Low crosstalk wavelength division demultiplexer based on inverse design and photonic crystal assistance

Abstract

The application discloses a low-crosstalk wavelength division demultiplexer based on reverse design and photonic crystal assistance, belongs to the field of photonic devices and integrated technology, and is constructed on a silicon-on-insulator (SOI) platform, comprising a buried layer, a waveguide layer and a substrate, and characterized in that the waveguide layer comprises a super-structure waveguide structure based on reverse design and a one-dimensional photonic crystal waveguide structure in cascade, the super-structure waveguide structure comprises a plurality of equal-size rectangular pixel points with nanometer holes, and the one-dimensional photonic crystal waveguide structure realizes band-pass filtering by etching two kinds of photonic crystals with different periods.The application is expected to construct a multi-channel wavelength division demultiplexer with small size and low crosstalk by combining a reverse design scheme and a photonic crystal structure, and can further improve the transmission capacity and integrated density of an on-chip wavelength division multiplexing system.

Description

Technical Field

[0001] This invention relates to the field of photonic devices and integration technology, and in particular to a low crosstalk demultiplexer based on reverse design and photonic crystal assistance. Background Technology

[0002] To meet the explosive growth in demand for communication capacity, bandwidth, and speed, as well as the exponential increase in the need for large transmission bandwidth in optical interconnect systems, on-chip multiplexing technology is considered a promising solution for increasing data capacity. Wavelength demultiplexers (WDMs) transmit data through multiple channels and are compatible with other multiplexing technologies to further increase data capacity. Currently, conventional WDM structures include multimode interferometer structures, ring resonators, and arrayed waveguide gratings, which have large device sizes, making them unsuitable for on-chip integration. Reverse engineering methods can achieve WDM functionality within a small area, but the number of channels is limited and channel crosstalk is significant. Photonic crystals, on the other hand, can utilize resonant characteristics to filter out specific wavelengths of light to reduce crosstalk. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a low crosstalk wavelength division multiplexer based on reverse design and photonic crystal assistance. Combining reverse design and photonic crystal structure, it is expected to build a small-size and low-crosstalk multi-channel wavelength division multiplexer, which can further improve the transmission capacity and integration density of on-chip wavelength division multiplexing system.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A low crosstalk demultiplexer based on reverse design and photonic crystal assistance is constructed on a silicon-on-insulator (SOI) platform, comprising a buried layer, a waveguide layer, and a substrate. The waveguide layer includes a cascaded meta-waveguide structure based on reverse design and a one-dimensional photonic crystal waveguide structure. The meta-waveguide structure includes several rectangular pixels of equal size with nanopores. The one-dimensional photonic crystal waveguide structure achieves bandpass filtering by etching two photonic crystals with different periods.

[0006] A further improvement of the technical solution of the present invention is that: the meta-waveguide structure includes M×N rectangular pixels with nanopores of equal size, and a nanopore with a diameter of R is etched at the center of the rectangular pixel according to the required wavelength demultiplexing function, wherein the value of R is in the range of 20-100nm, the value of M is in the range of 100-300, and the value of N is in the range of 60-180.

[0007] A further improvement to the technical solution of this invention lies in that: the distribution of the nanopores on the metamorphic waveguide structure is designed by a reverse design algorithm, which specifically includes the following steps:

[0008] S1. Divide the region of the metawaveguide structure into M×N rectangular pixels, etch nanopores in each pixel, and set the state of the nanopores to silicon material to form the initial structure for reverse design.

[0009] S2. The reverse design method of direct binarization search is used to optimize the device by changing the material of the nanopores one by one, setting the material to silicon and silicon dioxide.

[0010] S3. The nanopores are divided into two states: etched state and non-etched state. In the etched state, the nanopore material is set as silicon dioxide, and in the non-etched state, the nanopore material is set as silicon.

[0011] S4. By changing the state of the nanopore, the reverse-designed meta-waveguide structure is calculated. When the device efficiency increases, the state of the nanopore is maintained; when the device efficiency decreases, the state of the nanopore is restored.

[0012] S5. Repeat S4 to iterate through the metamorphic waveguide structure until a satisfactory device structure is achieved.

[0013] A further improvement of the technical solution of the present invention is that: the one-dimensional photonic crystal waveguide structure is configured as six, which are respectively cascaded at the six output ports of the metamorphic waveguide structure.

[0014] A further improvement of the technical solution of the present invention is that each of the six one-dimensional photonic crystal waveguide structures has two photonic crystals with different periods, which respectively form bandpass filters that filter out different wavelengths.

[0015] A further improvement of the technical solution of the present invention is that: one of the six one-dimensional photonic crystal waveguide structures includes photonic crystals with periods Λ1 and Λ2.

[0016] A further improvement to the technical solution of this invention lies in that: the period of one of the six one-dimensional photonic crystal waveguide structures is calculated using the formula based on the target center filtering wavelength λ:

[0017]

[0018] Wherein, λ1 is the center wavelength of the photonic crystal bandstop filter with period Λ1, and λ2 is the center wavelength of the photonic crystal bandstop filter with period Λ2.

[0019] A further improvement to the technical solution of this invention lies in that: the period Λ of one of the six one-dimensional photonic crystal waveguide structures is calculated according to the band-stop center filter wavelength formula:

[0020] λ=2n eff Λ

[0021] Where, n eff Λ is the effective refractive index of a one-dimensional photonic crystal filter, and Λ is the period of the photonic crystal.

[0022] The period of a photonic crystal with period Λ1 is calculated using the filter wavelength formula:

[0023] λ1=2n eff Λ1

[0024] The period of a photonic crystal with a period of Λ2 is calculated using the filter wavelength formula:

[0025] λ2=2n eff Λ2.

[0026] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0027] 1. The present invention provides a low crosstalk multichannel wave demultiplexer based on reverse design and photonic crystal assistance. According to the target requirements, the reverse design algorithm is used to calculate the meta-waveguide structure, which greatly reduces the device size and is conducive to on-chip dense integration.

[0028] 2. The present invention provides a low crosstalk multichannel wave demultiplexer based on reverse design and photonic crystal assistance. By cascading a one-dimensional photonic crystal waveguide structure at the output end of a metamorphic waveguide, interference wavelengths other than the target wavelength are filtered out, thereby greatly reducing crosstalk and improving device performance. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a low-crosstalk multichannel wave demultiplexer based on reverse design and photonic crystal assistance, according to an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of a wavelength division multiplexer based on a reverse-designed meta-waveguide structure according to an embodiment of the present invention.

[0031] Figure 3 The output curve of the incident light after passing through the metamorphic waveguide structure in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of a filter plane of a one-dimensional photonic crystal waveguide structure according to an embodiment of the present invention;

[0033] Figure 5 The filter curve of the filter of the one-dimensional photonic crystal waveguide structure in an embodiment of the present invention is shown.

[0034] Figure 6 This is an output curve of a low crosstalk multichannel wave demultiplexer based on reverse design and photonic crystal assistance according to an embodiment of the present invention.

[0035] Among them, 1. buried layer, 2. waveguide layer, 3. substrate, 4. metamorphic waveguide structure, and 5. one-dimensional photonic crystal waveguide structure. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0037] like Figure 1 As shown, a low crosstalk demultiplexer based on reverse design and photonic crystal assistance includes a substrate 3, a buried layer 1, and a waveguide layer 2 arranged sequentially from bottom to top; the waveguide layer 2 includes a rectangular metamorphic waveguide structure 4 and several one-dimensional photonic crystal waveguide structures 5 connected to the rectangular metamorphic waveguide structure 4.

[0038] like Figure 2 As shown, the length L of the metamorphic waveguide structure 4 R It is 12μm in diameter and has a width of W. R The device has a diameter of 7.2 μm, a dimensions of 12 μm × 7.2 μm, and a thickness h of 220 nm. It consists of 100 × 60 rectangular pixels with a side length Ws of 120 nm and nanopores R of 100 nm each. The output waveguides are designated O1-O6, and both the input and output waveguide widths Wo are 0.5 μm to ensure single-mode light transmission within the waveguides. The spacing Wg between the output waveguides is 1.5 μm to prevent crosstalk between channels. The nanopores in the rectangular pixels are configured in two states based on the target demultiplexing wavelength: etched and non-etched. In the etched state, the nanopore material is silicon dioxide; in the non-etched state, the nanopore material is silicon. Furthermore, the nanopores on the metawaveguide structure are optimized according to the quality factor FOM.

[0039]

[0040] Where i represents the i-th output channel, and (i = 1, 2, ..., 6), t i Let a represent the transmission efficiency of the i-th channel. i This represents the weighting coefficient of the i-th channel. The quality factor (FOM) of each nanopore under different states is calculated using the three-dimensional finite-difference time-domain (3D FDTD) method. When the quality factor (FOM) increases, the current state of the nanopore is retained; otherwise, the nanopore is set to another state.

[0041] The output curves of the reverse-designed meta-waveguide structures O1-O6 are shown in the figure below. Figure 3 As shown, the transmission loss of each output channel is 2.5dB, and the crosstalk is less than -8dB.

[0042] like Figure 4As shown, the width of the one-dimensional photonic crystal waveguide structure 5 is W, which is determined by the width of the output waveguides O1-O6 of the metamorphic waveguide structure and is 0.5 μm. It is composed of photonic crystals with periods Λ1 and Λ2. The radius of the photonic crystal with period Λ1 is R1, which is set to 50 nm according to the requirements. The number of photonic crystal arrays is N1, which is set to N1 = 30. The radius of the photonic crystal with period Λ2 is R2, which is set to 50 nm according to the requirements. The number of photonic crystal arrays is N2, which is set to N2 = 30.

[0043] The period Λ1 is given by the formula λ1=2n eff Λ1 is calculated. Where λ1 is the filtering wavelength of the photonic crystal with period Λ1, and n... eff Λ1 is the effective refractive index of the one-dimensional photonic crystal structure, and Λ1 is the period of the photonic crystal.

[0044] The period Λ2 is given by the formula λ2=2n eff Λ2 is calculated. Where λ2 is the filtering wavelength of the photonic crystal with period Λ2, and n... eff Λ2 represents the effective refractive index of the one-dimensional photonic crystal structure, and Λ2 represents the period of the photonic crystal.

[0045] The one-dimensional photonic crystal structure filtering wavelength curve for channel O5 is shown below. Figure 5 As shown, the wavelength of the photonic crystal is determined by the target center wavelength using the formula: The calculation is performed, where λ is the target center wavelength, which is 1577nm, λ1 is the filtering wavelength of the photonic crystal with period Λ1, and λ2 is the filtering wavelength of the photonic crystal with period Λ2. According to the formula, λ1 is calculated to be 1537nm, λ2 is 1617nm, the photonic crystal period Λ1 is calculated to be 313.7nm, and the photonic crystal period Λ2 is calculated to be 342.6nm.

[0046] Figure 6 This image shows the output curves (O1-O6) of a low-crosstalk multichannel wave demultiplexer based on reverse design and photonic crystal assistance. Combining the advantages of metamorphic waveguide structures and one-dimensional photonic crystal waveguides, it features low crosstalk, multiple channels, and small size. The crosstalk between adjacent output waveguides is less than -35 dB, and the overall size is less than 12 × 22 μm. 2 .

[0047] In summary, this invention, combining reverse engineering and photonic crystal structures, promises to construct small-sized, low-crosstalk multichannel wavelength division multiplexers, which can further improve the transmission capacity and integration density of on-chip wavelength division multiplexing systems.

Claims

1. A low crosstalk demultiplexer based on reverse design and photonic crystal assistance, constructed on a silicon-on-insulator (SOI) platform, comprising a buried layer (1), a waveguide layer (2), and a substrate (3), characterized in that: The waveguide layer (2) includes a cascaded meta-waveguide structure (4) based on reverse design and a one-dimensional photonic crystal waveguide structure (5). The meta-waveguide structure (4) includes several rectangular pixels with nanopores of equal size. The one-dimensional photonic crystal waveguide structure (5) achieves bandpass filtering by etching two photonic crystals with different periods. The meta-waveguide structure (4) includes M×N rectangular pixels with nanopores of equal size, and a nanopore with a diameter of R is etched at the center of the rectangular pixel according to the required wavelength demultiplexing function, wherein the value of R is in the range of 20-100nm, the value of M is in the range of 100-300, and the value of N is in the range of 60-180. The distribution of the nanopores on the metamorphic waveguide structure is designed using a reverse design algorithm. The nanopores on the metamorphic waveguide structure are optimized based on the quality factor (FOM), as shown in the following formula: Where i represents the i-th output channel. This represents the transmission efficiency of the i-th channel. The weight coefficient of the i-th channel is represented by the quality factor (FOM) of each nanopore in different states, which is calculated by the three-dimensional finite difference time-domain method. When the quality factor (FOM) increases, the state of the nanopore at this moment is retained; otherwise, the nanopore is set to another state. The one-dimensional photonic crystal waveguide structure (5) is set to six, which are cascaded at the six output ports of the metamorphic waveguide structure respectively; each of the six one-dimensional photonic crystal waveguide structures (5) has two photonic crystals with different periods, which respectively form bandpass filters that filter out different wavelengths. One of the six one-dimensional photonic crystal waveguide structures (5) includes a period of and period is Photonic crystal; The period of one of the six one-dimensional photonic crystal waveguide structures (5) is determined according to the target center filtering wavelength. Calculated using the formula: in, For period The center wavelength of the photonic crystal bandstop filter. For period The center wavelength of the photonic crystal bandstop filter; The period Λ of one of the six one-dimensional photonic crystal waveguide structures (5) is calculated according to the band-stop center filter wavelength formula: in, The effective refractive index of a one-dimensional photonic crystal filter. The period of the photonic crystal; The period is The period of the photonic crystal is calculated using the formula for the filtered wavelength: The period is The period of the photonic crystal is calculated using the formula for the filtered wavelength: 。 2. The low crosstalk demultiplexer based on reverse design and photonic crystal assistance according to claim 1, characterized in that: The reverse design algorithm specifically includes the following steps: S1. Divide the region of the metawaveguide structure (4) into M×N rectangular pixels, etch nanopores in each pixel, and set the state of the nanopores to silicon material, which is the initial structure for reverse design. S2. The reverse design method of direct binarization search is used to optimize the device by changing the material of the nanopores one by one, setting the material to silicon and silicon dioxide. S3. The nanopores are divided into two states: etched state and non-etched state. In the etched state, the nanopore material is set as silicon dioxide, and in the non-etched state, the nanopore material is set as silicon. S4. By changing the state of the nanopore, the reverse-designed meta-waveguide structure is calculated. When the device efficiency increases, the state of the nanopore is maintained; when the device efficiency decreases, the state of the nanopore is restored. S5. Repeat S4 to iterate through the metamorphic waveguide structure until a satisfactory device structure is achieved.

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