A tunable filter based on topological insulator materials

Abstract

The present invention relates to the technical field of filters, and in particular to a tunable filter based on topological insulator materials, comprising a substrate, a topological insulator layer, a waveguide, and a resonant cavity, wherein the topological insulator layer is placed on the substrate, the waveguide and the resonant cavity are placed on the topological insulator layer, the waveguide is an optical fiber, the resonant cavity is a silicon dioxide material, the resonant cavity is placed on one side of the waveguide, the waveguide exposes the fiber core near the resonant cavity, and the waveguide and the resonant cavity are partially placed in the topological insulator layer. When applied, an external light beam is applied to irradiate the resonant cavity. The present invention applies an external light beam to irradiate the resonant cavity, changes the refractive index of the topological insulator layer outside the resonant cavity, and efficiently realizes the regulation of electromagnetic waves propagated in the waveguide by a beam of light, and has good application prospects in the application field of wavelength tunable filters.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a tunable filter based on topological insulator materials. Background Art

[0002] Wavelength tunable filters have important applications in optical communications, optical sensing, lasers, spectral analysis and other fields: in the field of optical communications, wavelength tunable filters are used in wavelength division multiplexing networks; in the field of optical sensing, wavelength tunable filters are the core components of fiber Bragg grating demodulation systems and Fabry-Perot demodulation systems.

[0003] Traditional wavelength tunable filters are mostly based on electro-optical effect or nonlinear effect. For electro-optical tunable filters, invention patent CN106970483B discloses a tunable electro-optical filter, providing a tunable electro-optical filter including a reflective structure, the reflective structure includes a seismometer reflective layer arranged on the first side of the liquid crystal layer and a second reflective layer arranged on the second side of the liquid crystal layer, the first reflective layer includes a first pattern layer having a first metasurface structure, and the second reflective layer includes a second pattern layer having a second metasurface structure, and the electro-optical effect is used to change the refractive index to achieve filtering. Although the tuning speed is fast, the tuning range is limited. For nonlinear effect tunable filters, invention patent CN101320188B discloses a photon adjustable width RF phase shifter based on a silicon-based ring resonator. When a high-power pump light is injected into the silicon-based ring resonator, the silicon-based ring resonator converts the absorbed light energy into heat energy, generating a nonlinear thermal effect. This nonlinear thermal effect causes the resonance peak to redshift, resulting in a change in the phase of the signal.

[0004] The nonlinear effect of applied materials can achieve a wider range of modulation. The existing technology often introduces light that produces nonlinear effects into the resonant cavity through a waveguide, which cannot efficiently achieve the regulation of electromagnetic waves propagating in the waveguide by a beam of light. Summary of the invention

[0005] To solve the above problems, the present invention provides a tunable filter based on topological insulator materials, comprising a substrate, a topological insulator layer, a waveguide, and a resonant cavity. The topological insulator layer is placed on the substrate, the waveguide and the resonant cavity are placed on the topological insulator layer, the waveguide is an optical fiber, the resonant cavity is a silica material, the resonant cavity is placed on one side of the waveguide, the waveguide core is exposed near the resonant cavity, and the waveguide and the resonant cavity are partially placed in the topological insulator layer.

[0006] Furthermore, the resonant cavity is spherical.

[0007] Furthermore, half of the resonant cavity is placed inside the topological insulator layer.

[0008] Furthermore, half of the optical fiber is placed inside a topological insulator.

[0009] Furthermore, the material of the topological insulator layer is bismuth telluride or bismuth selenide.

[0010] Furthermore, the optical fiber is a multimode optical fiber.

[0011] Furthermore, the diameter of the resonant cavity is greater than 10 microns.

[0012] Furthermore, the material of the substrate is silicon.

[0013] Furthermore, the distance between the bottom of the resonant cavity and the substrate is less than 1 micron.

[0014] Furthermore, the resonant cavity is in contact with the fiber core.

[0015] Beneficial effects of the present invention: The present invention provides a tunable filter based on topological insulator materials, including a substrate, a topological insulator layer, a waveguide, and a resonant cavity. The topological insulator layer is placed on the substrate, the waveguide and the resonant cavity are placed on the topological insulator layer, the waveguide is an optical fiber, the resonant cavity is a silica material, the resonant cavity is placed on one side of the waveguide, the waveguide exposes the fiber core near the resonant cavity, and the waveguide and the resonant cavity are partially placed in the topological insulator layer. When applied, an external light beam is applied to irradiate the resonant cavity and is confined in the resonant cavity, which enhances the interaction between the external light beam and the topological insulator layer material, changes the refractive index of the surface of the topological insulator material layer, thereby changing the resonant wavelength of the resonant cavity, thereby realizing a wavelength-tunable filter. The present invention applies an external light beam to irradiate the resonant cavity, changes the refractive index of the topological insulator layer outside the resonant cavity, and efficiently realizes the regulation of electromagnetic waves propagated in the waveguide by a beam of light, and has good application prospects in the application field of wavelength tunable filters.

[0016] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A top-down view of a tunable filter based on topological insulator material.

[0018] Figure 2 A cross-sectional view of a tunable filter based on topological insulator material.

[0019] Figure 3 This is a cross-sectional view of another tunable filter based on topological insulator materials.

[0020] Figure 4 This is a cross-sectional view of another tunable filter based on topological insulator material.

[0021] Figure 5 This is a cross-sectional view of another tunable filter based on topological insulator material.

[0022] In the figure: 1. substrate; 2. topological insulator layer; 3. waveguide; 4. resonant cavity; 5. second topological insulator layer. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0024] Example 1

[0025] The present invention provides a tunable filter based on topological insulator materials, such as Figure 1 and Figure 2 As shown, it includes a substrate 1, a topological insulator layer 2, a waveguide 3, and a resonant cavity 4. The topological insulator layer 2 is placed on the substrate 1. The material of the substrate 1 is silicon dioxide. The material of the topological insulator layer 2 is a topological insulator material. Topological insulator is an electromagnetic substance with novel optical properties. The interior of the topological insulator is an insulating state and the surface is a metallic state. This property comes from the spin of the surface electrons. The material of the topological insulator layer 2 is bismuth telluride or bismuth selenide. The waveguide 3 and the resonant cavity 4 are placed on the topological insulator layer 2. The waveguide 3 is an optical fiber, specifically a multimode optical fiber. The core of the multimode optical fiber is relatively thick to increase the coupling between the waveguide 3 and the resonant cavity 4. The resonant cavity 4 is made of silicon dioxide, the resonant cavity 4 is spherical, and the diameter of the resonant cavity 4 is greater than 10 microns. The resonant cavity 4 is placed on one side of the waveguide 3, and the waveguide 3 exposes the core near the resonant cavity 4. That is to say, the core of the optical fiber is exposed near the resonant cavity 4 and on one side of the resonant cavity 4; the core is covered with a cladding on the outside of the core away from the resonant cavity 4 and on the side facing away from the resonant cavity 4. This is conducive to confining the propagation of light in the optical fiber and is also conducive to the coupling between the optical fiber and the resonant cavity 4. The waveguide 3 and the resonant cavity 4 are both partially placed in the topological insulator layer 2. Specifically, half of the resonant cavity 4 is placed in the topological insulator layer 2, and half of the optical fiber is placed in the topological insulator layer 2. By setting half of the resonant cavity 4 in the topological insulator layer 2, the resonant cavity 4 has more contact area with the topological insulator material, and the topological insulator layer 2 also confines the light more in the resonant cavity 4, thereby changing the refractive index of the topological insulator material more.

[0026] The topological insulator material has a high Kerr refractive index. When the light intensity irradiating the topological insulator material changes, the refractive index of the topological insulator material also changes, thereby changing the dielectric environment around the resonant cavity 4, thereby changing the resonant wavelength of the resonant cavity 4, and finally achieving tunable filtering.

[0027] In addition, in this embodiment, the material of the topological insulator layer 2 is bismuth telluride. The bismuth telluride material can undergo reversible transformation between crystal and amorphous. Crystal and amorphous have different optical properties, which leads to the bismuth telluride material being able to realize a tunable filter under external light beam irradiation.

[0028] For the present invention, when applied, an external light beam is applied to illuminate the resonant cavity 4, and is confined in the resonant cavity 4, thereby enhancing the interaction between the external light beam and the material of the topological insulator layer 2, changing the refractive index of the surface of the topological insulator material layer 2, thereby changing the resonant wavelength of the resonant cavity 4, thereby realizing a wavelength-tunable filter. The present invention applies an external light beam to illuminate the resonant cavity 4, changes the refractive index of the topological insulator layer 2 outside the resonant cavity 4, and efficiently realizes the regulation of the electromagnetic wave propagated in the waveguide 3 by a beam of light, and has good application prospects in the application field of wavelength-tunable filters.

[0029] In this embodiment, the resonant cavity 4 is a round sphere, a part of the sphere is arranged in the topological insulator layer 2, and the other part of the sphere is exposed from the topological insulator layer 2, which makes it convenient to use incident light beams with different incident directions to irradiate the resonant cavity 4, and all incident light can enter the resonant cavity 4.

[0030] Example 2

[0031] On the basis of Example 1, the material of the substrate 1 is silicon. Furthermore, the distance between the bottom of the resonant cavity 4 and the substrate 1 is less than 1 micron. In this way, a strong electric field is formed between the substrate 1 and the resonant cavity 4, or the strong electric field is confined between the substrate 1 and the resonant cavity 4, making full use of the incident light beam, forming a stronger electric field on the surface of the resonant cavity 4, thereby more changing the refractive index of the topological insulator material on the surface of the resonant cavity 4, thereby more changing the resonant wavelength of the resonant cavity 4. Therefore, when the light intensity of the incident light beam has a small change, the resonant wavelength of the resonant cavity 4 can produce a large change, thereby realizing a more sensitive tunable filter.

[0032] Example 3

[0033] On the basis of embodiment 1-2, the resonant cavity 4 is in contact with the core. When the core is not in contact with the resonant cavity 4, the coupling between the core and the resonant cavity 4 is greatly affected by the change in the refractive index of the topological insulator material therebetween. When the core is in contact with the resonant cavity 4, the amount of the topological insulator material between the core and the resonant cavity 4 is reduced, and the refractive index change of the topological insulator material slightly changes the coupling between the core and the resonant cavity 4. Therefore, when the refractive index of the topological insulator material changes, the transmission coefficient at the transmission valley in the waveguide 3 changes little.

[0034] Example 4

[0035] On the basis of Example 1, Figure 3As shown, the waveguide 3 is on the lower side of the resonant cavity 4. That is to say, the waveguide 3 is arranged in the topological insulator layer 2. Similarly, on the side close to the resonant cavity 4, the waveguide 3 exposes the core. In this embodiment, the optical fiber is placed in the topological insulator layer 2, and the material in the topological insulator layer 2 is in an insulating state. The change of the surface state of the topological insulator layer 2 will not affect the environment around the optical fiber. The change of the refractive index of the topological insulator material between the core and the resonant cavity 2 is small, resulting in a relatively stable coupling strength between the core and the resonant cavity 2.

[0036] Example 5

[0037] On the basis of Example 4, Figure 4 As shown, the resonant cavity 4 is hemispherical, and the hemispherical circular surface is flush with the surface of the topological insulator layer 2. In this way, under vertical incidence, the incident light easily enters the hemispherical resonant cavity 4, thereby forming a strong light field in the resonant cavity 4, thereby changing the refractive index around the resonant cavity 4 more, thereby achieving higher sensitivity filtering wavelength regulation.

[0038] Example 6

[0039] On the basis of Example 5, Figure 5 As shown, a second topological insulator layer 5 is also included, and the second topological insulator layer 5 covers the hemispherical circular surface. The thickness of the second topological insulator layer 5 is less than 10 nanometers. In this way, the incident light beam can penetrate the second topological insulator layer 5 and be confined in the hemisphere. Under the action of the light field in the hemisphere, the refractive index of the topological insulator layer 2 and the second topological insulator layer 5 changes, thereby changing the dielectric environment near the resonant cavity 4 more, thereby changing the resonant wavelength of the resonant cavity 4 more, thereby achieving higher sensitivity wavelength control.

[0040] In summary, in the present invention, the resonant cavity 4 is used to resonate the electromagnetic waves or light propagating in the waveguide 3 to form a filter; it is also used to absorb the external incident light beam, which enhances the electric field on the surface of the topological insulator material, thereby causing a large change in the refractive index of the topological insulator material. In addition, the resonant cavity 4 is embedded in the topological insulator layer 2, which expands the contact area between the topological insulator material and the resonant cavity 4. These effects result in the resonant wavelength of the resonant cavity 4 moving more when the external light beam is irradiated, thereby achieving high-sensitivity filter wavelength regulation.

[0041] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A tunable filter based on topological insulator material, characterized in that: The invention comprises a substrate, a topological insulator layer, a waveguide and a resonant cavity, wherein the topological insulator layer is placed on the substrate, the waveguide is an optical fiber, the resonant cavity is made of silica material, the resonant cavity is spherical, the resonant cavity is partially placed in the topological insulator layer, the waveguide is arranged at the lower side of the resonant cavity in the topological insulator layer, and the core of the waveguide is exposed near the resonant cavity; when in use, an external light beam is used to irradiate the resonant cavity.

2. The tunable filter based on topological insulator material as claimed in claim 1, characterized in that: One half of the resonant cavity is placed in the topological insulator layer.

3. The tunable filter based on topological insulator material as claimed in claim 1, characterized in that: The material of the topological insulator layer is bismuth telluride or bismuth selenide.

4. The tunable filter based on topological insulator material as claimed in claim 1, characterized in that: The optical fiber is a multimode optical fiber.

5. The tunable filter based on topological insulator material as claimed in claim 1, characterized in that: The diameter of the resonant cavity is greater than 10 microns.

6. The tunable filter based on topological insulator material as claimed in claim 1, characterized in that: The material of the substrate is silicon.

7. A tunable filter based on a topological insulator material as claimed in any one of claims 1 to 6, characterized in that: The resonant cavity is in contact with the fiber core.

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