Optical integrated circuit element

Abstract

The optical integrated circuit element has a first waveguide and a second waveguide. At least a portion of the first waveguide and at least a portion of the second waveguide are arranged side by side along the first direction. The first waveguide has a first port configured so as to be able to input or output an electromagnetic wave including the first polarized wave and the second polarized wave, and a second port configured so as to be able to output the separated first polarized wave or to be able to input the first polarized wave. The second waveguide has a third port configured so as to be able to output the separated second polarized wave or the separated and rotated second polarized wave, or to be able to input the second polarized wave. The shape of a cross-section of at least one of the first waveguide and the second waveguide, the cross-section having the first direction as a normal, is non-linearly symmetric.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Japanese Patent Application No. 2022-148604 (filed on September 16, 2022) and Japanese Patent Application No. 2022-203751 (filed on December 20, 2022), the entire disclosures of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to optical integrated circuit components. Background Art

[0004] An element that realizes polarization separation and rotation by combining a mode converter that converts from the TM0 mode to the TE1 mode and a directional coupler is known (for example, refer to Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application No. 2017-536572 Summary of the invention

[0008] An optical integrated circuit element of one embodiment of the present disclosure has a first waveguide and a second waveguide. At least a portion of the first waveguide and at least a portion of the second waveguide are arranged in a row along a first direction. The first waveguide has a first port and a second port, the first port being configured to be able to input or output an electromagnetic wave containing a first polarization wave and a second polarization wave, and the second port being configured to be able to output the separated first polarization wave, or to be able to input the first polarization wave. The second waveguide has a third port, and the third port is configured to be able to output the separated second polarization wave or the separated and rotated second polarization wave, or to be able to input the second polarization wave. The shape of a cross section of at least one of the first waveguide and the second waveguide with the first direction as a normal is non-linearly symmetric. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a block diagram showing a configuration example of an optical receiver according to one embodiment.

[0010] Figure 2 is a block diagram showing another structural example of an optical receiver.

[0011] Figure 3 It is shown in Figure 2 A block diagram of a configuration example of an optical receiver in which the polarization beam rotator is replaced by a polarization beam splitter in the configuration example.

[0012] Figure 4 It is shown in Figure 2 A block diagram of a structural example of an optical receiver in which a delay device connected before a photodiode in a structural example is replaced with a variable attenuator.

[0013] Figure 5 It is shown in Figure 4 A block diagram of a configuration example of an optical receiver in which a delay device is further provided between a variable attenuator connected before the photodiode and the photodiode in the configuration example.

[0014] Figure 6 It is a plan view showing a configuration example of a polarization beam rotator according to one embodiment.

[0015] Figure 7 yes Figure 6 BB cross-section diagram.

[0016] Figure 8 yes Figure 6 CC cross-section diagram.

[0017] Fig. 9 yes Figure 6 DD cross-sectional view.

[0018] Fig.10 yes Figure 6 EE cross-section diagram.

[0019] Fig.11 yes Figure 6 FF cross-section diagram.

[0020] Fig.12 This is a graph showing simulation results of output characteristics of a polarization beam rotator according to one embodiment.

[0021] Fig.13 This is a graph showing actual measurement results of output characteristics of the polarization beam rotator according to one embodiment.

[0022] Fig.14 FIG. 1 is a plan view showing another configuration example of the polarization beam rotator.

[0023] Fig.15 yes Fig.14 GG cross-section diagram.

[0024] Fig.16 yes Fig.14 HH cross-sectional view. DETAILED DESCRIPTION

[0025] In an element formed by combining two elements, a mode converter and a directional coupler, the performance may be reduced due to manufacturing errors of at least one of them. That is, it is not robust against manufacturing errors. Therefore, when the element formed by combining the two elements is manufactured by a process with a width of 0.18μm (180nm), which is technically easy to manufacture and has a low manufacturing cost compared to the most advanced processes, it is difficult to control the characteristics of the element. In addition, for a directional coupler with an asymmetric structure, it is also difficult to control the characteristics of the directional coupler when it is manufactured by a process with a width of 0.18μm. According to the present disclosure, it is possible to provide an optical integrated circuit element whose characteristics are easy to control even when it is manufactured by a process with a width of 0.18μm.

[0026] In optical communications within data centers, direct modulation and direct detection methods are widely used because digital signal processors are simple and low in power consumption. On the other hand, as the traffic volume of optical communications within data centers increases, higher-density data transmission is required, and optical integrated circuits using silicon, especially optical transceivers with small wavelength-multiplexed optical circuits, are being studied. Among them, a series Mach-Zehnder interference system or an arrayed waveguide grating can be used as a wavelength-multiplexed optical circuit implemented by silicon. These wavelength-multiplexed optical circuits all have the characteristic that their characteristics change greatly due to the polarization of light. On the other hand, single-mode optical fibers are widely used in existing optical fiber networks within data centers. However, this optical fiber does not have a polarization-maintaining characteristic. Therefore, whenever light passes through a curved portion or a connecting portion of the wiring, the polarization of the light changes randomly. Therefore, in order to make the characteristics of the optical receiver uniform for any polarization wave, it is necessary to set a polarization beam splitter rotator at the front stage of the optical circuit to separate the incident light into TE (Transverse Electric) component and TM (Transverse Magnetic) component, and make the TE (Transverse Electric) component and TM (Transverse Magnetic) component incident on different wavelength multiplexing optical circuits. In the direct modulation direct polarization wave method, after making the polarization light either TE or TM, it is necessary to receive the output of the wavelength multiplexing optical circuit with a photodiode and detect the sum of the outputs of the photodiodes corresponding to the components of each polarization wave.

[0027] In an element that combines two elements, a mode converter and a directional coupler, the performance may be reduced due to manufacturing errors of at least one side. That is, it is not robust to manufacturing errors. Therefore, when an element that combines two elements is manufactured by a process with a width of 0.18μm (180nm), which is technically easy to manufacture and has a low manufacturing cost compared to the most advanced processes, it is difficult to control the characteristics of the element. In addition, for a directional coupler with an asymmetric structure, it is also difficult to control the characteristics of the directional coupler when it is manufactured by a process with a width of 0.18μm. A structure that can control the characteristics even when it is manufactured by a process with a width of 0.18μm is required.

[0028] An optical receiver 1 (see Figure 1 The optical signal transmitting structure may include a light source and a modulator.

[0029] The light source may include, for example, a semiconductor laser such as an LD (Laser Diode) or a VCSEL (Vertical Cavity Surface Emitting LASER). The light source is not limited to visible light and may include a device that emits electromagnetic waves of various wavelengths. The modulator modulates by changing the intensity of the electromagnetic wave. The modulator may, for example, pulse modulate the electromagnetic wave.

[0030] The structure for transmitting an optical signal can further include a signal input unit. The signal input unit receives an input of a signal from an external device or the like. The signal input unit may include, for example, a D / A converter. The signal input unit outputs a signal to a modulator. The modulator modulates an electromagnetic wave based on the signal obtained by the signal input unit.

[0031] like Figure 2 As shown, the optical receiver 1 may further include a delay device 84 between the polarization beam splitter rotator 82 and each of the two splitters 83 and between the splitter 83 and each of the n photodiodes (PD: photodiode) 10-1 to n. The delay device 84 delays the transmission of the optical signal. The optical receiver 1 compensates for the deviation of the optical signal delay caused by the manufacturing error of the waveguide through the delay device 84. By including the delay device 84, the optical receiver 1 can reduce the jitter of the signal obtained by combining the TE mode optical signal output from the photodiode 10 and the TE mode optical signal converted from the TM mode optical signal.

[0032] The retarder 84 may be configured as a waveguide having a predetermined length, for example, and the effective refractive index of the waveguide may be adjusted by a heater. The retarder 84 may be configured as a phase modulator having a predetermined length, and the phase modulation amount may be adjusted by applying a voltage.

[0033] like Figure 3 As shown, in the optical receiver 1, the polarization beam splitter rotator 82 can be replaced by a polarization beam splitter (PS: Polarizing Splitter) 822. The polarization beam splitter 822 separates the input optical signal into a TE mode optical signal and a TM mode optical signal. The transmission speed of the TE mode optical signal is different from the transmission speed of the TM mode optical signal. The optical receiver 1 can have a delay device 84 to compensate for the deviation of the delay between the TE mode optical signal and the TM mode optical signal.

[0034] like Figure 4 As shown, in Figure 2 In the illustrated optical receiver 1, the delay device 84 connected between the splitter 83 and each of the n photodiodes 10-1 to 10-n can be replaced with a variable optical attenuator (VOA) 85. The variable optical attenuator 85 can be configured as, for example, a pin diode including silicon. The variable optical attenuator 85 absorbs light by injecting current to attenuate the light intensity. By adjusting the current injected into each variable optical attenuator 85, it is possible to compensate for the optical loss generated in the polarization beam rotator 82 or the splitter 83. Therefore, even if the optical loss in the polarization beam rotator 82 or the splitter 83 is not uniform due to the difference in polarization or wavelength of the optical signal, the optical reception sensitivity of the optical signal of any polarization or wavelength can be made close to uniform by reducing the current value of the variable optical attenuator 85 through which the optical signal under the condition of large optical loss passes and increasing the current value of the variable optical attenuator 85 through which the optical signal under the condition of small optical loss passes.

[0035] like Figure 5 As shown, the optical receiver 1 may include a variable optical attenuator 85 and a delay device 84 between the splitter 83 and each of the n photodiodes 10 - 1 ˜n.

[0036] As described above, the optical receiver 1 of the present embodiment can detect an optical signal by using the photodiode 10 configured to reduce the return light. By reducing the return light, the optical signal returned to the input unit 81 can be reduced. By reducing the optical signal returned to the input unit 81, the stable operation of the light source or modulator that sends the optical signal to the input unit 81 can be maintained. As a result, the reliability of the optical communication system using the optical receiver 1 can be improved.

[0037] <Light Detection Device>

[0038] The photodiode 10 disclosed in the present invention is used as a light detection device for detecting light signals. The light detection device is not limited to the photodiode 10, and other light receiving elements such as phototransistors can also be used. Even when other light receiving elements are used as light detection devices, the reliability of the optical communication system can be improved by reducing the return light.

[0039] (Configuration Example of Polarization Beam Rotator 82)

[0040] like Figure 6 and Figure 7 , Figure 8 , Fig. 9 , Fig.10 and Fig.11 By way of example, the polarization beam splitter rotator 82 of one embodiment includes a first waveguide 140 and a second waveguide 142. It is assumed that the first waveguide 140 and the second waveguide 142 are formed on an insulating layer 151 of a substrate 150. The substrate 150 may be made of various materials such as silicon. The insulating layer 151 may be made of various materials such as silicon dioxide. At least a portion of the first waveguide 140 and the second waveguide 142 extend in a first direction (Z-axis direction). At least a portion of the first waveguide 140 and at least a portion of the second waveguide 142 may be arranged in parallel with each other.

[0041] like Figure 8 , Fig. 9 and Fig.10 As shown in the example, the first waveguide 140 includes an asymmetric portion 141, and the asymmetric portion 141 is asymmetric in a cross section with the first direction (Z-axis direction) as a normal line. In addition, the first waveguide 140 is not line-symmetric with respect to the normal line of the surface of the substrate 50 in a cross section with the first direction as a normal line. In the present embodiment, the cross-sectional shape of the first waveguide 140 is asymmetric, but the cross-sectional shape of the second waveguide 142 may also be asymmetric. The cross-sectional shape of at least one of the first waveguide 140 and the second waveguide 142 may also be asymmetric.

[0042] The first waveguide 140 has a first port 143 at an end portion on one side in the negative direction of the Z axis, and has a second port 144 at an end portion on one side in the positive direction of the Z axis, that is, at an end portion opposite to the first port 143 .

[0043] The second waveguide 142 includes a first portion 146 disposed along the first waveguide 140 and a second portion 147 that is separated from the first waveguide 140 as it advances in the positive direction of the Z axis. The second portion 147 may be configured in a curved shape or in a straight line inclined with respect to the direction in which the first waveguide 140 extends. The second portion 147 is located closer to the positive direction of the Z axis than the first portion 146. The second portion 147 has a third port 145 at the end portion on the opposite side to the side connected to the first portion 146.

[0044] The first port 143 of the first waveguide 140 may be configured to be able to input electromagnetic waves. The second port 144 may be configured to be able to output electromagnetic waves. The third port of the second waveguide 142 may be configured to be able to output electromagnetic waves. The electromagnetic wave input to the first port 143 travels in the first waveguide 140 along the positive direction of the Z axis. At least a portion of the electromagnetic wave traveling in the first waveguide 140 is transferred to the second waveguide 142. The electromagnetic wave remaining in the first waveguide 140 travels to the second port 144 and is output from the second port 144. The electromagnetic wave transferred to the second waveguide 142 travels to the third port 145 and is output from the third port 145.

[0045] The second port 144 of the first waveguide 140 may be configured to be able to input electromagnetic waves. The third port 145 of the second waveguide 142 may be configured to be able to input electromagnetic waves. The first port 143 of the first waveguide 140 may be configured to be able to output electromagnetic waves. The electromagnetic wave input to the second port 144 travels in the first waveguide 140 along the negative direction of the Z axis. On the other hand, the electromagnetic wave input to the third port 145 is transferred to the first waveguide 140 while traveling in the first part 146 of the second waveguide 142 along the negative direction of the Z axis. As a result, in the first waveguide 140, the synthesized electromagnetic wave obtained by synthesizing the electromagnetic wave input to the second port 144 and the electromagnetic wave input to the third port 145 travels in the negative direction of the Z axis. The synthesized electromagnetic wave travels to the first port 143 and is output from the first port 143.

[0046] Here, the first waveguide 140 and the second waveguide 142 may be configured to separate the polarized waves when an electromagnetic wave including the first polarized wave and the second polarized wave is input to the first port 143, output the first polarized wave from the second port 144, and output the second polarized wave from the third port 145. On the contrary, the first waveguide 140 and the second waveguide 142 may be configured to output an electromagnetic wave synthesized from the first port 143 when an electromagnetic wave of the first polarized wave is input to the second port 144 and an electromagnetic wave of the second polarized wave is input to the third port 145. The above structure can be realized, for example, by appropriately designing the shape of the asymmetric portion 141 of the first waveguide 140, or the length or interval of the portions where the first waveguide 140 and the second waveguide 142 are arranged with each other. In the present embodiment, it is assumed that the first polarized wave is a polarized wave of the TE mode. It is assumed that the second polarized wave is a polarized wave of the TM mode.

[0047] Fig.12 The results of simulating the characteristics of the polarization beam rotator 82 of this embodiment are shown. Fig.12 In the graph, the horizontal axis represents the wavelength. The unit of wavelength is nm (nanometer). The vertical axis represents the connection loss (Insertion Loss: IL). The unit of the connection loss is dB (decibel). In the simulation, an electromagnetic wave including a TE mode polarization wave and a TM mode polarization wave is input to the first port 143. The component of the TE mode polarization wave output from the second port 144 is represented by a dotted line. The component of the TM mode polarization wave output from the second port 144 is represented by a double dotted line. The component of the TE mode polarization wave output from the third port 145 is represented by a solid line. The component of the TM mode polarization wave output from the third port 145 is represented by a dotted line. As shown Fig.12 As shown in the graph, the electromagnetic wave output from the second port 144 contains more TE mode polarization waves. The electromagnetic wave output from the third port 145 contains more TM mode polarization waves. That is, according to the simulation, the polarization beam splitter rotator 82 of this embodiment can separate the TE mode polarization wave and the TM mode polarization wave.

[0048] Fig.13 The actual measurement results of the characteristics of the polarization beam rotator 82 of this embodiment are shown. Fig.13In the graph, the horizontal axis represents the wavelength. The unit of wavelength is nm (nanometer). The vertical axis represents the connection loss (Insertion Loss: IL). The unit of the connection loss is dB (decibel). During the actual measurement, an electromagnetic wave including a TE mode polarization wave and a TM mode polarization wave is input to the first port 143. The measured value of the polarization wave component of the TE mode output from the second port 144 is represented by a dotted line. The measured value of the polarization wave component of the TM mode output from the second port 144 is represented by a double dotted line. The measured value of the polarization wave component of the TE mode output from the third port 145 is represented by a solid line. The measured value of the polarization wave component of the TM mode output from the third port 145 is represented by a dotted line. As shown Fig.13 As shown in the graph, the electromagnetic wave output from the second port 144 includes more TE mode polarization waves. The electromagnetic wave output from the third port 145 includes more TM mode polarization waves. That is, in the actual measurement results, the polarization beam splitter rotator 82 of this embodiment can also separate the TE mode polarization wave and the TM mode polarization wave.

[0049] The polarization beam splitter rotator 82 of the present embodiment may include a first waveguide 140 and a second waveguide 142. At least a portion of the first waveguide 140 and at least a portion of the second waveguide 142 may be aligned along a first direction ( Figure 6 The first waveguide 140 may include a first port and a second port, the first port being configured to input or output an electromagnetic wave including a first polarization wave (e.g., a polarization wave of a TE mode) and a second polarization wave (e.g., a polarization wave of a TM mode), and the second port being configured to output the separated first polarization wave or input the first polarization wave. The second waveguide 142 may have a third port, the third port being configured to output the separated second polarization wave or the separated and rotated second polarization wave, or to input the second polarization wave. At least one of the first waveguide 140 and the second waveguide 142 is arranged in the first direction ( Figure 6 The shape of the cross section of the first waveguide 140 with the first direction (Z-axis direction) as the normal line may be non-linesymmetric. Figure 6 The shape of the cross section with the Z-axis direction as the normal can be asymmetric.

[0050] The polarization beam splitter rotator 82 may be Fig.14 , Fig.15 and Fig.16 The first portion 146 of the second waveguide 142 may be configured so that the line width is not constant. For example, the first portion 146 may be configured in a tapered shape that becomes thinner on the side of the first port 143 and thicker on the side connected to the second portion 147. The first portion 146 may be configured as an adiabatic tapered waveguide.

[0051] Fig.15 A side of the first portion 146 close to the first port 143 and a cross section of the first waveguide 140 are shown. Fig.16 14 shows a cross section of the first portion 146 on a side away from the first port 143 and the first waveguide 140. A distance D1 between the first waveguide 140 and the second waveguide 142 on a side close to the first port 143 may be greater than a distance D2 between the first waveguide 140 and the second waveguide 142 on a side away from the first port 143. That is, the distance D1 between at least one of the first waveguide 140 and the second waveguide 142 and the first direction ( Fig.14 The width of the direction intersecting the Z-axis direction) may vary along at least a portion of the first direction. Fig.15 The cross-sectional position plays a role Fig.16 The distance from the cross-sectional position of the first waveguide 140 to the cross-sectional position of the first waveguide 140 can be set to, for example, several tens of μm (micrometers). The widths or distances D1 and D2 of the first waveguide 140 and the second waveguide 142 can be set to, for example, several hundreds of nm (nanometers).

[0052] The second waveguide 142 may be configured to rotate the polarized wave of the TM mode separated from the first waveguide 140 and output the polarized wave of the TE mode from the third port 145 .

[0053] The first waveguide 140 and the second waveguide 142 may be formed to include silicon. The first waveguide 140 and the second waveguide 142 may be formed on a silicon substrate 150. By forming the waveguides from silicon, it is possible to easily manufacture elements including the polarization beam rotator 82 by a silicon process. The first waveguide 140 and the second waveguide 142 are not limited to silicon, and may also be formed to include other various dielectric materials.

[0054] A polarization beam splitter rotator 82 of one embodiment may have an asymmetric directional coupler structure. The polarization beam splitter rotator 82 may be configured such that the shape of a first waveguide 140 having input and output ports on both sides is asymmetric, and the shape of a second waveguide having input and output ports on one side and branching from the first waveguide 140 or merging with the first waveguide 140 is symmetrical. In other words, the polarization beam splitter rotator 82 may set the cross-output port to a waveguide of a symmetrical shape. By configuring the polarization beam splitter rotator 82 in this way, the width of the asymmetric waveguide can be increased. For example, the width of the asymmetric waveguide can be above 300 nanometers (300nm). As a result, the polarization beam splitter rotator 82 can have a structure that can be manufactured in a commercial foundry. A commercial foundry may refer to a foundry that can perform mass production regardless of scale.

[0055] The size or shape of the components mass-produced in commercial foundries has manufacturing tolerances. As a structure for relaxing the manufacturing tolerances, the symmetrically shaped waveguide width can be designed to be non-constant. Thus, the components become structures that are robust to manufacturing tolerances.

[0056] In a polarization beam splitter rotator 82 of one embodiment, the line widths of the asymmetric first waveguide 140 and the symmetric second waveguide 142 can be greater than 200 nanometers (200nm) even in narrow places. In addition, the spacing between the first waveguide 140 and the second waveguide 142 can be greater than 200 nanometers (200nm) even in narrow places. In this case, the element also becomes a structure that is robust with respect to manufacturing tolerances. In the case where the line width or line spacing of the waveguide is greater than 200 nanometers even in narrow places, the waveguide can be manufactured with a process with a width of 180 nanometers (180nm). Generally, compared with the most advanced processes, the process with a width of 180 nanometers is technically easy to manufacture and has a low manufacturing cost. Therefore, in the case where the line width or line spacing of the waveguide is greater than 200 nanometers even in narrow places, the manufacturing yield of the element can be improved or the manufacturing cost can be reduced.

[0057] In the polarization beam rotator 82 of one embodiment, the asymmetric first waveguide 140 is configured to have input and output ports on both sides, thereby ensuring robustness even if the line widths of the first waveguide 140 and the second waveguide 142 are increased.

[0058] As described above, by using an asymmetric directional coupler structure, a simple structure of the polarization beam rotator 82 can be realized. In addition, the polarization beam rotator 82 is designed so that the width of the waveguide is not constant in a symmetrical shape, and thus can be manufactured in a commercial foundry.

[0059] Although the embodiments of the present disclosure have been described according to the drawings and embodiments, it should be noted that those skilled in the art can make various deformations or changes according to the present disclosure. Therefore, it should be noted that these deformations or changes are all included in the scope of the present disclosure. For example, the functions included in each structural part, etc. can be reconfigured in a logically non-contradictory manner, and multiple structural parts, etc. can be combined into one or divided. It should be understood that the scope of the present disclosure also includes these situations.

[0060] In the present disclosure, the records such as "first" and "second" are identifiers for distinguishing the structure. The structure distinguished by the records such as "first" and "second" in the present disclosure can replace the number in the structure. For example, the first waveguide 140 can replace the "first" and "second" as identifiers with the second waveguide 142. The replacement of the identifier is carried out simultaneously. After the replacement of the identifier, the structure can still be distinguished. The identifier can also be deleted. The structure with the identifier deleted is distinguished by the figure mark. The interpretation of the order of the structure and the basis for the existence of the smaller numbered identifier should not be based solely on the records of the identifiers such as "first" and "second" in the present disclosure.

[0061] In the present disclosure, the X-axis, Y-axis, and Z-axis are provided for convenience of description and can be interchanged. The structure of the present disclosure is described using an orthogonal coordinate system consisting of the X-axis, Y-axis, and Z-axis. The positional relationship of each structure of the present disclosure is not limited to an orthogonal relationship.

[0062] In one embodiment, (1) an optical integrated circuit element comprises a first waveguide and a second waveguide. At least a portion of the first waveguide and at least a portion of the second waveguide are arranged along a first direction. The first waveguide comprises a first port and a second port, the first port being configured to input or output an electromagnetic wave including a first polarization wave and a second polarization wave, and the second port being configured to output the separated first polarization wave, or to input the first polarization wave. The second waveguide comprises a third port, the third port being configured to output the separated second polarization wave or the separated and rotated second polarization wave, or to input the second polarization wave. The shape of a cross section of at least one of the first waveguide and the second waveguide with the first direction as a normal is non-linearly symmetric.

[0063] (2) In the optical integrated circuit element described in (1) above, the first waveguide may have an asymmetric cross-sectional shape whose normal line is the first direction.

[0064] (3) In the optical integrated circuit element described in (1) or (2) above, the width of at least one of the first waveguide and the second waveguide in a direction intersecting the first direction may vary in at least a portion along the first direction.

[0065] (4) In the optical integrated circuit element described in any one of (1) to (3) above, the first waveguide and the second waveguide may be formed to include silicon.

[0066] (5) In the optical integrated circuit element described in any one of (1) to (4) above, each of the first waveguide and the second waveguide may have a line width larger than 200 nm.

[0067] Description of reference numerals:

[0068] 1: Optical receiver (81: input unit, 82: polarization beam splitter rotator (PSR), 822: polarization beam splitter (PS), 83: demultiplexer (DEMUX), 84: delay device, 85: variable optical attenuator (VOA))

[0069] 10: Photodiode

[0070] 50: Substrate

[0071] 140: first waveguide (141: asymmetric portion, 143: first port, 144: second port)

[0072] 142: second waveguide (145: third port, 146: first part, 147: second part)

[0073] 150: substrate (151: insulation layer)

Claims

1. An optical integrated circuit element, wherein: having a first waveguide and a second waveguide, At least a portion of the first waveguide and at least a portion of the second waveguide are arranged in a row along a first direction, The first waveguide comprises: a first port configured to be able to input or output an electromagnetic wave including a first polarized wave and a second polarized wave; and a second port configured to be able to output the separated first polarized wave or to input the first polarized wave, The second waveguide has a third port, and the third port is configured to be able to output the separated second polarized wave or the separated and rotated second polarized wave, or to be able to input the second polarized wave. A shape of a cross section of at least one of the first waveguide and the second waveguide having the first direction as a normal line is non-line symmetric.

2. The optical integrated circuit element according to claim 1, wherein: The shape of a cross section of the first waveguide with the first direction as a normal line is asymmetric.

3. The optical integrated circuit element according to claim 1, wherein: A width of at least one of the first waveguide and the second waveguide in a direction intersecting the first direction varies along at least a portion of the first direction.

4. The optical integrated circuit element according to any one of claims 1 to 3, wherein The first waveguide and the second waveguide are formed to include silicon.

5. The optical integrated circuit element according to claim 4, wherein: The line width of each of the first waveguide and the second waveguide is greater than 200 nm.

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