On-chip integrated wavelength division demultiplexing structure and photonic integrated chip
By employing a combined structure of a slice demultiplexer and an optical multiplexer in a photonic integrated chip, the problems of high design difficulty and high optical loss of wave demultiplexing devices are solved, achieving wave demultiplexing with flat-top bandwidth and low loss, which is suitable for photonic integrated chips in optical communication.
Patent Information
- Application Number
- CN202411091797.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-09
- Publication Date
- 2026-02-10
AI Technical Summary
Existing wave demultiplexing devices are difficult to design, costly, and have high optical loss. In particular, the coupling efficiency between silicon nitride and silicon waveguides is low, making it difficult to achieve wave demultiplexing with flat-top bandwidth and low loss.
A combined structure of a slice demultiplexer and an optical multiplexer is adopted. The slice demultiplexer subdivides the optical signal into multiple narrow linewidth subwavelength division signals, and the optical multiplexer synthesizes the optical signal with a flat-top bandwidth. Combined with the stacked arrangement of single-mode and multi-mode waveguides, the design difficulty is reduced and the coupling efficiency is improved.
It enables easier implementation of wave demultiplexing with flat-top bandwidth and low loss, reduces design complexity and improves optical coupling efficiency, and is suitable for wave demultiplexing in photonic integrated chips.
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Figure CN121500481A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical communication technology, specifically to an on-chip integrated wave demultiplexing structure and a photonic integrated chip. Background Technology
[0002] Wavelength division multiplexing (WDM) carries multiple signals at different wavelengths and transmits and exchanges them in a single optical fiber / waveguide. It is a key technology for expanding the information capacity of optical communication. The devices used to implement WDM and demultiplexing are called WDM multiplexing devices (MUX) and WDM demultiplexing devices (DEMUX), and they are the core devices of WDM systems.
[0003] Currently, commercially available waveguide-type wave demultiplexing devices (DEMUX) generally employ an arrayed waveguide grating (AWG) structure. For example... Figure 1 As shown, the arrayed waveguide grating structure mainly comprises five parts: an input waveguide, an input planar waveguide region, an arrayed waveguide region, an output planar waveguide region, and an output waveguide. To reduce the requirement for stability of the system's light source center wavelength, the waveguide demultiplexing device also needs to meet broadband flat-top characteristics. The most common method is to use a multimode output waveguide for output to achieve a filtered spectrum with broadband flat-top characteristics. However, achieving broadband flat-top characteristics in this structure requires high precision and design of all device parameters, resulting in significant design difficulty and high manufacturing costs.
[0004] Furthermore, due to the excellent transmission characteristics of silicon nitride, passive optical devices in photonic integrated circuit chips, such as wavelength division multiplexers, are usually made of silicon nitride. However, integrated high-speed photodetectors use silicon waveguide transmission. When light couples from the multimode silicon nitride waveguide of the wavelength division multiplexer to the silicon waveguide, there is a large optical loss, which is not conducive to integration with waveguide-type photodetectors. Summary of the Invention
[0005] The purpose of this application is to provide an on-chip integrated wavelength division multiplexing structure and a photonic integrated chip to achieve wavelength division multiplexing with flat-top bandwidth, while reducing the design difficulty and requirements of wavelength division multiplexing devices.
[0006] According to one aspect of this application, an on-chip integrated wavelength division multiplexing (WDM) structure is provided, including a slice demultiplexer and M optical multiplexers; the slice demultiplexer has a first input waveguide and M groups of first output waveguides, each group of first output waveguides including at least two first output waveguides, the M optical multiplexers respectively corresponding to the M groups of first output waveguides, and each optical multiplexer being optically connected to a corresponding group of first output waveguides; the slice demultiplexer is used to demultiplex an optically multiplexed signal containing multiple optical channels received by the first input waveguide, and to subdivide the optical signal of each optical channel into N sub-channels of wavelength division multiplexing (WDM) signals, each group of first output waveguides corresponding to one optical channel, and each first output waveguide corresponding to one sub-channel to output one of the corresponding WDM signals of the optical channel.
[0007] Each of the optical multiplexers is used to receive the sub-wavelength division signals output from each of the first output waveguides of the corresponding group, and to combine the multiple sub-wavelength division signals received from the same optical channel into a single optical signal with a flat-top bandwidth for output; wherein, M≥2, N≥2, and M and N are both positive integers.
[0008] Furthermore, the first output waveguide is a single-mode waveguide; each of the optical multiplexers has a second output waveguide, which is a multimode waveguide.
[0009] In some embodiments, the slice demultiplexer is located in a first waveguide layer, the optical multiplexer is located in a second waveguide layer, the first waveguide layer and the second waveguide layer are stacked, and the first waveguide layer and the second waveguide layer are made of different materials;
[0010] Each of the optical multiplexers has multiple second input waveguides and one second output waveguide;
[0011] The plurality of second input waveguides of each optical multiplexer are respectively coupled to the plurality of first output waveguides of the corresponding group to receive the optical signal output by the first output waveguide; the second output waveguide of each optical multiplexer is used to output one optical signal after multiplexing.
[0012] In some embodiments, the first waveguide layer is any one of a silicon nitride layer, a silicon oxynitride layer, and a lithium niobate layer, and the second waveguide layer is a silicon layer.
[0013] In some implementations, the first output waveguide is a single-mode waveguide made of a corresponding material.
[0014] The second input waveguide is a single-mode Si waveguide, and the second output waveguide is a multimode Si waveguide.
[0015] In some implementations, the ends of the plurality of second input waveguides overlap one-to-one with the projections of the ends of the plurality of first output waveguides in the corresponding group on the first waveguide layer, so as to optically couple by means of thermal coupling.
[0016] In some implementations, the optical multiplexer is a mode multiplexer.
[0017] In some embodiments, the slice demultiplexer is composed of any of the following structures: an arrayed waveguide grating structure, an etched diffraction grating structure, or multiple cascaded Mach-Zehnder interferometer structures.
[0018] In some embodiments, the slice demultiplexer includes an arrayed waveguide grating structure, which includes an input planar waveguide, an output planar waveguide, and a plurality of arrayed waveguides connected between the input planar waveguide and the output planar waveguide, with a constant length difference between adjacent arrayed waveguides; the first input waveguide is connected to the input planar waveguide, and each of the first output waveguides is connected to the output planar waveguide for outputting a narrow-linewidth subwavelength division multiplexing (WDM) signal.
[0019] In some embodiments, the slice demultiplexer includes an arrayed waveguide grating structure or an etched diffraction grating, with n sub-channels between two adjacent sets of first output waveguides configured to omit the first output waveguide, where N > n ≥ 1, and n is a positive integer.
[0020] In some embodiments, the slice demultiplexer includes multiple cascaded Mach-Zehnder interferometer structures, each of which includes an input port and two output ports, for demultiplexing one optical signal received at one input port into two optical signals, and outputting the two optical signals from the two output ports respectively;
[0021] Each output port of each Mach-Zehnder interferometer structure in the final stage outputs a narrow-linewidth subwavelength division signal.
[0022] In some embodiments, the Mach-Zehnder interferometer structure includes a microring-assisted Mach-Zehnder interferometer structure.
[0023] In some implementations, the slice demultiplexer further includes multiple crosstalk filters, each of which is connected in series in a first output waveguide.
[0024] According to another aspect of this application, a photonic integrated chip is provided, the photonic integrated chip including any of the aforementioned on-chip integrated wave demultiplexing structure.
[0025] In some embodiments, the photonic integrated chip further includes multiple on-chip integrated photodetectors, each photodetector being used to receive an optical signal output from one of the optical multiplexers and convert it into an electrical signal output.
[0026] In the on-chip integrated wavelength demultiplexing structure and photonic integrated chip provided in this application embodiment, the wavelength demultiplexing structure includes a slice demultiplexer and M optical multiplexers. First, the slice demultiplexer demultiplexes the optical signals of each optical channel and subdivides the signal of each optical channel into multiple narrow-linewidth sub-wavelength division signals. Then, the multiple sub-wavelength division signals corresponding to the same channel are multiplexed into one optical signal with a flat-top bandwidth by the optical multiplexer. Compared with the prior art of directly designing a wavelength demultiplexer with a flat-top bandwidth, the slice demultiplexer and optical multiplexer have lower optical loss, reducing the design difficulty and requirements of wavelength demultiplexing devices, and thus making it easier to achieve wavelength demultiplexing with flat-top bandwidth and low loss. Attached Figure Description
[0027] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.
[0028] Figure 1 This is a schematic diagram of the structure of an on-chip integrated wavelength division multiplexer in the prior art.
[0029] Figure 2 This is a partial functional block diagram of an on-chip integrated wave decomposition and multiplexing structure provided in an embodiment of this application;
[0030] Figure 3 A functional block diagram of a wave decomposition and multiplexing structure based on an arrayed waveguide grating provided in an embodiment of this application;
[0031] Figure 4 for Figure 3 The complete spectrum of all sub-wavelength division signals corresponding to each optical channel is shown at the output of the slice demultiplexer based on arrayed waveguide gratings;
[0032] Figure 5 for Figure 3 The spectrum of the residual wavelength division multiplexed signal for each corresponding optical channel is shown before the input optical multiplexer;
[0033] Figure 6 for Figure 3 The diagram shows the spectrum after combining the signals through the various optical multiplexers.
[0034] Figure 7 A functional block diagram of an optical multiplexer provided in an embodiment of this application;
[0035] Figure 8 Functional block diagram of an on-chip integrated wave decomposition and multiplexing structure provided in another embodiment of this application;
[0036] Figure 9 This is a functional block diagram of a photonic integrated chip provided in an embodiment of this application;
[0037] Figure 10 This is a cross-sectional schematic diagram of a photonic integrated chip structure provided in an embodiment of this application;
[0038] Figure 11 A functional block diagram of an on-chip integrated wave decomposition and multiplexing structure provided in another embodiment of this application.
[0039] Key reference numerals:
[0040] 110, Slice demultiplexer; 210, Optical multiplexer; 100, First waveguide layer; 200, Second waveguide layer; 300, Germanium layer; 710, Photodetector; 104, Crosstalk filter; 111, First input waveguide; 112, First output waveguide; 211, Second input waveguide; 212, Second output waveguide;
[0041] 400, Mode Multiplexing Unit; 500, Bus Waveguide; 600, Cross Waveguide;
[0042] 601, Substrate layer; 603, Waveguide layer. Detailed Implementation
[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0044] The terms "first" and "second" used herein are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0045] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0046] The following disclosure provides many different implementations or examples for carrying out different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or reference letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.
[0047] As optical transmission rates continue to increase, the single-channel rate in wavelength division multiplexing (WDM) is also getting higher and higher, requiring WDM demultiplexers to have better flat-top characteristics and lower optical loss. These requirements increase the design difficulty of WDM demultiplexers.
[0048] One embodiment of this application provides an on-chip integrated wavelength division multiplexing (WDM) structure, including a slice demultiplexer and M optical multiplexers. The slice demultiplexer has a first input waveguide and M groups of first output waveguides, each group of first output waveguides including at least two first output waveguides. The M optical multiplexers correspond to the M groups of first output waveguides respectively, and each optical multiplexer is optically connected to its corresponding group of first output waveguides. The slice demultiplexer is used to demultiplex the optically multiplexed signal containing multiple optical channels received by the first input waveguide, and subdivide the optical signal of each optical channel into N sub-channel wavelength division multiplexing (WDM) signals. Each group of first output waveguides corresponds to one optical channel, and each first output waveguide corresponds to one sub-channel to output one sub-WDM signal of the corresponding optical channel. Each optical multiplexer is used to receive the sub-WDM signals output by each first output waveguide of the corresponding group, and combine the multiple sub-WDM signals of the same optical channel received into one optical signal with a flat-top bandwidth for output. Wherein, M≥2, N≥2, and M and N are both positive integers.
[0049] It should be noted that, in the embodiments of this application, subdivision is the process of dividing a single channel of light into multiple finer wavelength bands.
[0050] In the on-chip integrated wavelength demultiplexing structure provided in this application embodiment, the wavelength demultiplexing structure includes a slice demultiplexer and M optical multiplexers. First, the slice demultiplexer demultiplexes the optical signals of each optical channel and subdivides the signal of each optical channel into multiple narrow-linewidth sub-wavelength division signals. Then, the multiple sub-wavelength division signals corresponding to the same channel are multiplexed into one optical signal with a flat-top bandwidth by the optical multiplexer. Compared with the prior art of directly designing a wavelength demultiplexer with a flat-top bandwidth, the slice demultiplexer and optical multiplexer have lower optical loss, reducing the design difficulty and requirements of wavelength demultiplexing devices, and thus making it easier to achieve wavelength demultiplexing with flat-top bandwidth and low loss.
[0051] Figure 2 This is a partial functional block diagram of an on-chip integrated wave decomposition and multiplexing structure provided in an embodiment of this application.
[0052] The following will combine Figure 2 The structure and working mechanism of the on-chip integrated wave decomposition and multiplexing structure are described in further detail.
[0053] See Figure 2 As shown, exemplarily, in this embodiment, a 1x4 wave demultiplexing device (DEMUX) is used as an example, unlike conventional designs (e.g. Figure 1 The wavelength division multiplexing (WDM) structure of this embodiment includes a slice demultiplexer 110 and four optical multiplexers 210. During operation, the optically multiplexed signal containing four optical channels enters the WDM structure and is first divided by the slice demultiplexer 110 into 4xN (N≥2, N is a positive integer) sub-channel wavelength division multiplexing signals, for example, CH1-N, CH2-N, CH3-N, and CH4-N sub-channels, respectively. Each optical channel is divided into N sub-channels. Then, the four optical multiplexers 210 multiplex the wavelength division multiplexing signals of the corresponding four optical channels (e.g., CH1, CH2, CH3, CH4) into four optical signals with flat-top bandwidth, ultimately achieving the purpose of decomposing one optically multiplexed signal into four optical signals with flat-top bandwidth. Each sub-channel's wavelength division multiplexing signal includes one narrow-linewidth optical signal.
[0054] In some embodiments, the slice demultiplexer 110 may be constructed from any of the following structures: an arrayed waveguide grating structure, an etched diffraction grating structure, or multiple cascaded Mach-Zehnder interference structures.
[0055] Figure 3 A functional block diagram of a wave decomposition and multiplexing structure based on an arrayed waveguide grating provided in an embodiment of this application; Figure 4 for Figure 3The complete spectrum of all sub-wavelength division signals corresponding to each optical channel is shown at the output of the slice demultiplexer based on arrayed waveguide gratings; Figure 5 for Figure 3 The spectrum of the residual wavelength division multiplexed signal for each corresponding optical channel is shown before the input optical multiplexer; Figure 6 for Figure 3 The diagram shows the spectrum after combining the signals through the various optical multiplexers.
[0056] like Figure 3 As shown, in this embodiment, the slice demultiplexer 110 employs an arrayed waveguide grating structure. This arrayed waveguide grating structure includes an input planar waveguide, an output planar waveguide, and multiple arrayed waveguides connecting the input and output planar waveguides. Each arrayed waveguide includes a tapered waveguide, a straight waveguide, and a curved waveguide. Adjacent arrayed waveguides have a constant length difference to demultiplex multi-channel optical signals, subdividing the optical signal of each optical channel into N sub-channel wavelength division multiplexing (WDM) signals. Each WDM signal includes a narrow-linewidth fine-WDM signal. A first input waveguide 111 connects to the input planar waveguide, and each first output waveguide 112 connects to the output planar waveguide for outputting a narrow-linewidth WDM signal. Each optical multiplexer 210 is optically connected to a set of first output waveguides. Each set of first output waveguides corresponds to one optical channel, and each set of first output waveguides includes at least two first output waveguides 112, for example, two, three, four, or more. After the multi-channel optical multiplexed signal is demultiplexed into multiple sets of sub-wavelength division signals by the arrayed waveguide grating structure, each set of sub-wavelength division signals is transmitted to the corresponding optical multiplexer 210 through multiple first output waveguides 112 of the corresponding set. Each optical multiplexer 210 multiplexes the received set of sub-wavelength division signals into one optical signal with a flat top bandwidth for output.
[0057] It should be noted that if a conventional design is used to directly split a single optical multiplexed signal into four optical signals, the existing arrayed waveguide grating structure will find it difficult to achieve a flat-top bandwidth, and there will also be some additional loss problems, making it difficult to reduce optical loss.
[0058] In this embodiment, the optical signals of four optical channels are first demultiplexed using an arrayed waveguide grating structure, and the signal of each optical channel is further subdivided into multiple narrow-linewidth sub-wavelength division signals. Then, the multiple sub-wavelength division signals corresponding to the same channel are multiplexed into a single optical signal with a flat-top bandwidth via an optical multiplexer and output. Compared with the prior art, it is not only easier to achieve wavelength demultiplexing with a flat-top bandwidth, but also reduces the design difficulty and requirements of wavelength demultiplexing devices.
[0059] like Figure 3As shown, to reduce crosstalk between adjacent channels, the wavelet demultiplexing structure of this embodiment selectively removes n (where n≥1, n is a positive integer, and n=2 in this example) first output waveguides 112 between two adjacent groups of first output waveguides 112. That is, n first output waveguides 112 between two adjacent groups of first output waveguides 112 are configured to be missing, and then each group of first output waveguides 112 has Nn first output waveguides 112 remaining. The remaining Nn first output waveguides 112 are then multiplexed into a second output waveguide 212 through an optical multiplexer 210 with a corresponding optical connection for output.
[0060] For example, to achieve 1x4 wavelength division multiplexing, the arrayed waveguide grating structure needs to complete 1x4xN demultiplexing. That is, the arrayed waveguide grating structure demultiplexes the optical multiplexed signal containing 4 channels and subdivides the optical signal of each optical channel into N sub-channel wavelength division signals. Among them, the outermost first output waveguide 112 of each optical channel adjacent to the adjacent optical channel is configured to be missing, that is, the two edge first output waveguides 112 of each optical channel are not configured. The remaining N-2 sub-channels are respectively connected to N-2 first output waveguides 112. Then, the wavelength division signal of each optical channel is transmitted to the corresponding optical multiplexer 210 through the corresponding first output waveguide 112. After multiplexing and combining by the optical multiplexer 210, a single optical signal with a flat-top bandwidth is output. The two outermost sub-channels corresponding to each optical channel are not configured with the first output waveguide 112. Only the sub-wavelength division signals of the middle N-2 sub-channels can be transmitted to the optical multiplexer 210 of the corresponding channel through the N-2 first output waveguides 112 for multiplexing. This isolates the crosstalk between the two outermost sub-channels and the adjacent channels before the optical multiplexer 210, reducing the crosstalk between adjacent channels.
[0061] It should be understood that the slice demultiplexer in this embodiment takes an arrayed waveguide grating structure as an example. In some embodiments, the slice demultiplexer can also adopt an etched diffraction grating. Similarly, the n first output waveguides 112 between two adjacent optical channels can be configured to be missing, thereby reducing crosstalk between adjacent channels.
[0062] For details, please refer to Figures 4 to 6 , Figures 4 to 6 The complete spectrum of the output of the arrayed waveguide grating structure, the spectrum before entering the mode multiplexing device, and the spectrum after being combined by the optical multiplexer are shown respectively.
[0063] For example, such as Figure 4As shown, a 4-channel optical multiplexed signal is subdivided into multiple sub-channel wavelength division multiplexing (WDM) signals via an arrayed waveguide grating structure. In the illustration, the two middle optical channels are each divided into 7 sub-channels, and the two outer optical channels are each divided into 6 sub-channels. Crosstalk can easily occur between adjacent sub-channels of two adjacent optical channels. In this embodiment, the two adjacent first output waveguides 112 are configured to be missing to prevent the WDM signals of these two crosstalking sub-channels from entering the optical multiplexer 210. This isolates the WDM signals of the two crosstalking sub-channels before the optical multiplexer 210, increasing the spacing between adjacent first output waveguides 112, resulting in the following... Figure 5 The spectrum shown corresponds to the residual wavelength division multiplexing (WDM) signal for each optical channel. Finally, the spectrum is... Figure 5 The remaining sub-wavelength division signals corresponding to each optical channel are transmitted to the corresponding optical multiplexer 210 via the first output waveguide 112 of each group for multiplexing and beam combining, to obtain... Figure 6 The diagram shows the optical signals with flat-top bandwidth corresponding to each optical channel. It should be understood that in this embodiment, the number n of sub-channels without a first output waveguide 112 in each optical channel is 2 or 1; that is, n is 2 for the middle optical channel and 1 for the two outer optical channels. In other embodiments, n can be determined according to actual needs, or according to the bandwidth of the optical signal after multiplexing for each group of first output waveguides 112, or according to crosstalk between adjacent optical channels, for example, n is 4 or 3, etc.
[0064] In one embodiment of this application, the first output waveguide 112 is a single-mode waveguide. That is, before the light is input into the M optical multiplexers 210, the multiple narrow-linewidth sub-wavelength division signals are all single-mode optical signals and are transmitted in the corresponding single-mode waveguides. After being multiplexed and combined by the optical multiplexers 210, the synthesized optical signal is a multimode optical signal and is output through a second output waveguide 212 of the optical multiplexers 210, wherein the second output waveguide 212 is a multimode waveguide.
[0065] Figure 7 This is a functional block diagram of an optical multiplexer structure provided in an embodiment of this application.
[0066] In some implementations, optical multiplexer 210 is a mode multiplexer. For example... Figure 7As shown, the mode multiplexer includes a bus waveguide 500 and multiple cross waveguides 600 coupled to the bus waveguide 500. The bus waveguide 500 and each cross waveguide 600 are connected to a second input waveguide 211, and output the combined optical signal from the second output waveguide 212 of the optical multiplexer. When the number of first output waveguides 112 in each optical channel is greater than 2, the mode multiplexer can be constructed by cascading multiple mode multiplexing units 400. Each mode multiplexing unit 400 is used to mode multiplex two received sub-wavelength division multiplexing signals and output a multimode optical signal to the next level mode multiplexing unit 400. The next level mode multiplexing unit 400 then mode multiplexes the multimode optical signal with another sub-wavelength division multiplexing signal again, and so on, until the sub-wavelength division multiplexing signals of multiple sub-channels of the same optical channel are mode multiplexed into a single multimode optical signal, which is then output through the second output waveguide 212 of the optical multiplexer 210.
[0067] Specifically, taking an example where each group of first output waveguides 112 has four members, the same group of first output waveguides 112 are connected to the corresponding sub-channels of the same optical channel. When the subdivided narrow-linewidth sub-wavelength division signals λ11(TE0), λ12(TE0), λ13(TE0), and λ14(TE0) are transmitted to the second input waveguide 211 of the optical multiplexer 210, two of the optical signals λ11(TE0) and λ12(TE0) are input to the first-stage mode multiplexing unit for mode multiplexing, and a combined optical signal of λ11(TE0) and λ12(TE1) is output. Subsequently, the combined optical signal of λ11(TE0) and λ12(TE1) is combined with another sub-wavelength division signal λ13(TE0) and λ14(TE0). 0) The signals are then input into the second-level mode multiplexing unit. After mode multiplexing by the second-level mode multiplexing unit, a combined optical signal of λ11(TE0), λ12(TE1), and λ13(TE2) is output. Finally, the combined optical signal of λ11(TE0), λ12(TE1), and λ13(TE2) and another sub-wavelength division signal λ14(TE0) are input into the third-level mode multiplexing unit. After mode multiplexing, a combined optical signal of λ11(TE0), λ12(TE1), λ13(TE2), and λ14(TE3) is output.
[0068] Figure 8 This is a functional block diagram of an on-chip integrated wave decomposition and multiplexing structure provided in another embodiment of this application. Figure 9 This is a functional block diagram of a photonic integrated chip provided in one embodiment of this application. Figure 10 This is a cross-sectional schematic diagram of a photonic integrated chip structure provided in an embodiment of this application.
[0069] like Figure 8 , Figure 9As shown, in this embodiment, the on-chip integrated wavelet demultiplexing structure includes a slice demultiplexer 110 and four optical multiplexers 210. The slice demultiplexer 110 adopts an arrayed waveguide grating structure. The arrayed waveguide grating structure has a first input waveguide 111 and four sets of first output waveguides 112. Each set of first output waveguides includes at least two first output waveguides. The four optical multiplexers 210 correspond to the four sets of first output waveguides 112 respectively, and each optical multiplexer 210 is optically connected to its corresponding set of first output waveguides 112.
[0070] Unlike the previous embodiments, in this embodiment, the slice demultiplexer 110 and the optical multiplexer 210 employ waveguides made of different materials, such as... Figure 10 As shown, the slice demultiplexer 110 is located on a first waveguide layer 100, and the optical multiplexer 210 is located on a second waveguide layer 200. The first waveguide layer 100 and the second waveguide layer 200 are stacked, and the first waveguide layer 100 and the second waveguide layer 200 are made of different materials. Since the slice demultiplexer 110 and the optical multiplexer 210 use waveguides of different materials, the multiple second input waveguides 211 of each optical multiplexer 210 are coupled to a corresponding set of first output waveguides 112 to receive the optical signals output by the first output waveguides 112; the second output waveguides 212 of each optical multiplexer 210 are used to output one optical signal after multiplexing. In some embodiments, the first waveguide layer 100 is any one of a silicon nitride layer, a silicon oxynitride layer, and a lithium niobate layer, and the second waveguide layer 200 is a silicon layer.
[0071] For example, in this embodiment, the first waveguide layer 100 is a silicon nitride layer, that is, the slice demultiplexer 110 is made of silicon nitride, and its first output waveguides 112 are all single-mode silicon nitride waveguides. Therefore, when the slice demultiplexer 110 adopts a wavelet demultiplexing structure such as an arrayed waveguide grating structure, it is temperature insensitive, thereby avoiding the optical wavelength from deviating from the required wavelength range. The second waveguide layer 200 is a silicon layer, that is, the optical multiplexer 210 is made of silicon, and its multiple second input waveguides 211 are configured as single-mode silicon waveguides for coupling with the single-mode silicon nitride waveguides of the slice demultiplexer 110, which facilitates thermal coupling between the two, thereby reducing optical loss. Specifically, the ends of the multiple second input waveguides 211 respectively overlap with the ends of the multiple first output waveguides 112 of the corresponding group in a one-to-one correspondence on the projection of the first waveguide layer 100, so as to achieve optical coupling through thermal coupling. The second output waveguide 212 of the optical multiplexer 210 is configured as a multimode silicon waveguide for outputting the multimode optical signal after mode multiplexing, and facilitates direct optical coupling with the high-speed germanium silicon photodetector 710 based on the silicon waveguide, thereby improving the efficiency of optical coupling with the photodetector 710 and thus improving the responsivity of the photodetector 710.
[0072] In this embodiment, since the slice demultiplexer and the optical multiplexer are transitionally coupled using a single-mode silicon nitride waveguide and a single-mode silicon waveguide, and the multimode silicon waveguide of the optical multiplexer can be directly coupled to the silicon waveguide of the integrated photodetector, it has high coupling efficiency. This avoids the problem of low coupling efficiency when the multimode silicon nitride waveguide is directly coupled to the silicon waveguide in the prior art. Therefore, it can greatly reduce the loss of optical coupling into the photodetector and improve the detection accuracy of the photodetector.
[0073] Figure 11 This is a functional block diagram of an on-chip integrated wavelength division multiplexing (WDM) structure provided in another embodiment of this application. In this embodiment, the slice demultiplexer 110 includes multiple cascaded Mach-Zehnder interferometer structures. Each Mach-Zehnder interferometer structure includes one input port and two output ports, which are used to demultiplex a single optical signal received at one input port into two optical signals, and output the two optical signals from the two output ports respectively. Ultimately, each output port of each Mach-Zehnder interferometer structure in the last stage outputs a narrow-linewidth sub-wavelength division signal. The sub-wavelength division signals corresponding to the same optical channel are then transmitted to the same optical multiplexer, which multiplexes them into a single optical signal with a flat-top bandwidth.
[0074] Specifically, such as Figure 11 As shown, taking a three-stage cascaded MZ structure as an example, the above-mentioned cascaded MZ structure includes a first-stage cascaded MZ demux1, a second-stage cascaded MZ demux2 and cascaded MZ demux3, and a third-stage MZ demux4 to MZ demux7. When it is necessary to demultiplex a 4-channel optical multiplexed signal into 4 optical signals (with flat-top bandwidth), the wavelength division multiplexing structure includes a slice demultiplexer 110 and 4 optical multiplexers 210. In this embodiment, the slice demultiplexer 110 adopts the above-mentioned cascaded MZ structure of 7 MZ demux7 cascaded. The input optical multiplexed signal containing 4 optical channels is first divided into 4*2 sub-channels by multiple cascaded MZ demuxes within the dashed box. The optical signal of each sub-channel includes a narrow-linewidth sub-wavelength division signal, that is, each optical channel is divided into two sub-channels. Then, the two narrow-linewidth sub-wavelength division signals in the sub-channel group corresponding to the same optical channel are combined into one optical signal with flat-top bandwidth via the optical multiplexer 210 with corresponding optical connection, and finally the purpose of decomposing one optical multiplexed signal into four optical signals with flat-top bandwidth is achieved.
[0075] For example, when a single optical multiplexed signal is decomposed into four optical signals (with flat-top bandwidth), for instance, one four-channel optical multiplexed signal containing λ1, λ2, λ3, and λ4 is passed through a first-stage cascaded MZ demux1. Each channel of light is subdivided into two, outputting two optical multiplexed signals each containing four sub-wavelength division signals: one containing λ11, λ21, λ31, and λ41, and the other containing λ12, λ22, λ32, and λ42, all of which are optical signals with completely different wavelengths. λ11 and λ12 are two subdivided sub-wavelength division signals belonging to the same optical channel. Finally, λ11 and λ12 need to be multiplexed again to synthesize the optical channel signal corresponding to λ1. Similarly, λ21 and λ22 are two subdivided wavelength division multiplexing signals belonging to the same optical channel, λ31 and λ32 are two subdivided wavelength division multiplexing signals belonging to the same optical channel, and λ41 and λ42 are two subdivided wavelength division multiplexing signals belonging to the same optical channel. Finally, λ21 and λ22, λ31 and λ32, and λ41 and λ42 need to be multiplexed into three optical channel signals corresponding to λ2, λ3, and λ4, respectively.
[0076] Next, one optically multiplexed signal containing λ11, λ21, λ31, and λ41 is decomposed into two optically multiplexed signals by a second-stage cascaded MZ demux2: one containing λ11 and λ31, and the other containing λ21 and λ41. Similarly, one optically multiplexed signal containing λ12, λ22, λ32, and λ42 is decomposed into two optically multiplexed signals by a second-stage cascaded MZ demux3: one containing λ12 and λ32, and the other containing λ22 and λ42.
[0077] Subsequently, one optical signal containing λ11 and λ31 is decomposed into two wavelength division multiplexed signals via a third-stage cascaded MZ demux4: one wavelength division multiplexed signal of λ11 and the other wavelength division multiplexed signal of λ31. Another optical signal containing λ21 and λ41 is decomposed into two wavelength division multiplexed signals via a third-stage cascaded MZ demux3: one wavelength division multiplexed signal of λ21 and the other wavelength division multiplexed signal of λ41. Similarly, one optical signal containing λ12 and λ32 is decomposed into two optical multiplexed signals via a cascaded MZ demux3: one wavelength division multiplexed signal of λ12 and the other wavelength division multiplexed signal of λ32. Another optical signal containing λ22 and λ42 is decomposed into two optical multiplexed signals via a cascaded MZ demux3: one wavelength division multiplexed signal of λ22 and the other wavelength division multiplexed signal of λ42.
[0078] Finally, one wavelength division multiplexing (WDM) signal of λ11 and one wavelength division multiplexing (WDM) signal of λ12 are input to an optical multiplexer 210, and after multiplexing by the optical multiplexer 210, one multimode optical signal containing λ11 (TE0) and λ12 (TE1) is output. One wavelength division multiplexing (WDM) signal of λ21 and one wavelength division multiplexing (WDM) signal of λ22 are input to two input ports of an optical multiplexer 210, and after multiplexing by the optical multiplexer 210, one combined optical signal containing λ21 (TE0) and λ22 (TE1) is output. One wavelength division multiplexing (WDM) signal of λ31 and one wavelength division multiplexing (WDM) signal of λ32 are input to two input ports of an optical multiplexer 210, and after multiplexing by the optical multiplexer 210, one combined optical signal containing λ31 (TE0) and λ32 (TE1) is output. One wavelength division multiplexed signal of λ41 and another wavelength division multiplexed signal of λ42 are input to two input ports of an optical multiplexer 210, and then combined by the optical multiplexer 210 to output a combined optical signal containing λ41 (TE0) and λ42 (TE1). This achieves the goal of decomposing one optical multiplexed signal into four optical signals with flat-top bandwidth.
[0079] In one embodiment of this application, the cascaded MZ structure slice demultiplexer first divides the received optical multiplexed signal into two sub-optical multiplexed signals. Each sub-signal contains one wavelength division multiplexed signal from all channels, such as λ11+λ21+λ31+λ41 and λ12+λ22+λ32+λ42. That is, each channel is divided into two sub-channel wavelength division multiplexed signals, resulting in a large wavelength interval between the wavelength division multiplexed signals in each sub-signal, which is beneficial for subsequent wavelength division demultiplexing. Then, each sub-signal is demultiplexed separately, ultimately subdividing the optical multiplexed signal into multiple narrow-linewidth wavelength division multiplexed signals. By splitting the optical multiplexed signal in two using each cascaded DEMUX, not only are the performance requirements of each cascaded DEMUX reduced, but the passband bandwidth can be made wider and the loss can be reduced. This is because a single-stage DEMUX is sufficient to achieve this. Figure 6 The design results in very high performance requirements for DEMUX itself.
[0080] Furthermore, in some embodiments, the Mach-Zehnder interferometer structure can be a micro-ring-assisted Mach-Zehnder interferometer structure to improve the wave decomposition and multiplexing accuracy.
[0081] In some embodiments, crosstalk filters 104 may also be provided in each of the first output waveguides 112 of the slice demultiplexer 110. Each crosstalk filter 104 is connected in series in one of the first output waveguides 112 to filter each narrow linewidth subwavelength division signal, thereby reducing crosstalk between adjacent channels. This is similar to the function achieved by the design of missing the first output waveguide 112 in the aforementioned array waveguide grating structure.
[0082] For example, the crosstalk filter 104 is an MZI crosstalk filter 104. In some embodiments, other filters, such as micro-ring filters, may also be used.
[0083] This application also proposes a photonic integrated chip, which includes the on-chip integrated wavelength division multiplexing structure of any of the foregoing embodiments.
[0084] Furthermore, the photonic integrated chip also includes multiple on-chip integrated photodetectors, each photodetector being used to receive the optical signal output by an optical multiplexer 210 and convert it into an electrical signal output.
[0085] For example, continue to refer to Figure 10 The photonic integrated chip includes a stacked substrate layer 601, a dielectric layer 602, and a waveguide layer 603. The dielectric layer 602 is, for example, a buried oxide layer made of SiO2. A waveguide demultiplexing structure and a photodetector 710 are disposed in the waveguide layer 603. The waveguide demultiplexing structure includes a slice demultiplexer 110 and an optical multiplexer 210.
[0086] In one embodiment, waveguide layer 603 includes a first waveguide layer 100 and a second waveguide layer 200, which are stacked together. The first waveguide layer 100 and the second waveguide layer 200 are made of different materials. The slice demultiplexer 110 is located in the first waveguide layer 100, while the optical multiplexer 210 and the photodetector are both located in the second waveguide layer 200.
[0087] In some embodiments, the first waveguide layer 100 is any one of a silicon nitride layer, a silicon oxynitride layer, and a lithium niobate layer, and the second waveguide layer 200 is a silicon layer. For example, the photodetector 710 includes a silicon waveguide formed from the aforementioned silicon layer and a germanium layer 300 disposed on the silicon waveguide.
[0088] Combination Figures 8-10In this embodiment, the first waveguide layer 100 is a silicon nitride layer, meaning the slice demultiplexer 110 is made of silicon nitride, and its first output waveguides 112 are all single-mode silicon nitride waveguides. Therefore, when the slice demultiplexer 110 adopts a wavelet demultiplexing structure such as an arrayed waveguide grating structure, it is temperature insensitive, thereby preventing the light wavelength from deviating from the required wavelength range. The second waveguide layer 200 is a silicon layer, meaning the optical multiplexer 210 is made of silicon, and its multiple second input waveguides 211 are configured as single-mode silicon waveguides for coupling with the single-mode silicon nitride waveguides of the slice demultiplexer 110, facilitating thermal coupling between the two and reducing optical loss. Specifically, the ends of the multiple second input waveguides 211 overlap with the ends of the corresponding groups of multiple first output waveguides 112 in a one-to-one correspondence on the projection of the first waveguide layer 100, achieving optical coupling through thermal coupling. The second output waveguide 212 of the optical multiplexer 210 is configured as a multimode silicon waveguide for outputting the multimode optical signal after mode multiplexing, and is convenient to be directly optically coupled to the high-speed germanium silicon photodetector 710 based on the silicon waveguide, thereby improving the efficiency of optical coupling with the photodetector 710 and thus improving the responsivity of the photodetector 710 in the photonic integrated chip.
[0089] In the on-chip integrated wavelength demultiplexing structure and chip provided in this application embodiment, the wavelength demultiplexing structure includes a slice demultiplexer and M optical multiplexers. First, the slice demultiplexer demultiplexes the optical signals of each optical channel and subdivides the signal of each optical channel into multiple narrow-linewidth sub-wavelength division signals. Then, the multiple sub-wavelength division signals corresponding to the same channel are multiplexed into one optical signal with a flat-top bandwidth by the optical multiplexer. Compared with the prior art of directly designing a wavelength demultiplexer with a flat-top bandwidth, the slice demultiplexer and optical multiplexer have lower optical loss, reducing the design difficulty and requirements of wavelength demultiplexing devices, and thus making it easier to achieve wavelength demultiplexing with flat-top bandwidth and low loss.
[0090] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0091] The on-chip integrated wavelength division multiplexer and photonic integrated circuit chip provided in this application have been described in detail above with reference to the embodiments. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. An on-chip integrated wave decomposition and multiplexing structure, characterized in that, Includes a slice demultiplexer and M optical multiplexers; The slice demultiplexer has a first input waveguide and M groups of first output waveguides. Each group of first output waveguides includes at least two first output waveguides. The M optical multiplexers correspond to the M groups of first output waveguides respectively. Each optical multiplexer is optically connected to the corresponding group of first output waveguides. The slice demultiplexer is used to demultiplex the optical multiplexed signal containing multiple optical channels received by the first input waveguide, and to subdivide the optical signal of each optical channel into N sub-channel wavelength division signals. Each group of the first output waveguides corresponds to one optical channel, and each first output waveguide corresponds to one sub-channel to output one of the sub-wavelength division signals of the corresponding optical channel. Each of the optical multiplexers is used to receive the sub-wavelength division signals output from each of the first output waveguides of the corresponding group, and to combine the multiple sub-wavelength division signals received from the same optical channel into a single optical signal with a flat-top bandwidth for output. Where M≥2, N≥2, and M and N are both positive integers.
2. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The first output waveguide is a single-mode waveguide; Each of the optical multiplexers has a second output waveguide, which is a multimode waveguide.
3. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The slice demultiplexer is located in a first waveguide layer, and the optical multiplexer is located in a second waveguide layer. The first waveguide layer and the second waveguide layer are stacked together, and the first waveguide layer and the second waveguide layer are made of different materials. Each of the optical multiplexers has multiple second input waveguides and one second output waveguide; The plurality of second input waveguides of each optical multiplexer are respectively coupled to the plurality of first output waveguides of a corresponding set of first output waveguides to receive the optical signal output by the first output waveguide; the second output waveguide of each optical multiplexer is used to output one optical signal after multiplexing.
4. The on-chip integrated wave decomposition and multiplexing structure according to claim 3, characterized in that, The first waveguide layer is any one of silicon nitride, silicon oxynitride, and lithium niobate, and the second waveguide layer is a silicon layer.
5. The on-chip integrated wave decomposition and multiplexing structure according to claim 4, characterized in that, The first output waveguide is a single-mode waveguide made of the corresponding material. The second input waveguide is a single-mode Si waveguide, and the second output waveguide is a multimode Si waveguide.
6. The on-chip integrated wave decomposition and multiplexing structure according to claim 4, characterized in that, The ends of the plurality of second input waveguides overlap one-to-one with the projections of the ends of the plurality of first output waveguides in the corresponding group on the first waveguide layer, so as to optically couple by means of thermal coupling.
7. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The optical multiplexer is a mode multiplexer.
8. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The slice demultiplexer is composed of any of the following structures: an arrayed waveguide grating structure, an etched diffraction grating structure, or multiple cascaded Mach-Zehnder interference structures.
9. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The slice demultiplexer includes an arrayed waveguide grating structure, which includes an input planar waveguide, an output planar waveguide, and multiple arrayed waveguides connected between the input planar waveguide and the output planar waveguide, with a constant length difference between adjacent arrayed waveguides; the first input waveguide is connected to the input planar waveguide, and each of the first output waveguides is connected to the output planar waveguide to output a narrow-linewidth subwavelength division multiplexing (WDM) signal.
10. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The slice demultiplexer includes an arrayed waveguide grating structure or an etched diffraction grating. Between two adjacent sets of first output waveguides, there are n sub-channels configured to be missing the first output waveguide, where N > n ≥ 1, and n is a positive integer.
11. The on-chip integrated wave decomposition and multiplexing structure according to claim 1, characterized in that, The slice demultiplexer includes multiple cascaded Mach-Zehnder interference structures. Each Mach-Zehnder interference structure includes one input port and two output ports, which are used to demultiplex one optical signal received at one input port into two optical signals, and output the two optical signals from the two output ports respectively. Each output port of each Mach-Zehnder interferometer structure in the final stage outputs a narrow-linewidth subwavelength division signal.
12. The on-chip integrated wave decomposition and multiplexing structure according to claim 11, characterized in that, The Mach-Zehnder interferometer structure includes a micro-ring-assisted Mach-Zehnder interferometer structure.
13. The on-chip integrated wave decomposition and multiplexing structure according to claim 11, characterized in that, The slice demultiplexer also includes multiple crosstalk filters, each of which is connected in series in a first output waveguide.
14. A photonic integrated chip, characterized in that, Includes the on-chip integrated wave decomposition and multiplexing structure as described in any one of claims 1-13.
15. The photonic integrated chip according to claim 14, characterized in that, It also includes multiple on-chip integrated photodetectors, each of which is used to receive an optical signal output from one of the optical multiplexers and convert it into an electrical signal output.