A method for regulating a photonic spin Hall effect by using a bias auxiliary light

Abstract

The application discloses a method for regulating a photonic spin Hall effect by using bias auxiliary light, and relates to the field of applied optics and optical engineering, and comprises a resonant optical tunneling structure composed of a plurality of InP layers and SiO2 layers arranged alternately, wherein the optical refractive index of the InP layer is regulated by using bias auxiliary light injection, and then the photonic spin Hall effect is regulated; by the method, the spin-related displacement generated by the photonic spin Hall effect can be effectively regulated, and a new regulation method is provided for the photonic spin Hall effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of applied optics and optical engineering, in particular to a method for regulating photonic spin Hall effect by using bias auxiliary light. BACKGROUND

[0002] In recent years, the optical spin Hall effect has become a research hotspot in the field of photonics. When a linearly polarized light passes through the interface of different media, the photons with opposite spin directions in the reflected light and the transmitted light will deviate in the direction perpendicular to the incident plane, thereby splitting into two beams of left and right circularly polarized light. This phenomenon is called photonic spin Hall effect (PSHE). PSHE is closely related to the refractive index gradient, and it will play a huge potential application in the fields of precision measurement, new type of sensing, quantum information processing, etc. PSHE is a weak optical effect caused by photonic spin-orbit interaction, and the spin-dependent displacement produced is usually only nanometers. In order to realize its application, in recent years, the research on PSHE mainly focuses on the enhancement and flexible regulation of PSHE effect. In the aspect of PSHE effect enhancement, the more representative methods include the methods based on Brewster angle, multi-layer nanostructure, surface plasmon resonance, PT symmetric metamaterial, Tamm plasmon, black phosphorus and photonic crystal, etc. In the aspect of PSHE flexible regulation, the above methods can achieve to a certain extent, but most of them are based on changing the structure of the device, transforming the incident angle of the incident light, or replacing different materials to achieve, which cannot truly realize the flexible regulation of the photonic spin Hall effect. In view of this, it has become an important research direction to realize the flexible regulation of PSHE so that it can be widely applied in different scenes and environments. So far, the more effective methods are realized by electric field, magnetic field, optical pumping, etc. such as electro-optic, magneto-optic, thermo-optic or based on the special properties of the material itself. The more representative is the single / multi-layer graphene-based configuration based on electric field and optical pumping regulation. The main principle of single / multi-layer graphene-based PSHE based on electric field and optical pumping regulation is that the electric field and optical pumping cause the change of the Fermi level of graphene, which further causes the optical refractive index of graphene material, and then realizes the regulation of PSHE. However, the PSHE devices based on two-dimensional materials such as graphene have many drawbacks in preparation and stability, and most of the flexible regulation is for the PSHE of reflected light. It is necessary and of practical significance to explore new and flexible PSHE regulation methods for transmitted light. SUMMARY

[0003] The technical problem solved by the present application: the present application discloses a method for regulating photon spin Hall effect by using bias auxiliary light, which solves the above-mentioned problems existing in the flexible regulation of the existing photon spin Hall effect. The intensity and photon energy of the bias auxiliary light can be adjusted to realize the flexible regulation of the transmission light photon spin Hall effect, which is used for the research and development of new optical devices.

[0004] To solve the above technical problems, the present application provides the following technical solutions:

[0005] A method for regulating photon spin Hall effect by using bias auxiliary light, comprising a plurality of InP layers and SiO2 layers arranged to form a resonant optical tunneling structure;

[0006] The bias auxiliary light is injected vertically from the side of the resonant optical tunneling structure to excite the photo-generated carriers of the semiconductor material InP layer and realize the regulation of the refractive index of the InP layer;

[0007] The working light source selects linearly polarized light and irradiates the resonant optical tunneling structure with a refractive index gradient distribution at a certain incident angle. The refractive index gradient refers to the description of the refractive index distribution of the multilayer structure. The refractive index range of each layer structure is the refractive index value range of each layer of material, and the specific value is adjusted according to the working requirement of the device. The intensity or photon energy of the injected bias auxiliary light is adjusted to change the refractive index of the semiconductor material InP layer and realize the flexible regulation of the transmission light photon spin Hall effect. By injecting bias auxiliary light with different light intensity or photon energy, different concentrations of photo-generated carriers are excited in the semiconductor material InP, and the refractive index of the InP layer is changed by the different concentrations of photo-generated carriers, thereby realizing the regulation of the refractive index gradient arrangement of the multilayer structure.

[0008] Preferably, the refractive index value range of the InP layer is 3.4-3.5, the refractive index value range of the SiO2 layer is 1.42-1.55, and the InP layer and the SiO2 layer are alternately arranged to form a resonant optical tunneling structure. InP layers and SiO 2层 The multilayer structure arranged alternately is used as a PSHE device, the refractive index between the structure layers presents high-low alternating arrangement, the high refractive index material corresponds to the low optical potential, and the low refractive index medium corresponds to the high optical potential. Photons form resonance between adjacent potential barriers, and under certain conditions, incident light can penetrate the optical potential barrier that cannot be passed, which is similar to the characteristics of electrons passing through potential wells in quantum mechanical electron tunneling effect, and shows the resonant optical tunneling effect. When InP and SiO2 are arranged alternately in multiple layers, the entire resonant optical tunneling structure is equivalent to a double-potential barrier or a multi-potential barrier structure.

[0009] Preferably, the InP layer and the SiO2 layer are alternately arranged from top to bottom to form a multilayer film, and the resonant optical tunneling structure has a refractive index that presents high-low-high-low alternating arrangement.

[0010] Preferably, the resonant optical tunneling structure realizes the regulation of the Fresnel transmittance or other optical parameters of the resonant optical tunneling structure based on the InP layer by adjusting the intensity or photon energy of the bias auxiliary light. The bias auxiliary light is injected from the side of the layered resonant optical tunneling structure, excites the semiconductor material InP layer to generate photo-generated carriers, realizes the regulation of the refractive index of the InP layer, and considers three different effects of causing the refractive index change: band filling effect, band gap shrinkage effect and free carrier absorption.

[0011] Preferably, the incident angle range of the polarized light is 0°-90°.

[0012] By adjusting the injection light intensity or photon energy of the bias auxiliary light, the refractive index gradient arrangement of the multilayer structure is regulated, and the photonic spin Hall effect is flexibly and effectively regulated. The specific regulation object is the transmission light photonic spin Hall effect of H component and V component.

[0013] The present application has the following beneficial effects:

[0014] The present application provides a method for regulating the photonic spin Hall effect by using bias auxiliary light, wherein the bias auxiliary light is injected into a resonant optical tunneling structure containing InP. The method has the characteristics of simple device structure and flexible regulation mode. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 For a resonant optical tunneling effect (ROTE) structure of InP-SiO2-InP-SiO2-InP five-layer waveguide structure in the specific embodiment, the photonic spin Hall effect is regulated by using the bias auxiliary light injection method at the side of the waveguide.

[0016] Figure 2 For the regulation of the photonic spin Hall effect of the transmission H light of the InP-SiO2-InP-SiO2-InP five-layer resonant optical tunneling structure by the bias auxiliary light intensity of the present application.

[0017] Figure 3 For the regulation of the photonic spin Hall effect of the transmission V light of the InP-SiO2-InP-SiO2-InP five-layer resonant optical tunneling structure by the bias auxiliary light intensity of the present application.

[0018] Figure 4 For the regulation of the photonic spin Hall effect of the InP-SiO2-InP-SiO2-InP five-layer resonant optical tunneling structure by the photon energy of the bias auxiliary light of the present application. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application are further described in detail by the following description of embodiments with reference to the accompanying drawings. The present application concept, technical solutions are more complete, accurate and in-depth understanding of the skilled in the art.

[0020] Embodiment 1: a method for regulating photonic spin Hall effect by bias-assisted light. The structure is shown as Figure 1 five-layer optical tunneling structure composed of InP-SiO2-InP-SiO2-InP (the refractive index of SiO2 is 1.457, the initial refractive index of InP is 3.4, and the band gap energy E g of InP is 1.34eV). High-intensity bias-assisted light is injected from the side of the structure to excite photogenerated carriers in the semiconductor material InP. By adjusting the injection intensity of the bias-assisted light, different concentrations of photogenerated carriers are excited in InP, which can significantly change the refractive index of the semiconductor material InP layer, and realize flexible and effective regulation of the photonic spin Hall effect.

[0021] The nonlinear master equation for controlling the generation of light-induced carriers in a semiconductor is: where N is the concentration of free carriers, I b (E b ) is the intensity of the bias light (photon energy), α is the linear absorption coefficient, β is the nonlinear absorption coefficient, and τ is the carrier recombination lifetime. Under continuous illumination, the carrier concentration excited by strong light is considered to be in a steady state (i.e. ) and the material as a whole is neutral and uncharged (N=P). The above formula can be written as: Considering three carrier effects: band filling, band gap shrinkage and free carrier absorption, the refractive index change caused by them can be expressed as: Δn = Δn Bf+Bs (N, P, E) + Δn Fa (N, P, E), where E is the energy of the incident linearly polarized light. Band filling and band gap shrinkage have the same expression PV represents the Cauchy principal value integral, and Δα is the change in absorption coefficient caused by band filling and band gap shrinkage. Free carrier absorption m e and m h are the effective masses of electrons and holes, respectively.

[0022] Considering that the incident linearly polarized light beam is in Gaussian form and has a finite angular spectral width, it can be expressed as w0 is the waist width of the incident light beam. This incident linearly polarized light can be regarded as the superposition of left and right circularly polarized light of the same frequency, i.e. the horizontal (abbreviated as H) and vertical (abbreviated as V) polarized light can be expressed as and The symbols "+" and "-" represent left and right circularly polarized components, respectively. The relationship between the transmitted light angular spectrum and the incident light angular spectrum is: where θ i is the incident angle, t p and t s are the Fresnel transmission coefficients of p and s polarized light, respectively. The Fresnel transmission coefficients t p and t s of the five-layer optical tunneling structure can be obtained by the transfer matrix method. The spin shift of the transmitted light spin Hall effect can be expressed as

[0023] The wavelength of the incident light is set to 900 nm (close to the band gap energy of InP), the beam waist is 50 μm, the photon energy E b of the bias auxiliary light is 1.09 eV, the absorption coefficient α is 1 cm -1 , and the light intensity is selected to be 0 GW / cm 2 , 10 GW / cm 2 , 20 GW / cm 2 , and 30 GW / cm 2 . At this time, in order to realize the more obvious horizontal shift of the photon spin Hall effect of H polarized light and V polarized light, by optimizing the model, d2 = d4 = 740 nm and d3 = 17 nm are selected to realize the transmitted photon spin Hall effect of H polarized light (as shown in Figure 2 ), and d2 = d4 = 770 nm and d3 = 56 nm are selected to realize the transmitted photon spin Hall effect of V polarized light (as shown in Figure 3 ). The embodiment shows that the injection of the bias auxiliary light can significantly enhance the spin Hall effect of the transmitted light; and the angle and peak value of the horizontal shift peak of the photon spin Hall effect of the transmitted light change obviously when different intensities of the auxiliary light are applied, that is, the photon spin Hall effect can be adjusted by injecting auxiliary light with different intensities.

[0024] Embodiment 2: The above five-layer optical tunneling structure is used to adjust the photon spin Hall effect by applying bias auxiliary light with different photon energies.

[0025] Under the irradiation of bias auxiliary light with different wavelengths, the photon energy received by InP is different, the absorption coefficient also changes greatly, and the injected carrier concentration also changes greatly, so the photon energy of the injected light can also be considered as a control means. The light intensity I is fixed to 30 GW / cm 2 , the above five-layer optical tunneling structure is irradiated with injected light with different wavelengths (photon energies), and the influence of the injected light on the photon spin Hall effect is calculated. As shown in Figure 4 , the change of the photon energy (wavelength) of the bias auxiliary light has different effects on the H light and V light PSHE of the transmitted light: for the H transmitted light (as shown in Figure 4As shown in (a) of FIG. 6, when the wavelength of the auxiliary light increases, the PSHE transmission peak value gradually increases, and the angle corresponding to the peak value moves to a large incident angle; and for V transmission light (b) of FIG. 6, when the photon wavelength of the auxiliary light increases, the PSHE transmission peak value changes little, but the angle position changes obviously. It is shown that the photon spin Hall effect of the transmission light can be regulated by the bias auxiliary light of different photon energies. Figure 4

[0026] The above examples only illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application. The technologies not involved in the present application can be realized by the prior art.​

Claims

1. A method for modulating the photon spin Hall effect using bias-assisted light, characterized in that, A resonant optical tunneling structure comprising multiple InP and SiO2 layers arranged in a series; The refractive index of the InP layer ranges from 3.4 to 3.5, and the refractive index of the SiO2 layer ranges from 1.42 to 1.

55. The alternating arrangement of the InP and SiO2 layers constitutes a resonant optical tunneling structure. The multilayer thin film composed of the alternating arrangement of the InP and SiO2 layers from top to bottom constitutes a resonant optical tunneling structure, and its refractive index exhibits an alternating arrangement of high-low-high-low. Bias-assisted light is vertically injected from the side of the resonant optical tunneling structure to excite the InP layer of semiconductor material to generate photogenerated carriers, thereby achieving the control of the refractive index of the InP layer; The working light source is linearly polarized light, which is irradiated at a certain incident angle into a resonant optical tunneling structure with a refractive index gradient distribution. By adjusting the intensity or photon energy of the bias-assisted light injection, the refractive index of the InP layer of the semiconductor material can be changed, thereby achieving flexible control of the photon spin Hall effect of transmitted light.

2. The method for controlling the photon spin Hall effect using bias-assisted light according to claim 1, characterized in that: The resonant optical tunneling structure can control the Fresnel transmittance or other optical parameters of the InP-based resonant optical tunneling structure by adjusting the intensity or photon energy of the bias auxiliary light.

3. The method for controlling the photon spin Hall effect using bias-assisted light according to claim 1, characterized in that: The incident angle range of the polarized light is 0°-90°.

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