JP7396609B2 - grating array - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to diffraction grating arrays.

Non-Patent Document 1 discloses a technique using a diffraction grating array. This technology uses a diffraction grating for TE waves and a diffraction grating for TM waves to separate and detect TE waves (orthogonal polarization) and TM waves (parallel polarization) contained in light. It is comprised of parts of which are overlapped.

"A Grating-Coupler-Enabled CMOS Photonics Platform" IEEE Journal of Selected Topics in Quantum Electronics, Volume 17 Issue 3, May-June 2011.

By the way, as a measuring device for measuring the distance to an object to be measured (hereinafter referred to as "object"), there are known laser radar devices that use the reflected light when the object is irradiated with light. In order to efficiently detect the reflected light, an optical antenna is known that uses a diffraction grating in the part that receives the reflected light. Reflected light may be weak, and there is a need to improve light reception efficiency. On the other hand, according to the technique disclosed in Non-Patent Document 1, although it is possible to separate laser light into TE waves and TM waves using each diffraction grating, the light reception efficiency of the received light itself is not taken into account. In a diffraction grating, for example, in a grating pattern in which grooves are formed at predetermined intervals, the light receiving efficiency in the surrounding area is lower than the light receiving efficiency in the central part. Therefore, in order to receive light over a wide range as a light receiving section of an optical antenna, it is sufficient to arrange a plurality of optical antennas side by side. However, since the light receiving efficiency at the periphery of each adjacent diffraction grating is lower than the light receiving efficiency at the center, the light receiving efficiency when receiving light over a wide range is reduced. Therefore, there is room for improvement in order to improve the light receiving efficiency of the light receiving portion.

The present invention has been made in view of the above facts, and aims to provide a diffraction grating array that has a simple and small-scale configuration and can improve light reception efficiency when receiving light using a diffraction grating. purpose.

In order to achieve the above object, the diffraction grating array according to the first aspect has a plurality of grating patterns, and the center portions of adjacent grating patterns among the plurality of grating patterns do not overlap, and the diffraction grating array has a plurality of grating patterns. A diffraction grating configured such that a part of the peripheral region where the electric field strength of the diffracted light is smaller than the electric field strength of the diffracted light at the central region overlaps, and a diffraction grating that is in a direction that intersects the direction of incidence of the incident light to the diffraction grating. A waveguide in which the diffraction grating is formed on the light incidence side so as to change the direction of light in the propagation direction of light , and the waveguide propagates the diffracted light diffracted by the plurality of grating patterns of the diffraction grating. and an overlapping amount of a region in which a portion of the peripheral portion of the diffraction grating overlaps with the efficiency of light coupled to the waveguide by a single grating pattern among the plurality of grating patterns; Diffraction with a size that maximizes the light receiving efficiency determined by multiplying the area ratio expressed by the ratio of the total area when some of the plurality of grating patterns overlap to the total area when the grating patterns do not overlap. It is a grid array.

A second aspect is the diffraction grating array of the first aspect,
In the diffraction grating, the grating patterns are formed on the same plane.

A third aspect is the diffraction grating array of the first aspect or the second aspect,
The diffraction grating includes a plurality of diffraction members having the grating pattern, and is formed by overlapping parts of the adjacent diffraction members so that part of the grating patterns of adjacent diffraction members overlap among the plurality of diffraction members. do.

In a fourth aspect, in the diffraction grating array according to any one of the first to third aspects, adjacent regions of the peripheral region where the electric field strength of the diffracted light is equal to or less than a predetermined threshold overlap. The lattice pattern is configured so that a portion thereof overlaps.

In a fifth aspect, in the diffraction grating array according to any one of the first to fourth aspects, the diffraction grating preliminarily converts one of the incident light waves including the TM wave light and the TE wave light. A first diffraction grating group that diffracts at a predetermined diffraction angle, and diffracting the other wave of the incident light at a diffraction angle opposite in sign to the diffraction angle of the first diffraction grating group. a second diffraction grating group, wherein the arrangement direction of the grating patterns of the first diffraction grating group and the arrangement direction of the grating patterns of the second diffraction grating group are the same direction, and each diffraction light beam is The first diffraction grating group and the second diffraction grating group are arranged so that the diffraction gratings are directed in opposite directions, and the incident light is separated into the TM wave light and the TE wave light, respectively. The wave path propagates each of the TM wave light and the TE wave light separated by the diffraction grating.

As described above, according to the present disclosure, it is possible to improve the light reception efficiency when receiving light using a diffraction grating with a simple and small-scale configuration.

FIG. 1 is a block diagram showing an example of a schematic configuration of a laser radar device according to a first embodiment. FIG. 2 is a block diagram showing an example of a diffraction grating array included in the optical antenna according to the first embodiment. FIG. 2 is an image diagram showing an example of a diffraction grating array according to the first embodiment. FIG. 3 is an image diagram showing an example of some grating patterns included in the diffraction grating array according to the first embodiment. FIG. 2 is an image diagram showing an example of a lattice pattern group in which a plurality of lattice patterns partially overlap according to the first embodiment. FIG. 3 is an image diagram showing an example of a diffraction grating array included in an optical antenna having a structure in which grating patterns partially overlap according to the first embodiment. FIG. 3 is an image diagram showing an example of a grating pattern in the diffraction grating array according to the first embodiment. FIG. 6 is an image diagram showing an example of characteristics related to light reception efficiency when a portion of the grating pattern according to the first embodiment is overlapped. FIG. 7 is a conceptual diagram showing an example of a schematic configuration of a light receiving device according to a second embodiment. FIG. 7 is an explanatory diagram of a diffraction angle in one grating in a diffraction grating array according to a second embodiment. FIG. 12 is a configuration diagram showing an example of a diffraction grating array in which diffraction grating groups with opposite positive and negative diffraction angles are formed on a waveguide substrate in a diffraction grating array according to a second embodiment. FIG. 7 is an image diagram showing an example of the configuration of a diffraction grating array according to a second embodiment. FIG. 7 is an image diagram showing an example of the configuration of a diffraction grating array according to a third embodiment. FIG. 7 is an image diagram showing an example of the configuration of a diffraction grating array according to a third embodiment.

[First embodiment]
Embodiments that implement the technology of the present disclosure will be described in detail below with reference to the drawings. In this embodiment, an example will be described in which the technology of the present disclosure is applied to an incident-side optical antenna that detects an object using laser light in a laser radar device mounted on a vehicle, for example.

FIG. 1 shows an example of a schematic configuration of a laser radar device 10.
As shown in FIG. 1, the laser radar device 10 includes an optical antenna 12 that receives light from a target object SP, a signal processing unit 14 that converts the light detected by the optical antenna 12 into an electrical signal, and outputs the electrical signal. It includes an arithmetic processing section 16 that calculates the distance to the target object SP using the signal processed by the processing section 14. The optical antenna 12 includes a diffraction grating array 13 on the light incident side.

FIG. 2 shows an example of the diffraction grating array 13 that is included in the optical antenna 12 and receives light from the target object SP.
As shown in FIG. 2, in the diffraction grating array 13, a waveguide 13B for guiding light is formed on a substrate 13C. A grating pattern 13A is formed on the surface of the waveguide 13B opposite to the surface on which the substrate 13C is formed. The grating pattern 13A propagates the light to the waveguide 13B as diffracted light. Although details will be described later, the grating pattern 13A is designed to improve light receiving efficiency by forming a plurality of grating patterns. Moreover, the grating pattern 13A is designed to converge incident light. The example shown in FIG. 2 shows an example in which incident light is extracted as emitted light using a grating pattern. By arranging a photoelectric conversion sensor at the lattice pattern portion on the exit side in the example shown in FIG. 2, incident light can be converted into an electrical signal and output to the signal processing section 14.

Here, the light receiving efficiency of the diffraction grating array 13 included in the optical antenna 12 will be considered. The light receiving efficiency of the diffraction grating array 13 can be expressed by the following formula.

(light receiving efficiency)
= (diffraction grating array area ratio) x (in-plane mode overlap integral) x (coupling efficiency of layered structure)

Here, if the plane wave is G(x, y) and the propagation mode of the incident light, which has a Gaussian distribution when using a laser beam, is H(x, y), then the mode overlap integral is calculated by the following formula. can be expressed. Note that the coupling efficiency of the layered structure is a constant that can be measured when the diffraction grating array 13 is formed.

Therefore, in order to improve the light receiving efficiency of the diffraction grating array 13, the area ratio of the diffraction grating array 13 is dominant, and if the diffraction grating array 13 is formed so that the area ratio of the diffraction grating array 13 becomes large. good. For example, the diffraction grating array 13 receives a plane wave, but if the area of the luminous flux of the incident light on the light receiving surface of the diffraction grating array 13 is larger than the area of the light receiving surface of the grating pattern 13A constituting the diffraction grating, the grating pattern 13A , a plurality of them may be arranged side by side along the light receiving surface.

FIG. 3 shows an example of the diffraction grating array 13 that receives light from the target object SP. Further, FIG. 4 shows an example of some grating patterns included in the diffraction grating array 13.
In the example shown in FIG. 3, seven grating patterns 13A1 to 13A7 are arranged so that the light beam IB of the incident light on the light receiving surface of the optical antenna 12 can be received.

Incidentally, the electric field strength of a diffraction grating changes depending on the part of the grating pattern. As shown in FIG. 4, in each of the lattice patterns 13A2 and 13A3 arranged side by side, the electric field strength at the peripheral parts is smaller than that at the central part. Therefore, the light receiving efficiency decreases in areas around the grating pattern 13A where the electric field strength is low, and even if a plurality of them are arranged side by side along the light receiving surface, it is difficult to effectively utilize the incident light.

Therefore, in the present embodiment, the light receiving efficiency of the diffraction grating array 13 is improved by partially overlapping the grating patterns 13A in the diffraction grating array 13 and increasing the area ratio of the diffraction grating array 13.

FIG. 5 shows a grating pattern group 13Ax as an example in which the grating pattern 13A2 and the grating pattern 13A3 partially overlap.
As shown in FIG. 5, the grid pattern group 13Ax overlaps the surrounding areas where the electric field strength is low in each of the grid patterns 13A2 and 13A3, so as shown by the dotted line in FIG. increases. This improves light receiving efficiency.

FIG. 6 shows an example of a structure in which grating patterns 13A partially overlap in the diffraction grating array 13 shown in FIG. 3. Further, FIG. 7 shows an example of a grating pattern in the diffraction grating array 13 shown in FIG. 6.
As shown in FIG. 6, the diffraction grating array 13 includes a grating pattern group 13A-1 in which grating patterns 13A1 to 13A4 partially overlap, and a grating pattern group 13A-1 in which grating patterns 13A5 to 13A7 partially overlap. Two grating pattern groups, including pattern group 13A-2, are arranged so as to be able to receive the luminous flux IB of the incident light on the light receiving surface. In the example shown in FIG. 6, areas of overlapping lattice patterns are indicated by diagonal lines. Further, FIG. 7 shows an example of the lattice pattern group 13A-1. In this way, by partially overlapping the grating patterns 13A, light receiving efficiency can be improved.

Incidentally, by overlapping a portion of the plurality of lattice patterns 13A, the light receiving efficiency is improved, but the light receiving efficiency changes depending on the amount of overlap. That is, since a part of the pattern has been modified, there is a concern that efficiency may deteriorate.
Next, in order to verify concerns about efficiency deterioration, optimization of the amount of overlap in which a portion of the plurality of lattice patterns 13A overlaps will be described. Here, we will examine the case where the distance L between the center of the grating pattern 13A2 and the center of the grating pattern 13A3 (hereinafter referred to as center offset) is changed for the light receiving areas AR of the grating patterns 13A2 and 13A3 shown in FIG. did.

FIG. 8 shows an example of characteristics related to light reception efficiency when parts of the grating pattern 13A are overlapped at different overlap rates. The example shown in FIG. 8 shows a relationship indicating the efficiency of a single unit of the lattice pattern, a relationship indicating the light reception efficiency, and a relationship indicating the area ratio when the center offset L is changed.

The area ratio FF indicates the ratio of the area of the grating patterns 13A2 and 13A3 to the light receiving area AR, based on the case where the grating patterns 13A2 and 13A3 are arranged without overlapping each other. That is, the area ratio FF is defined as follows.
FF={Σ(area of single diffraction grating element)}/(footprint on chip)
Here, the single diffraction grating element refers to a diffraction grating that functions as a diffraction grating by itself before being superimposed. In many cases, (single diffraction grating element) x (number of diffraction gratings) = (total area of single diffraction grating elements). The footprint on the chip refers to the size of the diffraction grating formed as the diffraction grating array 13, that is, the total area on the diffraction grating array 13 of the diffraction grating in which a plurality of grating patterns are formed.
In the example shown in FIG. 8, the relationship between the area ratio when the center offset L is changed is shown by a dashed line. As shown in FIG. 8, from the area ratio of 1.0 when the center offset L1 is the case where the grid patterns 13A2 and 13A3 are arranged, as the center offset L becomes shorter, that is, the amount of overlap between the grid patterns 13A2 and 13A3 increases. As the area ratio FF increases, the area ratio FF increases.

On the other hand, the single efficiency of the grating pattern (hereinafter referred to as single efficiency) is the efficiency found from the value of the in-plane mode overlap integral of the grating pattern 13A2 or 13A3 and the coupling efficiency of the layered structure. Single element efficiency is the efficiency with respect to light coupled into one waveguide via one diffraction grating (diffraction grating single element). In the example shown in FIG. 8, the relationship of unit efficiency when the center offset L is changed is shown by a solid line. Moreover, the light receiving efficiency is obtained by multiplying the efficiency of a single grating pattern by the area ratio FF. In the example shown in FIG. 8, the relationship between the light receiving efficiency when the center offset L is changed is shown by a dotted line.

As shown in FIG. 8, when the center offset L is changed, the single efficiency and the light receiving efficiency increase as the center offset L becomes shorter, that is, as the amount of overlap between the grating patterns 13A2 and 13A3 increases, and The maximum value is reached at the center offset L (in the example shown in FIG. 8, the center offset L2). Then, as the center offset L becomes shorter from the center offset L2, the single element efficiency and the light receiving efficiency decrease.

In this way, when the center offset L2 is shortened with the predetermined center offset L2 as the boundary, the single efficiency and light reception efficiency decrease. This is thought to be because the diffraction grating eventually ceases to function as a diffraction grating. Therefore, it is preferable to overlap the grating patterns 13A at the distance to the center offset L2, and it is optimal to overlap the grating patterns 13A2 and 13A3 at the distance to the center offset L2 in order to maximize the light receiving efficiency.

The center offset L2 can be determined from the electric field strength of the diffracted light. For example, by experiment or calculation, a threshold value of the electric field strength that is preferably compensated for is determined in advance, and parts of adjacent grating patterns overlap so that regions where the electric field strength of the diffracted light is less than the predetermined threshold value overlap. You can configure it to do so.

As explained above, the diffraction grating array 13 included in the optical antenna 12 according to the present embodiment includes a plurality of grating patterns 13A, and the electric field strength of adjacent grating patterns 13A is higher than that at the center of the grating pattern 13A. The light receiving efficiency of the diffraction grating array 13 is improved by overlapping and overlapping the peripheral parts where the light is weak. Therefore, compared to the case where the diffraction grating array 13 is formed by arranging a plurality of diffraction gratings each having a grating pattern, it is possible to improve the light receiving efficiency of the diffraction grating array 13.

Moreover, the diffraction grating array 13 included in the optical antenna 12 according to the present embodiment has a plurality of grating patterns 13A, and has only a configuration in which adjacent grating patterns 13A are overlapped, so that it is simple and small-scale. With this configuration, the diffraction grating array 13 can be configured, and the optical antenna 12 including the diffraction grating array 13 can also be formed with a simple and small-scale configuration.

Furthermore, the laser radar device 10 using the optical antenna 12 according to the present embodiment can measure the distance to an object based on the transmitted light and the received light by the optical antenna 12 with a simple and small-scale configuration. , it can contribute to appropriate acceleration and deceleration control in automatic vehicle driving control.

[Second embodiment]
Next, a second embodiment will be described. In the second embodiment, the technology of the present disclosure is applied to a light receiving device that receives light using an optical integrated circuit chip. Note that, since the second embodiment has the same configuration as the first embodiment, the same parts are given the same reference numerals and detailed explanations will be omitted.

FIG. 9 shows an example of a schematic configuration of the light receiving device 20 according to this embodiment.
As shown in FIG. 9, a light receiving device 20 is provided in place of the optical antenna 12 included in the laser radar device 10. The light receiving device 20 includes a lens 22, a waveguide substrate 24 constituting an optical integrated circuit chip, and a diffraction grating array 26 that diffracts incident light to the waveguide substrate 24. The lens 22 is configured to condense the light and irradiate the light onto the diffraction grating array 26 of the optical integrated circuit chip as a beam IB.

The light receiving device 20 according to this embodiment separates and detects different polarized lights from incident light. For example, natural light contains polarized light with different phases, such as orthogonal polarized waves (Transverse Electric Waves: hereinafter referred to as TE waves) in which the electric field component is oriented transversely to the plane of incidence, and transverse electric waves (hereinafter referred to as TE waves) in which the electric field component is oriented transversely to the plane of incidence, and the magnetic field component is oriented transversely to the plane of incidence. On the other hand, transverse magnetic waves (hereinafter referred to as TM waves) coexist. The light receiving device 20 separates and detects these TE waves and TM waves. That is, in this embodiment, the incident TE wave and TM wave are separated into different directions in the diffraction grating array 26 and propagated through the waveguide substrate 24.

FIG. 10 shows an example of the diffraction angle θ _TE of the TE wave and the diffraction angle θ _TM of the TM wave in one grating in the diffraction grating array 26.
As shown in FIG. 10, when the TE wave _and the TM wave enter the diffraction gratings forming the diffraction grating array 26 at a diffraction angle θ TE and a TM wave at a diffraction angle θ _TM , the TE and TM propagate in the same direction. In FIG. 10, each of the diffraction angle θ _TE and the diffraction angle θ _TM is defined as an angle with respect to the normal vector N _V of the light-receiving surface of the diffraction grating constituting the diffraction grating array 26.

|Diffraction _angle θ _TE |=|Diffraction angle θ _TM | _, and the diffraction angle θ _TE and diffraction _angle are When the diffraction grating array 26 is configured so that the angle θ _TM is symmetrical, when a TE wave and a TM wave are incident on the diffraction grating array 26 from the same direction, the TE wave and TM wave are separated in opposite directions. Therefore, by forming different diffraction grating groups such that the polarity of the diffraction angle θ _TE and the diffraction angle θ _TM are opposite, the incident TE wave and TM wave are separated into different directions, and the waveguide substrate 24 is propagated.

FIG. 11 shows an example in which the waveguide substrate 24 is configured with diffraction grating groups 26A and 26B in which the diffraction angle θ _TE and the diffraction angle θ _TM have opposite polarities as the diffraction grating array 26.
As shown in FIG. 11, when a TM wave is incident on the diffraction grating group 26A at a diffraction angle θ _TM and a TE wave is incident on the diffraction grating group 26B and the diffraction grating group 26A at a diffraction angle θ _TE , the TE wave and the TM wave are Propagate in the opposite direction.

FIG. 12 shows an example of the configuration of the diffraction grating array 26 according to this embodiment.
As shown in FIG. 12, a diffraction grating group 26A that diffracts TM waves and a diffraction grating group 26B that diffracts TE waves are formed line-symmetrically in the arrangement direction of the grating patterns. As a result, among the light beams IB focused by the lens 22, the TM waves are diffracted by the diffraction grating array 26 of the optical integrated circuit chip at the diffraction angle θ _TM and the TE waves are diffracted at the diffraction angle θ _TE The TE wave and the TM wave are each separated into different directions and propagated through the waveguide substrate 24.

As described above, the light receiving device 20 according to the present embodiment converts incident light into TE waves and TM waves by including the diffraction grating groups 26A and 26B configured such that the diffraction angles are opposite in positive and negative directions. The separated light can be separated and the separated light can be propagated in the opposite direction. This makes it possible to independently control each of the TE waves and TM waves.

Further, the diffraction grating array according to the present embodiment includes a diffraction grating group exclusively for TE waves and a diffraction grating group exclusively for TM waves, that is, by simply forming a diffraction grating group with a grating pattern on the same substrate, With a simple and small-scale configuration, the device can be downsized and product manufacturing costs can be suppressed.

[Third embodiment]
Next, a third embodiment will be described. Note that, since the second embodiment has the same configuration as the first embodiment, the same parts are given the same reference numerals and detailed explanations will be omitted.

In the above embodiments, a diffraction grating array has been described which has a plurality of grating patterns in which grating patterns having sides in the direction in which light is propagated are arranged in the direction intersecting the direction in which light is propagated at the center of the grating pattern. In the third embodiment, the technology of the present disclosure is applied to the case where the diffraction grating array 13 is configured by combining a plurality of elements using a diffraction grating with one grating pattern as one element.

FIG. 13 shows an example of a plurality of diffraction gratings that constitute the diffraction grating array 26 according to this embodiment. Further, FIG. 14 shows an example in which a plurality of diffraction gratings forming the diffraction grating array 26 according to the present embodiment are arranged. FIG. 14(A) is a plan view of the diffraction grating array 26 according to this embodiment, and FIG. 14(B) is a side view of the diffraction grating array 26 according to this embodiment.

As shown in FIG. 13, the diffraction grating group 26A that diffracts TM waves includes diffraction gratings 26A1, 26A2, and 26A3 having one grating pattern. Furthermore, the diffraction grating group 26B that diffracts TE waves includes diffraction gratings 26B1, 26B2, and 26B3 having one grating pattern.

In order to improve light reception efficiency, adjacent diffraction gratings in the diffraction grating group 26A are arranged so as to partially overlap. That is, the distance Lya1 between the diffraction grating 26A1 and the diffraction grating 26A2 is made shorter than the distance where the diffraction grating 26A1 and the diffraction grating 26A2 are arranged so as not to overlap. Similarly, the distance Lya2 between the diffraction grating 26A2 and the diffraction grating 26A3 is made shorter than the distance at which the diffraction grating 26A2 and the diffraction grating 26A3 are arranged so as not to overlap. Also in the diffraction grating group 26B, adjacent diffraction gratings are arranged so that they partially overlap. That is, the distance Lyb1 between the diffraction grating 26B1 and the diffraction grating 26B2 is made shorter than the distance at which the diffraction grating 26B1 and the diffraction grating 26B2 are arranged so as not to overlap. Similarly, the distance Lyb2 between the diffraction gratings 26B2 and 26B3 is made shorter than the distance at which the diffraction gratings 26B2 and 26B3 are arranged so as not to overlap. On the other hand, the distance Lz between the diffraction grating group 26A and the diffraction grating group 26B is arranged such that the diffraction grating group 26A and the diffraction grating group 26B partially overlap. That is, the distance Lz between the diffraction grating group 26A and the diffraction grating group 26B is made shorter than the distance in which the diffraction grating group 26A and the diffraction grating group 26B are arranged so as not to overlap.

By arranging them as described above, as shown in FIG. 14(A), adjacent diffraction gratings partially overlap, making it possible to improve the light reception efficiency of incident light.

On the other hand, the diffraction grating array 26 includes a plurality of diffraction gratings 26A1 to 26A3 of a diffraction grating group 26A and a plurality of diffraction gratings 26B1 to 26B3 of a diffraction grating group 26B. Since the plurality of diffraction gratings 26A1 to 26A3 and 26B1 to 26B3 are each independent and single diffraction gratings, they interfere when moved on the YZ plane shown in FIGS. 13 and 14, and it is difficult to overlap them. Therefore, as shown in FIG. 14(B), by moving the adjacent diffraction gratings in the arrow X direction and in the opposite direction to the arrow It becomes possible to arrange them so that some of them overlap.

As described above, in this embodiment, the diffraction grating array 13 is constructed by combining a plurality of diffraction gratings each having a plurality of elements, with one element being a diffraction grating having one grating pattern. As a result, even when the diffraction grating array 13 is configured using a plurality of diffraction gratings formed as one element by one grating pattern, by overlapping a part of the diffraction gratings, the light reception of the diffraction grating array 13 is possible. It becomes possible to improve efficiency.

Moreover, the diffraction grating array 13 included in the optical antenna 12 according to the present embodiment has a plurality of grating patterns 13A, and has only a configuration in which adjacent grating patterns 13A are overlapped, so that it is simple and small-scale. With this configuration, the diffraction grating array 13 can be configured, and the optical antenna 12 including the diffraction grating array 13 can also be formed with a simple and small-scale configuration.

Note that the present invention is not limited to the embodiments described above, and it goes without saying that various modifications and applications can be made without departing from the gist of the present invention.

10 Laser radar device 12 Optical antenna 13 Diffraction grating array 13A Grating pattern (13A1, 13A2, 13A3, 13A4, 13A5, 13A6, 13A7)
13B Waveguide 13C Substrate 14 Signal processing unit 16 Arithmetic processing unit 20 Light receiving device 22 Lens 24 Waveguide substrate 26 Diffraction grating array 26A Diffraction grating group 26A1, 26A2, 26A3 Diffraction grating 26B Diffraction grating group 26B1, 26B2, 26B3 Diffraction grating AR Light receiving Area FF Area ratio IB Luminous flux L Center offset L1, L2 Center offset Lya1, Lya2 Distance Lyb1, Lyb2 Distance Lz Distance

Claims (5)

A surrounding area having a plurality of grating patterns, in which central areas of adjacent grating patterns among the plurality of grating patterns do not overlap, and the electric field intensity of the diffracted light is smaller than the electric field intensity of the diffracted light at the central area. a diffraction grating configured to partially overlap;
A waveguide in which the diffraction grating is formed on the light incidence side so as to change the direction of light to a propagation direction of diffracted light, which is a direction intersecting the direction of incidence of light incident on the diffraction grating , the diffraction grating a waveguide that propagates the diffracted light diffracted by the plurality of grating patterns;
Equipped with
The amount of overlap in a region where a portion of the peripheral portions of the diffraction gratings overlap is defined as the efficiency with respect to light coupled to the waveguide by a single grating pattern among the plurality of grating patterns, and the number of times the plurality of grating patterns do not overlap. The diffraction grating array has a size that maximizes the light receiving efficiency determined by multiplying the area ratio represented by the ratio of the total area when some of the plurality of grating patterns overlap to the total area when the grating patterns overlap. The diffraction grating array according to claim 1, wherein the diffraction grating has the grating pattern formed on the same plane. The diffraction grating includes a plurality of diffraction members having the grating pattern, and is formed by overlapping parts of the adjacent diffraction members so that part of the grating patterns of adjacent diffraction members overlap among the plurality of diffraction members. The diffraction grating array according to claim 1 or claim 2. Any one of claims 1 to 3, wherein adjacent grating patterns are configured so that a portion thereof overlaps so that regions of the peripheral region where the electric field strength of diffracted light is equal to or less than a predetermined threshold overlap. Diffraction grating array according to item 1. The diffraction grating includes a first diffraction grating group that diffracts one wave of incident light including TM wave light and TE wave light at a predetermined diffraction angle; a second diffraction grating group that diffracts the light of the wave at a diffraction angle opposite in positive and negative to the diffraction angle of the first diffraction grating group, and the arrangement direction of the grating pattern of the first diffraction grating group , the first diffraction grating group and the second diffraction grating group are arranged such that the arrangement direction of the grating patterns of the second diffraction grating group is the same direction and each diffracted light goes in an opposite direction. arranging and separating the incident light into each of the TM wave light and the TE wave light,
The waveguide propagates each of the TM wave light and the TE wave light separated by the diffraction grating in opposite directions.
The diffraction grating array according to any one of claims 1 to 4.