JP6697423B2 - Optical integrated circuit - Google Patents

Description

  The present invention relates to an optical integrated circuit, and more particularly, to an optical integrated circuit that outputs light of three primary colors of visible light RGB (R: red light, G: green light, B: blue light).

  In recent years, an RGB coupler module using a silica-based planar lightwave circuit (PLC) has been attracting attention as a circuit element for combining three primary color lights for eyeglass-type terminals and projectors (for example, Non-Patent Document 1). reference). PLC is to combine a plurality of basic optical circuits (eg, directional coupler, Mach-Zehnder interferometer, etc.) on a planar substrate by patterning by photolithography and etching to create an optical waveguide. To realize various functions.

  As a multiplexing circuit for the three primary color lights, there is, for example, one that uses a directional coupler and / or a Mach-Zehnder interferometer (see Non-Patent Document 1). In this specification, the case of using the simplest directional coupler will be described with reference to FIG. 1 as an example.

  FIG. 1 shows the basic structure of an RGB coupler module using a PLC. As shown in FIG. 1, the basic structure of an RGB coupler module using a PLC is formed by three optical waveguides, first to third optical waveguides 1 to 3, each coupled to a visible light laser. A first directional coupler 4 is coupled to the first optical waveguide 1. An output waveguide 5 is coupled to the second optical waveguide 2. A second directional coupler 6 is coupled to the third optical waveguide 3. The first directional coupler 4 couples the light of the wavelength λ1 from the first optical waveguide 1 to the second optical waveguide 2, and the light of the wavelength λ2 from the second optical waveguide 2 to the first optical waveguide. The waveguide length, the waveguide width, and the gap between the waveguides are designed so that they are coupled to each other and coupled from the first optical waveguide 1 to the second optical waveguide 2. The second directional coupler 6 couples the light of the wavelength λ3 from the third optical waveguide 3 to the second optical waveguide 2, and transmits the light of the wavelength λ1 and the wavelength λ2 with a waveguide length, The waveguide width and the gap between the waveguides are designed.

  As λ1 <λ2 <λ3, for example, blue light (wavelength λ1) enters the first optical waveguide 1, green light (wavelength λ2) enters the second optical waveguide 2, and third optical waveguide 3 The red light (wavelength λ3) is incident on. The lights of the three colors are combined via the first directional coupler 4 and the second directional coupler 6 and output from the output waveguide 5. The wavelength difference of the blue light (wavelength band 400 nm) and the wavelength of the red light (wavelength band 700 nm) are greatly different in the three-primary-color light multiplexing circuit, which is different from the communication light multiplexing circuit having a small bandwidth ratio. The wavelength dependence of the bond length is remarkable. Therefore, such a configuration can be realized.

A. Nakao, R. Morimoto, Y. Kato, Y. Kakinoki, K. Ogawa and T. Katsuyama, “Integrated waveguide-type red-green-blue beam combiners for compact projection-type displays”, Optics Communications 330 (2014) 45-48

  Since the visible light laser is manufactured on a material substrate that differs depending on the color of light to be output, the height of the active layer differs for each color. On the other hand, a multiplexing circuit using a PLC as shown in FIG. 1 is made so that the heights of the waveguides are on the same plane. Therefore, when laser lights of different colors are made incident on the PLC, it is necessary to make the heights of the emission surfaces of the visible light lasers of the respective colors uniform. Conventionally, it was necessary to mount a visible light laser on a different carrier for each color and to make the heights of the emission surfaces of the visible light lasers uniform.

  However, the conventional three-primary-color light multiplexing circuit as shown in FIG. 1 has a configuration in which the input ports of the first to third optical waveguides 1 to 3 are provided on one end face. Therefore, when the carriers carrying the respective visible light lasers are arranged in a line in order to couple the respective visible light lasers to the first to third optical waveguides 1 to 3, the first to third optical waveguides 1 to It is necessary to design the width of the optical multiplexing circuit in the arrangement direction of 3 large considering the width of each carrier and the interference of the mounting jig.

  Therefore, in the conventional multiplexing circuit for three-primary-color light as shown in FIG. 1, the chip becomes larger than the circuit size required for multiplexing, which is a factor that hinders miniaturization.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical integrated circuit that outputs three primary color lights that can be downsized.

In order to solve the above problems, one state like the present invention, an output end face, and a first input end face facing the output end face, and a second input end face and the third input end face facing each other, the blue light output and planar lightwave circuit, a red light laser for outputting pre Symbol first placed red light input end face of the planar lightwave circuit, a pre-Symbol blue light disposed on a second input end face comprising a laser, an optical integrated circuit and a green light laser for outputting green light placed on the third input end face, from the output end face, the red light, the blue light, and the green Color light is output , and the planar lightwave circuit includes first to third optical waveguides optically coupled to the red light laser, the blue light laser, and the green light laser, and the third optical waveguide. A first optical combining unit that transfers the green light that guides the light to the second optical waveguide and combines with the blue light that guides the second optical waveguide; and the first optical waveguide. A second optical combiner for migrating the guided red light to the second optical waveguide and combining with the light combined in the first optical combiner; The waveguide and the third optical waveguide each have a bending waveguide portion for optical path conversion of 90 ° configured to be bent in the direction of the output end face, and the second optical waveguide is An output port for outputting the light multiplexed by the second optical multiplexing unit, and intersecting the first optical waveguide at a waveguide portion between the input port and the bending waveguide portion, The angle of the intersection is 15 ° to 90 ° .

  According to the optical integrated circuit of the present invention, it is possible to realize miniaturization of the optical integrated circuit that outputs the three primary color lights.

It is a figure which shows the basic structure of the RGB coupler module which used PLC. FIG. 1 is a diagram illustrating a configuration of an optical integrated circuit according to a first embodiment of the present invention. It is a figure which illustrates the structure of the optical integrated circuit which concerns on Example 2 of this invention. It is a figure which illustrates the structure of the optical integrated circuit which concerns on Example 3 of this invention.

  In the present invention, the output end face, the first input end face that faces the output end face, the second and third input end faces that face each other, and the output end face and the first to third input end faces are arranged vertically. In a PLC chip having a hexahedral shape including a bottom surface and an upper surface facing each other, a visible light laser R that outputs red light, a visible light laser B that outputs blue light, and a visible light laser that outputs green light. G is respectively arranged on the first to third input end faces of the PLC chip. Then, the light of the three primary colors of light R, G, and B is output from the output end face.

  As a result, in the present invention, it is possible to configure an optical integrated circuit without being interfered by the widths of the carriers of the visible light lasers R, G, and B and the mounting jig, so that the three primary color lights are output. The miniaturization of the optical integrated circuit can be realized.

(Example 1)
FIG. 2 illustrates the configuration of the optical integrated circuit according to the first embodiment of the present invention. In FIG. 2, the PLC 100, the visible light laser R disposed on the first input end face 110 facing the output end face 140 of the PLC 100, and the visible light laser R disposed on the two opposing second and third input end faces 120 and 130, respectively. And the visible light lasers B and G are shown. Hereinafter, the lights output from the visible light lasers R, G, and B will be referred to as lights R, G, and B, respectively.

  As shown in FIG. 2, the PLC 100 includes a first to a third optical waveguides 101 to 103 optically coupled to the visible light lasers R, G, and B, and a light G guided in the third optical waveguide 103. The first optical multiplexing section 104 that moves to the second optical waveguide 102 and combines with the light B that propagates in the second optical waveguide 102, and the second light R that propagates in the first optical waveguide 101 A second optical multiplexing unit 105 that is coupled to the light multiplexed in the first optical multiplexing unit 104 by moving to the optical waveguide 102 of FIG. The second optical waveguide 102 has an output port that outputs the light multiplexed by the second optical multiplexer 105.

The second optical waveguide 102 has a bent waveguide portion 102 ₁ for 90 ° optical path conversion, and the third optical waveguide 103 has a 90 ° bent waveguide portion 103 ₁ for optical path conversion. The bending waveguide portion 102 ₁ and the bending waveguide portion 103 ₁ are configured to bend in the output end face direction of the PLC 100. Further, the bending waveguide portion 102 ₁ of the second optical waveguide 102 is configured so that the bending radius is smaller than that of the bending waveguide portion 103 _{1 of} the third optical waveguide 103. For example, when the refractive index difference of the waveguide is 0.45% and the waveguide width and thickness are 3.5 μm, the bending radius of the bending waveguide portion 102 ₁ of the second optical waveguide 102 is preferably 1.5 mm, The bending radius of the bending waveguide portion 103 ₁ of the third optical waveguide 103 can be preferably 2.0 mm.

  In the optical integrated circuit according to the first embodiment of the present invention, the lights G and B output from the visible light lasers G and B propagate through the second and third optical waveguides 102 and 103, respectively, and the first optical combined. The waves are combined in the wave unit 104. The combined light of the lights G and B combined in the first optical combiner 104 and the light R output from the visible light laser R are combined in the second optical combiner 105. The combined light of the lights R, G, and B combined by the second light combining unit 105 is output from the output port of the second optical waveguide 102.

Here, as shown in FIG. 2, the second optical waveguide 102 is a waveguide portion between the input port of the second optical waveguide 102 and the bending waveguide portion 102 ₁ and is the first optical waveguide 101. Crosses If the intersection angle is sufficiently large in the range of 15 ° to 90 °, for example, the lights guided in the first and second optical waveguides 101 and 102 can propagate without being affected by each other.

  According to the optical integrated circuit of the first embodiment, by providing the visible light lasers R, G, and B on different end faces, interference of the widths of the carriers of the visible light lasers R, G, and B and the mounting jig is prevented. Since it becomes possible to configure the optical integrated circuit without receiving the light, it is possible to realize the miniaturization of the optical integrated circuit that outputs the three primary color lights.

Note that the first optical multiplexing unit 104 brings the second optical waveguide 102 and the multimode (MM) conversion waveguide 104 ₁ into close proximity to each other, and the third optical waveguide 103 and the MM, as shown in FIG. 2, for example. A directional coupler configured by bringing the conversion waveguide 104 ₁ into close proximity can be used. In the first optical multiplexer 104 having such a configuration, the light G incident from the third optical waveguide 103 has the guided mode changed to a higher-order mode (eg, first-order mode) in the first optical multiplexer 104. The light is converted and transferred to the MM conversion waveguide 104 ₁ , the waveguide mode is converted to the fundamental mode (0th order mode) and transferred to the second optical waveguide 102, and the light is incident from the second optical waveguide 102. The converted light B can be transmitted through the first optical combining unit 104 without moving to the MM conversion waveguide 104 ₁ , whereby the lights G and B can be combined.

Similarly, the second optical multiplexer 105 brings the first optical waveguide 101 and the MM conversion waveguide 105 ₁ close to each other, and brings the second optical waveguide 102 and the MM conversion waveguide 105 ₁ close to each other. A configured directional coupler can be used. In the second optical multiplexer 105 having such a configuration, the light R incident from the first optical waveguide 101 has the guided mode changed to a higher-order mode (eg, first-order mode) in the second optical multiplexer 105. After being converted, the waveguide mode is converted to the MM conversion waveguide 105 ₁ , the waveguide mode is further converted to the fundamental mode (0th order mode) and transferred to the second optical waveguide 102, and at the same time, in the first optical multiplexer 104. The combined lights of the lights G and B that have been combined and propagated through the second optical waveguide 102 can be transmitted through the second optical combining unit 105 without being transferred to the MM conversion waveguide 105 ₁ , and as a result, R, G and B can be multiplexed.

In order to realize the above multiplexing function, in the first optical multiplexing unit 104, the effective refractive index in the 0th order mode of the light G with respect to the third optical waveguide 103 and the higher order mode of the light G with respect to the MM conversion waveguide 104 ₁ are. And the effective refractive index in the 0th order mode of the light B with respect to the second optical waveguide 102 and the effective refractive index in the higher order mode of the light B with respect to the MM conversion waveguide 104 ₁ are equal to each other. The waveguide widths of the second and third optical waveguides 102 and 103 and the MM conversion waveguide 104 ₁ may be designed so as not to be equal.

Similarly, in the second optical multiplexer 105, the effective refractive index of the light R in the 0th order mode for the first optical waveguide 101 and the effective refractive index of the light R in the higher order mode for the MM conversion waveguide 105 ₁ are equal. In addition, the effective refractive indices of the light G and B for the second optical waveguide 102 in the 0th-order mode and the effective refractive index of the light G and B for the MM conversion waveguide 105 _{1 in} the higher-order mode are not equal to each other. In addition, the waveguide widths of the first and second optical waveguides 101 and 102 and the MM conversion waveguide 105 ₁ may be designed.

  By using the directional coupler having such a configuration, the coupler length can be shortened, which can further contribute to the miniaturization of the optical integrated circuit. Of course, as the first and second optical multiplexing units 104 and 105, a directional coupler as shown in FIG. 1 or other circuits having an optical multiplexing function may be used.

(Example 2)
FIG. 3 illustrates the configuration of the optical integrated circuit according to the second embodiment of the present invention. In FIG. 3, the PLC 200, the visible light laser R disposed on the first input end face 210 facing the output end face 240 of the PLC 200, and the visible light laser R disposed on the two opposing second and third input end faces 220 and 230, respectively. And the visible light lasers B and G are shown.

The PLC 200 transfers the first to third optical waveguides 201 to 203 optically coupled to the visible light lasers R, G, and B and the light R guided in the first optical waveguide 201 to the third optical waveguide 203. Then, it includes an optical multiplexing unit 204 that multiplexes with the light G guided through the third optical waveguide 203. The optical multiplexer 204 can be a directional coupler using the MM conversion waveguide 204 ₁ as in the _first embodiment. The second optical waveguide 202 has an output port for outputting the light B input from the visible light laser B, and the third optical waveguide 203 has an output port for outputting the light combined by the optical combining unit 204.

The second optical waveguide 202 extends from the input port of the second optical waveguide 202 to the output port of the second optical waveguide 202, and the first to third bent waveguide portions 202 _{1 to} 202 for 90 ° optical path conversion. Have ₃ in order. The third optical waveguide 203 has a bent waveguide portion 203 ₁ for 90 ° optical path conversion. The first bending waveguide portion 202 ₁ is configured to bend toward the output end surface of the PLC 200, and the second bending waveguide portion 202 ₂ is configured to bend toward the side surface where the visible light laser G is arranged. The bent waveguide portion 202 ₃ is configured to bend in the output end face direction of the PLC 200. Bending waveguide portion 203 ₁ of the third optical waveguide 203 is configured to bend to the output end face direction of the PLC 200. Further, the first to third bending waveguide portions 202 ₁ and 202 ₃ of the second optical waveguide 202 are configured so that the bending radius is smaller than that of the bending waveguide portion 203 _{1 of} the third optical waveguide 203. ing. For example, when the refractive index difference of the waveguide is 0.45% and the waveguide width and thickness are 3.5 μm, the first to third bent waveguide portions 202 ₁ and 202 ₃ of the second optical waveguide 202 are bent. The radius can be preferably 1.5 mm, and the bending radius of the bending waveguide portion 203 ₁ of the third optical waveguide 203 can be preferably 2.0 mm.

  The output ports of the second and third optical waveguides 202 and 203 are close to each other so that the second and third optical waveguides 202 and 203 can be regarded as point light sources. For example, if there are two output ports within 15 μm, when light is output using this light source, the light output from each output port is output from one output port (point light source) to the human eye. Since it appears that the output ports of the second and third optical waveguides 202 and 203 are spaced from each other, the distance between the output ports can be set to 15 μm or less. However, it is desirable to keep the interval between the output ports to the minimum necessary because it causes blurring of the image when it is visualized.

In the optical multiplexing unit 204, in order to realize a multiplexing function, the effective refractive index of the light R with respect to the first optical waveguide 201 in the 0th mode and the effective refractive index of the light R with respect to the MM conversion waveguide 204 _{1 in} the higher order mode. Such that the effective refractive index of the light G in the 0th mode with respect to the third optical waveguide 203 does not become equal to the effective refractive index of the light G with respect to the MM conversion waveguide 204 _{1 in} the higher order mode. The waveguide widths of the first and third optical waveguides 201 and 203 and the MM conversion waveguide 204 ₁ are designed.

  In the optical integrated circuit according to the second embodiment of the present invention, the lights R and G output from the visible light lasers R and G propagate through the first and third optical waveguides 201 and 203, respectively, and the optical multiplexer 204. Are combined at. The combined light of the lights R and G combined in the light combining unit 204 is output from the output port of the third optical waveguide 203. On the other hand, the light B output from the visible light laser B propagates through the second optical waveguide 202 and is output from the output port of the second optical waveguide 202. The output ports of the second and third optical waveguides 202 and 203 are close to each other so that the second and third optical waveguides 202 and 203 can be regarded as point light sources. It seems that the combined light of the lights R, G, and B is output from the output port (point light source).

  When light of each of the three primary color lights is multiplexed into the same waveguide by using a multiplexing section such as a directional coupler, a strict manufacturing tolerance is required when manufacturing the multiplexing section, resulting in a reduced yield. There was a problem.

  In the optical integrated circuit according to the second embodiment, only one combining unit is used to output the three primary color lights that appear to be the combined light of the lights R, G, and B from the point light source to the human eye. Therefore, the required manufacturing tolerance is relaxed by the amount of one multiplexing part less than the case where two multiplexing parts are used. Therefore, according to the optical integrated circuit of the second embodiment, it is possible to improve the yield while reducing the size of the optical integrated circuit that outputs the three primary color lights.

(Example 3)
FIG. 4 illustrates the configuration of an optical integrated circuit according to the third embodiment of the present invention. In FIG. 4, the PLC 300, the visible light laser R disposed on the first input end face 310 facing the output end face 340 of the PLC 300, and the visible light laser R disposed on the two opposing second and third input end faces 320 and 330, respectively. And the visible light lasers B and G are shown.

The PLC 300 transfers the first to third optical waveguides 301 to 303 optically coupled to the visible light lasers R, G, and B and the light B guided in the second optical waveguide 302 to the first optical waveguide 301. Then, it includes an optical multiplexer 304 that multiplexes with the light R guided through the first optical waveguide 301. The optical multiplexer 304 can be a directional coupler using the MM conversion waveguide 304 ₁ as in the _first embodiment. The first optical waveguide 301 has an output port that outputs the light multiplexed by the optical multiplexer 304, and the third optical waveguide 303 has an output port that outputs the light G input from the visible light laser G.

The second optical waveguide 302 has a bent waveguide portion 302 ₁ for optical path conversion of 90 °, and the third optical waveguide 303 has a bent waveguide portion 303 ₁ for optical path conversion of 90 °. The bending waveguide portion 302 ₁ and the bending waveguide portion 303 ₁ are configured to bend in the output end face direction of the PLC 300. The bending waveguide portion 302 ₁ of the second optical waveguide 302 is configured to have a smaller bending radius than the bending waveguide portion 303 _{1 of} the third optical waveguide 303. For example, when the refractive index difference of the waveguide is 0.45% and the waveguide width and thickness are 3.5 μm, the bending radius of the bending waveguide portion 302 ₁ of the second optical waveguide 302 is preferably 1.5 mm, The bending radius of the bending waveguide portion 303 ₁ of the third optical waveguide 303 can be preferably 2.0 mm.

  The distance between the output ports of the first and third optical waveguides 301 and 303 is within 15 μm so that the first and third optical waveguides 301 and 303 can be regarded as a point light source, as in the second embodiment. Are so close together. As in the second embodiment, the interval between the output ports causes blurring of the image when it is visualized, and thus it is desirable to keep it to the minimum necessary.

In the optical multiplexing unit 304, in order to realize a multiplexing function, the effective refractive index of the light B in the 0th mode with respect to the second optical waveguide 302 and the effective refractive index of the light B in the higher mode with respect to the MM conversion waveguide 304 ₁ are increased. Such that the effective refractive index of the light R in the 0th mode with respect to the first optical waveguide 301 and the effective refractive index of the light R with respect to the MM conversion waveguide 304 _{1 in} the higher order mode do not become equal. The waveguide widths of the first and second optical waveguides 301 and 302 and the MM conversion waveguide 304 ₁ are designed.

  In the optical integrated circuit according to the third embodiment of the present invention, the lights R and G output from the visible light lasers R and B propagate through the first and second optical waveguides 301 and 302, respectively, and the optical multiplexer 304. Are combined at. The combined light of the lights R and B combined in the light combining unit 304 is output from the output port of the first optical waveguide 301. On the other hand, the light G output from the visible light laser G propagates through the third optical waveguide 303 and is output from the output port of the third optical waveguide 303. The output ports of the first and third optical waveguides 301 and 303 are close to each other so that the first and third optical waveguides 301 and 303 can be regarded as a point light source. It seems that the combined light of the lights R, G, and B is output from the output port (point light source).

  Therefore, according to the optical integrated circuit of the third embodiment, as in the second embodiment, it is possible to improve the yield while reducing the size of the optical integrated circuit that outputs the three primary color lights. Further, in the optical integrated circuit according to the third embodiment, since the optical multiplexing unit 304 may be designed to combine the lights R and B, the design is looser than that of the second embodiment where the lights R and G are combined. It becomes possible to design the waveguide width and the like under the conditions.

  Although the visible light laser B is disposed on the second input end face 20 and the visible light laser G is disposed on the third input end face 30 in the above embodiment, the visible light laser G is visible on the second input end face 20. The optical laser G may be arranged, and the visible light laser B may be arranged on the third input end face 30.

Claims (4)

An output end face, and a first input end face facing the output end face, and a second input end face and the third input end face facing each other, a planar lightwave circuit including the first pre-Symbol planar lightwave circuit the red light laser for outputting red light disposed on the input end face, before Symbol second blue light laser for outputting the arranged blue light to the input end face, the third green light placed on the input end face a green light laser for outputting, an optical integrated circuit with,
From the output end face, the red light, the blue light, and to output the result of the green light,
The plane lightwave circuit includes first to third optical waveguides optically coupled to the red light laser, the blue light laser, and the green light laser, respectively, and the green light guided through the third optical waveguide. The first light combining portion that moves to the second optical waveguide and combines with the blue light that propagates through the second optical waveguide, and the red light that propagates through the first optical waveguide are described above. A second optical combining unit that moves to a second optical waveguide and combines with the light combined in the first optical combining unit;
The second optical waveguide and the third optical waveguide each have a bending waveguide portion for optical path conversion of 90 ° configured to bend in the direction of the output end face,
Further, the second optical waveguide has an output port for outputting the light multiplexed by the second optical multiplexing section, and the waveguide portion between the input port and the bending waveguide portion has the output port. It intersects with the first optical waveguide, and the angle of the intersection is 15 ° to 90 °.
Optical integrated circuit, wherein the this. A planar lightwave circuit including an output end face, a first input end face facing the output end face, and a second input end face and a third input end face facing each other, and the first input of the planar lightwave circuit. A red light laser arranged on the end face to output red light, a blue light laser arranged on the second input end face to emit blue light, and a green light arranged on the third input end face to output. An optical integrated circuit including a green light laser,
From the output end face, for outputting the red light, the blue light, and the green light,
The planar lightwave circuit includes first to third optical waveguides optically coupled to the red light laser, the blue light laser, and the green light laser, respectively, and the red light guided in the first optical waveguide. An optical multiplexing unit that shifts to the third optical waveguide and multiplexes with the green light guided through the third optical waveguide;
The second optical waveguide has an output port for outputting the guided blue light, and includes first to third bent waveguide portions for optical path conversion of 90 ° from the input port to the output port. Have in order,
The third optical waveguide has an output port for outputting the light multiplexed by the optical multiplexer.
The first bending waveguide portion and the third bending waveguide portion are configured to bend in the direction of the output end face,
The second bending waveguide portion is configured to bend in the direction of the third input end face on which the green light laser is arranged,
The third optical waveguide is configured to bend in the direction of the output end face,
Further, the distance between the output ports of the second optical waveguide and the third optical waveguide is configured to be within 15 μm.
Optical integrated circuit shall be the feature and this. A planar lightwave circuit including an output end face, a first input end face facing the output end face, and a second input end face and a third input end face facing each other, and the first input of the planar lightwave circuit. A red light laser arranged on the end face for outputting red light, a blue light laser arranged for the second input end face for outputting blue light, and a green light arranged for the third input end face. An optical integrated circuit including a green light laser,
From the output end face, for outputting the red light, the blue light, and the green light,
The planar lightwave circuit includes first to third optical waveguides optically coupled to the red light laser, the blue light laser, and the green light laser, respectively, and the blue light guided in the second optical waveguide. An optical multiplexing unit that shifts to the first optical waveguide and multiplexes with the red light guided through the first optical waveguide;
The second optical waveguide and the third optical waveguide each have a bending waveguide portion for optical path conversion of 90 ° configured to bend in the direction of the output end face,
The first optical waveguide has an output port for outputting the light multiplexed by the optical multiplexer.
The third optical waveguide has an output port for outputting the green light guided through the third optical waveguide,
Furthermore, the distance between the output ports of the first optical waveguide and the third optical waveguide is configured to be within 15 μm.
Optical integrated circuit shall be the feature and this. The optical multiplexing unit, an optical integrated circuit according to any one of claims 1 to 3, characterized in that a directional coupler using a multi-mode conversion waveguide.

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