Dense wavelength division multiplexing structure and optical chip

Abstract

This application relates to the field of optical communication technology, specifically to a dense wavelength division multiplexing (DWDM) structure and optical chip, aiming to solve the technical problem of how to achieve a large-channel, low-crosstalk DWDM structure based on multiple coarse wavelength division multiplexers. To this end, the DWDM structure of this application includes: multiple sets of one-to-one corresponding micro-ring resonators and coarse wavelength division multiplexers, where the resonant wavelength of the micro-ring resonator includes the output wavelength of its corresponding coarse wavelength division multiplexer. Through the interleaving design of the output wavelengths of adjacent coarse wavelength division multiplexers, the channel spacing of the reduced coarse wavelength division multiplexers is achieved. Through the wavelength selection of the micro-ring resonators and the matching design between micro-ring resonators with different center resonant wavelengths and each coarse wavelength division multiplexer, the severe channel crosstalk problem caused by simply interleaving the coarse wavelength division multiplexers is reduced, thus forming a new large-channel, low-crosstalk DWDM structure, solving the problem of severe crosstalk in conventional large-channel DWDM designs.

Description

Technical Field

[0001] This application relates to the field of optical communication technology, specifically to a dense wavelength division multiplexing structure and an optical chip. Background Technology

[0002] Wavelength division multiplexers (WDMs), as important optical wavelength division multiplexing / demultiplexing devices, have been widely used in optical communications. Furthermore, due to their compact size, compatible manufacturing processes, and high integration, WDMs have been applied on multiple semiconductor material platforms.

[0003] However, with the increase in the number of optical communication channels, the size of wavelength division multiplexers (WDMs) increases significantly. This increase in size drastically amplifies the additional phase deviations in the array waveguide caused by the manufacturing process, leading to severe channel crosstalk. Furthermore, in WDM systems, when the wavelength spacing between two optical channels within a certain wavelength range decreases, the output optical signals of the channels are typically Gaussian in shape, and the smaller wavelength spacing will introduce even greater crosstalk into the system. The crosstalk problem of large-channel WDMs has become a bottleneck limiting their widespread application. Therefore, how to reduce the crosstalk problem of large-channel WDMs while also minimizing additional deviations caused by the manufacturing process has become an urgent problem to be solved. Utility Model Content

[0004] In order to overcome the above-mentioned deficiencies, this application is made to solve, or at least partially solve, the technical problem of how to realize a dense wavelength division multiplexing structure with large channels and low crosstalk based on multiple coarse wavelength division multiplexers.

[0005] In a first aspect, a dense wavelength division multiplexing (DWDM) structure is provided, wherein the channel spacing output by the DWDM structure is Δλ, and the DWDM structure includes a master micro-ring resonator array and a coarse wavelength division multiplexer array, wherein: The main microring resonator array includes a first input waveguide, N main microrings and N first output waveguides. The input end of the first input waveguide is used to receive a first broadband optical signal including multiple wavelengths. The N main microrings are arranged sequentially along the optical signal transmission direction of the first input waveguide. The first input waveguide, the nth main microring, and the nth first output waveguide constitute the nth main microring resonator. The nth main microring resonator filters and outputs the nth group of resonant optical signals from its download end based on its own first preset resonant wavelength. The coarse wavelength division multiplexer array includes N coarse wavelength division multiplexers, wherein the input terminal of the nth coarse wavelength division multiplexer is connected to the download terminal of the nth main microring resonator; the nth coarse wavelength division multiplexer includes Pn output channels to output the optical signals of Pn resonant wavelengths in the nth group of resonant optical signals from the corresponding output channels; Where N≥2, 1≤n≤N, Pn≥2.

[0006] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the free spectral range of the nth master microring resonator is equal to the channel spacing of the nth coarse wavelength division multiplexer.

[0007] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the free spectral range of each of the main microring resonators and the channel spacing of each of the coarse wavelength division multiplexers are both N*Δλ.

[0008] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the resonant wavelengths of the resonant optical signals included in each of the main micro-ring resonators are not equal, and the difference between the center resonant wavelength of the nth group of resonant optical signals and the center resonant wavelength of the (n+1)th group of resonant optical signals is Δλ.

[0009] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the difference between the center wavelength of the nth coarse wavelength division multiplexer and the center wavelength of the (n+1)th coarse wavelength division multiplexer is Δλ.

[0010] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the dense wavelength division multiplexing structure further includes: at least one phase shifter corresponding to each of the main microring resonators.

[0011] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, an auxiliary micro-ring resonator is also included. The input end of the auxiliary micro-ring resonator is used to receive a second broadband optical signal. The auxiliary micro-ring resonator filters and outputs a third broadband optical signal from its download end to the input end of the first input waveguide based on its own second preset resonant wavelength. The third broadband optical signal includes the resonant wavelengths output from the download ends of all the main micro-ring resonators.

[0012] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the auxiliary microring resonator includes a second input waveguide, an auxiliary microring, and a second output waveguide; Wherein, one end of the second input waveguide serves as the input end of the auxiliary micro-ring resonator, used to receive the second broadband optical signal; One end of the second output waveguide serves as the download end of the auxiliary micro-ring resonator and is connected to the input end of the first input waveguide to transmit the third broadband optical signal to the first input waveguide.

[0013] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the free spectral range of the auxiliary microring resonator is Δλ.

[0014] In one technical solution of the above-mentioned dense wavelength division multiplexing structure, the dense wavelength division multiplexing structure further includes at least one phase shifter corresponding to the auxiliary micro-ring resonator.

[0015] In a second aspect, an optical chip is provided, the optical chip including the dense wavelength division multiplexing structure according to any of the above technical solutions.

[0016] The above-described technical solutions of this application have at least one or more of the following beneficial effects: The dense wavelength division multiplexing (DWDM) structure of this application, by interleaving the output wavelengths of multiple coarse wavelength division multiplexers, achieves a reduction in the channel spacing of the coarse wavelength division multiplexers, thus obtaining a large-channel DWDM structure; simultaneously, by matching multiple sets of micro-ring resonators with different center wavelengths to the coarse wavelength division multiplexers, the channel crosstalk of the coarse wavelength division multiplexers can be reduced, thereby solving the problem of severe crosstalk in conventional large-channel DWDMs. Furthermore, using multiple technically mature conventional coarse wavelength division multiplexers to realize the DWDM structure can reduce the difficulty of optical chip design, reduce process complexity, and alleviate the optical chip channel crosstalk problem caused by process deviations. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a dense wavelength division multiplexing structure according to one embodiment of this application.

[0018] Figure 2 This is a schematic diagram of a dense wavelength division multiplexing structure (N=4) according to a specific embodiment of this application.

[0019] Figure 3 This is a schematic diagram of a dense wavelength division multiplexing structure (N=4) according to another specific embodiment of this application.

[0020] Figure 4 This is a top view schematic diagram of the heating electrode in an optical chip according to an embodiment of this application, relative to the position of the micro-ring, wherein... Figure 4 (a) and Figure 4 (b) shows the placement of the two heating electrodes.

[0021] Figure 5 It is based on Figure 4 (b) shows a schematic cross-sectional view of the heating electrode and microring along the AA' direction.

[0022] Figure 6 (a) is an optical simulation result of a dense wavelength division multiplexing structure that does not include the auxiliary micro-ring resonator and the main micro-ring resonator array; Figure 6(b) Optical simulation results of a dense wavelength division multiplexing structure according to a specific embodiment of this application. Detailed Implementation

[0023] Some embodiments of this application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0024] It should be noted that in the description of this application, terms such as "upper," "lower," "left," "right," "inner," and "outer," indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are used solely for ease of description and do not indicate or imply that the device, structure, or component must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "A and / or B" represents all possible combinations of A and B, such as only A, only B, or A and B. The singular forms of the terms "a" and "this" may also include plural forms.

[0025] Figure 1 This is a schematic diagram of a dense wavelength division multiplexing (DWDM) structure according to an embodiment of this application. The DWDM structure of this application includes a main microring resonator array 10 and a coarse wavelength division multiplexer array 20. The main microring resonator array 10 includes a first input waveguide 100, N main microrings (201, 202, ..., 20N) arranged sequentially along the optical signal transmission direction of the first input waveguide, and N first output waveguides (301, 302, ..., 30N).

[0026] The main microring resonator array 10 includes a total of N main microring resonators (11, 12, ..., 1N). Each main microring resonator is an add-drop type microring resonator composed of an input waveguide, a main microring, and an output waveguide. A portion of the first input waveguide, together with the nth main microring and the nth first output waveguide, constitutes the nth main microring resonator.

[0027] The coarse wavelength division multiplexer array 20 includes N coarse wavelength division multiplexers (401, 402, ..., 40N), wherein the nth coarse wavelength division multiplexer includes Pn output channels, and the input terminal of the nth coarse wavelength division multiplexer is connected to the input terminal of the nth main microring resonator. N, n, and Pn are all positive integers and have the following conventions: N≥2, 1≤n≤N, Pn≥2.

[0028] Please refer to the appendix for further details. Figure 2 , Figure 2This is a schematic diagram of a dense wavelength division multiplexing structure according to an embodiment of this application. Figure 2 In the embodiment shown, N=4, P1=P2=P3=P4=3, that is, the coarse wavelength division multiplexer array 20 includes 4 (N=4) coarse wavelength division multiplexers (401, 402, 403 and 404), each coarse wavelength division multiplexer has 3 output channels (P1=P2=P3=P4=3).

[0029] like Figure 2 and combined Figure 1 As shown, the main micro-ring resonator array 10 includes a first input waveguide 100, micro-rings 201, 202, 203, and 204, a first output waveguide 301, a first output waveguide 302, a first output waveguide 303, and a first output waveguide 304.

[0030] The first input waveguide 100 is composed of sequentially connected portions of the first input waveguides 101, 102, 103, and 104. A portion of the first input waveguide 101, the microring 201, and the first output waveguide 301 constitute the first main microring resonator 11; a portion of the first input waveguide 102, the microring 202, and the first output waveguide 302 constitute the second main microring resonator 12; a portion of the first input waveguide 103, the microring 203, and the first output waveguide 303 constitute the third main microring resonator 13; and a portion of the first input waveguide 104, the microring 204, and the first output waveguide 304 constitute the fourth main microring resonator 14.

[0031] for Figure 2 The following explanation uses the first main microring resonator 11 as an example to illustrate the meaning and function of each port of the uploading / downloading microring resonator. The end of part of the first input waveguide 101 connected to the first broadband optical signal is the input terminal of the microring resonator, used to receive the optical signal input to the microring resonator; the end of part of the first input waveguide 101 connected to part of the first input waveguide 102 is the through terminal of the microring resonator, used to output the optical signal of the non-resonant wavelength; the end of the first output waveguide 301 connected to the input terminal of the coarse wavelength division multiplexer 401 is the download terminal of the microring resonator, used to output the optical signal of the resonant wavelength.

[0032] The coarse wavelength division multiplexer array includes four coarse wavelength division multiplexers, WDN1 to WDN4, namely coarse wavelength division multiplexer 401, coarse wavelength division multiplexer 402, coarse wavelength division multiplexer 403 and coarse wavelength division multiplexer 404, each coarse wavelength division multiplexer including 3 output channels.

[0033] The download end of the first main microring resonator 11 (one end of the first output waveguide 301) is connected to the input end of the coarse wavelength division multiplexer 401. The download end of the second main microring resonator 12 (one end of the first output waveguide 302) is connected to the input end of the coarse wavelength division multiplexer 402. The download end of the third main microring resonator 13 (one end of the first output waveguide 303) is connected to the input end of the coarse wavelength division multiplexer 403. The download end of the fourth main microring resonator 14 (one end of the first output waveguide 304) is connected to the input end of the coarse wavelength division multiplexer 404.

[0034] In this embodiment, the dense wavelength division multiplexing structure is designed to output a set of optical signals λ1,λ2,...,λ with wavelength spacing of Δλ. m , where λ1 to λ m The wavelengths increase sequentially, meaning the number of output channels in the dense wavelength division multiplexing (DWDM) structure is m, and the channel spacing is Δλ.

[0035] The number of output channels of each coarse wavelength division multiplexer in the coarse wavelength division multiplexer array is designed to be P. Accordingly, to realize the dense wavelength division multiplexing structure of the embodiments of this application, N = m / P coarse wavelength division multiplexers are required.

[0036] As an example, such as Figure 2 As shown, the number of channels in the dense wavelength division multiplexing structure is 12 (m=12), and the number of output channels of each coarse wavelength division multiplexer is 3 (P=3). Therefore, 4 (N=m / P=12 / 3=4) coarse wavelength division multiplexers are needed. Correspondingly, 4 (N=4) main microring resonators are needed, each corresponding to one of the coarse wavelength division multiplexers.

[0037] Considering that a dense wavelength division multiplexing (DWDM) structure can be constructed by interleaving the center wavelengths of multiple coarse wavelength division multiplexers, when the difference between the center wavelength of the nth coarse wavelength division multiplexer and the center wavelength of the (n+1)th coarse wavelength division multiplexer is set to Δλ, the difference between the minimum output wavelength of the nth coarse wavelength division multiplexer and the minimum output wavelength of the (n+1)th coarse wavelength division multiplexer can be achieved. Simultaneously, setting the channel spacing of each coarse wavelength division multiplexer to 4*Δλ (N*Δλ) results in a uniform, large-channel (N*P = 4*3 = 12 output channels) DWDM structure with a channel spacing of Δλ.

[0038] However, simply controlling the wavelength interleaving is insufficient to solve the crosstalk problem caused by small channel spacing. Therefore, before the optical signal is input to each coarse wavelength division multiplexer (WDM), a master microring resonator corresponding to each WDM is added. The free spectral range (FSR) and resonant wavelength of each master microring resonator correspond to the channel spacing and center wavelength of each WDM. The FSR of each master microring resonator is also set to 4*Δλ (N*Δλ). The resonant wavelength output from the download end of each master microring resonator includes the output wavelengths of each output channel of the corresponding coarse WDM, thus achieving pre-filtering of the optical signal input to each coarse WDM filter and reducing channel crosstalk in the large-channel WDM structure. Furthermore, the resonant wavelengths of the resonant optical signals included by each master microring resonator are not equal. The difference between the center resonant wavelength of the nth group of resonant optical signals and the center resonant wavelength of the (n+1)th group of resonant optical signals is also Δλ. This difference design creates a dense WDM effect. Ultimately, a large-channel dense WDM structure is constructed.

[0039] The input terminal of the first input waveguide 100 is used to receive a first broadband optical signal, wherein the first broadband optical signal can contain λ1, λ2, ..., λ m The first broadband optical signal is a continuous broadband optical signal containing λ1, λ2, ..., λ. 12 (i.e., m=12) continuous broadband optical signal.

[0040] The first broadband optical signal enters the first main microring resonator (partially at one end of the first input waveguide 101). Based on its own first preset resonant wavelength, the first main microring resonator outputs the first group of resonant optical signals from the first broadband optical signal (i.e., when n=1, λ) from the download end of the first main microring resonator (one end of the first output waveguide 301). n ,λ n+N ,...,λ m-(N-n) (λ1, λ5, λ9). The first group of resonant optical signals enters the coarse wavelength division multiplexer 401, which sequentially focuses the optical signals with wavelengths of λ1, λ5, and λ9 into the respective output channels.

[0041] Optical signals that do not meet the resonant wavelength condition of the first main microring resonator are output from the through end of the first main microring resonator (the other end of part of the first input waveguide 101), continue to propagate along the first input waveguide 100, and enter the second main microring resonator (one end of part of the first input waveguide 102).

[0042] The second main microring resonator, based on its own first preset resonant wavelength, outputs the second group of resonant optical signals from the first broadband optical signal (i.e., when n=2, λ) from the download end of the second main microring resonator (one end of the first output waveguide 302).n ,λ n+N ,...,λ m-(N-λ) For n2,λ6,λ 10 The second group of resonant optical signals enters the coarse wavelength division multiplexer 402, which converts wavelengths λ2, λ6, and λ7 into multiplexed signals. 10 The optical signals are sequentially focused into each output channel for output.

[0043] Optical signals that do not meet the resonant wavelength conditions of the first and second main microring resonators are output from the through end of the second main microring resonator (the other end of part of the first input waveguide 102), continue to propagate along the first input waveguide 100, and enter the third main microring resonator (one end of part of the first input waveguide 103).

[0044] The third main microring resonator, based on its own first preset resonant wavelength, outputs the third group of resonant optical signals from the first broadband optical signal (i.e., when n=3, λ) from the download end of the third main microring resonator (one end of the first output waveguide 303). n ,λ n+N ,...,λ m-(N-n) For λ3, λ7, λ 11 ).

[0045] The third group of resonant optical signals enters the coarse wavelength division multiplexer 403, which converts wavelengths λ3, λ7, and λ8 into multiplexed signals. 11 The optical signals are sequentially focused into each output channel for output.

[0046] Similarly, optical signals that do not meet the resonant wavelength conditions of the first, second, and third main microring resonators are output from the through end of the third main microring resonator (the other end of part of the first input waveguide 103) and continue to propagate along the first input waveguide 100 into the fourth main microring resonator (one end of part of the first input waveguide 104).

[0047] The fourth main microring resonator, based on its own first preset resonant wavelength, outputs the fourth group of resonant optical signals from the first broadband optical signal (i.e., when n=4, λ) from the download end of the fourth main microring resonator (one end of the first output waveguide 304). n ,λ n+N ,...,λ m-(N-n) For λ4, λ8, λ 12 The fourth group of resonant optical signals enters the coarse wavelength division multiplexer 404, which converts wavelengths of λ4, λ8, and λ9 into multiplexed signals. 12 The optical signals are sequentially focused into each output channel for output.

[0048] As can be seen from the above embodiments, the difference between the shortest resonant wavelength in the nth group of resonant optical signals and the shortest resonant wavelength in the (n+1)th group of resonant optical signals is Δλ. The free spectral range of each main micro-ring resonator and the channel spacing of the corresponding coarse wavelength division multiplexer are both 4Δλ, so that the output wavelengths of the four coarse wavelength division multiplexers are interleaved, and finally a low crosstalk dense wavelength division multiplexing structure with m channels (m=12) and a channel spacing of Δλ is formed.

[0049] Based on the foregoing embodiments, another embodiment of this application provides a dense wavelength division multiplexing structure that may further include an auxiliary microring resonator. Figure 3 This is a schematic diagram of a dense wavelength division multiplexing structure (N=4) according to this embodiment.

[0050] like Figure 3 As shown, the auxiliary microring resonator 30 of the dense wavelength division multiplexing structure includes a second input waveguide 500, an auxiliary microring 600, and a second output waveguide 700. The input terminal of the auxiliary microring resonator 30 (one end of the second input waveguide 500) is used to receive a second broadband optical signal, and the output terminal of the auxiliary microring resonator 30 (one end of the second output waveguide 700) is connected to the input terminal of the first input waveguide 100.

[0051] The auxiliary microring resonator 30 selects a third broadband optical signal from the second broadband optical signal based on its own second preset resonant wavelength, and transmits the third broadband optical signal to the first input waveguide 100. The third broadband optical signal is a set of resonant wavelengths λ1, λ2, ..., λ1, which include the output wavelengths of all the main microring resonators. m (λ1,λ2,...,λ 12 The resonant optical signal of the auxiliary micro-ring resonator 30 is then processed. The free spectral range of this auxiliary micro-ring resonator 30 can be set to be the same as the channel spacing of the dense wavelength division multiplexing structure, both being Δλ. By selecting the resonant wavelength of the auxiliary micro-ring resonator 30, pre-filtering of the third broadband optical signal is achieved, further reducing the crosstalk level between adjacent channels.

[0052] Figure 2 or Figure 3 The dense wavelength division multiplexing structure shown also includes a phase shifter, such as a heating electrode disposed above at least one microring resonator. Figure 4 As shown in (a), the microring resonator (including the main microring resonator and / or the auxiliary microring resonator) has two bent heating electrodes 801 and 802 symmetrically arranged at the microring positions; as Figure 4 As shown in (b), a bent heating electrode 803 is provided at the microring position of the microring resonator.

[0053] In other embodiments, those skilled in the art can also adjust the arrangement of the heating electrode according to the actual situation. For example, the heating electrode can be arranged in the coupling area formed by the micro-ring and the waveguide, or the shape of the heating electrode can be set to a rectangle, etc.

[0054] By adjusting the voltage applied to the heating electrode, the resonant wavelength of the microring resonator can be tuned, shifting it within a preset range to compensate for the impact of manufacturing errors on the resonant wavelength of each microring resonator. Of course, other types of phase shifters can also be used besides heating electrodes, as long as the above objective is achieved.

[0055] It should be noted that, Figure 2 and Figure 3 The components in the dense wavelength division multiplexing (DWDM) structure shown (first input waveguide 100, second output waveguide 700, first output waveguide 301, coarse wavelength division multiplexer 401, etc.) can be connected via curved waveguides and / or straight waveguides. As an example, the first input waveguide 100 and the second output waveguide 700 are connected via curved waveguides; the first output waveguide 301 and the coarse wavelength division multiplexer 401 are connected via curved waveguides and straight waveguides.

[0056] It should be noted that this application does not limit the implementation method of the coarse wavelength division multiplexer. As an example, the coarse wavelength division multiplexer is implemented using methods such as arrayed waveguide grating and Mach-Zehnder interferometers.

[0057] It should be noted that the design of microring resonators, the calculation of the radius of the microrings in the microring resonator, and the design of waveguide dimensions are well-known technologies in the field, and this application does not limit them.

[0058] As an example, a suitable number (N) of coarse wavelength division multiplexers can be determined based on the total number (m) of output channels of the dense wavelength division multiplexing structure, the channel spacing (Δλ), and the center wavelength of each output channel, as well as the center wavelength and channel spacing (N*Δλ) of each output channel of each coarse wavelength division multiplexer.

[0059] The median of the center wavelengths of each output channel of the coarse wavelength division multiplexer (i.e., the center wavelength of the coarse wavelength division multiplexer) can be selected as the center resonant wavelength (first preset resonant wavelength) of the main micro-ring resonator.

[0060] Alternatively, the median of the center wavelength of each output channel of the dense multiplexing structure can be selected as the center resonant wavelength (first preset resonant wavelength) of all main microring resonators, and then the resonant wavelength of each main microring resonator can be finely adjusted through the heating electrodes configured in each main microring resonator.

[0061] The median of the center wavelengths of each output channel of the densely distributed multiplexing structure (the center wavelength of the densely distributed multiplexing structure) is selected as the center resonant wavelength (second preset resonant wavelength) of the auxiliary micro-ring resonator.

[0062] It should be noted that regarding the calculation of the median, when the number of output channels is even, either of the two middle center wavelengths should be selected, and the rule for selecting the two middle center wavelengths should be consistent throughout the same design. Then, according to the formula 2πRn... c =mλ、 The formulas are used to calculate the numerical values ​​of parameters such as the radius of the main / auxiliary microrings, where λ is the central resonant wavelength, R is the radius of the microring, and n... c n is the effective refractive index of the curved waveguide. g Let m be the group refractive index of the resonant cavity of the microring resonator, where m is a positive integer.

[0063] Furthermore, the aforementioned dense wavelength division multiplexing (DWDM) structure can be implemented using semiconductor processes. Therefore, this application also provides an optical chip that can be fabricated based on an SOI silicon wafer or a silicon substrate. Taking an SOI silicon wafer as an example, it includes a silicon substrate, a buried oxide layer (silicon dioxide), and a top silicon layer, wherein the buried oxide layer serves as the lower cladding layer of the waveguide. Figure 2 or Figure 3 Most components of the dense wavelength division multiplexing (DWDM) structure are formed in a patterned form within the top silicon layer, which serves as the core layer of the waveguide. A dielectric layer, which can be SiO2 or other materials suitable for waveguide cladding, covers the top silicon layer and fills the gaps between the components.

[0064] In one embodiment of this application, the thickness of the silicon substrate of the SOI silicon wafer is about 500 μm, the thickness of the buried oxide layer is about 8 μm, and the thickness of the top silicon layer is about 220 nm.

[0065] based on Figure 3 The dense wavelength division multiplexing structure shown can be fabricated in actual processing by photolithography and etching (i.e. patterning) of the top silicon layer to obtain the waveguide core structure. After cleaning, silicon dioxide is deposited as the dielectric layer using the PECVD method. Depending on the actual needs, the dielectric layer can be further planarized by CMP or other methods to obtain a relatively flat surface.

[0066] Continue reading Figure 5 , Figure 5 for Figure 4 (b) shows a cross-sectional view of the heating electrode and microring along the AA' direction, including a silicon substrate 910, a buried oxide layer 920, and a microring 930 obtained by patterning the top silicon layer, as well as a dielectric layer 940 covering the top silicon layer.

[0067] A heating electrode 950 is disposed on the dielectric layer 940 and corresponds to the position of the micro-ring 930. The heating electrode 950 includes a first open end and a second open end disposed opposite to each other. As an example, the heating electrode 950 can be made of TiN material. An interlayer dielectric layer 960 covers the heating electrode 950 and the dielectric layer 940. A first contact hole and a second contact hole are provided in the interlayer dielectric layer 960, exposing the first open end and the second open end, respectively. A first metal plug 971 and a second metal plug 972 are respectively provided in the first contact hole and the second contact hole. A metal wiring layer is provided on the interlayer dielectric layer 960. The metal wiring layer includes a first metal layer 981 and a second metal layer 982. The first metal layer 981 is electrically connected to the first open end of the heating electrode 950 through the first metal plug 971, and the second metal layer 982 is electrically connected to the second open end of the heating electrode 950 through the second metal plug 972.

[0068] As a concrete example, Figure 3 The diagram shows a 12-channel dense wavelength division multiplexing (DWDM) structure. The center wavelengths of each output channel are 1546.8nm, 1547.6nm, 1548.4nm, 1549.2nm, 1550nm, 1550.8nm, 1551.6nm, 1552.4nm, 1553.2nm, 1554nm, 1554.8nm, and 1555.6nm (m = 12, Δλ = 0.8nm). This 12-channel DWDM structure is implemented using four 3-channel coarse wavelength division multiplexers (N = 4, P1 = P2 = P3 = P4 = 3). The channel spacing of each coarse wavelength division multiplexer is 4 * Δλ = 3.2nm.

[0069] In an embodiment of a dense wavelength division multiplexing (DWDM) structure including an auxiliary microring resonator, the radius of the auxiliary microring 600 can be 8 μm, the spacing between the auxiliary microring 600 and the second input waveguide 500 and the second output waveguide 700 is 0.25 μm, and the FSR of the auxiliary microring resonator is 0.8 nm.

[0070] The radius of the main microrings (201, 202, 203, 204) of each main microring resonator is 31 μm, and the spacing between each main microring and its corresponding first input waveguide and first output waveguide is 0.2 μm. The FSR of each main microring resonator is the same as that of its corresponding coarse wavelength division multiplexer, which is also 3.2 nm.

[0071] By using the heating electrodes at each main microring position, the resonant wavelength of the main microring resonator is finely adjusted so that the resonant wavelength of each main microring resonator is aligned with the center wavelength of each output channel of the corresponding coarse wavelength division multiplexer.

[0072] All straight waveguides (including the first input waveguide, first output waveguide, second input waveguide, second output waveguide, etc.) and curved waveguides in the transmission waveguides have a cross-sectional dimension of 450nm × 220nm. The input end of the second input waveguide 500 is configured as an end-face coupler with a tip size of 0.2μm, and the second input waveguide 500 is located at the edge of the optical chip.

[0073] A second broadband optical signal with a wavelength range of 1500nm-1600nm, input through a tapered optical fiber, enters the second input waveguide 500 via the aforementioned end-face coupler. A third broadband optical signal with wavelengths including 1546.8nm, 1547.6nm, 1548.4nm, 1549.2nm, 1550nm, 1550.8nm, 1551.6nm, 1552.4nm, 1553.2nm, 1554nm, 1554.8nm, and 1555.6nm is resonated and enhanced in the auxiliary micro-ring resonator, and then output from the download end of the auxiliary micro-ring resonator to the input end of the first input waveguide 100.

[0074] The first group of resonant optical signals (1546.8nm, 1550nm, and 1553.2nm) are filtered and enhanced by the first main micro-ring resonator, and then transmitted to the coarse wavelength division multiplexer 401 from the download end of the first main micro-ring resonator. The optical signals with wavelengths of 1546.8nm, 1550nm, and 1553.2nm are output sequentially from the three output channels of the coarse wavelength division multiplexer 401 in order of increasing wavelength.

[0075] The second group of resonant optical signals (1547.6nm, 1550.8nm, and 1554nm) are filtered and enhanced by the second main microring resonator, and then transmitted to the coarse wavelength division multiplexer 402 from the download end of the second main microring resonator. The optical signals with wavelengths of 1547.6nm, 1550.8nm, and 1554nm are output sequentially from the three output channels of the coarse wavelength division multiplexer 402 in order of increasing wavelength.

[0076] The third group of resonant optical signals (1548.4nm, 1551.6nm, and 1554.8nm) are filtered and enhanced by the third main micro-ring resonator, and then transmitted to the coarse wavelength division multiplexer 403 from the download end of the third main micro-ring resonator. The optical signals with wavelengths of 1548.4nm, 1551.6nm, and 1554.8nm are output sequentially from the three output channels of the coarse wavelength division multiplexer 403 in order of increasing wavelength.

[0077] The fourth group of resonant optical signals (1579.2nm, 1552.4nm, and 1555.6nm) are filtered and enhanced by the fourth main micro-ring resonator, and then transmitted to the coarse wavelength division multiplexer 404 from the download end of the fourth main micro-ring resonator. The optical signals with wavelengths of 1579.2nm, 1552.4nm, and 1555.6nm are output sequentially from the three output channels of the coarse wavelength division multiplexer 404 in order of increasing wavelength.

[0078] Figure 6 (a) is a broadband optical signal with a wavelength range of 1500nm-1600nm, directly input without the auxiliary micro-ring resonator and main micro-ring resonator array. Figure 3 The optical simulation diagram of the four coarse wavelength division multiplexers in the dense wavelength division multiplexing structure is shown.

[0079] Figure 6 (b) is a second broadband optical signal with a wavelength range of 1500nm-1600nm, input. Figure 3 The image shown is an optical simulation diagram of a dense wavelength division multiplexing structure, including an auxiliary micro-ring resonator and a main micro-ring resonator array.

[0080] Depend on Figure 6 (a) It can be seen that, without the auxiliary micro-ring resonator and the main micro-ring resonator array, the optimal crosstalk between adjacent channels of the output optical signal of the four coarse wavelength division multiplexers is -1.5dB; Figure 6 (b) It can be seen that after the auxiliary micro-ring resonator and the main micro-ring resonator array, the crosstalk between adjacent channels of the output optical signal of the four coarse wavelength division multiplexers is optimally -14dB, and the crosstalk problem between adjacent channels is greatly reduced.

[0081] In other embodiments, including Figure 2 or Figure 3 The optical chip with the dense wavelength division multiplexing structure shown can also be fabricated based on other material platforms such as silicon nitride (Si3N4) and indium phosphide (InP). Without departing from the principles of this application, these modified or replaced technical solutions will fall within the protection scope of this application.

[0082] As can be seen from the above embodiments, the dense wavelength division multiplexing (DWDM) structure of this application achieves a reduction in the channel spacing of the coarse wavelength division multiplexer by interleaving the output wavelengths of multiple coarse wavelength division multiplexers, thus obtaining a large-channel DWDM structure. At the same time, by matching multiple sets of micro-ring resonators with different center wavelengths to the coarse wavelength division multiplexer, the channel crosstalk of the coarse wavelength division multiplexer can be reduced, thereby solving the problem of severe crosstalk in conventional large-channel DWDM multiplexers.

[0083] Furthermore, using multiple technically mature conventional coarse wavelength division multiplexers to realize dense wavelength division multiplexing structures can reduce design difficulty, reduce process complexity, and mitigate channel crosstalk problems caused by process deviations.

[0084] It should be noted that the optical chip described in this application can be an optical chip that only includes the dense wavelength division multiplexing (DWDM) structure described in this application. In this case, the DWDM structure, after packaging, becomes a wavelength division multiplexer, which can be applied in data centers as a repeater for data upload and download. Alternatively, other structures can be added to the DWDM structure described in this application. Examples include lasers, large-scale optical switch arrays, optical beam splitters and combiners, etc., to form an optical computing chip for use in data centers and other fields. Or it can be integrated with high-speed modulators, SOA arrays, etc., to achieve on-chip transceiver integration and form a high-speed optical communication chip.

[0085] The technical solution of this application has been described above with reference to one embodiment shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A dense wavelength division multiplexing (DWDM) structure, wherein the channel spacing output by the DWDM structure is Δλ, characterized in that, The dense wavelength division multiplexing structure includes a main micro-ring resonator array and a coarse wavelength division multiplexer array, wherein: The main microring resonator array includes a first input waveguide, N main microrings and N first output waveguides. The input end of the first input waveguide is used to receive a first broadband optical signal including multiple wavelengths. The N main microrings are arranged sequentially along the optical signal transmission direction of the first input waveguide. The first input waveguide, the nth main microring, and the nth first output waveguide constitute the nth main microring resonator. The nth main microring resonator filters and outputs the nth group of resonant optical signals from its download end based on its own first preset resonant wavelength. The coarse wavelength division multiplexer array includes N coarse wavelength division multiplexers, wherein the input terminal of the nth coarse wavelength division multiplexer is connected to the download terminal of the nth main microring resonator; the nth coarse wavelength division multiplexer includes Pn output channels to output the optical signals of Pn resonant wavelengths in the nth group of resonant optical signals from the corresponding output channels; Where N≥2, 1≤n≤N, Pn≥2.

2. The dense wavelength division multiplexing structure according to claim 1, characterized in that, The main micro-ring resonator satisfies at least one of the following conditions: The free spectral range of the nth master microring resonator is equal to the channel spacing of the nth coarse wavelength division multiplexer; The free spectral range of each of the main microring resonators and the channel spacing of each of the coarse wavelength division multiplexers are both N*Δλ.

3. The dense wavelength division multiplexing structure according to claim 2, characterized in that, The resonant wavelengths of the resonant optical signals included in each of the main micro-ring resonators are not equal, and the difference between the center resonant wavelength of the nth group of resonant optical signals and the center resonant wavelength of the (n+1)th group of resonant optical signals is Δλ.

4. The dense wavelength division multiplexing structure according to claim 1, characterized in that, The difference between the center wavelength of the nth coarse wavelength division multiplexer and the center wavelength of the (n+1)th coarse wavelength division multiplexer is Δλ.

5. The dense wavelength division multiplexing structure according to any one of claims 1 to 4, characterized in that, The dense wavelength division multiplexing structure further includes at least one phase shifter corresponding to each of the main microring resonators.

6. The dense wavelength division multiplexing structure according to any one of claims 1 to 4, characterized in that, It also includes an auxiliary microring resonator, the input of which is used to receive a second broadband optical signal. The auxiliary microring resonator filters and outputs a third broadband optical signal from its download end to the input end of the first input waveguide based on its own second preset resonant wavelength. The third broadband optical signal includes the resonant wavelengths output from the download ends of all the main microring resonators.

7. The dense wavelength division multiplexing structure according to claim 6, characterized in that, The auxiliary microring resonator includes a second input waveguide, an auxiliary microring, and a second output waveguide. Wherein, one end of the second input waveguide serves as the input end of the auxiliary micro-ring resonator, used to receive the second broadband optical signal; One end of the second output waveguide serves as the download end of the auxiliary micro-ring resonator and is connected to the input end of the first input waveguide to transmit the third broadband optical signal to the first input waveguide.

8. The dense wavelength division multiplexing structure according to claim 6, characterized in that, The free spectral range of the auxiliary microring resonator is Δλ.

9. The dense wavelength division multiplexing structure according to claim 6, characterized in that, The dense wavelength division multiplexing structure further includes at least one phase shifter corresponding to the auxiliary microring resonator.

10. An optical chip, characterized in that, Includes a dense wavelength division multiplexing structure according to any one of claims 1 to 9.

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