CN116203742A - Asymmetric MMI power distributor based on phase change material - Google Patents

Asymmetric MMI power distributor based on phase change material Download PDF

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CN116203742A
CN116203742A CN202310228557.XA CN202310228557A CN116203742A CN 116203742 A CN116203742 A CN 116203742A CN 202310228557 A CN202310228557 A CN 202310228557A CN 116203742 A CN116203742 A CN 116203742A
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silicon
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刘鸿葆
赵瑛璇
朱子健
甘甫烷
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Shanghai Institute of Microsystem and Information Technology of CAS
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  in optical waveguides, not otherwise provided for in this subclass
    • G02F1/0113—Glass-based, e.g. silica-based, optical waveguides
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/0009—Materials therefor
    • G02F1/009—Thermal properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12035—Materials
    • G02B2006/12038—Glass (SiO2 based materials)
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12035—Materials
    • G02B2006/12061—Silicon
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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Abstract

The invention relates to an asymmetric MMI power divider based on a phase change material, which comprises a silicon substrate, a silicon dioxide layer and a silicon waveguide layer which are arranged from bottom to top, wherein one side of the silicon waveguide layer is connected with a strip waveguide as input, and the other side of the silicon waveguide layer is connected with a plurality of strip waveguides as output; the silicon waveguide layer is divided into a plurality of nano pixel point type structures, filling areas are arranged in the nano pixel point type structures, and the material filled in each filling area is one of silicon, silicon dioxide and phase change materials. The invention can realize on-chip adjustment of the splitting ratio without increasing the area of the device.

Description

Asymmetric MMI power distributor based on phase change material
Technical Field
The invention relates to a power divider, in particular to an asymmetric MMI power divider based on a phase change material.
Background
With the information transmission and processing in the big data age, the requirements on hardware performance are continuously improved, and the traditional electric interconnection is challenged in various aspects such as bandwidth, time delay, power consumption and the like. Optical interconnection based on silicon photon technology is widely considered to replace electrical interconnection due to the advantages of high speed, low power consumption, compatibility of process and CMOS, and the like, and meets the requirements of mass data transmission on chip or between chips. One fundamental technology required to implement integrated optical internetworks is on-chip optical power distribution. A typical silicon-based passive device commonly used for optical power splitting in integrated optical circuits is a multimode interference coupler (Multimode Interference, MMI for short).
The MMI structure designed by the traditional method is generally based on a priori device model library, the adjustable structural parameters are few, the common size is tens of micrometers or hundreds of micrometers, the occupied area is large, and the requirement on the device integration level under the photoelectric integration background is difficult to meet. In recent years, reverse engineering has become the method of choice for designing compact passive devices. The designer firstly determines the core function of the device, defines a Figure of merit (FOM) to reflect the performance of the device, then divides the initial structure of the device into the combination of nano pixel points, continuously iterates simulation through an automatic control algorithm, and independently selects the material used by each pixel point, regulates the effective refractive index of the device, and gradually obtains the optimal FOM. The design method has the advantage that almost any initial structure can be optimized to have a well-behaved result, and can be used for designing an ultra-compact asymmetric multimode interference coupler structure.
With the deep development of the photoelectric integration technology, the defects of the traditional adjustable photon device are also increasingly prominent. Conventional on-chip tunable devices generally change the refractive index of silicon or polymer materials based on thermo-optic or electro-optic effects, but this approach is volatile and requires continuous energy to maintain a specific state, which is disadvantageous for large scale integration. The use of phase change materials mixed with silicon-based devices is an effective solution to achieve on-chip non-volatile tuning. The phase change material has two stable states of crystalline state and amorphous state, and can realize rapid, multiple and reversible conversion under the induction of electric or optical pulse. The two states of the phase change material have large refractive index differences and can be used for on-chip optical path or intensity adjustment, and meanwhile, as the two states are stable, no extra energy consumption is needed except for the phase change process.
The prior MMI power divider with reverse design comprises structural designs with special shapes such as asymmetry and the like, and has smaller occupied area, however, the design of combined phase change materials is less, the power distribution ratio of most structures is not adjustable, and the power distribution ratio is required to be optimized again in an iterating way to obtain a new pixel point arrangement structure so as to realize different light splitting ratios. If the beam splitting ratio is to be adjusted on the chip, other devices such as an optical switch and the like are required to be added at the output end of the device, so that the area of the device is indirectly increased.
Disclosure of Invention
The invention aims to solve the technical problem of providing an asymmetric MMI power divider based on a phase change material, which can realize on-chip adjustment of a splitting ratio without increasing the area of a device.
The technical scheme adopted for solving the technical problems is as follows: the asymmetric MMI power distributor based on the phase change material comprises a silicon substrate, a silicon dioxide layer and a silicon waveguide layer which are arranged from bottom to top, wherein one side of the silicon waveguide layer is connected with a strip waveguide as input, and the other side of the silicon waveguide layer is connected with a plurality of strip waveguides as output; the silicon waveguide layer is divided into a plurality of nano pixel point type structures, filling areas are arranged in the nano pixel point type structures, and the material filled in each filling area is one of silicon, silicon dioxide and phase change materials.
The nano pixel point type structure is a square structure, and the filling area is in a round shape and is in the center of the square structure.
The silicon waveguide is square, and the side length is 2.5 μm.
The strip waveguide as an input is provided at an edge position of one side of the silicon waveguide layer.
The phase change material is Ge 2 Sb 2 Se 4 Te 1 。
The materials filled in the filling area are determined by a two-time direct binary search method, a first objective function and a second objective function, and specifically:
determining a filling area needing to be filled with silicon dioxide according to a first objective function by adopting a first direct binary search method;
and determining the material to be filled in the filling area of the unfilled silicon dioxide according to a second objective function by adopting a second direct binary search method.
When a first direct binary search method is adopted and a filling area needing to be filled with silicon dioxide is determined according to a first objective function, filling silicon into the filling area in the nano pixel point type structure as a first state, and filling silicon into the filling area in the nano pixel point type structure as a second state; randomly extracting a nano pixel point type structure, changing the state of the nano pixel point type structure, performing FDTD simulation once, calculating a first objective function, comparing the calculation result with the calculation result when the state is unchanged, if the calculation result is smaller, retaining the state of the nano pixel point type structure, otherwise, recovering the nano pixel point type structure to the original state; and (3) completing a first direct binary search method for each nano pixel point type structure to complete one round of iteration, if the calculated value of the first objective function converges, finishing optimization, otherwise, performing the next round of iteration.
The first objective function is: FOM (FOM) 1 ＝α 1 ×(1-T 1 -T 2 -…-T n )+β 1 ×(T 1 -T 2 |+|T 2 -T 3 |+…+|T N-1 -T N |+|T N -T 1 I), wherein alpha 1 And beta 1 As the weight coefficient, T N Indicating the transmissivity of the nth output waveguide.
When determining a material to be filled in a filling area of unfilled silicon dioxide according to a second objective function by adopting a second direct binary search method, filling silicon in the filling area in the nano pixel point type structure as a first state, and filling phase change material in the filling area in the nano pixel point type structure as a third state; randomly extracting a nano pixel point type structure with a filling area filled with silicon as a filling material, changing the nano pixel point type structure into a third state, performing FDTD simulation twice, enabling all phase change materials to be amorphous in the first FDTD simulation, enabling all phase change materials to be crystalline in the second FDTD simulation, calculating a second objective function, comparing a calculation result with a calculation result in an unchanged state, and if the calculation result is small, keeping the state of the nano pixel point type structure, otherwise, restoring the nano pixel point type structure to the original state; and (3) completing a second direct binary search method for each nano pixel point structure with the filling material not being silicon dioxide in each filling area to complete one round of iteration, if the calculated value of the second objective function is converged, finishing optimization, otherwise, performing the next round of iteration.
The second objective function is:
Figure BDA0004119322690000031
wherein alpha is 2 And beta 2 As the weight coefficient, T N-a Indicating the transmissivity of the Nth output waveguide when all phase change materials are amorphous, T N-c Indicating the transmissivity of the nth output waveguide when all phase change materials are crystalline, N 1 :n 2 :…:n N The split ratio for N output waveguides.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects: the invention combines the phase change material GSST with the 220nm SOI waveguide, provides a nonvolatile adjustable MMI power distributor, realizes on-chip switching of the splitting ratio through the refractive index difference of two states of the phase change material, and has practicability; the invention uses the pixel point structure of reverse design, has realized the MMI power divider with adjustable split ratio in the compact design area of 2.5 um by 2.5 um, the floor area is small, adopt the asymmetric structure at the same time, the input waveguide is placed on the edge of the device, facilitate the connection and expansion among the devices, facilitate the integration of the optical network; according to the invention, based on two-round direct binary search algorithm optimization, after a quality factor calculation formula is defined, the position of the SiO2 pixel point is determined firstly, and then the position of the GSST pixel point is determined, so that on-chip adjustment of any two light splitting ratios can be realized theoretically, and the method has a good application prospect; compared with the traditional on-chip adjustable device, the device has the advantages that the device does not need to continuously supply energy to maintain a certain state, the overall power consumption of the device is reduced based on the stability of the phase change material, and meanwhile, the influence of thermal crosstalk on the device is avoided.
Drawings
FIG. 1 is a schematic diagram of an asymmetric MMI power splitter in accordance with an embodiment of the invention;
FIG. 2 is a flowchart of an optimization process for performing a first-round DBS algorithm in an embodiment of the invention;
FIG. 3 is a block diagram of a device optimized by a first-round DBS algorithm in an embodiment of the invention;
FIG. 4 is a 1550nm TE mode field diagram of the device after first round optimization in an embodiment of the invention;
FIG. 5 is a flowchart of an optimization process of a secondary-round DBS algorithm of a device when a target crystalline state spectroscopic ratio is 1:1:2 in an embodiment of the invention;
FIG. 6 is a block diagram of a device with GSST being amorphous after optimization by a secondary DBS algorithm in an embodiment of the invention;
FIG. 7 is a graph of 1550nm TE mode field for a sub-round optimized GSST of the device in an amorphous state in an embodiment of the invention;
FIG. 8 is a block diagram of a device with GSST being crystalline after optimization by a secondary DBS algorithm in an embodiment of the invention;
FIG. 9 is a graph of 1550nm TE mode field for a sub-round optimized GSST of the device in crystalline state in an embodiment of the invention;
FIG. 10 is a process diagram of optimization of the secondary DBS algorithm for a device with a target crystalline state split ratio of 1:2:1;
FIG. 11 is a graph of the optimization process of the secondary DBS algorithm for a device with a target crystalline state splitting ratio of 2:1:2.
Detailed Description
The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. Further, it is understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
The embodiment of the invention relates to an asymmetric MMI power divider based on a phase change material, which is shown in figure 1 and comprises a silicon substrate, a silicon dioxide layer and a silicon waveguide layer which are arranged from bottom to top, wherein one side of the silicon waveguide layer is connected with a strip waveguide as input, and the other side of the silicon waveguide layer is connected with a plurality of strip waveguides as output; the silicon waveguide layer is divided into a plurality of nano pixel point type structures, filling areas are arranged in the nano pixel point type structures, and the material filled in each filling area is one of silicon, silicon dioxide and phase change materials.
The initial material structure of the device comprises a silicon substrate and SiO of 2 mu m from bottom to top 2 Layer, 220nm Si waveguide (design layer) and SiO on top 2 And (3) cladding. The area of the device design area is 2.5 μm by 2.5 μm, and the width of the input and output waveguides is 500nm. The design layer is divided into a plurality of nano pixel point matrixes, the size of each nano pixel point matrix is 100nm x 100nm, a cylindrical hole with the center diameter of 90nm and the height of 220nm of the nano pixel point matrix is used as a filling area, and three types of materials capable of being filled in the filling area are respectively: si, siO 2 Or a phase change material. The materials filled in the filling area can be arranged randomly, and the phase change material is combined with the 220nm SOI waveguide in the embodiment, so that the nonvolatile adjustable MMI power divider is provided, and the on-chip switching of the light splitting ratio is realized by utilizing the refractive index difference of the two states of the phase change material.
Taking the device of fig. 1 as an example, in order to make the spectral ratio of three waveguides at the output end adjustable from 1:1:1 to m:n:p, in determining the material filled in the filling area, the present embodiment may use two direct binary search methods, a first objective function and a second objective function to determine, and specifically design the following procedure:
step 1, determining the area of MMI design area and the position of input/output port. Considering that the optical network scene requires smaller area occupied by device expansion, an input waveguide is arranged at the edge of a multimode region, so that an asymmetric MMI structure is formed. The input light source is set as 1550nm TE mode light source, and the upper, middle and lower three are collectedTransmittance T of output port upper 、T mid 、T lower Determining a figure of merit FOM 1 The calculation mode of (namely, the first objective function) is as follows:
FOM 1 ＝α×(1-T upper -T mid -T lower )+β×(|T upper -T mid |+|T mid -T lower |+|T lower -T upper |)
the optimization objective is to obtain lower parasitic loss and ensure that the transmittance of each port is basically the same (1×3 optical power sharing is realized), and FOM in the process 1 The definition of (2) preferably ensures low loss, thus having the weight coefficient α=0.8, β=0.2;
and 2, equally dividing the multimode interference area (i.e. the design layer) of the device into a plurality of square pixel points (i.e. a nano pixel point matrix), wherein each pixel point only has a cylinder with a fixed center size as a design part, and independently selecting the used materials. First of all, siO is determined 2 Distribution of pixel points. Each pixel point has two states of 0 and 1, wherein 1 represents that the pixel point is not etched (the material is Si), and 0 represents that the pixel point is etched (the material is SiO of the cladding layer) 2 )；
Step 3, randomly extracting a pixel point to change the state (from 0 to 1 or from 1 to 0), performing FDTD simulation once, and calculating FOM 1 Comparing the result with the result before changing the state of the pixel point, if FOM 1 If the pixel point is smaller, a new state of the pixel point is reserved, otherwise, the pixel point is restored to the original state;
step 4, covering the operation of step 3 to each pixel point and operating each pixel point only once, wherein the process is an iteration round, if FOM is obtained after the iteration round 1 FOM is considered to be hardly reduced or has reached a desired level 1 Converging, finishing the first round of optimization, entering a step 5, adding a phase change material to realize nonvolatile adjustable spectral ratio, and if FOM 1 If not, returning to the step 3 to continue iteration; in this embodiment, the phase change material is Ge 2 Sb 2 Se 4 Te 1 。
Step 5, verifying whether the optimal structure obtained in the steps 1-4 can reach higher transmissivity or not, and the light splitting ratio between the output ports is 1:1:1.
and 6, performing a second round of DBS algorithm optimization. In the optimization process, only the pixel point with Si material is changed, and SiO 2 The pixel points are fixed. The pixel point optimized in the round has two states of 0 and 1, wherein 1 represents that the pixel point material is silicon, and 0 represents that the pixel point material is changed into a phase change material GSST;
step 7, the phase change material GSST has two stable states of amorphous (amorphlus) and crystalline (crystalline), so that two FDTD electromagnetic simulations are needed in each quality factor calculation process, and the transmittance of upper, middle and lower ports of MMI devices is respectively collected when all the phase change material GSST in the devices are in amorphous (a state) and crystalline (c state), FOM 2 (i.e., the second objective function) is defined as:
FOM 2 ＝α×(1-T upper-a -T mid-a -T lower-a )+β×(|n·T upper-c -m·T mid-c |+|p·T mid-c -n·T lower-c |+|m·T lower-c -p·T upper-c |)
wherein, the expected spectral ratio is m: n: p, FOM when the phase change material GSST of the device is crystalline 2 The device is composed of two parts of quality factors of an amorphous state and a crystalline state respectively, wherein the quality factor of the first part is the additional loss of the device in the amorphous state, and the quality factor of the second part is the difference between the transmittance of each output port and the expected spectral ratio in the crystalline state. Since the optimization of steps 2-4 has reduced the loss of the whole device, and the refractive index of a-GSST is basically the same as that of silicon, the light absorption capacity at 1550nm wave band is very weak, so the weight coefficient alpha of the amorphous quality factor in the total FOM is set to be 0.2; the core of the optimization is that the effect of c-GSST on the light absorption output by different ports meets the expected light splitting ratio, so beta is set to be 0.8;
step 8, after randomly extracting pixel points with Si as filling material and changing the material, performing FDTD simulation twice, wherein the first simulation makes all the phase change materials GSST in the device amorphous, the second simulation makes all the phase change materials GSST in the device crystalline, and FOM in step 7 2 The calculation method calculates the calculationComparing the result with the calculation result when the state is not changed, if the calculation result is smaller, retaining the state of the nano pixel point type structure, otherwise, recovering the nano pixel point type structure to the original state;
step 9, randomly executing the operation of step 8 to each non-SiO 2 Completes one round of iteration, if FOM 2 FOM is considered to be no longer reduced or has reached a desired level 2 Converging and finishing optimization; if FOM 2 If not, the operation of step 8 is continued.
Taking the target performance of crystalline state light splitting ratio 1:1:2 as an example, the target light splitting ratio of the first round design process of the embodiment is 1:1:1, and the results are as shown in fig. 2-4, and the normalized transmittance of the upper, middle and lower three output single-mode waveguides at 1550nm wavelength is respectively as follows: 0.3125, 0.3153, 0.3118, the device attach loss is about 0.27dB. Completing the first round of optimization and determining SiO 2 After pixel distribution, m: n: p=1:1:2 is substituted into the FOM 2 In the definition formula, the second round of DBS optimization is performed. The optimized quality factor is divided into an amorphous state and a crystalline state, and the spectral ratio under the crystalline state is greatly optimized while the amorphous loss of the device is not seriously influenced, and the optimization process is shown in figure 5. Final optimization results: when the GSST is amorphous, the normalized transmittance of the upper, middle and lower ports is 0.3117, 0.3206 and 0.3025 respectively, the spectral ratio is slightly deviated, but the additional loss is still at a lower level (0.29 dB); the normalized transmittance of the upper, middle and lower ports in the crystalline state is 0.1815, 0.1820 and 0.3634, respectively, and the ratio is basically 1:1:2. The pixel structure and the mode field diagram of the device in the amorphous state and the crystalline state are shown in fig. 6-9. In addition, this embodiment also provides other examples, in which the amorphous state spectral ratio is set to be 1:1:1, and devices with crystalline state spectral ratios of 1:2:1 and 2:1:2 are designed, and it can be found that after a certain number of pixel points are selected by the sub-round optimized DBS algorithm, the quality factor of the device is improved to a great extent.
It is easy to find that the combination of the phase change material GSST and the 220nm SOI waveguide provides a nonvolatile adjustable MMI power divider, and the on-chip switching of the light splitting ratio is realized through the refractive index difference of the two states of the phase change material, so that the power divider has practicability; the invention uses the pixel point structure of reverse design, has realized the MMI power divider with adjustable split ratio in the compact design area of 2.5 um by 2.5 um, the floor area is small, adopt the asymmetric structure at the same time, the input waveguide is placed on the edge of the device, facilitate the connection and expansion among the devices, facilitate the integration of the optical network; according to the invention, based on two-round direct binary search algorithm optimization, after a quality factor calculation formula is defined, the position of the SiO2 pixel point is determined firstly, and then the position of the GSST pixel point is determined, so that on-chip adjustment of any two light splitting ratios can be realized theoretically, and the method has a good application prospect; compared with the traditional on-chip adjustable device, the device has the advantages that the device does not need to continuously supply energy to maintain a certain state, the overall power consumption of the device is reduced based on the stability of the phase change material, and meanwhile, the influence of thermal crosstalk on the device is avoided.

Claims (10)

1. An asymmetric MMI power divider based on phase change materials comprises a silicon substrate, a silicon dioxide layer and a silicon waveguide layer which are arranged from bottom to top, and is characterized in that one side of the silicon waveguide layer is connected with one strip waveguide as input, and the other side of the silicon waveguide layer is connected with a plurality of strip waveguides as output; the silicon waveguide layer is divided into a plurality of nano pixel point type structures, filling areas are arranged in the nano pixel point type structures, and the material filled in each filling area is one of silicon, silicon dioxide and phase change materials.
2. The asymmetric MMI power divider based on phase change material of claim 1, wherein the nano-pixel dot structure is a square structure and the filling region is a center of the square structure and is circular.
3. The asymmetric MMI power divider based on phase change material according to claim 1, wherein the silicon waveguide is square with a side length of 2.5 μm.
4. The asymmetric MMI power splitter based on phase change material according to claim 1, characterized in that a strip waveguide as input is arranged at an edge position on one side of the silicon waveguide layer.
5. The asymmetric MMI power divider based on phase change material of claim 1, wherein the phase change material is Ge 2 Sb 2 Se 4 Te 1 。
6. The asymmetric MMI power divider based on phase change material according to claim 1, wherein the material filled in the filled region is determined by a two-time direct binary search method, a first objective function and a second objective function, in particular:
determining a filling area needing to be filled with silicon dioxide according to a first objective function by adopting a first direct binary search method; and determining the material to be filled in the filling area of the unfilled silicon dioxide according to a second objective function by adopting a second direct binary search method.
7. The asymmetric MMI power divider based on phase change material according to claim 7, wherein when determining a filling area to be filled with silicon dioxide according to a first objective function by using a first direct binary search method, filling silicon into the filling area in the nano-pixel dot-type structure is used as a first state, and filling silicon into the filling area in the nano-pixel dot-type structure is used as a second state; randomly extracting a nano pixel point type structure, changing the state of the nano pixel point type structure, performing FDTD simulation once, calculating a first objective function, comparing the calculation result with the calculation result when the state is unchanged, if the calculation result is smaller, retaining the state of the nano pixel point type structure, otherwise, recovering the nano pixel point type structure to the original state; and (3) completing a first direct binary search method for each nano pixel point type structure to complete one round of iteration, if the calculated value of the first objective function converges, finishing optimization, otherwise, performing the next round of iteration.
8. The asymmetric MMI power divider based on phase change material of claim 8Characterized in that the first objective function is: FOM (FOM) 1 ＝α 1 ×(1-T 1 -T 2 -…-T n )+β 1 ×(|T 1 -T 2 |+|T 2 -T 3 |+…+|T N-1 -T N |+|T N -T 1 I), wherein alpha 1 And beta 1 As the weight coefficient, T N Indicating the transmissivity of the nth output waveguide.
9. The asymmetric MMI power divider based on phase change material according to claim 7, wherein when determining the material to be filled in the filling area of the unfilled silicon dioxide according to the second objective function by using the second direct binary search method, filling the filling area in the nano-pixel dot-shaped structure with silicon is used as the first state, and filling the filling area in the nano-pixel dot-shaped structure with phase change material is used as the third state; randomly extracting a nano pixel point type structure with a filling area filled with silicon as a filling material, changing the nano pixel point type structure into a third state, performing FDTD simulation twice, enabling all phase change materials to be amorphous in the first FDTD simulation, enabling all phase change materials to be crystalline in the second FDTD simulation, calculating a second objective function, comparing a calculation result with a calculation result in an unchanged state, and if the calculation result is small, keeping the state of the nano pixel point type structure, otherwise, restoring the nano pixel point type structure to the original state; and (3) completing a second direct binary search method for each nano pixel point structure with the filling material not being silicon dioxide in each filling area to complete one round of iteration, if the calculated value of the second objective function is converged, finishing optimization, otherwise, performing the next round of iteration.
10. The phase change material based asymmetric MMI power divider of claim 9, wherein the second objective function is: FOM (FOM) 2 ＝α 2 ×(1-T 1-a -T 2-a -…-T N-a )+β 2 ×(|n 2 ·T 1-c -n 1 ·T 2-c |+|n 3 ·T 2-c -n 2 ·T 3-c |+…+|n N ·T N-1-c -n N-1 ·T N-c |+|n 1 ·T N-c -n N ·T 1-c I) wherein alpha 2 And beta 2 As the weight coefficient, T N-a Indicating the transmissivity of the Nth output waveguide when all phase change materials are amorphous, T N-c Indicating the transmissivity of the nth output waveguide when all phase change materials are crystalline, N 1 :n 2 :…:n N The split ratio for N output waveguides.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116774351A (en) * 2023-08-21 2023-09-19 之江实验室 Lithium niobate-based optical power distributor with arbitrary proportion and design method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116774351A (en) * 2023-08-21 2023-09-19 之江实验室 Lithium niobate-based optical power distributor with arbitrary proportion and design method

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