CN217561775U - Asymmetric directional coupler, controllable mode generator and optical circulator - Google Patents

Abstract

The utility model provides an asymmetric directional coupler, a controllable mode generator, and an optical circulator. The asymmetric directional coupler includes a substrate on which a top layer silicon is arranged, and the top layer silicon includes a first port, a coupling region, a first output waveguide and a second output waveguide, one end of the coupling region is connected to the first port, the other end is connected to the first output waveguide and the second output waveguide, the coupling region is covered with The phase change material layer, the coupling area is divided into N×M rectangular units, and by adjusting the state of the rectangular units, an aperiodic first punching array that satisfies a predetermined first output target is formed, and the first output target It refers to the sum of the transmittances of the first output waveguide and the second output waveguide; the asymmetric directional coupler provided by the utility model is small in size, easy to process, stable in performance, and can realize the regulation of the light propagation path.

Description

Asymmetric directional coupler, controllable mode generator and optical circulator

technical field

The utility model belongs to the technical field of micro-nano optoelectronic components, in particular to an asymmetric directional coupler, a controllable mode generator and an optical circulator.

Background technique

Due to the compatibility with existing complementary metal-oxide semiconductor (CMOS) technology and dense integration technology, silicon photonics is a very potential optical interconnect platform. Photonics integrated circuits (PICs) have also grown tremendously in the past decade.

Today, state-of-the-art photonic integrated circuits can integrate hundreds of optical devices. Among them, the optical switch is an essential component, which is used for the dynamic routing of light in different paths. On-chip optically tunable devices are usually implemented based on electro-optic or thermo-optic effects, both of which use electricity or heat to act on the waveguide to slightly change the refractive index of the waveguide to switch the optical transmission channel, that is, the switching effect. . However, this optical switch mechanism is volatile and requires continuous energy to maintain the state of the switch, and the optical switch designed by this mechanism is complicated in process and large in size, so it is not suitable for large-scale integration.

In order to expand the data capacity, Mode Division Multiplexing (MDM) technology has been widely concerned. Among them, the mode generator must be an indispensable component, which can excite and switch the different modes of the carrier in the optical waveguide. In addition, an optical isolator and an optical circulator are non-reciprocal devices that allow light to propagate in one direction. Among them, an opto-isolator is a two-port device, a one-way street for light that plays a vital role in preventing unwanted back reflections and light interactions. Similarly, an optical circulator is a multi-port device, a detour of the optical path, with light being routed at each input port to an output port in a non-reciprocal manner. They are all indispensable components in the optical network. Although mode generators and optical circulators have been reported, most of them have shortcomings such as uncontrollable, large size and complicated design methods.

In recent years, germanium-antimony-tellurium compound optical phase change materials, such as Ge ₂ Sb ₂ Te ₅ (GST) and Ge ₂ Sb ₂ Se ₄ Te ₁ (GSST), integrated on silicon waveguides have demonstrated the feasibility of designing tunable devices . Different from the electro-optic or thermo-optic effect that uses electricity or heat to act on the waveguide to slightly change the refractive index, the germanium-antimony-tellurium compound can not only greatly change the refractive index of the waveguide, which is conducive to the design of small-sized optical control devices, but also Phase transitions are nonvolatile and do not require constant external energy to maintain their state. It can be seen that the realization of tunable devices based on phase change materials is a very potential solution.

In view of this, designing a tunable mode generator and circulator based on phase change materials is of great significance for solving the problems of uncontrollable and large size of existing devices.

Utility model content

The technical problem to be solved by the utility model is to overcome the shortcomings of the existing optical switches such as volatility and large size, and to provide a silicon-based asymmetric directional coupler based on phase change materials.

In order to achieve the above purpose, the technical solution of the present invention is as follows. An asymmetric directional coupler includes a substrate on which a top layer of silicon is provided, and the top layer of silicon includes a first port, a coupling region, and a first output. a waveguide and a second output waveguide, one end of the coupling region is connected to the first port, and the other end is connected to the first output waveguide and the second output waveguide, the coupling region is covered with a phase change material layer, and the coupling region is divided into N×M rectangular units, by adjusting the state of the rectangular units, an aperiodic first punching array that satisfies a predetermined first output target is formed, and the first output target refers to the first output waveguide and the second output The sum of the transmittances of the waveguides.

Preferably, the coupling region includes an upper waveguide, a waveguide gap and a lower waveguide, the first port, the upper waveguide and the first output waveguide are connected in sequence, the lower waveguide is connected to the second output waveguide, and the phase change material layer Covered on the top surface of the lower waveguide, a waveguide gap is set between the upper waveguide and the lower waveguide.

Preferably, the phase change material layer is a GSST material.

Preferably, at least one of the first output waveguide and the second output waveguide is a curved waveguide.

Preferably, the thickness of the substrate is 3 μm, the thickness of the top layer silicon is 220 nm, the length of the coupling region is 10 μm, the width of the upper waveguide is 380 nm, and the upper waveguide is divided into 4×100 first rectangular units, The size of each first rectangular unit is 95nm×100nm, the depth is 220nm, and the initial state is no punching; the widths of the lower waveguide and the phase change material layer are both 350nm, the thickness of the phase change material layer is 40nm, and the phase change material layer is 40nm thick. The variable material layer is divided into 4×100 second rectangular units, each second rectangular unit has a size of 87.5nm×100nm, a depth of 40nm, and the initial state is no punching; the waveguide spacing is divided into 2×100 The third rectangular unit, the size of each third rectangular unit is 100 nm×100 nm, the depth is 220 nm, and the initial state is punching.

The present invention also provides a controllable mode generator, comprising the above-mentioned asymmetric directional coupler, a mode division multiplexer optimization region and a third output waveguide, one end of the mode division multiplexer optimization region is respectively connected with the first The output waveguide is connected to the second output waveguide, and the other end is connected to the third output waveguide. The mode division multiplexer optimization area is divided into X×Y fourth rectangular units. By adjusting the state of the fourth rectangular unit, An aperiodic second perforated array that satisfies a predetermined second output target is formed, and the second output target refers to the sum of the transmittances of the two output different modes in the third output waveguide.

Preferably, the width of the third output waveguide is 900 nm, and the two different modes are the TE ₀ mode in the band from 1540 nm to 1560 nm and the TE ₁ mode in the band from 1540 nm to 1560 nm.

Preferably, the size of the optimized area is 2400 nm×3000 nm, the optimized area of the mode division multiplexer is divided into 24×30 fourth rectangular units of 100 nm×100 nm, and the first output waveguide and the second output waveguide are combined with the mode division multiplexer. The spacing between the terminals in the user-optimized region is 1635 nm.

The present invention also provides an optical circulator, comprising the above-mentioned asymmetric directional coupler, a plurality of asymmetric directional couplers in a ring-shaped array, and the first output waveguide of one of the asymmetric directional couplers is connected to an adjacent asymmetric directional coupler. The second output waveguide of the directional coupler is connected.

Preferably, the ring light mode is a TE ₀ mode in the band from 1540 nm to 1560 nm.

The beneficial effect of the utility model is that the product is small in size, easy to process, stable in performance, can realize low-loss transmission, and solves the problems of uncontrollable, large size and complicated design method of the existing optical switch.

Description of drawings

FIG. 1 is a schematic structural diagram of an asymmetric directional coupler provided by an embodiment of the present invention.

FIG. 2 is a schematic diagram of the initial structure of the embodiment shown in FIG. 1 .

FIG. 3 is a parameter sweep result of the embodiment shown in FIG. 1 .

FIG. 4 is a schematic diagram of a two-dimensional plane structure of the embodiment shown in FIG. 1 .

FIG. 5 is a transmission spectrum of the embodiment shown in FIG. 1 .

FIG. 6 is a schematic structural diagram of a controllable pattern generator according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of a two-dimensional planar structure of the embodiment shown in FIG. 6 .

FIG. 8 is a schematic diagram of the initial structure of the optimization area of the modulo division multiplexer according to the embodiment shown in FIG. 6 .

FIG. 9 is a transmission spectrum of the embodiment shown in FIG. 6 .

FIG. 10 is a schematic structural diagram of an optical circulator provided by an embodiment of the present invention.

FIG. 11 is a schematic diagram of a two-dimensional planar structure of the embodiment shown in FIG. 10 .

FIG. 12 is a transmission spectrum of the embodiment shown in FIG. 10 .

In the figure, 1, the first port; 2, the coupling region; 21, the upper waveguide; 22, the lower waveguide; 221, the second rectangular unit; 23, the waveguide gap; 231, the third rectangular unit; 24, the phase change material layer 3. The first output waveguide; 4. The second output waveguide; 5. The mode division multiplexer optimization area; 51. The fourth rectangular unit; ; 9, the fourth port; 10, the fifth port; 11, the first asymmetric directional coupler; 12, the second asymmetric directional coupler; 13, the third asymmetric directional coupler; 14, the fourth asymmetric directional coupler coupler; 15, first curved waveguide; 16, second curved waveguide; 17, third curved waveguide; 18, fourth curved waveguide.

Detailed ways

Below in conjunction with the accompanying drawings and specific embodiments, the technical scheme of the present utility model is further described in detail:

Example 1

Please refer to FIGS. 1-5 together. The asymmetric directional coupler provided by the present invention includes a substrate 100 . The substrate 100 is provided with a top layer of silicon. The top layer of silicon includes a first port 1 , a coupling region 2 , For the first output waveguide 3 and the second output waveguide 4, one end of the coupling region 2 is connected to the first port 1, and the other end is connected to the first output waveguide 3 and the second output waveguide 4, and the coupling region 2 is covered with The phase change material layer 24 and the coupling region 2 are divided into N×M rectangular units. By adjusting the states of the rectangular units, an aperiodic first punching array that satisfies a predetermined first output target is formed. The output target refers to the sum of the transmittances of the first output waveguide 3 and the second output waveguide 4 .

More specifically, the coupling region 2 includes an upper waveguide 21, a lower waveguide 22 and a waveguide gap 23. The first port 1, the upper waveguide 21 and the first output waveguide 3 are connected in sequence and keep the same width. 22 is connected to the second output waveguide 4 with the same width, a waveguide gap 23 is formed between the upper waveguide 21 and the lower waveguide 22 , and the phase change material layer 24 covers the top surface of the lower waveguide 22 .

More specifically, the phase change material layer 24 is a GSST material.

More specifically, at least one of the first output waveguide 3 and the second output waveguide 4 is a curved waveguide for the purpose of decoupling and reducing crosstalk.

More specifically, the asymmetric directional coupler is designed on a silicon-on-insulator (SOI) platform, the thickness of the top layer of silicon is 220 nm, the thickness of the silicon dioxide of the substrate 100 is 3 μm, the upper cladding layer is air, and the coupling region is The length W ₄ of 2 is 10 μm, the width W ₁ of the upper waveguide 21 is 380 nm, the upper waveguide 21 is divided into 4×100 first rectangular units, the size of each first rectangular unit is 95 nm×100 nm, and the depth is 220nm, the initial state is no perforation; the width W2 of the lower waveguide 22 and the phase change material layer ₂₄ are both 350nm, the thickness of the phase change material layer 24 is 40nm, and the phase change material layer 24 is divided into 4×100 The second rectangular unit 221, the size of each second rectangular unit 221 is 87.5 nm×100 nm, the depth is 40 nm, and the initial state is no punching; the width W ₃ of the waveguide gap 23 is 200 nm, and the waveguide gap 23 is divided into 2×100 third rectangular units 231 , each third rectangular unit 231 has a size of 100 nm×100 nm, a depth of 220 nm, and an initial state of punched holes.

Compared with traditional methods, the use of intelligent algorithms to design optical devices can rely less on physical models for optimization under high degrees of freedom, and is more conducive to the design of small-sized and complex-structured devices. Before using the direct binary search algorithm to optimize, the coupling area 2 is divided into several rectangular units, each rectangular unit has two material states, namely punching and non-punching. Punching means that the rectangular unit is filled with air and not punched. The holes, ie rectangular cells, are filled with silicon. The state of each rectangular unit is determined by the algorithm to satisfy the objective function, specifically: setting the objective function reflecting the device performance in the direct binary search algorithm, and then using the algorithm to calculate the objective function values of the two states of each rectangular unit in turn, Then keep the state when the objective function value is improved.

When computing rectangular cells using the direct binary search algorithm, compute all cells alternately between row-wise and column-wise computations. All units traversed once is called one iteration. After multiple iterations, compared with the objective function value after the previous iteration, if the change value of the two objective function values is less than 0.1%, the objective function converges and the algorithm stops. The calculation by row refers to sequentially from left to right in the horizontal direction, and from top to bottom in the vertical direction; the calculation by column refers to from top to bottom in the vertical direction, and from left to right in the horizontal direction.

In the present invention, the phase-change material layer 24 on the asymmetric directional coupler is rapidly reversibly transformed by light or electricity, which affects the refractive index of the waveguide and realizes the regulation of the propagation path of light. Therefore, before completing the device of the present invention, an asymmetric directional coupler needs to be designed. When optimizing the asymmetric directional coupler, the objective function reflecting the performance of the device is set as the sum of the transmittances of the two output waveguides.

Since the direct binary search algorithm is a search algorithm, it is prone to premature local convergence, resulting in unsatisfactory optimization results. In order to overcome this problem, when optimizing the asymmetric directional coupler, the initial structure as shown in Fig. 2 is manually set, that is, the initial state of all the first rectangular elements on the upper waveguide 21 is no perforation, and the lower waveguide 22 is not perforated, The initial state of all the third rectangular units 231 on the waveguide gap 23 is punching, and the initial state of all the second rectangular units 221 on the phase change material layer 24 is no punching. In order to obtain excellent initial structure parameters, it is necessary to optimize the parameters of the initial structure.

First, constrain some parameters. The width of the waveguide gap 23 is set to W ₃ is set to 200 nm, and the coupling length W ₄ is set to 10 μm. The width of the phase change material layer 24 covering the surface of the lower waveguide 22 is consistent with the width of the lower waveguide 22. The thickness is 40nm. Under the condition of determining these parameters, the width parameter W 1 of the upper waveguide 21 and the width parameter W ₂ of the lower waveguide ₂₂ are scanned, and an initial structure with better performance is optimized. The parameter scanning result is shown in FIG. 3 , it can be found that when the width W ₁ of the upper waveguide 21 is about 380 nm, and the width W ₂ of the lower waveguide 22 is about 350 nm, the GSST of the phase change material layer 24 is adjusted to be amorphous. Matching, the light is better coupled into the lower waveguide 22 ; the GSST of the phase change material layer 24 is adjusted to be in a crystalline state, due to the phase mismatch, the coupling efficiency is poor, and the light still propagates in the upper waveguide 21 . Considering trade-offs, the width W ₁ of the upper waveguide 21 is finally selected to be 380 nm, the width W ₂ of the lower waveguide 22 is 350 nm, and the width of the phase change material layer 24 on the surface of the lower waveguide 22 is also 350 nm.

In addition, since the coupling effect will occur in the upper and lower waveguides, the distance between the two waveguides needs to be enlarged at the output position to suppress the coupling effect and not affect the propagation of light in the waveguide. Therefore, at least one of the output parts connected by the upper and lower waveguides needs to be designed as a curved waveguide, that is, at least one of the first output waveguide 3 and the second output waveguide 4 is a curved waveguide. a curved waveguide.

After obtaining the artificially designed initial structure, it is necessary to divide the coupling area 2 into N×M rectangular units, where N and M are integers, and the setting of the rectangular side length also needs to consider the machinability. To this end, the coupling region 2 is divided into three parts, a total of 10×100 rectangular units, including 4×100 first rectangular units in the upper waveguide 21 part and 4×100 second rectangular units in the phase change material layer 24 part. 2×100 third rectangular cells 231 of the cell 221 and the waveguide gap 23 part. Each rectangular unit has two material states, namely perforated and non-perforated. Perforated means that the rectangular unit is filled with air, and without perforation, the rectangular unit is filled with silicon.

The upper waveguide 21 is divided into 4×100 rectangular units, the size of each first rectangular unit is 95 nm×100 nm, the depth is 220 nm, and the initial state is no punching; because the utility model is to pass a 40 nm thick phase change material layer 24 changes the effective refractive index to achieve the adjustment effect, so the lower waveguide 22 is not divided into rectangular units and does not punch holes; the phase change material layer 24 is divided into 4×100 second rectangular units 221, the size of each second rectangular unit 221 It is 87.5nm×100nm, the depth is 40nm, only the phase change material layer 24 is penetrated, and the initial state is no punching; the waveguide gap 23 is divided into 2×100 third rectangular units 231, and each third rectangular unit 231 has The size is 100 nm × 100 nm, the depth is 220 nm, and the initial state is punched.

The direct binary search algorithm optimizes a total of 10 × 100 rectangular cells on the initial structure. First, the algorithm selects the rectangular cells in the first row and the first column, and uses the Finite difference time domain method (FDTD) to calculate the performance of the two states with and without holes, respectively. The performance judgment is determined by the objective function set inside the algorithm, which is called Figure of Merit (FOM), which is defined as:

FOM=T _A-GSST +T _C-GSST

In the formula, T _A-GSST is the transmittance of the second output waveguide 4 in the wavelength range from 1540nm to 1560nm when the GSST material is amorphous; T _C-GSST is in the wavelength range from 1540nm to 1560nm, when the GSST material is crystalline the transmittance of the first output waveguide 3 in the state.

It then scans row by row to the last rectangular cell, which is called an iteration. The next iteration scans the last rectangular cell by column in the same manner. Alternately scan and optimize by row and column, and iterate multiple times until the FOM value changes within 0.1% after two iterations, the algorithm converges, and the device performance is stable. The calculation by row refers to sequentially from left to right in the horizontal direction, and from top to bottom in the vertical direction; the calculation by column refers to from top to bottom in the vertical direction, and from left to right in the horizontal direction.

Figure 4 is a schematic diagram of the two-dimensional planar structure of the asymmetric directional coupler after optimization using the direct binary search algorithm, and Figure 5 is the transmitted light spectrum of the asymmetric directional coupler. In the bandwidth range of 1540nm to 1560nm, when GSST is amorphous , the crosstalk of the TE ₀ mode in the first output waveguide 3 is lower than -16.4dB, and the insertion loss in the second output waveguide 4 is less than 0.6dB; when the GSST is crystalline, the TE ₀ mode is inserted into the first output waveguide 3 The loss is less than 1.0dB, and the crosstalk in the second output waveguide 4 is less than -16.0dB;

The specific working principle is as follows: TE ₀ mode light with a bandwidth of 1540nm to 1560nm is injected into the first port 1, and the phase transition of the GSST is regulated by light or electricity. When the GSST is amorphous, the input light is efficiently transmitted from the second output waveguide 4. and the crosstalk in the first output waveguide 3 is very low; when the GSST is in a crystalline state, the input light is transmitted through the first output waveguide 3 with high efficiency, and the crosstalk in the second output waveguide 4 is very low. The simulated transmission spectrum of the asymmetric directional coupler provided in this embodiment also shows its excellent performance. Compared with optical switches designed by other methods, it has the advantages of good performance, small size, and easy processing.

Embodiment 2

Please refer to FIGS. 6-9 together. This embodiment provides a controllable mode generator, including the above-mentioned asymmetric directional coupler, a mode division multiplexer optimization region 5 and a third output waveguide 6. The mode division multiplexer One end of the user optimization area 5 is respectively connected with the first output waveguide 3 and the second output waveguide 4, and the other end is connected with the third output waveguide 6, and the mode division multiplexer optimization area 5 is divided into X×Yth Four rectangular units 51 , by adjusting the state of the fourth rectangular unit 51 , an aperiodic second punching array that satisfies a predetermined second output target is formed, and the second output target refers to two of the third output waveguide 6 The sum of transmittances of different modes is output.

More specifically, the two different modes are the TE ₀ mode in the band from 1540 nm to 1560 nm and the TE ₁ mode in the band from 1540 nm to 1560 nm, and the width of the third output waveguide 6 is 900 nm.

More specifically, the size of the mode division multiplexer optimization area 5 is 2400nm×3000nm, and the mode division multiplexer optimization area 5 is divided into 24×30 fourth rectangular units 51 of 100nm×100nm. The distance W ₅ between the output waveguide 3 and the second output waveguide 4 and the connection ends of the mode division multiplexer optimization region 5 is 1635 nm.

In this embodiment, both the first output waveguide 3 and the second output waveguide 4 are curved waveguides.

The optimization area 5 of the mode division multiplexer is also designed by the direct binary search algorithm. Figure 8 shows the initial structure of the optimization area 5 of the mode division multiplexer. ×30 fourth rectangular units 51 of 100 nm×100 nm, each fourth rectangular unit 51 has two material states, namely punched and non-punched, punched, that is, the fourth rectangular unit 51 is filled with air and not punched That is, the fourth rectangular unit 51 is filled with silicon. The direct binary search algorithm optimizes a total of 24 × 30 rectangular cells on the initial structure. The performance is determined by the objective function set inside the algorithm, which is defined as:

为在波段为1540nm到1560nm，TE₀模式从第一输出波导3注入，维持TE₀模式在第三输出波导6的透过率；

为在波段为1540nm到1560nm，TE₀模式从第二输出波导 4注入转化为TE₁模式在第三输出波导6的透过率。输出波导宽度为900nm，可以无损耗的支持TE₀和TE₁模式的传播。In the formula,

In order to inject the TE ₀ mode from the first output waveguide 3 in the wavelength range from 1540 nm to 1560 nm, the transmittance of the TE ₀ mode in the third output waveguide 6 is maintained;

In order to convert the TE ₀ mode from the second output waveguide 4 into the transmittance of the TE ₁ mode in the third output waveguide 6 in the wavelength band of 1540 nm to 1560 nm. The output waveguide width is 900nm, which can support the propagation of TE ₀ and TE ₁ modes without loss.

The working principle of the mode generator is to generate different modes of light by adjusting the GSST phase transition on the asymmetric directional coupler. The details are as follows: when the TE ₀ mode light source is injected from the first port 1, the GSST is adjusted to the crystalline state, the TE ₀ mode passes through the asymmetric directional coupler, and enters the mode division multiplexer optimization area 5 from the first output waveguide 3, maintaining TE ₀ The mode is output from the third output waveguide 6; when the TE ₀ mode light source is injected from the first port 1, the GSST is adjusted to be amorphous, and the TE ₀ mode passes through the asymmetric directional coupler and enters the mode division multiplexer from the second output waveguide 4 In the optimized region 5 , the TE ₀ mode is converted into the TE ₁ mode and output from the third output waveguide 6 .

FIG. 9 is the transmission spectrum of the mode generator provided in this embodiment. When the GSST is in the crystalline state, the mode generator outputs the TE ₀ mode, the insertion loss is less than 1.5dB, and the crosstalk is less than -13.9dB; when the GSST is in the amorphous state , the pattern generator outputs a TE ₁ pattern with an insertion loss of less than 2.2dB and a crosstalk of less than -14.8dB. The pattern generator provided by this embodiment can solve the problems that the existing pattern generator is uncontrollable, large in size, and complicated in design method.

Embodiment 3

Please refer to FIGS. 10-12 together, the present invention also provides an optical circulator, including the above-mentioned asymmetric directional coupler. An output waveguide 3 is connected to the second output waveguide 4 of the adjacent asymmetric directional coupler.

In this embodiment, the first output waveguide 3 is connected with the second output waveguide 4 to form a curved waveguide, and the optical circulator is composed of four asymmetric directional couplers 11-14 passing through the first curved waveguide 15 and the second curved waveguide 16 respectively. The third curved waveguide 17 and the fourth curved waveguide 18 are connected in series in sequence, and both ends of each curved waveguide have the same width as the connecting portion respectively.

It can be understood that, according to different usage requirements, the optical circulator may be formed of three, four, five or more asymmetric directional couplers in series, and the number of curved waveguides can be increased or decreased accordingly.

The working principle of the optical circulator is that by adjusting the GSST phase transition on the asymmetric directional coupler, the TE ₀ mode light source is output from the adjacent port clockwise or counterclockwise. The details are as follows: when the TE ₀ mode light source is injected from the second port 7, the GSST on the first asymmetric directional coupler 11 is in a crystalline state, the second asymmetric directional coupler 12, the third asymmetric directional coupler 13 and the fourth asymmetric directional coupler 13. The GSST on the symmetric directional coupler 14 is amorphous, and the TE ₀ mode is output from the third port ₈ in the clockwise direction, and so on. 9-the fifth port 10-the direction of the second port 7 propagates clockwise; when the TE ₀ mode light source is injected from the second port 7, the GSST on the first asymmetric directional coupler 11 is amorphous, and the second asymmetric directional The GSST on the coupler 12, the third asymmetric directional coupler 13 and the fourth asymmetric directional coupler 14 is in a crystalline state, and the TE ₀ mode is output from the fifth port ₁₀ in the counterclockwise direction, and so on. The direction of the second port 7 - the fifth port 10 - the fourth port 9 - the third port 8 - the second port 7 is circulated counterclockwise.

12 is the transmission spectrum of the optical circulator provided in this embodiment, when the TE ₀ mode is injected into the second port 7, the GSST layer on the first asymmetric directional coupler 11 is crystalline, and the GSST layers at other ports are amorphous , TE ₀ mode light propagates clockwise in the direction of the second port 7 - the third port 8 - the fourth port 9 - the fifth port 10 - the second port 7, the insertion loss is less than 1.2dB, and the crosstalk is less than -20.0dB ; When the TE ₀ mode is injected into the second port 7, the GSST layer on the first asymmetric directional coupler 11 is amorphous, and when the GSST layer of the other ports is crystalline, the TE ₀ mode light presses the second port 7-fifth The direction of port 10 - fourth port 9 - third port 8 - second port 7 propagates counterclockwise, the insertion loss is less than 1.2dB, and the crosstalk is less than -29.4dB. Compared with devices designed by other methods, the optical circulator provided in this embodiment has the advantages of controllability, small size, and intelligent design.

The above embodiments are only used to illustrate the technical solutions of the present utility model, but not to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be used for the foregoing implementations. The technical solutions described in the examples are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (8)

1. An asymmetric directional coupler, characterized by: the phase change material layer covers the top surface of the lower waveguide, and a waveguide gap is formed between the upper waveguide and the lower waveguide.

2. The asymmetric directional coupler as recited in claim 1, wherein: the phase change material layer is a GSST material.

3. The asymmetric directional coupler as recited in claim 1 or 2, wherein: at least one of the first output waveguide and the second output waveguide is a curved waveguide.

4. The asymmetric directional coupler as recited in claim 3, wherein: the thickness of the substrate is 3 microns, the thickness of the top layer silicon is 220nm, the length of the coupling region is 10 microns, the width of the upper waveguide is 380nm, the upper waveguide is divided into 4 x 100 first rectangular units, the size of each first rectangular unit is 95nm x 100nm, the depth of each first rectangular unit is 220nm, and no hole is drilled in the initial state; the widths of the lower waveguide and the phase change material layer are 350nm, the thickness of the phase change material layer is 40nm, the phase change material layer is divided into 4 x 100 second rectangular units, the size of each second rectangular unit is 87.5nm x 100nm, the depth of each second rectangular unit is 40nm, and holes are not punched in the initial state; the waveguide pitch is divided into 2 × 100 third rectangular units, each of which has a size of 100nm × 100nm, a depth of 220nm, and is initially perforated.

5. An adjustable mode generator, comprising: the asymmetric directional coupler of any one of claims 1-4, a mode division multiplexer optimization area and a third output waveguide, wherein one end of the mode division multiplexer optimization area is connected to the first output waveguide and the second output waveguide respectively, and the other end of the mode division multiplexer optimization area is connected to the third output waveguide, the mode division multiplexer optimization area is divided into X X Y fourth rectangular units, and a non-periodic second puncturing array meeting a predetermined second output target is formed by adjusting the states of the fourth rectangular units, and the second output target is the sum of transmittances of two output different modes in the third output waveguide.

6. The controllable mode generator of claim 5, wherein: the two different modes are TE wave bands from 1540nm to 1560nm ₀ Mode sum TE from 1540nm to 1560nm ₁ Mode, the width of the third output waveguide is 900nm.

7. The controllable mode generator of claim 5, wherein: the size of the mode division multiplexer optimization area is 2400nm multiplied by 3000nm, the mode division multiplexer optimization area is divided into 24 multiplied by 30 fourth rectangular units with the size of 100nm multiplied by 100nm, and the distance between the connection ends of the first output waveguide and the second output waveguide and the mode division multiplexer optimization area is 1635nm.

8. An optical circulator, comprising: comprising an asymmetric directional coupler according to any one of claims 1 to 4, a plurality of asymmetric directional couplers in a ring array, the first output waveguide of one of said asymmetric directional couplers being connected to the second output waveguide of an adjacent asymmetric directional coupler.

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