JP2012047855A - Light input/output structure for multilayer optical wiring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light input/output structure for multilayer optical wiring that achieves efficient optical coupling at a diffraction grating of each layer by radiating and diffracting light with a homogeneous phase without need of individually preparing an optical coupling structure for each layer and separately preparing an optical circuit for branching light from an optical coupling structure to each layer.SOLUTION: In the light input/output structure for multilayer optical wiring, a plurality of diffraction grating couplers 1-1 and 1-2 for diffracting a light beam 10 incident to a substrate from a vertical direction X1 into a substrate in-plane direction are laminated in multistage in a thickness direction X1 of the substrate. A plurality of wave guides are prepared for guiding the light diffracted by the plurality of diffraction grating couplers 1-1 and 1-2 to each layer optical circuit. Optical path lengths 1-1 and 1-2 of diffraction grating couplers in adjacent layers are equivalent to nλ/2 (here, λis a wavelength in vacuum of light that is guided to an upper layer optical circuit, and nis a natural number).

Description

  The present invention relates to an optical input / output interface structure that realizes optical input / output between a planar optical circuit having a fine optical waveguide and an external optical system such as an optical fiber, and is particularly applicable to multilayer optical circuits. The present invention relates to an optical input / output structure for a plane type multilayer optical wiring.

Optical wiring for performing data communication inside or between semiconductor chips such as LSIs with light has been studied.
In such intra-chip or inter-chip optical communication, it is necessary to exchange optical signals inside and outside the chip.
In such an optical circuit in the chip, a fine optical waveguide is used, and therefore, high-precision alignment is usually required for optical coupling with an optical fiber or the like outside the chip.
Therefore, a surface-type optical coupling structure using a diffraction grating that can relatively relax the alignment accuracy has been proposed (see Patent Document 1, Non-Patent Document 1, Non-Patent Document 2, and FIG. 6).

  As shown in FIG. 6, in these structures, a reflector 23 is provided on the side opposite to the incident side of the incident light 26 in order to improve the optical coupling efficiency, and the light transmitted through the diffraction grating 21 is reflected. This reflected light is recombined with the diffraction grating 21.

  6 shows an optical coupling structure using the diffraction grating disclosed in Non-Patent Document 1. Reference numeral 22 in FIG. 6 indicates an optical fiber, and reference numeral 24 in FIG. 6 indicates an optical waveguide. Reference numeral 25 in FIG. 6 denotes an integrated circuit.

  However, with higher performance and higher speed of chips, circuits are becoming more complex and denser, and the optical wiring layer is considered to follow a multi-layered path like electrical wiring. There has not yet been proposed a method for effectively guiding light to the optical waveguides of the layers constituting the multilayered optical wiring layer.

US2004 / 0156589

F. V. Laere et al., IEEE J. lightwave Technol. 25, 151 (2007) B. Analui et al., IEEE J. Solid-State Circuits 41, 2945 (2006)

  Using a diffraction grating coupled optical input / output structure that inputs and outputs optical signals from an external optical fiber to an optical circuit having a fine optical waveguide, light enters the optical waveguide of each layer of the multilayered optical circuit. In order to perform output, it is necessary to individually provide an optical input / output structure corresponding to each layer, or to separately provide an optical demultiplexing circuit for distributing light to each layer from one optical input / output structure, etc. There was a problem.

  Therefore, in the present invention, an optical input / output structure capable of simultaneously inputting / outputting light to / from a plurality of optical waveguides using a multilayered diffraction grating coupled optical input / output structure is proposed. When a plurality of diffraction grating couplers are simply stacked without controlling the distance, the phase of light incident from above and the phase of reflected light reflected from the lower diffraction grating coupler and incident from below are There is a problem that the light is random and, in some cases, cancels each other out in opposite phases, and the intensity of light guided to the waveguide is weakened.

  In addition, a reflector is provided below the multilayered diffraction grating coupler to increase the optical coupling efficiency, but without any control of the distance between the diffraction grating coupler and the reflector, When a plurality of diffraction grating couplers are stacked, the phase of light incident from above one diffraction grating and the phase of reflected light reflected from the lower reflector and incident from below become random, and in some cases, the phases are opposite. There was a problem that the intensity of the light that canceled each other and led to the waveguide was weakened.

Furthermore, when a plurality of diffraction grating couplers are simply stacked without any modification to the positional relationship between the line portion and the space portion of each layer of the diffraction grating coupler, incident light passes through the plurality of diffraction grating couplers. In the meantime, the wave front is disturbed, and an ideal operation cannot be obtained in the lower diffraction grating coupler, and it becomes difficult to effectively guide the optical signal to the waveguide by diffraction.
Also, when the incident light reaches the lowermost reflector, the wavefront is completely disturbed, and effective reflected light cannot be obtained, and each layer diffraction grating coupler uses almost the reflected light from below. In other words, there is a problem that high coupling efficiency cannot be obtained.

  Therefore, the present invention solves these conventional problems. That is, the object of the present invention is to provide an optical input / output structure corresponding to the optical circuit of each layer individually, or from one optical input / output structure to each layer. There is no need to separately provide an optical demultiplexer for distributing light to the optical circuit, and the intensity of light coupled to the optical circuit of each layer can be controlled by controlling the distance between the optical circuits of each layer. By controlling the distance between the diffraction grating coupler and the reflector, and by controlling the positional relationship between the line part and the space part of the diffraction grating coupler of the layer, the disturbance of the wave front of the incident light toward the lower layer is suppressed. Thus, it is possible to effectively guide the incident light to the optical circuit in the diffraction grating coupler of each layer, and to provide a multilayer optical wiring structure capable of efficiently distributing and guiding the light to the optical waveguide of each layer That is.

  Furthermore, in an optical input / output structure for a multilayer optical interconnection in which the same diffraction grating coupler is simply laminated, incident light is optically coupled by optical coupling each time it passes through the diffraction grating coupler from the upper layer to the lower layer. Since it decreases, the light output taken out by the lower diffraction grating coupler becomes smaller.

  Therefore, the present invention is to provide a structure in which the amount of light distributed to the optical circuit of each layer can be freely set regardless of the upper and lower layers of the position of the optical circuit.

  Furthermore, in the optical input / output structure for a multi-layer optical wiring in which diffraction grating couplers having the same period are simply stacked in multiple layers, the wavelength of the diffracted light is the same in every layer. Optical signals cannot be exchanged.

  Accordingly, the present invention is to provide a structure in which an optical signal distributed to the optical circuit of each layer can be exchanged for a different signal for each layer.

In the optical input / output structure for multilayer optical wiring of the present invention, a plurality of diffraction grating couplers that diffract a light beam incident on the substrate from the vertical direction in the in-plane direction of the substrate are stacked in multiple stages in the thickness direction of the substrate. A plurality of optical waveguides for guiding the light diffracted by the plurality of diffraction grating couplers to each layer optical circuit, and the optical path length of the diffraction grating coupler in the optical circuit of the adjacent layer is n ₁ λ _{It corresponds to} 1/2 (λ ₁ is the wavelength in the vacuum of light guided to the upper optical circuit among the adjacent layers, and n ₁ is a natural number), thereby solving the above-mentioned problem.

In the optical input / output structure for multilayer optical wiring of the present invention, a plurality of diffraction grating couplers that diffract a light beam incident on the substrate from the vertical direction in the in-plane direction of the substrate are stacked in multiple stages in the thickness direction of the substrate. A plurality of optical waveguides for guiding the light diffracted by the plurality of diffraction grating couplers to respective layer optical circuits, and the plurality of diffraction grating couplings disposed at the bottom of the plurality of diffraction grating couplers. A reflector for reflecting incident light transmitted through the reflector and recombining the incident light to at least one of the plurality of diffraction grating couplers, and between the reflector and the diffraction grating coupler to be recombined the optical path _{length, (n 2 +1/2) λ 2} /2 (λ 2 is the wavelength in vacuum of the light guided to the optical circuit of the diffraction grating to the recombining, n ₂ is a natural number) by corresponding to This solves the aforementioned problems.

  In the optical input / output structure for multilayer optical wiring of the present invention, a plurality of diffraction grating couplers that diffract a light beam incident on the substrate from the vertical direction in the in-plane direction of the substrate are stacked in multiple stages in the thickness direction of the substrate. A plurality of optical waveguides for guiding the light diffracted by the plurality of diffraction grating couplers to each layer optical circuit, and among the plurality of diffraction grating couplers, the diffraction grating coupling has the same period of the diffraction gratings There are at least two units, and the positional relationship between the line portions and the space portions of the plurality of diffraction gratings having the same period is shifted between the upper and lower layers, thereby solving the above-described problem.

  In the optical input / output structure for multilayer optical wiring according to the present invention, the positional relationship between the line portions and the space portions of the plurality of diffraction gratings having the same period does not overlap each other when viewed from the light incident direction between the upper and lower layers. In this way, the above-described problems are solved by shifting the positions little by little.

  The light input / output structure for a multilayer optical wiring of the present invention has a width between the line part and the space part of the plurality of diffraction grating couplers having the same period, while keeping the diffraction period constant, to have a change between the respective layers, By controlling the amount of light coupled to the optical waveguide of each layer, the above-described problems are solved.

  In the optical input / output structure for multilayer optical wiring according to the present invention, the line width of the diffraction grating in each diffraction grating coupler having the same period is larger than the line width of the upper diffraction grating. By narrower, the above-mentioned problems are solved.

  In the optical input / output structure for multilayer optical wiring of the present invention, a plurality of diffraction grating couplers that diffract a light beam incident on the substrate from the vertical direction in the in-plane direction of the substrate are stacked in multiple stages in the thickness direction of the substrate. A plurality of optical waveguides for guiding the light diffracted by the plurality of diffraction grating couplers to the respective layer optical circuits, and the periods of the diffraction gratings of the plurality of diffraction grating couplers being different between the layers. By diffracting only light in the wavelength band corresponding to the period of the diffraction grating using light of different wavelengths, optical signals can be input and output independently between the optical circuits in each layer, as described above. It solves the problem.

  According to the optical input / output structure for multilayer optical wiring of the present invention, the lower layer diffraction grating coupler is disposed under the upper layer diffraction grating coupler so that the light transmitted through the upper diffraction grating coupler can be transmitted to the lower layer diffraction grating coupler. Since it can be received by the diffraction grating coupler, the light from one optical fiber can be made to enter and exit simultaneously into the multilayer optical circuits arranged above and below.

Further, the optical path length of the diffraction grating coupler in the optical circuit of the adjacent _{layer, n 1 λ 1/2 (} λ 1 , of the adjacent layer, the wavelength in vacuum of the light guided to the upper layer of the optical circuit, n ₁ is a natural number) so that the phase of light incident from above one diffraction grating coupler and the phase of light reflected from the lower diffraction grating coupler and incident from below are matched. As a result, light incidence and emission can be performed with high efficiency.

Further, the optical path length between the diffraction grating coupler for recombining a _{reflector, (n 2 +1/2) λ 2} /2 (λ 2 , the vacuum of the light guided to the optical circuit of the diffraction grating to the recombining The phase of the light incident from above the diffraction grating coupler and the phase of the light reflected from the lower reflector and incident from below are set by setting so as to correspond to the middle wavelength, n ₂ is a natural number). By combining them, it is possible to enter and exit light with high efficiency.

  In addition, by shifting the positional relationship of the space portions of the line portions of the plurality of diffraction grating couplers, it is possible to suppress the disturbance of the wave front of the incident light reaching the lower layer, which is sufficient even in the lower diffraction grating couplers. Diffraction efficiency can be obtained.

  Also, by adjusting the position of the line part of the plurality of diffraction gratings in the pitch direction, the phase of the diffracted light diffracted by one diffraction grating coupler and the diffracted light diffracted by another diffraction grating coupler The phase can be adjusted between.

  In addition, the amount of light coupled to the optical waveguide of each layer is controlled by changing the width of the line and space of multiple diffraction grating couplers with the same period between layers while keeping the diffraction period constant. can do.

  In addition, by setting the line width of the upper diffraction grating to be narrower than the line width of the lower diffraction grating, the diffraction efficiency of the upper diffraction grating coupler is lowered and the upper diffraction grating coupler is reduced. Therefore, the intensity of the diffracted light in the upper layer and the diffracted light in the lower layer can be made uniform, and the light incident from the vertical direction can be changed between the upper optical circuit and the lower optical circuit. Can be evenly distributed.

In addition, by making the period of the diffraction gratings of the plurality of diffraction grating couplers different between the respective layers, only light having a wavelength corresponding to the period of the diffraction grating couplers of the respective layers can be applied to incident light including different wavelengths. By diffracting, optical signals can be input and output independently between the optical circuits of each layer.
Therefore, if wavelength-multiplexed incident light is used, optical signals can be exchanged independently between optical circuits in each layer.

1 is a schematic diagram of an optical input / output structure for multilayer optical wiring as a first embodiment of the present invention. It is the schematic of the optical input-output structure for multilayer optical wiring as 2nd Example of this invention. It is the schematic which shows the modification of 2nd Example which varied the coupling light quantity of the diffraction grating coupler of an upper layer and a lower layer. It is the schematic of the optical input-output structure for multilayer optical wiring as 3rd Example of this invention. It is the schematic which shows the modification of this invention which diffracts only the light of the wavelength band corresponding to the period of a diffraction grating using the light of a different wavelength. It is the schematic which shows the conventional optical coupling structure.

  Hereinafter, preferred embodiments of the optical input / output structure for multilayer optical wiring of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram of an optical input / output structure for multilayer optical wiring as a first embodiment of the present invention.

  The optical input / output structure for multilayer optical wiring according to the first embodiment of the present invention is an optical input / output structure for two-layer optical wiring, and is perpendicular to the optical circuit plane (incident as shown in FIG. 1). Direction) comprising a diffraction grating coupler 1-1 that diffracts incident light (light beam) 10 irradiated from X1, and a core 2-1 that guides the diffracted light 11-1 diffracted by the diffraction grating coupler 1-1. The upper layer optical circuit, the diffraction grating coupler 1-2 that is disposed below the diffraction grating coupler 1-1, and diffracts the incident light 10 transmitted through the diffraction grating coupler 1-1, and the diffraction grating coupler 1 -2 is a lower-layer optical circuit composed of a core 2-2 that guides the diffracted light 11-2 diffracted at -2, and a cladding 3 that covers the periphery of the diffraction grating couplers 1-1 and 1-2 and the cores 2-1 and 2-2. And a reflector 4 for reflecting the incident light 10 transmitted through the diffraction grating couplers 1-1 and 1-2.

As the base optical waveguide, both the cores 2-1 and 2-2 and the cladding 3 may be silica-based optical waveguides made of SiO2, the cores 2-1 and 2-2 are made of Si, and the cladding 3 is made of SiO2. A silicon optical waveguide may be used.
Naturally, in the case of a silicon-based optical waveguide, the operating wavelength is limited to a wavelength of 1 μm or more without light absorption by Si.

As shown in FIG. 1, each diffraction grating coupler 1-1, 1-2 includes a plurality of line portions 1-1a, 1-2a arranged in parallel at a predetermined pitch P and between the line portions 1-1a, 1-2a. It is comprised from several space part 1-1b and 1-2b located in.
In general, the line portions 1-1a and 1-2a of the diffraction grating couplers 1-1 and 1-2 are formed of the same high refractive index material as the cores 2-1 and 2-2 of the optical waveguide. The space portions 1-1b and 1-2b of the devices 1-1 and 1-2 are formed of the same low refractive index material as that of the cladding 3 of the optical waveguide.

  The pitch (grating pitch) P referred to in the present invention is the pitch direction X2 of the line portions 1-1a and 1-2a of the diffraction grating couplers 1-1 and 1-2, as shown in FIG. Means the dimension from the center position in FIG. 1 to the center position in the pitch direction X2 of the line portions 1-1a, 1-2a adjacent to the line portions 1-1a, 1-2a in the pitch direction X2.

  Further, a part of the light incident on the diffraction grating couplers 1-1 and 1-2 is transmitted without being coupled to the diffraction grating couplers 1-1 and 1-2, but has a high refractive index. Since the space portions 1-1b and 1-2b having a lower refractive index pass more easily like slits than the line portions 1-1a and 1-2a, more light is emitted from the space portions 1-1b and 1-2b. Comes out transparently.

  In addition, the light transmitted through the space portions 1-1b and 1-2b and the light transmitted through the line portions 1-1a and 1-2a may cause a phase difference due to a difference in refractive index, thereby disturbing the wavefront.

In this embodiment, as shown in FIG. 1, the pitch P between the plurality of line portions 1-1a of the diffraction grating coupler 1-1, and between the plurality of line portions 1-2a of the diffraction grating coupler 1-2. The pitch P is set with the same dimensions.
The line width W1 in the pitch direction X2 of the line part 1-1a of the diffraction grating coupler 1-1 is the same as the line width W2 in the pitch direction X2 of the line part 1-2a of the diffraction grating coupler 1-2. It is set with dimensions.
Further, the line width W1 and the line width W2 are set to be half the pitch P.
And the position in the pitch direction (longitudinal direction of the optical waveguide) X2 of the line part 1-1a of the diffraction grating coupler 1-1, and the position in the pitch direction X2 of the line part 1-2a of the diffraction grating coupler 1-2 1, are shifted from each other by half the length of the pitch P in the pitch direction X2, that is, the line portion 1-1a of the diffraction grating coupler 1-1 and the diffraction grating coupler 1- The second line portion 1-2a is arranged so as not to overlap with the incident direction X1.

  Therefore, since the incident light 10 transmitted through the space 1-1b of the diffraction grating coupler 1-1 can be strongly coupled by the line 1-2a of the diffraction grating coupler 1-2, the light can be used efficiently. Can do.

  Further, as shown in FIG. 1, the light transmitted through the line part 1-1a of the diffraction grating coupler 1-1 passes through the space part 1-2b in the diffraction grating coupler 1-2, and passes through the diffraction grating coupler 1-. The light transmitted through the one space portion 1-1b passes through the line portion 1-2a in the diffraction grating coupler 1-2.

  Therefore, the light transmitted through the diffraction grating coupler 1-1 and the diffraction grating coupler 1-2 cancels out the phase difference caused by the difference in refractive index, and the wave fronts are aligned. When coupling to the coupler 1-2 again, the wave fronts are aligned.

  A part of the incident light 10 transmitted through the diffraction grating coupler 1-1 is reflected by the diffraction grating coupler 1-2 and returns to the diffraction grating coupler 1-1. Since the generated phase difference is canceled and the wavefronts are aligned, the wavefronts are aligned when recombining with the diffraction grating coupler 1-1.

Here, the optical path length L1 between the diffraction grating coupler 1-1 and the diffraction grating coupler _{1-2, n 1 λ 1/2} (λ 1 , of the adjacent layer, of the light guided to the upper layer of the optical circuit By setting so as to correspond to the wavelength in vacuum, n ₁ is a natural number), a part of the incident light 10 is transmitted through the diffraction grating coupler 1-1 and reflected by the diffraction grating coupler 1-2. When recombining with the diffraction grating coupler 1-1, the wavefronts are not only aligned but in phase with the incident light 10, so that the incident light 10 is first diffracted by the diffraction grating coupler 1-1. The light and the diffracted light recombined with the diffraction grating coupler 1-1 are intensified.

Also, here, the optical path length L2 of a diffraction grating coupler 1-2 and the reflector _4, leading to _{(n 2 +1/2) λ 2/} 2 (λ 2 , the optical circuit of the diffraction grating for recombining light Is set so as to correspond to the wavelength in vacuum, and n ₂ is a natural number), so that a part of the incident light 10 is transmitted through and reflected by the diffraction grating coupler 1-1 and the diffraction grating coupler 1-2. When the light is reflected by the unit 4 and recombined by the diffraction grating coupler 1-2, not only the wave fronts are aligned, but also the same phase as when a part of the incident light 10 first enters the diffraction grating coupler 1-2. Therefore, a part of the incident light 10 is first diffracted by the diffraction grating coupler 1-2, and the diffracted light recombined with the diffraction grating coupler 1-2 is strengthened.

  In the above example, the space portions 1-1b and 1-2b of the diffraction grating couplers 1-1 and 1-2 are completely free of the materials of the cores 2-1 and 2-2. It is obvious that the thickness may be smaller than that of 1-1a and 1-2a, and in that case, the optical distance may be considered similarly.

  With the above configuration, the widths of the line portions 1-1a and 1-2a of the upper diffraction grating coupler 1-1 and the lower diffraction grating coupler 1-2 are half the diffraction grating period, and the mutual line portions When the positional relationship between 1-1a and 1-2a is shifted by half of the diffraction grating period, the light incident from the vertical direction X1 is effective between the upper optical circuit and the lower optical circuit. It is possible to provide an optical input / output structure that can be used in a practical manner.

  Further, the light transmitted through the upper diffraction grating coupler 1-1 and reflected by the lower diffraction grating coupler 1-2, or the upper diffraction grating coupler 1-1 and the lower diffraction grating coupler 1-2 are transmitted. Not only are the wavefronts of the light transmitted and reflected by the reflector 4 aligned, but the diffracted light when recombining with the diffraction grating couplers 1-1 and 1-2 and the first diffracted light are in phase, Since the output can be strengthened, an efficient optical input / output structure can be provided.

  In addition, the position of the line part 1-1a and the space part 1-1b of the upper diffraction grating coupler 1-1, and the line part 1-2a and the space part 1-2b of the lower diffraction grating coupler 1-2. Since the phase relationship of the light waves guided to the optical waveguide of each layer is determined depending on the position, the phase relationship of the light waves guided to the optical waveguide of each layer can be arbitrarily adjusted by arbitrarily shifting the mutual positional relationship. .

  Accordingly, the incident light 10 is diffracted by the diffraction grating coupler 1-1 in the upper layer and guided to the optical waveguide, and is diffracted by the diffraction grating coupler 1-2 in the lower layer to enter the optical waveguide. Whether the phase relationship with the guided light is in phase, out of phase, or shifted by π / 2, the line portions of the diffraction grating couplers 1-1 and 1-2 between the layers It can be freely controlled by the positional relationship between 1-1a and 1-2a and the space portions 1-1b and 1-2b.

  Therefore, when the light beams of the layers are finally combined and guided to one optical waveguide, they may be shifted so as to be in phase.

  In addition, since light can be supplied to the upper and lower optical circuits at one place, a small optical input / output structure can be provided, and a connector and the like can be made inexpensive.

  In the above description, the optical input / output structure on the input side has been described. However, there is no problem even if it is used as the optical input / output structure on the output side, and an efficient output can be obtained similarly.

Next, an optical input / output structure for multilayer optical wiring that is a second embodiment of the present invention will be described with reference to FIG.
Here, the configuration of the second embodiment of the present invention other than the specific design of the diffraction grating coupler of the optical input / output structure for multilayer optical wiring and the arrangement relationship between the diffraction grating couplers is the same as the first embodiment described above. Since this is exactly the same as the optical input / output structure for multilayer optical wiring, only differences from the optical input / output structure for multilayer optical wiring of the first embodiment will be described.

  As shown in FIG. 2, the optical input / output structure for the multilayer optical wiring of the second embodiment is substantially the same as the optical input / output structure for the multilayer optical wiring of the first embodiment shown in FIG. The line width W2 of the lower diffraction grating coupler 1-2 is made wider than the line width W1 of the diffraction grating coupler 1-1.

  Also in this case, the sum of the line width W1 and the line width W2 is made equal to the pitch P of the diffraction grating couplers 1-1 and 1-2 as in the example of FIG. The center position in the pitch direction X2 of the first line portion 1-1a and the center position in the pitch direction X2 of the line portion 1-2a of the lower diffraction grating coupler 1-2 are pitch directions by a dimension half the pitch P. By shifting to X2, the positions of the line portion 1-1a of the upper diffraction grating coupler 1-1 and the line portion 1-2a of the lower diffraction grating coupler 1-2 are prevented from overlapping with the incident direction X1. ing.

  Since the lower-layer diffraction grating coupler 1-2 uses light that has not been diffracted by the upper-layer diffraction grating coupler 1-1, the diffraction efficiency of the upper-layer diffraction grating coupler 1-1 is reduced. When the diffraction efficiency of the diffraction grating coupler 1-2 is the same, the diffracted light 11-1 in the upper layer is larger than the diffracted light 11-2 in the lower layer.

  Therefore, by adjusting the line width W1 of the upper diffraction grating coupler 1-1 and the line width W2 of the lower diffraction grating coupler 1-2 to change the diffraction efficiency of each diffraction grating coupler, FIG. As shown in FIG. 3, the combined light amounts of the upper and lower diffraction grating couplers 1-1 and 1-2 can be made equal, or as shown in FIG. The coupling light quantity of the coupler 1-2 can be made larger than the coupling light quantity of the upper diffraction grating coupler 1-1.

  For example, as shown in FIG. 2, the line width W1 of the upper diffraction grating coupler 1-1 is reduced to lower the diffraction efficiency, and conversely, the line width W2 of the lower diffraction grating coupler 1-2 is increased. By increasing the diffraction efficiency, the intensity of the diffracted light 11-1 in the upper layer and the intensity of the diffracted light 11-2 in the lower layer can be made uniform, so that the multilayer optical wiring can be easily used.

  With the above configuration, the line width W1 of the upper diffraction grating coupler 1-1 and the line width W2 of the lower diffraction grating coupler 1-2 are adjusted, and the upper diffraction grating coupler 1-1 and the lower diffraction grating are adjusted. The coupling light quantity of the grating coupler 1-2 can be made equal or different.

  For example, compared to the line width W1 of the upper diffraction grating coupler 1-1, the line width W2 of the lower diffraction grating coupler 1-2 can be increased to increase the diffraction efficiency. In addition to the effect of the optical input / output structure for the multilayer optical wiring of the embodiment, the light input for the multilayer optical wiring capable of evenly distributing the light incident from the vertical direction X1 to the upper optical circuit and the lower optical circuit. An output structure can be provided.

Next, an optical input / output structure for multilayer optical wiring that is a third embodiment of the present invention will be described with reference to FIG.
Here, the configuration of the third embodiment of the present invention other than the number of installed diffraction grating couplers of the optical input / output structure for multilayer optical wiring, the specific design of the diffraction grating couplers, the arrangement relationship between the diffraction grating couplers, etc. Since this is exactly the same as the optical input / output structure for multilayer optical wiring of the first embodiment described above, only the differences from the optical input / output structure for multilayer optical wiring of the first embodiment will be described.

  The optical input / output structure for multilayer optical wiring of the third embodiment shown in FIG. 4 is an optical coupling structure for three-layer optical wiring, and guides light to the upper layer optical circuit, the middle layer optical circuit, and the lower layer optical circuit. It has three diffraction grating couplers 1-1, 1-2, 1-3, and line sections 1-1a, 1-2a, 1- of the diffraction grating couplers 1-1, 1-2, 1-3. The total of the line widths W1, W2, and W3 of 3a is equal to the pitch P of the diffraction grating couplers 1-1, 1-2, and 1-3, as in the embodiment shown in FIGS.

  In addition, the line widths W1, W2, and W3 of the diffraction grating couplers 1-1, 1-2, and 1-3 of each layer are gradually increased from the upper layer to the lower layer, and the line portions 1-1a, 1-2a, By shifting the position of the pitch direction X2 of 1-3a in the pitch direction X2, the positions of the upper, middle, and lower line portions 1-1a, 1-2a, and 1-3a do not overlap with the incident direction X1. It has become.

  Therefore, the incident light 10 is diffracted light 11- of equal intensity to the respective cores 2-1, 2-2, 2-3 by the diffraction grating couplers 1-1, 1-2, 1-3. 1, 11-2 and 11-3 can be efficiently distributed.

  In the third embodiment, the optical wiring has three layers. However, if the relationship between the line widths and the position in the pitch direction of each line are set in the same manner, it can be applied to further multilayer optical wiring. .

  With the above configuration, the line width W2 (W3) of the lower diffraction grating coupler 1-2 (1-3) is compared with the line width W1 (W2) of the upper diffraction grating coupler 1-1 (1-2). ), And the positions of the line portions 1-1a, 1-2a, and 1-3a in the pitch direction X2 are sequentially shifted so as not to overlap the incident direction X1, so that the light is incident from the vertical direction X1. Thus, it is possible to provide an optical input / output structure for a multilayer optical wiring that can efficiently and uniformly distribute the incident light 10 to each optical wiring layer.

  In the description of the embodiment shown in FIGS. 1 to 4 described above, the light is described as having a single wavelength. However, as shown in FIG. 5, a plurality of wavelengths are used and diffraction corresponding to each wavelength is used. By combining a plurality of diffraction grating couplers 1-1, 1-2, and 1-3 having a grating period, the incident light 10 that is wavelength-multiplexed and includes different wavelengths 10-1, 10-2, and 10-3 can be obtained. Also, it is possible to realize an optical input / output structure for multilayer optical wiring that guides the diffracted light beams 11-1, 11-2, and 11-3 having different wavelengths to optical circuits of different layers corresponding to the wavelengths.

  In addition, when using a diffraction grating coupler with a plurality of wavelengths, it is an effective means to change the diffraction direction by changing the direction of the diffraction grating coupler in order to suppress the influence of the mutual line portion and space portion as much as possible. It is.

  In particular, when two wavelengths are used, it is an effective means to make the directions of the diffraction grating couplers orthogonal to each other so that the diffraction directions are different by 90 degrees.

  In particular, when the difference between the two wavelengths is small, it is an indispensable condition to make the directions of the diffraction grating couplers orthogonal to each other so that the diffraction directions are different by 90 degrees.

1-1, 1-2, 1-3 ... Diffraction grating coupler 1-1a, 1-2a, 1-3a ... Line part 1-1b, 1-2b, 1-3b ... Space part 2-1, 2-2, 2-3 ... core 3 ... clad 4 ... reflector 10 ... incident light 11-1, 11-2, 11-3 ... diffracted light W1, W2, W3 ... Line width L1, L2, L3 ... Optical path length X1 ... Incident direction (vertical direction, thickness direction of substrate)
X2 ... Pitch direction (longitudinal direction of optical waveguide)

Claims (7)

A plurality of diffraction grating couplers that diffract a light beam incident on the substrate from a vertical direction in the in-plane direction of the substrate are stacked in multiple stages with respect to the thickness direction of the substrate, and are diffracted by the plurality of diffraction grating couplers. A plurality of optical waveguides that guide light to each layer optical circuit,
The optical path length of the diffraction grating coupler in the optical circuit of the adjacent _{layers, n 1 λ 1/2 (} λ 1 , of the adjacent layer, the wavelength in vacuum of the light guided to the upper layer of the optical circuit, n ₁ is , An optical input / output structure for multilayer optical wiring, characterized by A plurality of diffraction grating couplers that diffract a light beam incident on the substrate from a vertical direction in the in-plane direction of the substrate are stacked in multiple stages with respect to the thickness direction of the substrate, and are diffracted by the plurality of diffraction grating couplers. A plurality of optical waveguides for guiding the light to each layer optical circuit, and the bottom of the plurality of diffraction grating couplers, and reflecting incident light transmitted through the plurality of diffraction grating couplers; A reflector for recombining incident light into at least one of the grating couplers;
Optical path length between the grating coupler for the recombination and the _{reflector, (n 2 +1/2) λ 2} /2 (λ 2 , the vacuum of the light guided to the optical circuit of the diffraction grating to the recombining An optical input / output structure for multilayer optical wiring, characterized in that the middle wavelength, n ₂ is a natural number). A plurality of diffraction grating couplers that diffract a light beam incident on the substrate from a vertical direction in the in-plane direction of the substrate are stacked in multiple stages with respect to the thickness direction of the substrate, and are diffracted by the plurality of diffraction grating couplers. A plurality of optical waveguides that guide light to each layer optical circuit,
Among the plurality of diffraction grating couplers, there are at least two or more diffraction grating couplers having the same period of the diffraction grating, and the positional relationship between the line part and the space part of the plurality of diffraction gratings having the same period is An optical input / output structure for multilayer optical wiring, characterized by being shifted between layers.   The positional relationship between the line portions and the space portions of the plurality of diffraction gratings having the same period is arranged so as to be slightly shifted between the upper and lower layers so as not to overlap each other when viewed from the incident direction of the light. The optical input / output structure for multilayer optical wiring according to claim 3.   The amount of light coupled to the optical waveguide of each layer is controlled by changing the width of the line part and the space part of the plurality of diffraction grating couplers having the same period between the respective layers while keeping the diffraction period constant. The optical input / output structure for multilayer optical wiring according to claim 3.   The line width of a diffraction grating in each diffraction grating coupler having the same period is narrower than that of a lower diffraction grating. 6. The optical input / output structure for multilayer optical wiring according to any one of 5 above.   A plurality of diffraction grating couplers that diffract a light beam incident on the substrate from a vertical direction in the in-plane direction of the substrate are stacked in multiple stages with respect to the thickness direction of the substrate, and are diffracted by the plurality of diffraction grating couplers. A plurality of optical waveguides for guiding light to each layer optical circuit are provided, and the diffraction grating periods of the plurality of diffraction grating couplers are made different between the layers, so that light of different wavelengths can be used. An optical input / output structure for multilayer optical wiring, wherein optical signals can be input / output independently between optical circuits in each layer by diffracting only light in a wavelength band corresponding to a period.

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