90-degree phase mixing chip for on-chip integrated coherent receiver

Abstract

The invention relates to a 90-degree phase mixing chip for an on-chip integrated coherent receiver. A first input waveguide receives signal light, and a second input waveguide receives intrinsic light; the input end of the first polarization beam splitter is coupled with the first input waveguide, the first output end of the first polarization beam splitter is coupled with the first input end of the first phase mixer, and the second output end of the first polarization beam splitter is coupled with the first input end of the second phase mixer; the input end of the second polarization beam splitter is coupled with the second input waveguide, the first output end of the second polarization beam splitter is coupled with the second input end of the first phase mixer, and the second output end of the second polarization beam splitter is coupled with the second input end of the second phase mixer; waveguides in the first input waveguide, the second input waveguide, the first polarization beam splitter, the second polarization beam splitter, the first phase mixer and the second phase mixer are all made of silicon nitride; both the first input waveguide and the second input waveguide are tapered gradient waveguides; and ultra-long distance transmission is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of optical communication, in particular to a 90-degree phase mixing chip for an on-chip integrated coherent receiver. BACKGROUND

[0002] In a high-speed optical communication system, a coherent receiving technology significantly improves channel capacity and transmission distance by detecting amplitude, phase and polarization information of an optical signal. Among them, a multi-phase mixer (such as a 90-degree mixer) is a core component of a coherent receiver, which is used to realize interference mixing of signal light and local oscillator light.

[0003] However, the transmission loss of the traditional 90-degree mixer is high, which is difficult to meet the demand of ultra-long distance transmission, and the 90-degree mixer mainly depends on discrete components or complex circuits to generate multi-phase difference, and the integration degree is low. SUMMARY

[0004] Therefore, it is necessary to provide a 90-degree phase mixing chip for an on-chip integrated coherent receiver, which has low transmission loss and high integration degree.

[0005] The application provides a 90-degree phase mixing chip for an on-chip integrated coherent receiver, which comprises a substrate and a first input waveguide, a second input waveguide, a first polarization beam splitter, a second polarization beam splitter, a first phase mixer and a second phase mixer arranged on the same side of the substrate.

[0006] The first input waveguide is used for receiving signal light, and the second input waveguide is used for receiving eigenlight.

[0007] The input end of the first polarization beam splitter is coupled with the first input waveguide, the first output end of the first polarization beam splitter is coupled with the first input end of the first phase mixer, and the second output end of the first polarization beam splitter is coupled with the first input end of the second phase mixer.

[0008] The input end of the second polarization beam splitter is coupled with the second input waveguide, the first output end of the second polarization beam splitter is coupled with the second input end of the first phase mixer, and the second output end of the second polarization beam splitter is coupled with the second input end of the second phase mixer.

[0009] The materials of the waveguides in the first input waveguide, the second input waveguide, the first polarization beam splitter, the second polarization beam splitter, the first phase mixer and the second phase mixer are all silicon nitride.

[0010] The first input waveguide and the second input waveguide are both tapered waveguides.

[0011] The on-chip integrated coherent receiver uses a 90-degree phase mixing chip to integrate the input waveguide (i.e., the first input waveguide and the second input waveguide), the polarization beam splitter (i.e., the first polarization beam splitter and the second polarization beam splitter), and the phase mixer (i.e., the first phase mixer and the second phase mixer) on a single SiN (silicon nitride) chip, realizing monolithic integration, monolithic integration of multi-phase mixing function, supporting C+L band (1530nm~1625nm) operation, which is conducive to simplifying the coherent receiver architecture and reducing system cost; and using SiN as the waveguide core material, the wide bandgap characteristic supports ultra-low transmission loss (transmission loss less than 0.1dB / cm), and the input waveguide (including the first input waveguide and the second input waveguide) is a tapered waveguide, which has a mode field conversion function to support efficient matching (coupling loss less than 1dB) between the fiber mode field and the waveguide mode field, thereby realizing ultra-long distance transmission (transmission distance greater than 1000km).

[0012] In one of the embodiments, the tapered waveguide includes a first film layer, a second film layer, a third film layer, a fourth film layer, and a fifth film layer which are sequentially stacked on the substrate.

[0013] The lengths of the first film layer, the second film layer, the third film layer, the fourth film layer, and the fifth film layer are in a decreasing trend.

[0014] The widths of the first film layer, the second film layer, the third film layer, the fourth film layer, and the fifth film layer all start from the same maximum width size at the same end and gradually decrease to the first width size, the second width size, the third width size, the fourth width size, and the fifth width size at the other end, respectively.

[0015] In one of the embodiments, the second width size, the third width size, the fourth width size, and the fifth width size are the same, and the first width size is greater than the second width size.

[0016] In one of the embodiments, the second width size, the third width size, the fourth width size, and the fifth width size are all [0.701, 0.709]μm, and the first width size is [0.851, 0.859]μm.

[0017] The maximum width size is [12.501, 12.509]μm.

[0018] In one of the embodiments, the thicknesses of the first film layer, the second film layer, the third film layer, the fourth film layer, and the fifth film layer are in an increasing trend.

[0019] In one of the embodiments, thicknesses of the first film layer, the second film layer, the third film layer, the fourth film layer and the fifth film layer are [0.451, 0.459] μm, [0.501, 0.509] μm, [1.501, 1.509] μm, [3.001, 3.009] μm, [3.001, 3.009] μm, respectively.

[0020] In one of the embodiments, the refractive index of the waveguide formed by silicon nitride is [1.8, 2.2].

[0021] In one of the embodiments, the roughness of the surface of the waveguide formed by silicon nitride is [50, 100] nm.

[0022] In one of the embodiments, the first input waveguide, the second input waveguide, the first polarization beam splitter, the second polarization beam splitter, the first phase mixer and the second phase mixer are provided with a buffer layer between the substrate.

[0023] In one of the embodiments, the waveguides in the first polarization beam splitter, the second polarization beam splitter, the first phase mixer and the second phase mixer are all ridge waveguides.

[0024] The 90-degree phase mixing chip for the above-mentioned on-chip integrated coherent receiver integrates the input waveguide (i.e., the first input waveguide and the second input waveguide), the polarization beam splitter (i.e., the first polarization beam splitter and the second polarization beam splitter) and the phase mixer (i.e., the first phase mixer and the second phase mixer) on a single SiN (silicon nitride) chip, realizes monolithic integration, supports monolithic integration and multi-phase mixing functions, supports C+L waveband (1530 nm~1625 nm) operation, is conducive to simplifying the coherent receiver architecture and reducing system cost; and the use of SiN as the waveguide core material supports ultra-low transmission loss (transmission loss less than 0.1 dB / cm) due to the wide bandgap characteristics, the input waveguide (including the first input waveguide and the second input waveguide) is a tapered waveguide, the mode field conversion function supports efficient matching (coupling loss less than 1 dB) between the fiber mode field and the waveguide mode field, thereby realizing ultra-long distance transmission (transmission distance greater than 1000 km). BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1Structure diagram of a 90-degree phase mixing chip for an embodiment of an on-chip integrated coherent receiver;

[0027] Figure 2 Structure diagram of a tapered graded waveguide for an embodiment.

[0028] Figure 3 Refractive index curve of a SiN waveguide for an embodiment.

[0029] Label explanation: 11-first input waveguide, 12-second input waveguide, 21-first polarization beam splitter, 22-second polarization beam splitter, 31-first phase mixer, 32-second phase mixer, 41-first film layer, 42-second film layer, 43-third film layer, 44-fourth film layer, 45-fifth film layer. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the relevant drawings. The drawings show embodiments of the present application. However, the present application can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used herein in the specification merely describe specific embodiments of the present application for the purpose of describing the embodiments, and are not intended to limit the present application.

[0032] It can be understood that the terms "first", "second" and the like used in the present application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first resistor can be referred to as the second resistor, and similarly, the second resistor can be referred to as the first resistor. The first resistor and the second resistor are both resistors, but they are not the same resistor.

[0033] It can be understood that "connection" in the following embodiments, if the circuits, modules, units and the like connected to each other have the transmission of electrical signals or data, should be understood as "electrically connected", "communicatively connected" and the like.

[0034] It can be understood that "at least one" means one or more, and "multiple" means two or more. "At least part of the element" means part or all of the element.

[0035] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", or the like, when used in this specification, specify the presence of stated features, integers, steps, operations, components, parts, or the like, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or the like.

[0036] In one exemplary embodiment, referring to Figure 1 A 90-degree phase mixing chip for an on-chip integrated coherent receiver is provided, which can be applied to a coherent receiver, and includes a substrate and a first input waveguide 11, a second input waveguide 12, a first polarization beam splitter 21, a second polarization beam splitter 22, a first phase mixer 31, and a second phase mixer 32 disposed on the same side of the substrate.

[0037] The substrate (not shown in the figure) is, for example, a silicon substrate.

[0038] The first input waveguide 11 is configured to receive signal light, and the second input waveguide 12 is configured to receive eigen light. Exemplarily, the first input waveguide 11 can be coupled with an optical fiber outside the chip, or receive spatial light input.

[0039] The first input waveguide 11 and the second input waveguide 12 are both tapered waveguides, to produce a gradual change of the mode field, realize mode field tapering, i.e., mode field conversion, so as to realize efficient matching between the fiber mode (LP 01 ) and the waveguide mode (TE0), with a coupling loss less than 1 dB.

[0040] The first polarization beam splitter 21 and the second polarization beam splitter 22 are both polarization beam splitters (PBS).

[0041] The input end of the first polarization beam splitter 21 is coupled with the first input waveguide 11, the first output end of the first polarization beam splitter 21 is coupled with the first input end of the first phase mixer 31, and the second output end of the first polarization beam splitter 21 is coupled with the first input end of the second phase mixer 32. Exemplarily, the first polarization beam splitter 21 splits the signal light into two orthogonal polarized lights Sx and Sy, the first output end of the first polarization beam splitter 21 is configured to output the polarized light Sx, and the second output end of the first polarization beam splitter 21 is configured to output Sy.

[0042] The input end of the second polarization beam splitter 22 is coupled with the second input waveguide 12, the first output end of the second polarization beam splitter 22 is coupled with the second input end of the first phase mixer 31, and the second output end of the second polarization beam splitter 22 is coupled with the second input end of the second phase mixer 32. For example, the second polarization beam splitter 22 divides the eigen light into two orthogonal polarized lights Lx and Ly, the first output end of the second polarization beam splitter 22 is used to output the polarized light Lx, and the second output end of the second polarization beam splitter 22 is used to output the polarized light Ly.

[0043] The first phase mixer 31 and the second phase mixer 32 can be a multimode interference coupler (MMI coupler). The size of the MMI coupler can be 20x50μm². By precisely setting the waveguide length difference ΔL=λ / (4n_eff) (λ=1550nm, n_eff=1.8), the first phase mixer 31 and the second phase mixer 32 can realize 90-degree four-way phase difference optical signal output, i.e., 0-degree, 90-degree, 180-degree and 270-degree optical signal output.

[0044] The 90-degree optical mixer chip based on the multimode interference waveguide (MMI) structure has the advantages of compact structure and easy integration. Specifically, the MMI structure usually has a small size, can realize the mixing function on a small chip area, is convenient for integration with other optoelectronic devices on the same chip, is conducive to the manufacture of highly integrated optical communication modules, meets the miniaturization needs of communication systems, has a relatively not extremely harsh requirement on the precision of the manufacturing process, can still maintain good performance within a certain process error range, reduces the difficulty and cost of chip manufacturing, improves the production efficiency and yield, the input and output ports of the MMI type beam splitter are single-mode waveguides, the single-mode waveguide is connected with the multimode waveguide through a taper, which can reduce the loss caused by interface reflection, has a low insertion loss, can effectively reduce the energy loss of the optical signal in the transmission process, is not sensitive to the polarization state of the input light, does not need to accurately control the polarization mode of the input light, simplifies the optical path design and system debugging process, improves the applicability and stability of the device, based on the multimode interference principle, without external complex control circuit or element, can realize stable 90-degree phase difference, can provide a relatively stable basis for the in-phase component and quadrature component separation of the optical signal, and ensure the stability of the mixer performance.

[0045] The 90-degree phase mixing chip for on-chip integrated coherent receiver can further include output waveguides (not shown in the figure), such as a first output waveguide, a second output waveguide, a third output waveguide, and a fourth output waveguide. The first output end and the second output end of the first phase mixer 31 can be coupled to the first output waveguide and the second output waveguide, respectively, and the first output end and the second output end of the second phase mixer 32 can be coupled to the third output waveguide and the fourth output waveguide, respectively.

[0046] The materials of the waveguides in the first input waveguide 11, the second input waveguide 12, the first polarization beam splitter 21, the second polarization beam splitter 22, the first phase mixer 31, and the second phase mixer 32 are all silicon nitride (SiN). It should be understood that in the 90-degree phase mixing chip for on-chip integrated coherent receiver provided in the embodiments of the present application, the materials of all the waveguides are silicon nitride.

[0047] The 90-degree phase mixing chip for on-chip integrated coherent receiver described above integrates the input waveguide, the polarization beam splitter, the phase mixer, and the output waveguide in a single SiN chip with a size of <5*5 mm², realizes monolithic integration, supports C+L band (1530nm~1625nm) operation, and has a monolithic multi-phase mixing function, which is conducive to simplifying the architecture of the coherent receiver and reducing the system cost. In addition, the use of SiN as the core material of the waveguide supports ultra-low transmission loss (transmission loss less than 0.1dB / cm) due to its wide bandgap characteristics. The input waveguide (including the first input waveguide 11 and the second input waveguide 12) is a tapered waveguide, and its mode field conversion function supports efficient matching (coupling loss less than 1dB) between the fiber mode field and the waveguide mode field, thereby realizing ultra-long distance transmission (transmission distance greater than 1000km). In addition, the embodiments of the present application integrate symmetric y-branch waveguides to ensure uniformity of phase splitting. In the embodiments of the present application, the input signal light and the local oscillator light generated by the local oscillator are introduced into a specific waveguide structure, and the mode interference effect in the waveguide is used to generate precise phase differences at multiple output ends, thereby separating the in-phase component (I) and the quadrature component (Q) of the optical signal, so as to facilitate subsequent signal processing and recovery.

[0048] In an exemplary embodiment, with reference to Figure 2The tapering waveguide includes a first film layer 41, a second film layer 42, a third film layer 43, a fourth film layer 44, and a fifth film layer 45 which are sequentially stacked on the substrate. The lengths of the first film layer 41, the second film layer 42, the third film layer 43, the fourth film layer 44, and the fifth film layer 45 are in a decreasing trend. The widths of the first film layer 41, the second film layer 42, the third film layer 43, the fourth film layer 44, and the fifth film layer 45 all start from the same maximum width dimension M at the same end and gradually decrease to the first width dimension N1, the second width dimension N2, the third width dimension N3, the fourth width dimension N4, and the fifth width dimension N5 at the other end, respectively. The first width dimension N1, the second width dimension N2, the third width dimension N3, the fourth width dimension N4, and the fifth width dimension N5 are all smaller than the maximum width dimension M.

[0049] For example, the first end of the first film layer 41, the first end of the second film layer 42, the first end of the third film layer 43, the first end of the fourth film layer 44, and the first end of the fifth film layer 45 are all one end for coupling with a polarization beam splitter. The first end of the first film layer 41, the first end of the second film layer 42, the first end of the third film layer 43, the first end of the fourth film layer 44, and the first end of the fifth film layer 45 can be aligned or flush. The second end of the first film layer 41, the second end of the second film layer 42, the second end of the third film layer 43, the second end of the fourth film layer 44, and the second end of the fifth film layer 45 are all one end for coupling with an optical fiber or receiving spatial light input. The width of the first film layer 41 gradually decreases from the maximum width dimension M at the first end to the first width dimension N1 at the second end. The width of the second film layer 42 gradually decreases from the maximum width dimension M at the first end to the second width dimension N2 at the second end. The width of the third film layer 43 gradually decreases from the maximum width dimension M at the first end to the third width dimension N3 at the second end. The width of the fourth film layer 44 gradually decreases from the maximum width dimension M at the first end to the fourth width dimension N4 at the second end. The width of the fifth film layer 45 gradually decreases from the maximum width dimension M at the first end to the fifth width dimension N5 at the second end.

[0050] The embodiments of the present application are related to input waveguides (including the first input waveguide 11 and the second input waveguide 12) which realize mode field transformation through the tapering of the structure, for example, the tapering of the structure includes the tapering of the widths of the film layers to generate the tapering of the mode field, and realize the tapering of the mode field through the layering of the structure. That is, the multi-layer waveguide stack expands the mode field diameter (MFD) and reduces the transverse mode mismatch through the multi-layer cascaded SiN waveguide structure.

[0051] Optionally, the second width dimension N2, the third width dimension N3, the fourth width dimension N4 and the fifth width dimension N5 are the same, and the first width dimension N1 is greater than the second width dimension N2; in this way, the structure can also be gradually changed to produce the gradual change of the mode field, and the mode field is gradually changed through the structure layering, that is, the mode field conversion is realized.

[0052] Optionally, the second width dimension N2, the third width dimension N3, the fourth width dimension N4 and the fifth width dimension N5 are all [0.701, 0.709] μm, and the first width dimension N1 is [0.851, 0.859] μm; wherein, the maximum width dimension M is [12.501, 12.509] μm; in this way, the width of each film layer is controlled within an appropriate range, the structure is gradually changed to produce the gradual change of the mode field, and the mode field is gradually changed through the structure layering, that is, the mode field conversion is realized; that is, the multi-layer waveguide stack expands the mode field diameter (MFD) and reduces the transverse mode mismatch through the multi-layer cascaded SiN waveguide structure.

[0053] Optionally, the lengths of the first film layer 41, the second film layer 42, the third film layer 43, the fourth film layer 44 and the fifth film layer 45 in the z direction are 1200 μm, 1090 μm, 900 μm, 800 μm and 700 μm, respectively. In this embodiment, the structure of the input waveguide (including the first input waveguide 11 and the second input waveguide 12) can also include the gradual change of the length of each film layer to produce the gradual change of the mode field, and the mode field is gradually changed through the structure layering, that is, the mode field conversion is realized; that is, the multi-layer waveguide stack expands the mode field diameter (MFD) and reduces the transverse mode mismatch through the multi-layer cascaded SiN waveguide structure.

[0054] In one exemplary embodiment, the thicknesses of the first film layer 41, the second film layer 42, the third film layer 43, the fourth film layer 44 and the fifth film layer 45 show an increasing trend. In this embodiment, the structure of the input waveguide (including the first input waveguide 11 and the second input waveguide 12) can also include the gradual change of the thickness of each film layer to produce the gradual change of the mode field, and the mode field is gradually changed through the structure layering, that is, the mode field conversion is realized; that is, the multi-layer waveguide stack expands the mode field diameter (MFD) and reduces the transverse mode mismatch through the multi-layer cascaded SiN waveguide structure.

[0055] Optionally, the thicknesses of the first film layer 41, the second film layer 42, the third film layer 43, the fourth film layer 44 and the fifth film layer 45 are [0.451, 0.459] μm, [0.501, 0.509] μm, [1.501, 1.509] μm, [3.001, 3.009] μm, [3.001, 3.009] μm, respectively; in this way, the thicknesses of the film layers are controlled within appropriate ranges, the mode field is gradually changed through the gradual change of the structure, and the mode field is gradually changed through the structure layering, so as to realize the mode field conversion; that is, the multi-layer waveguide stack expands the mode field diameter (MFD) through the multi-layer cascaded SiN waveguide structure, and reduces the transverse mode mismatch.

[0056] In an exemplary embodiment, the waveguide formed of silicon nitride has a refractive index n of [1.8, 2.2], so as to further reduce the scattering loss and realize the ultra-long distance transmission. Figure 3

[0057] In an exemplary embodiment, the waveguide formed of silicon nitride has a surface roughness of [50, 100] nm, so as to further reduce the scattering loss and realize the ultra-long distance transmission.

[0058] The embodiments of the present application can control the refractive index and the surface roughness of the SiN thin film by optimizing the chemical vapor deposition (CVD) process parameters (such as temperature, gas ratio), further reduce the scattering loss, and realize the ultra-long distance transmission.

[0059] Optionally, the thickness of the waveguide formed of silicon nitride is 500 nm, so that the structure of the frequency mixing chip is simple, easy to realize, and has better performance.

[0060] In an exemplary embodiment, the first input waveguide 11, the second input waveguide 12, the first polarization beam splitter 21, the second polarization beam splitter 22, the first phase frequency mixer 31 and the second phase frequency mixer 32 are provided with a buffer layer between the waveguide and the substrate, so that the structure of the frequency mixing chip is more reliable, and the performance is more reliable.

[0061] Optionally, the thickness of the buffer layer is 2 μm, so that the structure of the buffer layer is simple and easy to manufacture.

[0062] Optionally, the material of the buffer layer is silicon dioxide (SiO2), so that the buffer layer has low cost and is easy to realize.

[0063] In an exemplary embodiment, the waveguides in the first polarization beam splitter 21, the second polarization beam splitter 22, the first phase frequency mixer 31 and the second phase frequency mixer 32 are all ridge waveguides, so that the structure of the frequency mixing chip is simple, easy to realize, and has better performance.

[0064] ​The 90-degree phase mixing chip provided by the embodiment of the application is integrated on a chip with a coherent receiver, combines the low-loss characteristics of SiN material and process optimization, realizes ultra-long distance (>1000 km) transmission, breaks through the traditional coupling limit of mode field conversion, significantly improves the compatibility of the chip and the optical fiber, integrates multiple phase mixing functions on a single chip, simplifies the architecture of the coherent receiver, and reduces the system cost. Through mode field conversion and process optimization, the 90-degree phase mixing chip realizes ultra-low transmission loss (<0.1 dB / cm), high coupling efficiency (loss <1 dB) and high-precision (phase error <±1°) multi-phase mixing functions, and meets the long-distance optical communication requirements.

[0065] The 90-degree phase mixing chip is further integrated with other optoelectronic devices such as lasers, detectors, modulators, etc. on the same chip to form a more complex and powerful optical transceiver module or photonic integrated system, which can reduce the connection loss and volume between devices, improve the reliability and stability of the system.

[0066] With the continuous development of communication technology, the requirement for data transmission rate is getting higher and higher. The 90-degree phase mixing chip needs to continuously improve its bandwidth and response speed to support higher-order modulation formats and faster signal processing, and meet the communication requirements of 100 Gbps or even higher rates.

[0067] In addition, the application fields of the 90-degree phase mixing chip also include data center optical interconnection: used to realize high-speed optical communication connection between servers, switches and other devices in the data center, support high-order modulation scheme and wavelength division multiplexing technology, improve spectrum utilization, reduce energy consumption, and improve data transmission efficiency; optical fiber communication system: in the metropolitan area network, backbone network and other optical fiber communication networks, it can be combined with new modulation technologies such as dual-polarity quadrature phase shift keying (DP-QPSK), etc. to reduce the channel rate, improve the dispersion tolerance, realize long-distance and high-speed optical signal transmission under the same communication rate; 5G and future communication: in the 5G network backhaul and future higher-speed communication systems, as a key optoelectronic device, it helps to realize efficient reception and processing of signals, supports higher frequency bands and data transmission rates.

[0068] In the description of the specification, the description with reference to the terms "some embodiments", "other embodiments" and the like is intended to indicate that the described implementation or example is included in at least one embodiment or example of the present application. Descriptive descriptions of the above terms in the specification do not necessarily refer to the same embodiment or example. Each technical feature of the above-described embodiments can be combined with any other technical feature, and in order to make the description simple, each technical feature of the above-described embodiments is not described in all possible combinations, but it should be considered that any combination of technical features is within the scope of the present application as long as the combination does not contradict. The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the present application. It should be noted that for those skilled in the art, some modifications and improvements can be made without departing from the concept of the present application, and these are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A 90-degree phase mixing chip for an on-chip integrated coherent receiver, characterized by include: A substrate and a first input waveguide, a second input waveguide, a first polarization beam splitter, a second polarization beam splitter, a first phase mixer, and a second phase mixer arranged on the same side of the substrate; The first input waveguide is used to receive signal light, and the second input waveguide is used to receive intrinsic light; The input end of the first polarization beam splitter is coupled to the first input waveguide, the first output end of the first polarization beam splitter is coupled to the first input end of the first phase mixer, and the second output end of the first polarization beam splitter is coupled to the first input end of the second phase mixer; An input end of the second polarization beam splitter is coupled to the second input waveguide, a first output end of the second polarization beam splitter is coupled to the second input end of the first phase mixer, and a second output end of the second polarization beam splitter is coupled to the second input end of the second phase mixer; The waveguides in the first input waveguide, the second input waveguide, the first polarization beam splitter, the second polarization beam splitter, the first phase mixer, and the second phase mixer are all made of silicon nitride; The first input waveguide and the second input waveguide are both tapered waveguides.

2. The chip according to claim 1, characterized in that, The tapered waveguide comprises a first film layer, a second film layer, a third film layer, a fourth film layer, and a fifth film layer stacked in sequence on the substrate; The lengths of the first film layer, the second film layer, the third film layer, the fourth film layer, and the fifth film layer are in a decreasing trend; The widths of the first film layer, the second film layer, the third film layer, the fourth film layer and the fifth film layer all start from the same maximum width dimension at the same end and gradually decrease to the first width dimension, the second width dimension, the third width dimension, the fourth width dimension and the fifth width dimension at the other end, respectively.

3. The chip of claim 2, wherein The second width dimension, the third width dimension, the fourth width dimension, and the fifth width dimension are the same, and the first width dimension is greater than the second width dimension.

4. The chip of claim 2, wherein The second width dimension, the third width dimension, the fourth width dimension, and the fifth width dimension are all in a range of [0.701, 0.709] μm, and the first width dimension is in a range of [0.851, 0.859] μm; The maximum width dimension has a size range of [12.501, 12.509] μm.

5. The chip of claim 2, wherein The thicknesses of the first film layer, the second film layer, the third film layer, the fourth film layer and the fifth film layer tend to increase.

6. The chip of claim 2, wherein The thickness ranges of the first film layer, the second film layer, the third film layer, the fourth film layer and the fifth film layer are [0.451, 0.459] μm, [0.501, 0.509] μm, [1.501, 1.509] μm, [3.001, 3.009] μm, and [3.001, 3.009] μm, respectively.

7. The chip of claim 1, wherein The refractive index of the waveguide formed of silicon nitride is in the range of [1.8, 2.2].

8. The chip according to any one of claims 1 to 7, characterized in that The surface roughness of the waveguide formed of silicon nitride is in the range of [50, 100] nm.

9. The chip of claim 1, wherein, The first input waveguide, the second input waveguide, the first polarization beam splitter, the second polarization beam splitter, the first phase modulator and the second phase modulator are provided with a buffer layer between the substrate.

10. The chip of claim 1, wherein, The waveguides in the first polarization beam splitter, the second polarization beam splitter, the first phase modulator and the second phase modulator are all ridge waveguides.

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