CN217561775U - Asymmetric directional coupler, adjustable mode generator and optical circulator - Google Patents
Asymmetric directional coupler, adjustable mode generator and optical circulator Download PDFInfo
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Abstract
The utility model provides an asymmetric directional coupler and can regulate and control mode generator, optical circulator, asymmetric directional coupler, including the substrate, be equipped with top silicon on the substrate, top silicon includes first port, coupling region, first output waveguide and second output waveguide, the regional one end of coupling is connected with first port, and the other end is connected with first output waveguide and second output waveguide, the coupling region coats and is stamped the phase change material layer, and the coupling region is divided into N M rectangle unit, through adjusting the state of rectangle unit, forms a first aperiodicity array that punches that satisfies predetermined first output target, first output target means the transmittance sum of first output waveguide and second output waveguide; the utility model provides an asymmetric directional coupler size is little and workable, and the regulation and control of light propagation path can be realized to the stable performance.
Description
Technical Field
The utility model belongs to the technical field of receive photoelectron components and parts a little, specifically relate to an asymmetric directional coupler and can regulate and control mode generator, optical circulator.
Background
Silicon photonics is a very promising optical interconnect platform due to its compatibility with existing Complementary metal-oxide semiconductor (CMOS) technologies and dense integration technologies. Photonic Integrated Circuits (PICs) have also grown enormously over the past decade.
Today, the most advanced photonic integrated circuits have been able to integrate hundreds or thousands of optical devices. Among them, the optical switch is an indispensable constituent element for dynamic routing of light in different paths. The on-chip optically controllable devices are usually implemented based on electro-optical or thermo-optical effects, both of which are implemented by using electricity or heat to act on the waveguide, thereby slightly changing the refractive index of the waveguide to implement the switching, i.e. switching, of the optical transmission channel. However, the optical switch mechanism is volatile, requires continuous energy to maintain the switch state, and the optical switch designed by the mechanism has complex process and large size, and is not suitable for large-scale integration.
In order to expand data capacity, mode Division Multiplexing (MDM) technology is widely focused. The mode generator is, among other things, an indispensable component that excites and switches different modes of the carrier wave in the optical waveguide. Further, an Optical isolator (Optical isolator) and an Optical circulator (Optical circulator) are non-reciprocal devices that can make light propagate in one direction. Among them, the optical isolator is a dual port device, a single line of light, and plays a vital role in preventing unnecessary back reflection and interaction of light. Similarly, an optical circulator is a multi-port device, which is a roundabout of optical paths, where light is routed in a non-reciprocal manner at each input port to an output port. They are all indispensable components of optical networks. Although pattern generators and optical circulators have been reported, most of them have the disadvantages of being uncontrollable, large in size, and complicated in design method.
In recent years, germanium antimony tellurium compound optical phase change materials, such as Ge, integrated on silicon waveguides 2 Sb 2 Te 5 (GST) and Ge 2 Sb 2 Se 4 Te 1 (GSST), demonstrating the feasibility of designing a tunable device. Unlike the electro-optic or thermo-optic effect in which electricity or heat acts on a waveguide to minutely change the refractive index, the germanium antimony tellurium compound not only can greatly change the refractive index of the waveguide and is beneficial to designing a small-sized optical control device, but also the phase change is nonvolatile and does not need external continuous energy to maintain the state of the optical control device. It can be seen that implementing a controllable device based on phase change materials is a very promising approach.
In view of this, the design of the adjustable mode generator and the circulator based on the phase-change material has great significance for solving the problems that the existing device is not adjustable and has larger size.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is to overcome that the current optics switch of needle is volatile, the size is great etc. is not enough, provides a silica-based asymmetric directional coupler based on phase change material.
In order to achieve the above object, according to the technical solution of the present invention, an asymmetric directional coupler includes a substrate, a top silicon is disposed on the substrate, the top 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 a phase change material layer, the coupling region is divided into N × M rectangular units, and an aperiodic first perforation array satisfying a predetermined first output target is formed by adjusting states of the rectangular units, where the first output target is a sum of transmittances of the first output waveguide and the second output waveguide.
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 sequentially connected, the lower waveguide is connected with the second output waveguide, the phase change material layer covers the top surface of the lower waveguide, and the waveguide gap is formed 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 substrate thickness is 3 μm, the top silicon thickness is 220nm, the coupling region length is 10 μm, the upper waveguide width is 380nm, the upper waveguide is divided into 4 × 100 first rectangular units, each first rectangular unit has a size of 95nm × 100nm and a depth of 220nm, and no hole is formed 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.
The utility model provides a mode generator can be regulated and control, including foretell asymmetric directional coupler, mode division multiplexer optimization area and third output waveguide, the one end in mode division multiplexer optimization area is connected with first output waveguide and second output waveguide respectively, and the other end is connected with third output waveguide, mode division multiplexer optimization area is divided into X Y fourth rectangle unit, through the adjustment the state of fourth rectangle unit forms a non-periodic second that satisfies predetermined second output object and punches the array, second output object means the sum of the transmittance of two different modes of output in the third output waveguide.
Preferably, the width of the third output waveguide is 900nm, and the two different modes are TE bands from 1540nm to 1560nm 0 Mode and TE band from 1540nm to 1560nm 1 Mode(s).
Preferably, the size of the optimized area is 2400nm × 3000nm, the mode division multiplexer optimized area is divided into 24 × 30 fourth rectangular units with the size of 100nm × 100nm, and the distance between the connection ends of the first output waveguide and the second output waveguide and the mode division multiplexer optimized area is 1635nm.
The utility model also provides an optical circulator, including foretell asymmetric directional coupler, a plurality of asymmetric directional couplers are annular array, one asymmetric directional coupler's first output waveguide is connected with adjacent asymmetric directional coupler's second output waveguide.
Preferably, the ring-shaped optical mode is TE wave band from 1540nm to 1560nm 0 Mode(s).
The beneficial effects of the utility model are that, the product size is little and workable, and the stable performance can realize low-loss transmission, has solved the problem that current optical switch can not regulate and control, the size is great, the design method is complicated.
Drawings
Fig. 1 is a schematic structural diagram of an asymmetric directional coupler according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an initial structure of the embodiment shown in fig. 1.
FIG. 3 shows the parameter scanning 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 an adjustable mode generator according to an embodiment of the present invention.
Fig. 7 is a schematic diagram of a two-dimensional plane structure of the embodiment shown in fig. 6.
Fig. 8 is a schematic diagram of an initial structure of the optimization area of the mode division multiplexer in 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 according to an embodiment of the present invention.
Fig. 11 is a schematic diagram of a two-dimensional plane 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. a coupling region; 21. an upper waveguide; 22. a lower waveguide; 221. a second rectangular unit; 23. A waveguide gap; 231. a third rectangular unit; 24. a phase change material layer; 3. a first output waveguide; 4. a second output waveguide; 5. A mode division multiplexer optimization area; 51. a fourth rectangular unit; 6. a third output waveguide; 7. a second port; 8. a third port; 9. A fourth port; 10. a fifth port; 11. a first asymmetric directional coupler; 12. a second asymmetric directional coupler; 13. a third asymmetric directional coupler; 14. a fourth asymmetric directional coupler; 15. a first curved waveguide; 16. a second curved waveguide; 17. a third curved waveguide; 18. and a fourth curved waveguide.
Detailed Description
The technical scheme of the present invention is further specifically described below with reference to the accompanying drawings and specific embodiments:
example one
Referring to fig. 1-5, the present invention provides an asymmetric directional coupler, including a substrate 100, the substrate 100 is provided with a top layer silicon, the top layer silicon includes a first port 1, a coupling region 2, a first output waveguide 3 and a second output waveguide 4, one end of the coupling region 2 is connected to the first port 1, the other end is connected to the first output waveguide 3 and the second output waveguide 4, the coupling region 2 is covered with a phase change material layer 24, the coupling region 2 is divided into N × M rectangular units, and by adjusting states of the rectangular units, an aperiodic first punching array satisfying a predetermined first output target is formed, where the first output target is a sum of 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 sequentially connected and maintain the same width, the lower waveguide 22 is connected with the second output waveguide 4 and maintains the same width, the 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 in order to decouple and thereby reduce crosstalk.
More specifically, the asymmetric directional coupler is designed on a Silicon On Insulator (SOI) platform, the top Silicon thickness is 220nm, the thickness of the substrate 100 silica is 3 μm, the upper cladding is air, and the length W of the coupling region 2 is 4 Is 10 μm, the width W of the upper waveguide 21 1 380nm, the upper waveguide 21 is divided into 4 × 100 first rectangular units, each of which has a size of 95nm × 100nm and a depth of 220nm, and is initially non-perforated; width W of the lower waveguide 22 and the phase change material layer 24 2 350nm, the thickness of the phase change material layer 24 is 40nm, the phase change material layer 24 is divided into 4 × 100 second rectangular units 221, each second rectangular unit 221 has a size of 87.5nm × 100nm and a depth of 40nm, and the initial state is not perforated; width W of the waveguide gap 23 3 At 200nm, the waveguide gap 23 is divided into 2 × 100 third rectangular units 231, each third rectangular unit 231 having a size of 100nm × 100nm and a depth of 220nm, and is initially perforated.
Compared with the traditional method for designing the optical device, the intelligent algorithm is used, so that the optimization can be performed by depending on a physical model less under high degree of freedom, and the design of a device with small size and a complex structure is facilitated. Before optimization using the direct binary search algorithm, the coupling region 2 is divided into several rectangular units, each having two material states, perforated, i.e. the rectangular units are filled with air, and non-perforated, i.e. the rectangular units are filled with silicon. Each rectangular unit state is determined by an algorithm to satisfy an objective function, specifically: an objective function reflecting the device performance is set in a direct binary search algorithm, then the objective function values of two states of each rectangular unit are calculated in sequence by using the algorithm, and then the state when the objective function values are improved is reserved.
When rectangular cells are computed using the direct binary search algorithm, all cells are computed using alternately row-wise and column-wise computations. And traversing all the units once to form one iteration, and comparing the objective function values after the last iteration through multiple iterations, wherein the change value of the objective function values of two times is lower than 0.1%, the objective function is converged, and the algorithm is stopped. The calculation by rows means that the calculation is sequentially from left to right in the horizontal direction and from top to bottom in the vertical direction; the calculation by column means that the vertical direction is from top to bottom, and the horizontal direction is from left to right.
The utility model discloses a light or electricity make phase change material layer 24 on the asymmetric directional coupler take place reversible phase transition fast, influence the refracting index of waveguide and realize regulating and controlling the propagation path of light. Therefore, before the device of the present invention is completed, the asymmetric directional coupler needs to be designed first, and when the asymmetric directional coupler is optimized, 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, premature local convergence is easy, and thus the optimization result is not ideal. To overcome this problem, in optimizing the asymmetric directional coupler, the initial configuration as shown in fig. 2 is manually set, i.e., the initial state of all the first rectangular cells on the upper waveguide 21 is non-perforated, the lower waveguide 22 is non-perforated, the initial state of all the third rectangular cells 231 on the waveguide gap 23 is perforated, and the initial state of all the second rectangular cells 221 on the phase change material layer 24 is non-perforated. In order to obtain excellent initial structure parameters, certain optimization of the initial structure parameters is required.
First of all, the width of the waveguide gap 23 is W 3 Set to 200nm, coupling length W 4 And 10 μm, the width of the phase change material layer 24 covering the surface of the lower waveguide 22 is identical to the width of the lower waveguide 22, and the thickness of the phase change material layer 24 is 40nm. For the width W of the upper waveguide 21 under the condition of determining these parameters 1 And width parameter W of lower waveguide 22 2 Scanning is carried out, and an initial structure with better performance is optimized. The results of the parametric scan are shown in FIG. 3, and it can be found that when the width W of the upper waveguide 21 is large 1 About 380nm, the width W of the lower waveguide 22 2 Is 350nmWhen left and right, the GSST of the phase change material layer 24 is adjusted to be amorphous, and light is better coupled into the lower waveguide 22 due to phase matching; the GSST of the phase change material layer 24 is adjusted to be crystalline, and light still propagates on the upper waveguide 21 due to poor coupling efficiency due to phase mismatch. The width W of the upper waveguide 21 is finally selected in consideration of trade-off 1 380nm, width W of lower waveguide 22 2 350nm, and the width of the phase change material layer 24 on the surface of the lower waveguide 22 is also 350nm.
In addition, since the upper and lower waveguides generate a coupling effect, the distance between the two waveguides needs to be increased at the output position, the coupling effect is suppressed, and the propagation of light in the waveguides is not affected. Therefore, at least one of the output portions of the upper and lower waveguides needs to be designed to be a curved waveguide, that is, at least one of the first output waveguide 3 and the second output waveguide 4 is a curved waveguide.
After the artificially designed initial structure is obtained, the coupling region 2 needs to be divided into N × M rectangular units, where N and M are integers, and the rectangular side length setting also needs to consider the workability. For this, the coupling region 2 is divided into three sections, for a total of 10 × 100 rectangular units, including 4 × 100 first rectangular units of the upper waveguide 21 section, 4 × 100 second rectangular units 221 of the phase change material layer 24 section, and 2 × 100 third rectangular units 231 of the waveguide gap 23 section. Each rectangular unit has two material states, namely, a punched state and a non-punched state, wherein the punched state is that the rectangular unit is filled with air, and the non-punched state is that the rectangular unit is filled with silicon.
The upper waveguide 21 is divided into 4 × 100 rectangular units, each first rectangular unit having a size of 95nm × 100nm and a depth of 220nm, and is initially non-perforated; because the utility model realizes the adjusting function by changing the effective refractive index through the phase-change material layer 24 with the thickness of 40nm, the lower waveguide 22 does not divide a rectangular unit and does not punch; the phase change material layer 24 is divided into 4 × 100 second rectangular units 221, each second rectangular unit 221 has a size of 87.5nm × 100nm and a depth of 40nm, penetrates only the phase change material layer 24, and is initially non-perforated; the waveguide gap 23 is divided into 2 × 100 third rectangular units 231, each third rectangular unit 231 having a size of 100nm × 100nm and a depth of 220nm, and is initially perforated.
The direct binary search algorithm optimizes a total of 10 × 100 rectangular units on the initial structure. First, the algorithm selects the rectangular cells in the first row and the first column, and calculates the performance of the two states of punching and non-punching by using a time domain Finite difference method (FDTD). The performance decision is determined by an objective function set inside the algorithm, called Figure of merit (FOM), defined as:
FOM＝T A-GSST +T C-GSST
in the formula, T A-GSST The transmittance of the second output waveguide 4 is 1540nm to 1560nm when the GSST material is amorphous; t is C-GSST The transmittance of the first output waveguide 3 when the GSST material is crystalline is 1540nm to 1560nm in the wavelength band.
And then line-wise scan to the last rectangular cell, which is called an iteration. The next iteration scans the last rectangular cell in the same manner by column. And (4) alternately scanning and optimizing by rows and columns, and iterating for multiple times until the FOM value after two iterations is changed within 0.1%, so that the algorithm is converged and the performance of the device is stable. The calculation by rows means that the calculation is sequentially from left to right in the horizontal direction and from top to bottom in the vertical direction; the calculation by column means that the vertical direction is from top to bottom, and the horizontal direction is from left to right.
FIG. 4 is a schematic diagram of a two-dimensional planar structure of an asymmetric directional coupler optimized by using a direct binary search algorithm, and FIG. 5 is a schematic diagram of a transmission spectrum of the asymmetric directional coupler, wherein the transmission spectrum is within a bandwidth range of 1540nm to 1560nm, and when GSST is in an amorphous state, TE is added 0 The crosstalk of the mode in the first output waveguide 3 is lower than-16.4 dB, and the insertion loss in the second output waveguide 4 is less than 0.6dB; when GSST is crystalline, TE 0 The mode insertion loss in the first output waveguide 3 is less than 1.0dB, and the crosstalk in the second output waveguide 4 is lower than-16.0 dB;
the specific working principle is as follows: TE with bandwidth of 1540nm to 1560nm 0 Injecting mode light into the first port 1, controlling the phase change of GSST by light or electricity, and outputting when GSST is amorphousThe incident light efficiently penetrates through the second output waveguide 4, and the crosstalk at the first output waveguide 3 is low; when the GSST is crystalline, the input light is efficiently transmitted through the first output waveguide 3 and the crosstalk at the second output waveguide 4 is low. The transmission spectrum simulated by the asymmetric directional coupler provided by the embodiment also shows the excellent performance, and compared with an optical switch designed by other methods, the asymmetric directional coupler has the advantages of good performance, small size, easiness in processing and the like.
Example two
Referring to fig. 6-9, the present embodiment provides a controllable mode generator, including the above asymmetric directional coupler, a mode division multiplexer optimization area 5 and a third output waveguide 6, where one end of the mode division multiplexer optimization area 5 is connected to the first output waveguide 3 and the second output waveguide 4, respectively, and the other end is connected to the third output waveguide 6, the mode division multiplexer optimization area 5 is divided into X × Y fourth rectangular units 51, and a non-periodic second puncturing array meeting a predetermined second output target is formed by adjusting states of the fourth rectangular units 51, where the second output target is a sum of transmittances of two output different modes in the third output waveguide 6.
More specifically, the two different modes are TE bands from 1540nm to 1560nm 0 Mode sum TE from 1540nm to 1560nm 1 Mode, the third output waveguide 6 has a width of 900nm.
More specifically, the size of the mode division multiplexer optimization area 5 is 2400nm × 3000nm, the mode division multiplexer optimization area 5 is divided into 24 × 30 fourth rectangular units 51 of 100nm × 100nm, and the distances W between the connection ends of the first output waveguide 3 and the second output waveguide 4 and the mode division multiplexer optimization area 5 are 5 1635nm.
In the present embodiment, the first output waveguide 3 and the second output waveguide 4 are both curved waveguides.
The mode division multiplexer optimization area 5 is also designed by using a direct binary search algorithm, for example, fig. 8 shows an initial structure of the mode division multiplexer optimization area 5, the size of the mode division multiplexer optimization area 5 is 2400nm × 3000nm, the mode division multiplexer optimization area is divided into 24 × 30 fourth rectangular units 51 with 100nm × 100nm, each fourth rectangular unit 51 has two material states, namely, a punched state and a non-punched state, the punched state is that the fourth rectangular unit 51 is filled with air, and the non-punched state is that the fourth rectangular unit 51 is filled with silicon. The direct binary search algorithm optimizes a total of 24 × 30 rectangular units on the initial structure. The decision of performance is determined by an objective function arranged inside the algorithm, defined as:
in the formula (I), the compound is shown in the specification,
TE is generated in the wave band of 1540nm to 1560nm 0 Mode injection from the first output waveguide 3, maintaining TE 0 The transmittance of the mode at the third output waveguide 6;
TE is measured at a wave band of 1540nm to 1560nm 0 Mode injection conversion from the second output waveguide 4 to TE 1 The transmittance of the mode at the third output waveguide 6. The output waveguide width is 900nm, and the TE can be supported without loss 0 And TE 1 Propagation of the mode.
The mode generator operates on the principle of generating different modes of light by adjusting the GSST phase change on the asymmetric directional coupler. The method comprises the following specific steps: when TE 0 The mode light source is injected from the first port 1, GSST is adjusted to be crystalline state, TE 0 The mode enters the optimization region 5 of the mode division multiplexer from the first output waveguide 3 through the asymmetric directional coupler to maintain TE 0 The mode is output from the third output waveguide 6; when TE 0 The mode light source is injected from the first port 1, GSST is adjusted to be amorphous state, TE 0 The mode enters the mode division multiplexer optimization region 5 from the second output waveguide 4 through the asymmetric directional coupler 0 Mode conversion to TE 1 The mode is output from the third output waveguide 6.
FIG. 9 shows the transmission spectrum of the pattern generator provided in this embodiment, when GSST is crystalline, the output TE of the pattern generator 0 Mode, insertion loss less than 1.5dB, crosstalk less than-13.9 dB; when GSST is amorphous, the mode generator outputs TE 1 Mode, with insertion loss less than 2.2dB, crosstalk is lower than-14.8 dB. The pattern generator provided by the embodiment can solve the problems that the existing pattern generator is not adjustable and controllable, has large size and is complex in design method.
EXAMPLE III
Referring to fig. 10-12, the present invention further provides an optical circulator, which includes the above-mentioned asymmetric directional coupler, a plurality of asymmetric directional couplers are in an annular array, and a first output waveguide 3 of one of the asymmetric directional couplers is connected to a second output waveguide 4 of an adjacent asymmetric directional coupler.
In this embodiment, the first output waveguide 3 and the second output waveguide 4 are connected to form a curved waveguide, the optical circulator is formed by sequentially connecting four asymmetric directional couplers 11-14 through a first curved waveguide 15, a second curved waveguide 16, a third curved waveguide 17 and a fourth curved waveguide 18 in series, and both ends of each curved waveguide are respectively the same as the width of the connection part.
It can be understood that, according to different use requirements, the optical circulator may be formed by connecting three, four, five or more asymmetric directional couplers in series, and the number of the curved waveguides is increased or decreased accordingly.
The working principle of the optical circulator is that the GSST phase change and TE on the asymmetric directional coupler are adjusted 0 The mode light sources are output from adjacent ports either clockwise or counterclockwise. The method comprises the following specific steps: when TE 0 The mode light source is injected from the second port 7, GSST on the first asymmetric directional coupler 11 is in a crystalline state, GSST on the second asymmetric directional coupler 12, the third asymmetric directional coupler 13 and the fourth asymmetric directional coupler 14 is in an amorphous state, TE 0 The mode is output from the third port 8 in the clockwise direction, and so on, TE 0 The mode light source can circularly and clockwise propagate in the direction of the second port 7, the third port 8, the fourth port 9, the fifth port 10 and the second port 7; when TE 0 The mode light source is injected from the second port 7, GSS on the first asymmetric directional coupler 11T is amorphous, GSST on the second 12, third 13 and fourth 14 asymmetric directional couplers is crystalline, TE 0 The pattern is output from the fifth port 10 in the counterclockwise direction, and so on, TE 0 The mode light sources can travel circularly counterclockwise in the direction from the second port 7 to the fifth port 10 to the fourth port 9 to the third port 8 to the second port 7.
FIG. 12 shows the transmission spectrum of the optical circulator provided in this embodiment when TE is measured 0 Injecting mode into the second port 7, when GSST layer on the first asymmetric directional coupler 11 is crystalline state, and GSST layers of other ports are amorphous state, TE 0 The mode light circularly and clockwise propagates in the direction of the second port 7, the third port 8, the fourth port 9, the fifth port 10 and the second port 7, the insertion loss is less than 1.2dB, and the crosstalk is lower than-20.0 dB; when TE 0 Injecting mode into the second port 7, when GSST layer on the first asymmetric directional coupler 11 is amorphous, and GSST layer on other ports is crystalline, TE 0 The mode light circularly and anticlockwise propagates in the direction of the second port 7, the fifth port 10, the fourth port 9, the third port 8 and the second port 7, the insertion loss is less than 1.2dB, and the crosstalk is lower than-29.4 dB. Compared with devices designed by other methods, the optical circulator provided by the embodiment has the advantages of adjustability, controllability, small size, intelligent design and the like.
The above embodiments are only used for illustrating the technical solution of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.
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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