Topological state control device and method based on point source phase modulation

Abstract

The invention provides a topological state control device and method based on point source phase modulation. The device comprises a microwave vector network analyzer, a microwave transmission line, a power divider, a phase shifter and a microwave probe, one end of the microwave transmission line is connected with an output port of the vector network analyzer, and the other end is connected with the power divider; the power divider is connected with the two microwave probes and used for generating a point source group, the point source group comprises two coherent point sources, and one point source is connected to the phase shifter so that an adjustable phase difference can be generated between the two coherent point sources. By modulating the phase difference of the point source groups, the control of the topological state with specific spatial symmetry can be realized. The phase-adjustable point source group is constructed by utilizing the spatial symmetry of the topological state, so that the controllable excitation of the topological state is realized, the problems of high cost and long time of physical structure reconstruction in topological state control are solved, and the method can be applied to the representation of the topological state and the design of an adjustable topological device.

Description

Technical Field

[0001] The present invention belongs to the field of microstructure technology, and in particular relates to a topological state control device and method based on microwave point source phase modulation. Background Art

[0002] In integrated photonic devices, freely manipulating light in different dimensions is an important topic, which can promote the rapid development of optical communications and optical computing. However, the current realization of multidimensional light manipulation based on traditional optical cavities and waveguides faces fragility and scattering losses, which are inevitable in practical manufacturing. For example, whispering gallery modes require extremely smooth interfaces, while the inhomogeneity of the dielectric constant of the material may lead to energy loss. Therefore, achieving stable and low-loss light manipulation in multiple dimensions is crucial for on-chip photonic devices. Thanks to the symmetry-protected boundary states in topological phases, reconfigurable and controllable stable devices are expected to be achieved through clever artificial microstructures.

[0003] In recent years, higher-order topological phases, such as higher-order topological insulators and higher-order topological semimetals, have attracted extensive attention due to their multidimensional topological boundary states and surface states. In two-dimensional systems, second-order topological insulators have zero-dimensional corner states and one-dimensional boundary states. These higher-order topological phases have been verified in a variety of systems such as optics, acoustics, and circuits. However, most current studies focus on static physical properties, such as bulk-boundary correspondence and pseudospin degrees of freedom. The overall characteristics of the structure determine the existence of topological states in form. Therefore, the manipulation of topological states often requires changing the entire sample structure. This high-cost, high-time method is not conducive to the application and development of topological optical devices. Controllable excitation of multidimensional interface states without changing the geometric structure of the device is crucial for practical applications and needs further exploration. At present, there is still a lack of feasible solutions for the realization of multidimensional stable optical manipulation. Summary of the invention

[0004] The present invention provides a topological state manipulation device and method based on point source phase modulation, the purpose of which is to regulate multi-dimensional stable anti-scattering optical modes, that is, to controllably excite high-order topological states.

[0005] The technical solution adopted by the device of the present invention is as follows:

[0006] A topological state manipulation device based on point source phase modulation, the device comprising a microwave vector network analyzer, a microwave transmission line, a power divider, a phase shifter and a microwave probe; one end of the microwave transmission line is connected to the output port of the vector network analyzer, and the other end is connected to the power divider; the power divider is connected to two microwave probes to generate a point source group, the point source group comprises two coherent point sources, one of the point sources is connected to the phase shifter so that an adjustable phase difference is generated between the two coherent point sources.

[0007] Furthermore, the operating frequency range of the microwave vector network analyzer, microwave transmission line, power divider, phase shifter and microwave probe covers 2 GHz-18 GHz.

[0008] Furthermore, the power divider divides the input microwave signal into two signals evenly without generating any additional phase difference.

[0009] Furthermore, the phase adjustment range of the phase shifter is 0-2π.

[0010] Furthermore, the two microwave probes are arranged in the structure to be controlled, and their positions are arranged in accordance with mirror symmetry.

[0011] The present invention also provides a control method using the above-mentioned topological state control device based on point source phase modulation, which realizes the control of the topological state with specific spatial symmetry by modulating the phase difference of two coherent point sources in the point source group.

[0012] Furthermore, when the point source group has the same symmetry as the topological state, the topological state is excited; when the point source group has the opposite symmetry to the topological state, the excitation of the topological state is suppressed.

[0013] Furthermore, the control method specifically comprises the following steps:

[0014] (1) two circular holes are opened in the sample to be manipulated, and two microwave probes are passed through the circular holes through the sample to be manipulated;

[0015] (2) selecting a set of frequencies near the topological state resonance frequency of the sample to be manipulated as the excitation of the microwave source;

[0016] (3) Adjust the phase of the phase shifter in the range of 0-2π to manipulate the excitation of the topological state;

[0017] (4) Determine the symmetry of the topological state and point source group: in is the mirror symmetry operator, ψ and are the wave functions of the topological state and point source group respectively, the coefficient a = ±1, θ is the continuously adjustable phase difference between two coherent point sources, when θ = a, the topological state is excited, when θ = -a, the excitation of the topological state is suppressed.

[0018] The present invention utilizes the spatial symmetry of the topological state to construct a phase-adjustable point source group, thereby achieving controllable excitation of the topological state, overcoming the high cost and long time of physical structure reconstruction in topological state manipulation, and can be applied to the characterization of topological states and the design of adjustable topological devices. Compared with the prior art, the present invention has the following significant advantages: (1) It overcomes the cumbersome problem of topological state regulation requiring changes in the overall sample structure; (2) It extends topological state regulation to multi-dimensional high-order topological states; (3) It utilizes phase modulation of the point source group to achieve controllable excitation of the topological state. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a topological state control device based on point source phase modulation of the present invention;

[0020] Figure 2 is a schematic diagram of a topological mode used in an embodiment of the present invention;

[0021] Figure 3 is the experimental result of the sample with even symmetry mode;

[0022] Figure 4 is the experimental result of a sample with an odd symmetry mode. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0024] The present invention provides a topological state manipulation device based on point source phase modulation, comprising a microwave vector network analyzer, a microwave transmission line, a power divider, a phase shifter and a microwave probe; one end of the microwave transmission line is connected to the output port of the vector network analyzer, and the other end is connected to the power divider; the power divider is connected to two microwave probes to generate a point source group, the point source group includes two coherent point sources, one of which is connected to the phase shifter so that an adjustable phase difference is generated between the two coherent point sources. By modulating the phase difference of the point source group, the manipulation of the topological state with a specific spatial symmetry can be achieved.

[0025] In this embodiment, the microwave vector network analyzer, microwave transmission line, power divider, phase shifter and microwave probe have an operating frequency range of 2 GHz to 18 GHz. The power divider evenly divides the input microwave signal into two signals without generating an additional phase difference. The phase shifter has a phase adjustment range of 0 to 2π.

[0026] The method for topological state manipulation using the above device of the present invention specifically comprises the following steps:

[0027] (1) Two circular holes are opened in the sample to be manipulated, the positions of which are required not to destroy the symmetry of the sample's topological state, so that two microwave probes pass through the sample to be manipulated from the bottom;

[0028] (2) selecting a set of frequencies near the topological state resonance frequency of the sample to be manipulated as the excitation of the microwave source;

[0029] (3) Adjust the phase of the phase shifter in the range of 0-2π to manipulate the excitation of the topological state;

[0030] (4) Determine the symmetry of the topological state and point source group: in is the mirror symmetry operator, ψ and are the wave functions of the topological state and point source group respectively, the coefficient a = ±1, θ is the continuously adjustable phase difference between two coherent point sources, when θ = a, the topological state is excited, when θ = -a, the excitation of the topological state is suppressed.

[0031] In this embodiment, microwave absorbing materials are also provided around the sample to be manipulated to prevent microwaves scattered out of the sample from being reflected back into the sample. In addition, the top of the microwave probe does not exceed the upper surface of the sample to be manipulated. In order to ensure that both the point source group and the topological state have mirror symmetry, the position of the microwave probe should be kept unchanged throughout the process.

[0032] like Figure 1 As shown, there are three layers of structure in the schematic diagram. The bottom layer is the experimental sample and the point source group device. The middle and upper layers are schematic diagrams of topological state suppression and excitation, respectively. Stars of different colors represent microwave point sources of different phases.

[0033] The regulated structure used in the present invention has mirror symmetry, and the states it supports include mirror symmetric and mirror antisymmetric topological states. Figure 1 The mirror-antisymmetric topological state is shown. The positions of the two microwave probes in the point source group follow the mirror symmetry, and the phase difference θ between the two point sources is controlled by a phase shifter. When the phase difference θ is 0, a mirror-symmetric point source group is formed. As shown in the figure, the mirror-antisymmetric topological state cannot be excited; when the phase difference θ is π, a mirror-antisymmetric point source group is formed, and the aforementioned topological state can be excited.

[0034] like Figure 2 As shown, the experimental structures selected in this embodiment are two photonic crystal slabs. The triangular structure sample supports a mirror-symmetric 60° topological angle state, and the diamond structure sample supports a mirror-antisymmetric 120° topological angle state.

[0035] Based on the above topological state manipulation method, this embodiment specifically includes the following steps:

[0036] (1) passing two microwave probes through the experimental sample from the bottom as excitation sources;

[0037] (2) Continuously adjust the phase of the phase shifter in the range of 0-2π;

[0038] (3) Another probe is hovered above the structure that produces the topological state to measure S 21 Parameters, thereby obtaining the spectrum at the topological state;

[0039] (4) The probe in step (3) was placed 1 mm above the sample structure and traversed the entire field, and S was measured every 2 mm using a vector network analyzer. 21 Parameters are obtained to obtain the electric field distribution in the entire two-dimensional plane at the resonance frequency of the eigenmode of the experimental sample.

[0040] The measurement results of this embodiment are as follows Figure 3 and Figure 4 As shown, for the triangular experimental sample supporting the mirror symmetry mode ( Figure 3 ), at the resonant frequency of 9.89 GHz, the topological state can be excited by a point source group with a phase difference of θ = 0, while the excitation is suppressed when θ = π. For the diamond-shaped experimental sample ( Figure 4 ), at the resonant frequency of 9.77 GHz, the topological state can be excited by a point source group with a phase difference of θ = π, but cannot be excited when θ = 0.

[0041] Therefore, the topological state manipulation method based on point source phase modulation described in the present invention realizes the controllable excitation of high-order topological states without changing the overall structure, and can be applied to topological optical mode regulation and the design of new optical devices.

Claims

1. A topological state manipulation device based on point source phase modulation, characterized in that: The device comprises a microwave vector network analyzer, a microwave transmission line, a power divider, a phase shifter and a microwave probe; one end of the microwave transmission line is connected to the output port of the vector network analyzer, and the other end is connected to the power divider; the power divider is connected to two microwave probes to generate a point source group, the point source group comprises two coherent point sources, one of the point sources is connected to the phase shifter so that an adjustable phase difference is generated between the two coherent point sources.

2. A topological state manipulation device based on point source phase modulation according to claim 1, characterized in that: The operating frequency range of the microwave vector network analyzer, microwave transmission line, power divider, phase shifter and microwave probe covers 2 GHz-18 GHz.

3. A topological state manipulation device based on point source phase modulation according to claim 1, characterized in that: The power divider divides the input microwave signal into two signals evenly without generating any additional phase difference.

4. A topological state manipulation device based on point source phase modulation according to claim 1, characterized in that: The phase adjustment range of the phase shifter is 0-2π.

5. The topological state manipulation device based on point source phase modulation according to claim 1, characterized in that: The two microwave probes are arranged in the structure to be controlled, and their positions are arranged in accordance with mirror symmetry.

6. A control method using a topological state control device based on point source phase modulation as claimed in claim 1, characterized in that: By modulating the phase difference between two coherent point sources in the point source group, the manipulation of topological states with specific spatial symmetry can be achieved.

7. The control method according to claim 6, characterized in that: When the point source group has the same symmetry as the topological state, the topological state is excited; when the point source group has the opposite symmetry to the topological state, the excitation of the topological state is suppressed.

8. The control method according to claim 7, characterized in that: The method specifically comprises the following steps: (1) two circular holes are opened in the sample to be manipulated, and two microwave probes are passed through the circular holes through the sample to be manipulated; (2) selecting a set of frequencies near the topological state resonance frequency of the sample to be manipulated as the excitation of the microwave source; (3) Adjust the phase of the phase shifter in the range of 0-2π to manipulate the excitation of the topological state; (4) Determine the symmetry of the topological state and point source group: in is the mirror symmetry operator, ψ and are the wave functions of the topological state and point source group respectively, the coefficient a = ±1, θ is the continuously adjustable phase difference between two coherent point sources, when θ = a, the topological state is excited, when θ = -a, the excitation of the topological state is suppressed.

9. The control method according to claim 8, characterized in that: In step (1), a microwave absorbing material is arranged around the periphery of the sample to be manipulated.

10. The control method according to claim 8, characterized in that: In step (1), when the two microwave probes pass through the sample to be manipulated from the circular hole, the tops of the microwave probes do not exceed the upper surface of the sample to be manipulated.

Images