers provided along the waveguide, and the plurality of directional characteristics. The grating coupler according to any one of claims 1 to 3, wherein the introduction waveguide is connected to a coupler and a plurality of the rectangular couplers are arranged with the sides of the substantially rectangular shape facing each other in the predetermined direction. Including a plurality of line grating couplers, the plurality of line grating couplers are arranged in a direction intersecting the predetermined direction, a plurality of the grating couplers constituting the plurality of line grating couplers are arranged in a matrix. It is a thing.

In order to achieve the above object, the imaging optical system according to claim 8 includes the grating coupler array according to claim 7 and a lens corresponding to each of the plurality of the grating couplers forming the grating coupler array. And a lens array provided therein.

In order to achieve the above object, the laser radar device according to claim 9 is a light source, the imaging optical system according to claim 8, wherein one end of the waveguide of the grating coupler array is connected to the light source. 9. A light projecting unit that includes a plurality of optical switches connected to each of a plurality of the line grating couplers and emits light from the grating coupler array, the grating coupler array according to claim 8, and the grating coupler array. And a light receiving section that is connected to the waveguide and receives the light that has entered the grating coupler array.

According to the present invention, a grating coupler, a grating coupler array, an imaging optical system, an optical scanner, and a laser radar that can increase the integration density and facilitate mutual connection when arranged in an array. It is possible to provide the device.

It is a top view showing an example of composition of a grating coupler concerning a 1st embodiment. FIG. 4 is a plan view showing a comparison between a light receiving section including the grating coupler according to the first embodiment and a light receiving section including a grating coupler according to a conventional technique. It is a figure explaining the shape of the grating coupler which concerns on 1st Embodiment. It is a figure which compares the simulation result of the radiation characteristic of the grating coupler which concerns on 1st Embodiment with the simulation result of the radiation characteristic of a condensing type grating coupler. It is a figure which shows the measured result of NFP of the grating coupler which concerns on 1st Embodiment in comparison with the measured result of NFP of the condensing type grating coupler. It is a figure explaining an example of composition of an optical scanner concerning a 2nd embodiment. It is a figure which shows an example of a structure of the grating coupler array which concerns on 2nd Embodiment. It is a figure explaining an example of the optical array antenna composition concerning a 3rd embodiment. It is a figure which shows an example of a structure of the light projection part of the optical array antenna which concerns on 3rd Embodiment. It is a figure which shows the structure of the grating coupler which concerns on a prior art. It is a figure which shows the structure of the light receiver which concerns on a prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
The grating coupler 10 according to the present embodiment and its characteristics will be described with reference to FIGS. 1 to 5.

As shown in FIG. 1, the grating coupler 10 includes a diffraction grating section 12, a taper section 14 (spot size conversion section), and an introduction waveguide 16. The diffraction grating portion 12 is a portion that emits or enters light, and the taper portion 14 is a portion that efficiently couples the emitted light or the incident light with the introduction waveguide 16. The introduction waveguide 16 is a portion for connecting to another waveguide or another grating coupler 10 when the grating coupler 10 is formed into an array.

As shown in FIG. 1, the grating coupler 10 has a diffraction grating portion 12 formed in an arc shape, and has a rectangular shape (a substantially square shape or a substantially rhombus shape) as a whole. It is arranged at one apex of a rectangle and has a symmetrical shape with respect to a line segment connecting the one apex and the apex on the diagonal of the one apex. The diffraction grating of the diffraction grating portion 12 according to the present embodiment is formed by the substantially fan-shaped concavo-convex shape centered on the connection point between the tapered portion 14 and the introduction waveguide 16 and has a light condensing function. The size of the grating coupler 10 according to the present embodiment is, for example, about 18 μm×18 μm.

Next, with reference to FIG. 2, a light receiving section 400 using the grating coupler 10 according to the present embodiment will be described in comparison with a light receiving section 800 using the conventional grating coupler 80. 2A shows the light receiving unit 800, and FIG. 2B shows the light receiving unit 400. 2C shows the light receiving area RA of the grating coupler 80 according to the related art, FIG. 2D shows the light receiving area RA of the grating coupler 90 according to the related art, and FIG. Each of the light receiving regions RA of the grating coupler 10 according to the embodiment is shown. The light receiving area RA shown in FIGS. 2C to 2E is a light emitting area in the case of a light emitting section.

As shown in FIG. 2C, in the grating coupler 80, the length of the tapered portion 84 is increased to maintain the single mode of the propagating light, and the ratio of the light receiving area RA to the entire grating coupler (effective aperture ratio). Becomes smaller. In the condensing type grating coupler 90, this point is improved and the size itself is further miniaturized. However, since the bending of the diffraction grating portion 92 for condensing the light at the focus f causes a limitation, the miniaturization can be further reduced. difficult.

In contrast to the above-described conventional technique, in the grating coupler 10, as shown in FIG. 2E, a portion having a large contribution to the received light is left and a portion having a small contribution to the received light is deleted to form a rectangular shape as a whole. As a result, it has become possible to greatly reduce the size. Moreover, by performing the waveguide wiring along the wiring directions D1 and D2 along the two sides of the rectangular shape, wasteful space is suppressed and high-density wiring becomes possible.

The characteristics of the outer shape of the grating coupler 10 will be described in more detail with reference to FIG. FIG. 3 is a diagram for explaining the process of determining the shape of the grating coupler 10, starting from the original shape, and selecting the shape of each part with respect to the shape of the grating coupler 10.

FIG. 3A shows a prototype shape which is a starting point in examining the shape. As the next process, as shown in FIG. 3B, in order to improve the coupling efficiency between the taper portion 14 and the introduction waveguide 16 and improve the reproducibility in the manufacturing process, the taper portion 14 and the introduction waveguide 16 are formed. A taper T is provided at the connecting portion with. As the next process, as shown in FIG. 3C, a flare F was provided to suppress unintended reflection at the taper T. As a next process, as shown in FIG. 3D, a region (low contribution region) N having a small contribution to light projection or light reception at the apex of the figure shown in FIG. Through the above determination process, the final shape of the grating coupler 10 shown in FIG. 3E was determined.

Next, a comparison between the light receiving unit 400 and the light receiving unit 800 will be described. As shown in FIG. 2A, the light receiving unit 800 includes a grating coupler 80 and an optical switch 802 connected to the grating coupler 80 by a waveguide 804. On the other hand, the light receiving unit 400 includes a grating coupler array 402 and an optical switch array 404 connected to the grating coupler array 402 by a waveguide 406. Since the grating coupler 10 has the above-described characteristics, the grating coupler array 402 can significantly increase the integration density of the grating coupler 10. Therefore, as shown in FIGS. 2A and 2B, in the light receiving unit 400 according to the present embodiment, the effective light receiving area can be significantly expanded as compared with the light receiving unit 800 according to the conventional technique. Became.

Next, with reference to FIGS. 4 and 5, the examination result of the low contribution region N will be described. FIG. 4 is a diagram showing a light irradiation state of the diffraction grating section 12 of the grating coupler 10 in comparison with a light irradiation state of the diffraction grating section 92 of the grating coupler 90.

FIG. 4A shows a result of simulating a state where the light propagating through the introduction waveguide 16 is radiated by the diffraction grating section 12 in the grating coupler 10 shown in FIG. 4B. On the other hand, FIG. 4C shows a result of simulating a state in which the light propagating through the introduction waveguide 96 is radiated by the diffraction grating section 12 in the grating coupler 90 shown in FIG. 4D. As is clear from comparison between FIGS. 4A and 4C, there is no great difference between the density of the emitted light in the grating coupler 10 and the density of the emitted light in the grating coupler 90. It turns out that the selection is appropriate.

FIG. 5 shows the results of measuring the NFPs (Near Field Patterns) of the both using the actually manufactured grating coupler 10 and the grating coupler 90. FIG. 5A is a schematic configuration diagram showing an NFP measurement system 50. As shown in FIG. 5A, a tip spherical fiber 56 is coupled to a chip 58 on which the grating coupler 10 or 90 is formed, and the input light Pin is made incident to perform TE mode excitation. The NFP of the radiated light 54 generated as a result is measured by the NFP measuring device 52 including a camera and the like.

FIG. 4(d) shows the NFP measurement result of the grating coupler 90 shown in FIG. 4(c), and FIG. 4(f) shows the NFP measurement result of the grating coupler 10 shown in FIG. 4(e). ing. As is clear from a comparison between FIG. 5D and FIG. 5F, there is no big difference between the two, and the grating coupler 10 according to the present embodiment, which has a smaller shape, is the grating coupler according to the related art. It can be said that the performance of is maintained.

Note that FIG. 5B shows a simulation result of radiated light in the grating coupler 90, and as is clear from comparison between FIG. 5B and FIG. The results are in good agreement.

As described above in detail, the grating coupler according to the present embodiment has a configuration suitable for forming an imaging optical system, for example, and according to the grating coupler according to the present embodiment, It is possible to provide a grating coupler capable of increasing the integration density and facilitating mutual connection when the grating couplers are arranged in a line.

[Second Embodiment]
The optical scanner 100 according to the present embodiment will be described with reference to FIGS. 6 and 7. The optical scanner 100 is a form in which a mechanical coupler is realized by applying a grating coupler array in which the grating couplers 10 are arranged in an array to an optical scanner. The mechanicalless scan is a scan that does not include a movable part.

As shown in FIG. 6D, the optical scanner 100 includes an optical integrated circuit 102, a microlens 104, an optical fiber 106, a mount 108, and a control board 110.

As shown in FIG. 6B, the optical integrated circuit 102 includes a grating coupler array 120 (see FIG. 7A) in which the grating couplers 10 are arrayed, and the input light Pin is incident/non-incident on the grating coupler array 120. The optical switch 118 and the like for switching between are integrated by optical waveguide technology.

The microlens 104 has microlenses corresponding to the individual grating couplers 10 constituting the grating coupler array 120 arranged in an array, and collects light emitted from the grating coupler array 120.

The optical fiber 106 is a spherical fiber that couples the input light Pin from the light source to the optical integrated circuit 102. The mount 108 is a substrate on which the optical integrated circuit 102 is mounted. The control board 110 is a part that performs overall control of the optical scanner 100, such as on/off control of the optical switch 118.

FIG. 6C is a photograph showing the irradiation light from the grating coupler array 120 observed by the camera. It can be seen that the respective light spots shown in FIG. 6C are emitted light from the grating couplers 10, and the emitted light is emitted from the grating couplers 10 substantially evenly. FIG. 6A shows a measurement system of the radiated light of FIG. 6C, which is configured so that the light emitted from the optical integrated circuit 102 and transmitted through the microlens 104 is observed by the infrared camera 114. ing. The photograph of FIG. 6C is taken by the infrared camera 114.

Next, the grating coupler array 120 according to the present embodiment will be described in more detail with reference to FIG. 7A is a plan view showing the entire grating coupler array 120, FIG. 7B is a partially enlarged view of the grating coupler array 120 shown in FIG. 7A, and FIG. 7C is a grating coupler. 6 is a photograph showing irradiation light from the array 120.
It should be noted that FIG. 7C is a reprint of the same drawing as FIG. 6C.

As shown in FIGS. 7A and 7B, the grating coupler array 120 is configured by connecting 50 grating couplers 10 in series via the waveguide 18. As shown in FIG. 7B, the grating coupler 10 is arranged along the wiring direction D3 while being branched by the directional coupler 20 and the MMI (Multimode Interference) brancher 22. At that time, the grating coupler 10 is inclined by 45° with respect to the wiring direction D3, and is arranged such that the sides of the substantially square grating coupler 10 face each other. By arranging in this way, the grating coupler 10 can be densely arranged. The grating coupler array 120 according to the present embodiment is configured by arranging 50 grating couplers 10 of about 18 μm×18 μm at intervals of about 2 μm.

When the input light Pin enters from one end of the waveguide 18 of the grating coupler array 120 configured as described above, it enters the respective grating couplers 10 from the directional coupler 20 and the MMI branching device 22 via the introducing waveguide 16. The input light Pin is distributed, the light is emitted from each grating coupler 10, and the light is output in the light irradiation pattern shown in FIG. 7C.

As described above in detail, the optical scanner according to the present embodiment uses the grating coupler that can increase the integration density and facilitate mutual connection when arranged in an array. It is possible to provide an optical scanner.

[Third Embodiment]
A light projecting/receiving device 300 according to the present embodiment will be described with reference to FIGS. 8 and 9.
The light projecting/receiving device 300 is mounted on, for example, a laser radar device, and includes a light projecting unit that emits light and a light receiving unit that receives light.

First, the overall configuration of the light projecting/receiving device 300 will be described with reference to FIGS. 8E is a side view of the light projecting/receiving device 300, and FIG. 8D is a plan view of the optical integrated circuit 302. As shown in FIG. 8E, a light projecting/receiving device 300 includes a light projecting unit 308, a light receiving unit 310, an optical integrated circuit 302 in which elements such as an optical switch related to light projecting and light receiving are formed, and a microlens. 306 and PD (Photodiode) 304 are included.

As shown in FIG. 8D, the optical integrated circuit 302 includes a light projecting unit 308 including a grating coupler array 312 (optical array antenna) and a light receiving unit 310 including a grating coupler array 320 (optical array antenna). Are arranged.

The input light Pin enters from one end of the waveguide 316, and passes through the optical switch array 314 in which the optical switches 322 corresponding to the respective grating couplers of the grating coupler array 312 are arranged in an array, and the grating coupler of the light projecting unit 308. Input to the array 312. When the input light Pin is transmitted by the optical switch 322, the light projection light Po is emitted from the corresponding grating coupler 10.

On the other hand, a part of the input light Pin is branched by a directional coupler or the like and supplied to the grating coupler array 320 of the light receiving unit 310 as the reference light Pref. The reference light Pref is mixed with the received light Pr incident on the grating coupler array 320, for example, homodyne detection is performed, and the distance to the object O or the like is calculated.

FIG. 8A shows an example of the configuration of the optical switch 322 according to this embodiment. As shown in FIG. 8A, the optical switch 322 is configured by, for example, a ring resonator type optical switch including a ring waveguide 328 configured in a ring shape and a heater 326. In the optical switch 322, the heater 326 controls the refractive index of the ring waveguide 328, and the light having the resonance frequency of the ring waveguide 328 is transmitted.

FIG. 8B shows a distribution state of the input light Pin in the grating coupler array 312. As shown in FIG. 8( b ), the grating coupler 10 is arranged in a state of being inclined by approximately 45° with respect to the traveling direction of the input light Pin, and the introduction coupler coupled by the waveguide 316 and the directional coupler 324 is provided. The input light Pin is distributed via the waveguide 16.

FIG. 8C shows how the received light Pr is condensed in the grating coupler array 320. As shown in FIG. 8C, the grating coupler 10 is arranged in a state of being inclined by about 45° with respect to the traveling direction of the received light Pr, and is coupled by the waveguide 316 and the directional coupler 324. The received light Pr is condensed via the waveguide 16.

The light projecting unit 308 according to the present embodiment will be described in more detail with reference to FIG. As shown in FIG. 9, the grating coupler array 312 according to the present embodiment is configured, for example, by arranging the grating couplers 10 in an 8×20 matrix. As described with reference to FIG. 8B, in the grating coupler array 312, the individual grating couplers 10 are tilted by about 45° with respect to the waveguide 316, and substantially square sides are arranged so as to face each other. 10 most closely arranged. As shown in FIG. 9, the grating coupler array 312 is connected to the waveguide 316 in units of eight grating couplers 10 (line grating couplers) connected in series in the traveling direction of the waveguide 316. Light from the optical switch 322 is input.

On the other hand, the optical switch array 314 is connected to the grating coupler array 312 by the waveguide 316. Each optical switch 322 includes a ring waveguide 328 and a heater 326 arranged on the ring waveguide 328 as described with reference to FIG. 8A, and both ends of the heater 326 are connected to a power source (not shown) by electric wiring 318. It is connected. The refractive index of the ring waveguide 328 is controlled by the heater 326, and when the resonance frequency of the ring waveguide 328 matches, the input light Pin is transmitted to the grating coupler array 312, and when it does not match, the input light Pin is blocked.

As described above in detail, according to the light projecting/receiving device of this embodiment, it is possible to increase the integration density and facilitate mutual connection in the case of arranging them in an array. It is possible to provide a laser radar device using the.

10 Grating Coupler 12 Diffraction Grating Part 14 Tapered Part 16 Introducing Waveguide 18 Waveguide 20 Directional Coupler 22 MMI Branching Device 50 Measuring System 52 Measuring Device 54 Emitted Light 56 Tip Fiber 58 Chip 80 Grating Coupler 82 Diffraction Grating Part 84 Taper Part 86 Introduction waveguide 90 Grating coupler 92 Diffraction grating part 94 Condensing part 96 Introduction waveguide 100 Optical scanner 102 Optical integrated circuit 104 Microlens 106 Optical fiber 108 Mount 110 Control board 114 Infrared camera 118 Optical switch 120 Grating coupler array 300 Emitter/receiver 302 Optical integrated circuit 304 PD
306 Microlens 308 Light projecting unit 310 Light receiving unit 312 Grating coupler array 314 Optical switch array 316 Waveguide 318 Electrical wiring 320 Grating coupler array 322 Optical switch 324 Directional coupler 326 Heater 328 Ring waveguide 400 Light receiving unit 402 Grating coupler array 404 Optical switch array 406 Waveguide 800 Light receiving unit 802 Optical switch 804 Waveguide 900 Light receiver 902 Grating coupler 904 Grating coupler 906 Light emitting area 908 Light receiving area 910 Grating coupler array 912 Lens D1, D2, D3 Wiring direction F Flare N Low contribution area O object Pin input light Po light projection light Pr light reception light Pref reference light RA light reception area T taper

Claims (9)

An introduction waveguide for introducing light,
An end portion having a predetermined width is connected to one end of the introduction waveguide, and a spot size conversion for expanding the spot size of light propagating through the introduction waveguide while expanding from both ends of the end portion into a substantially fan shape. Department,
A diffraction grating portion comprising a plurality of arc-shaped concavo-convex portions formed concentrically along the arc portion of the spot size conversion portion and centered on the connection portion between the introduction waveguide and the spot size conversion portion. ,
The introduction waveguide, the spot size conversion unit, and the diffraction grating unit are integrated in an optical integrated circuit, and the length of the circular arc gradually increases and then gradually decreases, so that the overall shape of the optical integrated circuit exhibits a substantially rectangular shape. At the same time, the introduction waveguide is arranged at one vertex of the substantially rectangular shape, and the grating has a shape symmetrical with respect to a line segment connecting the one vertex and a vertex on a diagonal of the one vertex. Coupler. In the vicinity of the connection point with the spot size conversion portion, the introduction waveguide has a tapered portion in which the width of the introduction waveguide in plan view is tapered in the traveling direction of the propagation light in the introduction waveguide. The grating coupler according to Item 1. The grating coupler according to claim 2, wherein the end portion of the spot size conversion portion is formed in a flare shape by being folded back in a direction opposite to the traveling direction in the vicinity of a connection point with the introduction waveguide. A waveguide extending in a predetermined direction,
A plurality of directional couplers provided along the waveguide,
The plurality of directional couplers are connected to the introduction waveguide, and the plurality of directional couplers are arranged with the sides of the substantially rectangular shape facing each other in the predetermined direction. Including the grating coupler described in
Grating coupler array. A grating coupler array according to claim 4;
A lens array provided with a lens corresponding to each of the plurality of grating couplers constituting the grating coupler array,
Imaging optics including. A light source,
The imaging optical system according to claim 5, wherein one end of the waveguide of the grating coupler array is connected to the light source.
A plurality of optical switches connected to each of the plurality of grating couplers constituting the grating coupler array,
Optical scanner including. A waveguide extending in a predetermined direction, a plurality of directional couplers provided along the waveguide, and the introduction waveguide connected to the plurality of directional couplers, and in the predetermined direction A plurality of line grating couplers including the plurality of grating couplers according to any one of claims 1 to 3, which are arranged so that sides of a substantially rectangular shape are opposed to each other,
A grating coupler array in which a plurality of the line grating couplers are arranged in a direction intersecting with the predetermined direction, and a plurality of the grating couplers configuring the plurality of the line grating couplers are arranged in a matrix. A grating coupler array according to claim 7,
A lens array provided with a lens corresponding to each of the plurality of grating couplers constituting the grating coupler array,
Imaging optics including. A light source, an imaging optical system according to claim 8 in which one end of the waveguide of the grating coupler array is connected to the light source, and a plurality of optical switches connected to each of the plurality of line grating couplers, A light projecting section for emitting light from the grating coupler array,
9. The grating coupler array according to claim 8, and a light receiving unit that is connected to the waveguide of the grating coupler array and receives light incident on the grating coupler array.
Laser radar device including.