Vertical coupling 90-degree optical mixer
By designing a vertically coupled 90° optical mixer, using a vertically coupled photonic chip and multi-mode interferometer, the existing optical mixers have complex design, low integration and large coupling loss in multi-channel, multi-polarized optical signal processing, and efficient optical signal separation, mixing and phase control are achieved, meeting the high integration and low loss requirements of modern optical communication systems.
Patent Information
- Application Number
- CN202411871690.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-18
- Publication Date
- 2025-03-21
AI Technical Summary
When handling multi-channel and multi-polarized optical signals, existing optical mixers have problems such as complex design, low integration, and large coupling loss, which is difficult to meet the requirements of modern optical communication systems for high integration, low loss and multiple polarization signal processing.
A vertically coupled 90° optical mixer is designed, using a vertically coupled first and second photonic chips, including a polarization separator and a multi-mode interferometer, respectively. Through the combination of a waveguide cross structure and a multi-mode interferometer, efficient separation, mixing and phase control of optical signals are achieved.
It realizes efficient separation and mixing of optical signals, which is suitable for the precise control and combination of phase and amplitude of multi-polarized light, improves integration and coupling efficiency, reduces optical loss, and meets the needs of complex optical signal processing.
Smart Images
Figure CN119667855A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of optical communication technology, and in particular to a vertically coupled 90° optical mixer. Background Art
[0002] In modern optical communication systems, optical mixers are important devices for optical signal processing, demodulation, and signal conversion. With the continuous development of optical communication networks, the requirements for optical signal processing are getting higher and higher. Traditional optical devices face many challenges when processing multi-channel and multi-polarization optical signals. For example, in optical fiber communications, it is often necessary to separate, mix, phase modulate, and perform other operations on optical signals of different wavelengths and polarization states, which puts higher requirements on the design of optical mixers.
[0003] In the prior art, optical mixers mostly use structures based on beam splitters, waveguide interferometers or planar waveguides, but most of them are insufficient in efficiency and integration. Traditional optical mixer structures are often bulky and difficult to meet the requirements of modern optical communication systems for high integration and low loss. In addition, in terms of the separation and mixing of multi-polarized light, existing designs also have limitations, and it is difficult to process optical signals of multiple polarization states at the same time, affecting the accuracy of the signal and the stability of the system. Although these devices can achieve basic optical signal mixing and separation functions, they have the following limitations: complex design, traditional optical mixers usually use multiple discrete optical waveguide devices, and need to rely on complex waveguide network design to achieve the mixing and separation of multi-channel optical signals, which increases the difficulty of design and manufacturing. Low integration, the traditional mixer structure occupies a large chip area, for example, the three functions of optical fiber and waveguide coupling, polarization separation, and beam separation need to be realized by three devices, which is difficult to meet the needs of highly integrated photonic systems, especially when integrating a large number of optical components, facing the problem of insufficient space. The coupling loss is large. Traditional devices use multiple discrete optical waveguide devices. The coupling efficiency of optical signals between different optical waveguides is limited, resulting in large optical power loss, which affects the quality of signal transmission.
[0004] With the evolution of optical communication technology, photonic integrated circuits have gradually become an important research direction in modern photonics. By using materials with high refractive index contrast, high-density optical device integration can be achieved on a smaller chip area. In addition, these photonic devices also have the advantages of mature manufacturing processes and easy large-scale production. However, when processing multi-beam, multi-polarization optical signals, the following challenges still exist:
[0005] (1) Polarization control and separation: How to effectively separate and control optical signals with different polarizations in the device.
[0006] (2) Multi-channel coupling efficiency: How to achieve efficient optical coupling from the optical fiber to the optical waveguide for transmitting signals, as well as to achieve efficient coupling and mixing within the optical chip to ensure the transmission quality of the signal, are still issues that need to be resolved.
[0007] (3) Complex signal processing: As the demand for communication systems increases, optical devices need to be able to process more complex signals, such as processing optical signals of multiple frequencies and multiple polarization states at the same time. Summary of the invention
[0008] The present application provides a vertically coupled 90° optical mixer, which can realize efficient separation and mixing of optical signals and is suitable for precise control and combination of phase and amplitude of multi-polarized light.
[0009] The embodiment of the present application provides a vertically coupled 90° optical mixer, the vertically coupled 90° optical mixer comprising:
[0010] A first photonic chip and a second photonic chip are vertically coupled;
[0011] The first photonic chip includes a first polarization separator, which is used to depolarize and beam-separate the incident dual-polarization object light signal to obtain two object light separated light signals in a first polarization direction and two object light separated light signals in a second polarization direction;
[0012] The second photonic chip includes a second polarization separator, which is used to depolarize and beam-separate the incident dual-polarization reference optical signal to obtain two reference light separation optical signals in a first polarization direction and two reference light separation optical signals in a second polarization direction;
[0013] A waveguide crossing structure, which is used to allow the object light separation optical signal and the reference light separation optical signal to be cross-transmitted without interference when the optical waveguides transmitting the object light separation optical signal and the reference light separation optical signal are crossed;
[0014] Four multimode interferometers are used to combine the object light separated optical signal in the first polarization direction with the reference light separated optical signal in the first polarization direction, and to combine the object light separated optical signal in the second polarization direction with the reference light separated optical signal in the second polarization direction, and output corresponding mixing signals.
[0015] In one embodiment, the first polarization separator is further used to depolarize and separate the incident dual-polarization object light signal to obtain a first object light separated light signal in a first polarization direction. The second beam of object light of the first polarization direction separates the optical signal The first beam of object light with the second polarization direction separates the optical signal The optical signal is separated from the second object light beam of the second polarization direction
[0016] The second polarization depolarizer is also used to depolarize and separate the incident dual-polarization reference light signal to obtain a first reference light separated light signal in a first polarization direction. The second reference light beam of the first polarization direction separates the optical signal The first reference beam of the second polarization direction separates the optical signal The optical signal is separated from the second reference light beam of the second polarization direction.
[0017] Wherein, x is the first polarization direction, and y is the second polarization direction.
[0018] In one embodiment, the waveguide intersection structure comprises:
[0019] The first waveguide cross is used to separate the optical signal from the first beam of object light of the second polarization direction. Separate the optical signal from the first reference light beam of the first polarization direction Perform cross transmission without interference;
[0020] The second waveguide cross is used to separate the optical signal from the second beam of object light of the second polarization direction. The optical signal is separated from the second reference light beam of the first polarization direction Cross-transmission without interference.
[0021] In one embodiment, the four multi-mode interferometers include:
[0022] A first multimode interferometer is used to separate the first beam of object light of the first polarization direction into an optical signal Separating the optical signal from the first reference light beam of the first polarization direction Combine and output the first mixed signal and the second mixing signal
[0023] A second multimode interferometer is used to separate the second beam of object light of the first polarization direction into an optical signal Separating the optical signal from the second reference beam of the first polarization direction Combine and output the third mixed signal and the fourth mixing signal
[0024] A third multimode interferometer is used to separate the first beam of object light of the second polarization direction into an optical signal Separate the optical signal from the first reference beam of the second polarization direction Combine and output the fifth mixed signal and the sixth mixing signal
[0025] A fourth multimode interferometer is used to separate the second beam of object light of the second polarization direction into an optical signal Separating the optical signal from the second reference beam of the second polarization direction Combine and output the seventh mixed signal and the eighth mixing signal
[0026] In one embodiment, the vertically coupled 90° optical mixer further comprises: four phase shifters;
[0027] Each phase shifter is respectively arranged on one of the input optical waveguides of each multimode interferometer, and is used to adjust the phase of the optical signal in the corresponding input optical waveguide, so as to control the two optical signals input to each multimode interferometer to reach the target phase difference.
[0028] In one embodiment, the dual-polarized object light signal is incident on the first photonic chip perpendicular to the xOy plane of the first photonic chip;
[0029] The dual-polarization reference light signal is incident on the second photonic chip perpendicular to the xOy plane of the second photonic chip.
[0030] In one embodiment, the areas of the first photonic chip and the second photonic chip are both 16 to 100 square micrometers.
[0031] In one embodiment, the material of the optical mixer includes silicon-based material, silicon nitride material or polymer material.
[0032] In one embodiment, the first photonic chip, the second photonic chip, each waveguide intersection structure and each multi-mode interferometer are optimized by inverse design optimization based on topology optimization.
[0033] In one embodiment, the first photonic chip and the second photonic chip are fabricated on a standard SOI platform.
[0034] The embodiment of the present application provides a vertically coupled 90° optical mixer, the vertically coupled 90° optical mixer comprising: a first photonic chip and a second photonic chip that are vertically coupled; the first photonic chip comprising a first polarization separator, which is used to depolarize and beam separate an incident dual-polarization object light signal to obtain two object light separation light signals in a first polarization direction and two object light separation light signals in a second polarization direction; the second photonic chip comprising a second polarization separator, which is used to depolarize and beam separate an incident dual-polarization reference light signal to obtain two reference light beams in the first polarization direction. A separation optical signal and two reference light separation optical signals in the second polarization direction; a waveguide crossing structure, which is used to make the object light separation optical signal and the reference light separation optical signal cross-transmitted without interference when the optical waveguides transmitting the object light separation optical signal and the reference light separation optical signal cross; four multimode interferometers, used to combine the object light separation optical signal in the first polarization direction with the reference light separation optical signal in the first polarization direction, combine the object light separation optical signal in the second polarization direction with the reference light separation optical signal in the second polarization direction, and output the corresponding mixing signal. The combination of the polarization separation vertical coupler and the multimode interferometer structure realizes the efficient separation and mixing of optical signals, realizes the mixing and output of the phases and amplitudes of multiple optical signals, and can meet the complex optical signal processing requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 This is a schematic diagram of the structure of the vertically coupled 90° optical mixer of the present application. DETAILED DESCRIPTION
[0036] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0037] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.
[0038] In a first aspect, an embodiment of the present application provides a vertically coupled 90° optical mixer.
[0039] In one embodiment, referring to Figure 1 , Figure 1 This is a flow chart of an embodiment of a vertically coupled 90° optical mixer of the present application. Figure 1 As shown, the vertically coupled 90° optical mixer comprises:
[0040] The first photonic chip S and the second photonic chip R are vertically coupled. The areas of the first photonic chip and the second photonic chip are both between 16 and 100 square microns. In this embodiment, a small-area photonic chip is used, which is suitable for large-scale integration into a photonic system and meets the requirements of future optical communication systems for high integration and low power consumption.
[0041] The first photonic chip includes a first polarization splitter, and the second photonic chip includes a second polarization splitter.
[0042] The dual-polarization object light signal is incident on the first photonic chip through an optical fiber perpendicular to the xOy plane of the first photonic chip, and optical signal transmission is realized through vertical coupling. After the dual-polarization object light signal enters the first photonic chip, the first polarization separator is used to depolarize and separate the dual-polarization object light signal to obtain two object light separation light signals in the first polarization direction and two object light separation light signals in the second polarization direction, specifically including the first object light separation light signal in the first polarization direction. The second beam of object light of the first polarization direction separates the optical signal The first beam of object light with the second polarization direction separates the optical signal The optical signal is separated from the second object light beam of the second polarization direction
[0043] The dual-polarization reference light signal is incident on the second photonic chip through an optical fiber perpendicular to the xOy plane of the second photonic chip, and optical signal transmission is realized through vertical coupling. After the dual-polarization reference light signal enters the second photonic chip, the second polarization separator is used to depolarize and separate the dual-polarization reference light signal, and obtain two reference light separation light signals in the first polarization direction and two reference light separation light signals in the second polarization direction, specifically including the first reference light separation light signal in the first polarization direction. The second reference light beam of the first polarization direction separates the optical signal The first reference beam of the second polarization direction separates the optical signal The optical signal is separated from the second reference light beam of the second polarization direction. Wherein, x is the first polarization direction, and y is the second polarization direction.
[0044] It is worth noting that in this embodiment, the optical signal is incident on the photonic chip through an optical fiber perpendicular to the xOy plane of the photonic chip, and the vertical coupling between the optical fiber and the chip is utilized to simplify the structural design of the device, improve the coupling efficiency, and reduce the loss of the optical signal during transmission.
[0045] Furthermore, the vertically coupled 90° optical mixer further includes: a waveguide crossing structure. The first photonic chip and the second photonic chip each introduce the optical signal after depolarization and beam separation into the corresponding waveguide, and the waveguide crossing structure is used to enable the object light separation optical signal and the reference light separation optical signal to be cross-transmitted without interference when the optical waveguides transmitting the object light separation optical signal and the reference light separation optical signal cross.
[0046] Specifically, the waveguide crossing structure includes: a first waveguide crossing Crossing_1 and a second waveguide crossing Crossing_2.
[0047] The first waveguide cross is used to separate the optical signal from the first beam of object light of the second polarization direction. and a first reference beam of a first polarization direction to separate the optical signal Cross-transmission without interference.
[0048] The second waveguide cross is used to separate the optical signal from the second beam of object light of the second polarization direction. The optical signal is separated from the second reference light beam of the first polarization direction Cross-transmission without interference.
[0049] Furthermore, the vertically coupled 90° optical mixer further includes: four multimode interferometers MMI, namely: a first multimode interferometer MMI_1, a second multimode interferometer MMI_2, a third multimode interferometer MMI_3 and a fourth multimode interferometer MMI_4. The MMI_1, MMI_2, MMI_3 and MMI_4 are respectively connected to four output ports, for combining the object light separation optical signal of the first polarization direction with the reference light separation optical signal of the first polarization direction, combining the object light separation optical signal of the second polarization direction with the reference light separation optical signal of the second polarization direction, and outputting corresponding mixing signals.
[0050] Specifically, the first multimode interferometer MMI_1 separates the first beam of object light of the first polarization direction into optical signals Separating the optical signal from the first reference light beam of the first polarization direction Combine and output the first mixed signal and the second mixing signal
[0051] The second multi-mode interferometer MMI_2 is used to separate the second beam of object light of the first polarization direction into an optical signal Separating the optical signal from the second reference beam of the first polarization direction Combine and output the third mixed signal and the fourth mixing signal
[0052] The third multi-mode interferometer MMI_3 is used to separate the first beam of object light of the second polarization direction into an optical signal Separate the optical signal from the first reference beam of the second polarization direction Combine and output the fifth mixed signal and the sixth mixing signal
[0053] The fourth multimode interferometer MMI_4 is used to separate the second beam of the second polarization direction of the object light into an optical signal Separating the optical signal from the second reference beam of the second polarization direction Combine and output the seventh mixed signal and the eighth mixing signal
[0054] It is worth noting that, in this embodiment, by integrating the functions of optical fiber and waveguide coupling, polarization separation, and beam separation in the optical fiber and waveguide coupling region in the photonic chip, a 90° optical mixer can be realized without multiple devices.
[0055] As a preferred real-time method, the vertically coupled 90° optical mixer further includes: four phase shifters. Specifically, it includes a first phase shifter PS_1, a second phase shifter PS_2, a third phase shifter PS_3 and a fourth phase shifter PS_4. Each phase shifter is respectively arranged on one of the input optical waveguides of each multimode interferometer, and is used to adjust the phase of the optical signal in the corresponding input optical waveguide to control the two optical signals input to each multimode interferometer to reach the target phase difference. Each intersection is phase-adjusted by a corresponding phase shifter to control the phase difference of the two optical signals input to the multimode interferometer.
[0056] For example, the two input optical waveguides of the first multimode interferometer are: the first beam of object light with the first polarization direction separated optical signal The corresponding first input optical waveguide and the first reference light of the first polarization direction separate the optical signal The first phase shifter PS_1 can be arranged on the first input optical waveguide or the second input optical waveguide of the first multimode interferometer. When the first phase shifter PS_1 is arranged on the second input optical waveguide, the first reference light of the first polarization direction can be adjusted to separate the optical signal The phase of the first reference light beam of the first polarization direction is controlled to separate the optical signal Separate the optical signal from the first beam of object light of the first polarization direction The phase difference reaches the target phase difference.
[0057] Explanatory, because the actual processed photonic chip inevitably has errors with the design, it cannot be guaranteed that the phase difference between the two beams entering the multi-mode interferometer MMI meets the design requirements, and this error can be compensated by setting a phase shifter. And the four phase shifters (PS_1, PS_2, PS_3, PS_4) can independently adjust the phase of the corresponding optical signal in the input optical path to meet different coupling requirements.
[0058] In one embodiment, the first photonic chip, the second photonic chip, each waveguide intersection and each multimode interferometer are optimized through reverse design optimization based on topology optimization to ensure that efficient coupling and mixing effects can be maintained under complex structures. Through this optimized design, the device can maximize the coupling efficiency of optical signals and achieve stable performance under different operating conditions, thereby achieving higher optical coupling efficiency and signal processing capabilities.
[0059] In an optional embodiment, the first photonic chip and the second photonic chip are manufactured on a standard SOI (Silicon-On-Insulator) platform to meet the requirements of efficient frequency mixing and high integration.
[0060] In one embodiment, the material of the vertically coupled 90° optical mixer includes silicon-based, silicon nitride material or polymer material (such as polymethyl methacrylate (PMMA) acrylic or organic glass), etc., which is suitable for standard CMOS process and easy to achieve large-scale integration.
[0061] The vertically coupled 90° optical mixer provided in this embodiment effectively solves the shortcomings of existing optical mixers in terms of miniaturization, high integration, high coupling efficiency and low loss, can efficiently process dual-polarization optical signals, and has good manufacturability and compatibility. Compared with the traditional design, the present invention has the following technical advantages: 1. Efficient coupling and low loss: the vertical coupling technology is used to optimize the coupling efficiency of optical signals between photonic chips and reduce the optical loss of the device; 2. High integration: the chip area is small and the structural design is compact, which is convenient for large-scale integration on the standard SOI platform; 3. Multi-function output: through the combination of waveguide crossing and multi-mode interferometer MMI structure, the phase and amplitude mixing and output of multiple optical signals are realized, which can meet the complex optical signal processing requirements; 4. Simple manufacturing: the device design is compatible with CMOS process and is easy to achieve mass production; 5. Reverse design and optimization: by performing reverse design based on topological optimization on the device, it is no longer confined to the a priori of traditional physical devices, and the structure of the required device can be designed in a higher dimension, ensuring high-performance output under complex structures.
[0062] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.
[0063] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.
[0064] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.
[0065] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.
[0066] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.
Claims
1. A vertically coupled 90° optical mixer, characterized in that: The vertically coupled 90° optical mixer comprises: A first photonic chip and a second photonic chip are vertically coupled; The first photonic chip includes a first polarization separator, which is used to depolarize and beam-separate the incident dual-polarization object light signal to obtain two object light separated light signals in a first polarization direction and two object light separated light signals in a second polarization direction; The second photonic chip includes a second polarization separator, which is used to depolarize and beam-separate the incident dual-polarization reference optical signal to obtain two reference light separation optical signals in a first polarization direction and two reference light separation optical signals in a second polarization direction; A waveguide crossing structure, which is used to allow the object light separation optical signal and the reference light separation optical signal to be cross-transmitted without interference when the optical waveguides transmitting the object light separation optical signal and the reference light separation optical signal are crossed; Four multimode interferometers are used to combine the object light separated optical signal in the first polarization direction with the reference light separated optical signal in the first polarization direction, and to combine the object light separated optical signal in the second polarization direction with the reference light separated optical signal in the second polarization direction, and output corresponding mixing signals.
2. The vertically coupled 90° optical mixer according to claim 1, characterized in that: The first polarization separator is also used to depolarize and separate the incident dual-polarization object light signal to obtain a first object light separated light signal in a first polarization direction. The second beam of object light of the first polarization direction separates the optical signal The first beam of object light with the second polarization direction separates the optical signal The optical signal is separated from the second object light beam of the second polarization direction The second polarization separator is also used to depolarize and separate the incident dual-polarization reference light signal to obtain a first reference light separation light signal in a first polarization direction. The second reference light beam of the first polarization direction separates the optical signal The first reference beam of the second polarization direction separates the optical signal The optical signal is separated from the second reference light beam of the second polarization direction. Wherein, x is the first polarization direction, and y is the second polarization direction.
3. The vertically coupled 90° optical mixer according to claim 2, characterized in that: The waveguide intersection structure comprises: The first waveguide cross is used to separate the optical signal from the first beam of object light of the second polarization direction. Separate the optical signal from the first reference light beam of the first polarization direction Perform cross transmission without interference; The second waveguide cross is used to separate the optical signal from the second beam of object light of the second polarization direction. The optical signal is separated from the second reference light beam of the first polarization direction Cross-transmission without interference.
4. The vertically coupled 90° optical mixer according to claim 3, characterized in that: The four multi-mode interferometers include: A first multimode interferometer is used to separate the first beam of object light of the first polarization direction into an optical signal Separating the optical signal from the first reference light beam of the first polarization direction Combine and output the first mixed signal and the second mixing signal A second multimode interferometer is used to separate the second beam of object light of the first polarization direction into an optical signal Separating the optical signal from the second reference beam of the first polarization direction Combine and output the third mixed signal and the fourth mixing signal A third multimode interferometer is used to separate the first beam of object light of the second polarization direction into an optical signal Separate the optical signal from the first reference beam of the second polarization direction Combine and output the fifth mixed signal and the sixth mixing signal A fourth multimode interferometer is used to separate the second beam of object light of the second polarization direction into an optical signal Separating the optical signal from the second reference beam of the second polarization direction Combine and output the seventh mixed signal and the eighth mixing signal 5. The vertically coupled 90° optical mixer according to claim 4, characterized in that: The vertically coupled 90° optical mixer further comprises: four phase shifters; Each phase shifter is respectively arranged on one of the input optical waveguides of each multimode interferometer, and is used to adjust the phase of the optical signal in the corresponding input optical waveguide, so as to control the two optical signals input to each multimode interferometer to reach the target phase difference.
6. The vertically coupled 90° optical mixer according to claim 1, characterized in that: The dual-polarization object light signal is incident on the first photonic chip perpendicular to the xOy plane of the first photonic chip; The dual-polarization reference light signal is incident on the second photonic chip perpendicular to the xOy plane of the second photonic chip.
7. The vertically coupled 90° optical mixer according to claim 1, characterized in that: The areas of the first photonic chip and the second photonic chip are both 16 to 100 square micrometers.
8. The vertically coupled 90° optical mixer according to claim 1, characterized in that: The material of the optical mixer includes silicon-based material, silicon nitride material or polymer material.
9. The vertically coupled 90° optical mixer according to claim 1, characterized in that: The first photonic chip, the second photonic chip, each waveguide intersection structure and each multi-mode interferometer are optimized by inverse design optimization based on topology optimization.
10. The vertically coupled 90° optical mixer according to claim 1, characterized in that: The first photonic chip and the second photonic chip are manufactured on a standard SOI platform.