Spin hall shift of light-based chirality parameter detection method and system

Abstract

A spin Hall shift of light-based chirality parameter detection method and system. The method comprises: acquiring the dielectric constant, the magnetic permeability and the radius of chiral nanoparticles under test; on the basis of the dielectric constant, the magnetic permeability and the radius, determining spin Hall shifts of light of chiral nanoparticles having different chirality parameters under duality symmetry conditions, and obtaining a mapping relationship between the spin Hall shifts of light and the different chirality parameters; using circularly polarized light to irradiate the chiral nanoparticles under test to generate a spin Hall effect of light; and under the spin Hall effect of light, adjusting the wavelength of incident light until duality symmetry is satisfied, and obtaining an optimal spin Hall shift of light; and on the basis of the optimal spin Hall shift of light and the mapping relationship, determining a chirality parameter of the chiral nanoparticles under test. The method effectively avoids the occurrence of a destructive effect, improves the capability to characterize near-field chiral information, and enables near-field chiral features to be captured and parsed more accurately and comprehensively.

Description

A method and system for detecting chiral parameters based on optical spin Hall displacement TECHNICAL FIELD

[0001] The present application relates to the field of nano-optics, and particularly to a method and system for detecting chiral parameters based on optical spin Hall displacement. BACKGROUND

[0002] Chirality is a geometric property that an object is considered to have chiral structure when it cannot coincide with its mirror image. This feature not only exists in geometric shapes, but also can be embodied in some knotted and twisted fields, such as left and right circularly polarized light or fluid vortexes. For a long time, chiral electromagnetic fields have been widely used to characterize chiral substances, but in recent years, their application range has been extended to enantioselective biosensing, enantiomer differentiation, asymmetric catalysis, and nonlinear spectral imaging.

[0003] When nanostructures have chiral properties, they can exhibit high optical activity and excite highly twisted chiral near fields. In order to study the characteristics of these near fields, the common method is to use circular dichroism (CD) technology. Since chiral structures exhibit polarization-dependent interaction with light, optical analysis techniques are very suitable for detecting and characterizing chirality. Chiral objects have optical activity, which means that their enantiomers react differently to different polarized light. One type of optical activity is dichroism, that is, the absorption of chiral objects is polarization-dependent.

[0004] As shown in FIG. 1, first, natural light is passed through a polarizer to form linearly polarized light, and then passed through a photoelastic modulator to form circularly polarized light. When chiral molecules interact with left and right circularly polarized light, CD spectroscopy can sense the difference in absorption. Circularly polarized light is itself chiral because it is propagated by two linear components with a phase difference of ±π / 2, resulting in a three-dimensional circular helical motion. Chiral molecules preferentially absorb light that matches their chirality. Although in the extinction coefficient of small molecules, the absorption component is dominant, for large nanoparticles and macromolecules, the scattering component in the extinction coefficient can significantly enhance the measured CD signal.

[0005] However, when CD spectroscopy uses the difference in extinction between left and right circularly polarized light, it can result in the appearance of a destructive effect. This effect causes the peak intensity and the positive and negative values of the CD spectrum to change, which cannot accurately reflect the essential characteristics of the near-field chirality information. Specifically, it shows insufficient measurement sensitivity and poor accuracy, which to some extent limits the application effect of CD spectroscopy. SUMMARY

[0006] To this end, the technical problem to be solved by the present application is to overcome the emergence of the cancellation effect when the CD spectrum adopts the extinction difference of left and right circularly polarized light in the prior art, so that the peak intensity and the positive and negative changes of the numerical value of the CD spectrum cannot accurately reflect the essential characteristics of the near-field chirality information, thereby affecting the sensitivity and accuracy of the measurement.

[0007] In a first aspect, to solve the above technical problem, the present application provides a chiral parameter detection method based on optical spin Hall displacement, including but not limited to the following steps:

[0008] S1, obtaining the dielectric constant, magnetic permeability and particle radius of the chiral nanoparticles to be measured;

[0009] S2, determining the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under the condition of dual symmetry, and obtaining the mapping relationship between the optical spin Hall displacement and different chiral parameters according to the dielectric constant, the magnetic permeability and the particle radius;

[0010] S3, irradiating the chiral nanoparticles to be measured with circularly polarized light to generate the optical spin Hall effect; under the condition of generating the optical spin Hall effect, adjusting the wavelength of the incident light until the condition of dual symmetry is met, and obtaining the optimal optical spin Hall displacement;

[0011] S4, determining the chiral parameter of the chiral nanoparticles to be measured according to the optimal optical spin Hall displacement and the mapping relationship;

[0012] In an embodiment of the present application, the step S2 of determining the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under the condition of dual symmetry according to the dielectric constant, the magnetic permeability and the particle radius is:

[0013] According to the dielectric constant, the magnetic permeability and the particle radius, the constitutive relation of the chiral nanoparticles to be measured is obtained;

[0014] An incident field model and a scattering field model are constructed, and the optical spin Hall displacement expression is obtained according to the incident field model, the scattering field model and the constitutive relation;

[0015] Under the condition of dual symmetry, the optical spin Hall displacement of chiral nanoparticles with different chiral parameters is determined according to the optical spin Hall displacement expression.

[0016] In an embodiment of the present application, in the step S2, the step of obtaining the mapping relationship between the optical spin Hall displacement and different chiral parameters is:

[0017] An internal field model of chiral nanoparticles is constructed to obtain the first scattering coefficient and the second scattering coefficient;

[0018] The amplitudes of the first and second scattering matrices are calculated based on the first and second scattering coefficients.

[0019] Based on the amplitudes of the first and second scattering matrices, a mapping relationship between the optical spin Hall shift and different chiral parameters is obtained.

[0020] In one embodiment of the present invention, the step of constructing an internal field model of chiral nanoparticles to obtain a first scattering coefficient and a second scattering coefficient is as follows:

[0021] The optical field that enters any chiral medium is divided into a left-handed field component and a right-handed field component.

[0022] Construct the first expansion coefficient and the first wavenumber of the left-handed field component; construct the second expansion coefficient and the second wavenumber of the right-handed field component; construct the internal field model of the chiral nanoparticles based on the first expansion coefficient, the first wavenumber, the second expansion coefficient, and the first wavenumber;

[0023] Obtain the incident field model and the scattering field model, and calculate the first scattering coefficient and the second scattering coefficient based on the incident field model, the scattering field model and the internal field model.

[0024] In one embodiment of the present invention, the expression for the optical spin Hall displacement is:

[0025] Where, Δ SH Let be the optical spin Hall displacement, k be the wavenumber in the surrounding medium, θ be the second component of the coordinate vector in spherical coordinates, Re(·) represent the real part of the numerical value, n be the first summation index, and i be the imaginary sign. The first scattering coefficient is the summation index of 1. This is the second scattering coefficient when the second summation index is 1. Let S1 be the associated Legendre polynomial when the second summation index is 1, and S2 be the amplitude of the first scattering matrix; S2 be the amplitude of the second scattering matrix. * This indicates that the numerical values ​​are conjugate.

[0026] In one embodiment of the present invention, step S2, in which the process of determining the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on the dielectric constant, the magnetic permeability and the particle radius, further includes constructing a transfer function, and adjusting the incident light wavelength to make the transfer function reach a minimum value, thereby obtaining the dual symmetry condition.

[0027] In one embodiment of the present invention, the expression of the transfer function is:

[0028] Where T is the transfer function and n is the first summation index. The first scattering coefficient is the summation index of 1. This is the second scattering coefficient when the second summation index is 1.

[0029] In one embodiment of the present invention, step S3, after adjusting the incident light wavelength until dual symmetry is satisfied, further includes measuring the optical spin Hall displacement of the chiral nanoparticle to be tested. The step of measuring the optical spin Hall displacement is as follows:

[0030] The beam passes through the first polarizer to achieve the pre-selection state;

[0031] Based on the preselected state, the beam is weakly coupled through a material with high refractive index contrast, resulting in lateral displacement.

[0032] The scattered field feature value related to the lateral displacement is extracted by a second polarizer; wherein the projection directions of the first polarizer and the second polarizer are opposite.

[0033] Secondly, to solve the above-mentioned technical problems, the present invention provides a chiral parameter detection system based on optical spin Hall displacement, comprising:

[0034] The acquisition module is used to acquire the dielectric constant, magnetic permeability, and particle radius of the chiral nanoparticles to be tested.

[0035] The comparison mapping relationship acquisition module is used to determine the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on the dielectric constant, the magnetic permeability and the particle radius, and to obtain the comparison mapping relationship between the optical spin Hall displacement and different chiral parameters.

[0036] An adjustment module is used to irradiate the chiral nanoparticle under test with circularly polarized light to generate an optical spin Hall effect; under the condition of generating the optical spin Hall effect, the wavelength of the incident light is adjusted until dual symmetry is satisfied to obtain the optimal optical spin Hall shift.

[0037] The determination module is used to determine the chiral parameters of the chiral nanoparticle under test based on the optimal optical spin Hall shift and the control mapping relationship.

[0038] Thirdly, to solve the above-mentioned technical problems, the present invention provides a chiral molecule detection device, including the above-mentioned chiral parameter detection system based on optical spin Hall displacement.

[0039] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0040] (1) The present invention discloses a method and system for detecting chiral parameters based on optical spin Hall displacement, establishing a detailed mapping relationship between optical spin Hall displacement and chiral parameters. This mapping relationship simplifies the complex calculation and analysis process, providing an innovative and efficient method for the efficient identification of chiral parameters. By adjusting the wavelength of the incident light to achieve dual symmetry, the present invention can enhance the amplitude of the optical spin Hall displacement, thereby significantly improving the sensitivity and accuracy of the measurement. This optimization method ensures that the measurement is performed under optimal experimental conditions, effectively reducing errors.

[0041] (2) This invention uses single circularly polarized light to irradiate the chiral nanoparticles under test, effectively avoiding the occurrence of destructive effects. By further optimizing the incident light wavelength, the effect of optical spin Hall shift is maximized, enhancing signal contrast. This not only improves the characterization ability of near-field chiral information, but also enables near-field chiral features to be captured and analyzed more accurately and comprehensively. Attached Figure Description

[0042] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0043] Figure 1 is a schematic diagram of a conventional spectrum used for detecting chirality;

[0044] Figure 2 is a flowchart of a method for detecting chiral parameters based on optical spin Hall displacement in a preferred embodiment of the present invention.

[0045] Figure 3 is a schematic diagram of the spin Hall displacement caused by chiral nanoparticles under circularly polarized light incident in a preferred embodiment of the present invention.

[0046] Figure 4 is a distribution diagram of the peak value of the optical spin Hall shift of the chiral nanoparticles and the logarithm of the transfer function in a preferred embodiment of the present invention;

[0047] Figure 5 shows the near-field orbital momentum density streamlines and corresponding orbital momentum density intensity distribution of chiral nanoparticles under different chiral parameters in a preferred embodiment of the present invention. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0049] Example 1

[0050] Referring to Figure 2, this embodiment of the invention provides a method for detecting chiral parameters based on optical spin Hall shift, including but not limited to the following steps:

[0051] S1. Obtain the dielectric constant, magnetic permeability, and particle radius of the chiral nanoparticles to be tested;

[0052] S2. Determine the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on dielectric constant, magnetic permeability and particle radius, and obtain the comparison mapping relationship between optical spin Hall displacement and different chiral parameters.

[0053] S3. Irradiate the chiral nanoparticles under test with circularly polarized light to generate the optical spin Hall effect; under the condition of generating the optical spin Hall effect, adjust the wavelength of the incident light until dual symmetry is satisfied to obtain the optimal optical spin Hall shift.

[0054] S4. Determine the chiral parameters of the chiral nanoparticles to be tested based on the optimal optical spin Hall shift and the reference mapping relationship.

[0055] This invention provides a method for detecting chiral parameters based on optical spin Hall displacement. By adjusting the wavelength of the incident light to satisfy the dual symmetry condition, the effect of optical spin Hall displacement can be significantly enhanced, thereby improving the sensitivity and accuracy of the measurement. This optimization step ensures that the measurement is performed under optimal conditions, reducing errors. By establishing a correlation mapping relationship between optical spin Hall displacement and chiral parameters, chiral parameters can be quickly and accurately deduced from experimental measurement results. This mapping relationship provides an efficient method for rapid identification of chiral parameters, reducing complex calculation and analysis processes. Irradiating the chiral nanoparticles under test with single circularly polarized light avoids the occurrence of destructive effects. By optimizing the incident light wavelength, the effect of optical spin Hall displacement can be maximized, thereby enhancing signal contrast and improving the characterization ability of near-field chiral information, enabling near-field chiral features to be captured and analyzed more accurately and comprehensively.

[0056] Specifically, in step S1, relevant parameters of the particles and incident light are determined. The relevant parameters of the particles include dielectric constant, permeability, and particle radius, while the relevant parameters of the incident light include the incident light wavelength. The particle radius can be obtained using a nanoparticle size analyzer, which has a measurable range of 0.3 nanometers to 10 micrometers. The dielectric constant and permeability can be obtained using an impedance analyzer. Utilizing the extremely high sensitivity of optical spin Hall displacement to the dielectric constant, permeability, and particle radius of chiral nanoparticles, this embodiment demonstrates a significant advantage in chiral detection due to its high sensitivity.

[0057] Specifically, in step S2, the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions is determined based on the dielectric constant, magnetic permeability and particle radius of the chiral nanoparticles to be tested, so as to determine the comparison mapping relationship between the optical spin Hall displacement and different chiral parameters.

[0058] Furthermore, based on the dielectric constant, permeability, and particle radius, the constitutive relation of the chiral nanoparticles under test is obtained. As shown in Figure 3, the spin Hall shift induced by the chiral nanoparticles under incident circularly polarized light is expressed mathematically as follows:

[0059] Where E0 is the amplitude of the incident wave; It is the unit vector in the x-direction of the first component of the coordinate vector in a spatial rectangular coordinate system; ω is the unit vector in the y-direction of the second component of the coordinate vector in the spatial rectangular coordinate system; i is the imaginary number; k is the wave number in the environmental medium; ω is the angular frequency of the incident wave; z is the unit vector in the z-direction of the third component of the coordinate vector in the spatial rectangular coordinate system; t is time.

[0060] [Corrected according to Rule 91, August 18, 2025] For the general case, the constitutive relation is D = c E,B=μ c For substances containing H, these substances are generally not optically active. There are many constitutive relations for optically active chiral media, but most of them have been shown to be equivalent. This invention employs the Condon-Rosenfeld constitutive relation, whose mathematical expression is:

[0061] [Corrected according to Rule 91, August 18, 2025] Wherein, D is the electric displacement vector of the chiral nanoparticle; B is the magnetic induction intensity of the chiral nanoparticle; ∈ c denoted as κ, where κ is the dielectric constant of the chiral nanoparticle; κ is the chiral parameter of the chiral nanoparticle (usually taken between -1 and 1); ε₀ is the dielectric constant in vacuum; μ₀ is the permeability in vacuum; H is the magnetic field strength; E is the electric field strength; μ₀ is the electric field strength. c denoted as , where is the magnetic permeability of the chiral nanoparticles.

[0062] Furthermore, incident field and scattering field models are constructed, and the expression for the optical spin Hall displacement is obtained based on these models and constitutive relations. Specifically, firstly, incident field and scattering field models for chiral nanoparticles are constructed, where the scattering field model is the key physical quantity used to calculate the optical spin Hall displacement. The incident field and scattering field models for chiral nanoparticles are derived from Mie scattering theory, and their specific expressions are as follows:

[0063] Among them, E ip H represents the electric field component of the incident wave. ip denoted as the incident wave magnetic field component; n is the first summation index; m is the second summation index; in this embodiment, both n and m can be assigned values ​​according to actual needs. and All are first-kind spherical harmonic vector wave functions; in this embodiment, the coordinate vector in spherical coordinates uses three components. Represents; r is the second component of the coordinate vector in spherical coordinates; E s Represents the electric field scattering field; The first scattering coefficient; This is the second scattering coefficient; and All are third-kind spherical harmonic vector wave functions; H s denoted by , where p represents the incident polarization state. and All are the expansion coefficients of the incident wave.

[0064] Furthermore, regarding the value of the expansion coefficient of the incident wave, for example, when right-handed polarized light is incident, we have:

[0065] in, This is the first expansion coefficient of right-handed polarized light. δ is the second expansion coefficient of right-handed polarized light. m,1 For Kroneck's symbol.

[0066] [Corrected according to Rule 91, August 18, 2025] Further, an internal field model of the chiral nanoparticles is constructed to calculate the first and second scattering coefficients. Inside the chiral nanoparticles, any light field entering the chiral medium can be divided into two different polarization components (i.e., left-handed and right-handed field components). These two components have different amplitudes, phases, and wave numbers. The amplitude and phase are determined by the expansion coefficient A of the internal field. mn (i.e., the first expansion coefficient of the left-handed field component) and B mn The wavenumber is described by the second expansion coefficient of the right-handed polarization component, while the wavenumber is affected by the chirality of the medium. The wavenumbers of the left-handed and right-handed polarization components are respectively: the wavenumber of the left-handed polarized light (i.e., the first wavenumber). And the wavenumber of right-handed polarized light (i.e., the second wavenumber). Therefore, the interior field model can be expressed as:

[0067] Among them, E int H represents the internal electric field of the chiral nanoparticles. int This refers to the internal magnetic field of chiral nanoparticles.

[0068] Furthermore, according to the boundary condition r×E int =r×(E ip +E s ) and r×H int =r×(H ip+H s By substituting the expressions for the inner field model and the outer field model (i.e., the incident field model and the scattered field model) into the equations, the first scattering coefficient can be obtained. Second scattering coefficient

[0069] For example, constructing the first scattering coefficient Second scattering coefficient The expression:

[0070] in, This is the first expansion coefficient of right-handed polarized light; This is the second expansion coefficient for right-handed polarized light; As the first intermediate variable; It is the second intermediate variable; It is the third intermediate variable; As the fourth intermediate variable, it satisfies:

[0071] [Corrected according to detailed rule 91, August 18, 2025] Wherein, Ψ n (·) represents the first kind of Riccati-Bessel equation; ξ n (·) represents the third type of Riccati-Bessel equation; The logarithmic derivative of the first kind of Riccati-Bessel equation, Ψ′ n (·) represents Ψ n The derivative of (·); η r It is the fifth intermediate variable; denoted as ρ, where μ is the dielectric constant of the surrounding medium; μ is the magnetic permeability of the surrounding medium; ∈ c μ is the dielectric constant of the chiral nanoparticles. c The magnetic permeability of the chiral nanoparticles; For the third kind of Riccati-Bessel equation, ξ′ n (·) is ξ n The derivative of (·); a is the radius of the chiral nanoparticle; k is the wavenumber in the environmental medium; ω is the angular frequency of the incident wave; k1 is the wavenumber of the left-handed polarized light; k2 is the wavenumber of right-handed polarized light; κ is the chiral parameter of the chiral nanoparticle; μ0 is the magnetic permeability in vacuum; ∈0 is the dielectric constant in vacuum.

[0072] An expression for the optical spin Hall displacement in the chiral sphere model was derived using Mie scattering theory. Since the spin Hall displacement is a function of the scattering angle, this embodiment focuses only on the peak value of the spin Hall displacement under this set of chiral parameters when adjusting the chiral parameters. This allows for a clearer observation of changes in the peak value. However, besides chiral parameters, dual symmetry is also a crucial factor affecting the spin Hall displacement. Therefore, this embodiment of the invention further includes adjusting the wavelength of the incident wave to reconcile the dual symmetry.

[0073] Specifically, duality can be described by a transfer function. In this embodiment of the invention, by constructing and analyzing the transfer function, an externally adjustable parameter can be optimized to achieve the maximum optical spin Hall shift. In this process, the externally adjustable parameter is the wavelength of the incident light. By selecting a suitable wavelength, the effect of the optical spin Hall shift can be significantly enhanced, making it more pronounced. This not only helps improve the sensitivity of the measurement but also effectively reduces errors during comparative analysis, improving the accuracy and reliability of the measurement results.

[0074] Furthermore, the definition of the transfer function is: In other words, it's the ratio of the energy in the scattered field that has the opposite helicity to that in the incident field to the energy in the part with the same helicity. Substituting this into the scattering field model expression in the transfer function, it can be expressed as:

[0075] When the dual symmetry condition is met, T is 0 (that is, when it is infinitely close to dual symmetry, the size of the transfer function will be infinitely close to 0).

[0076] The spin Hall effect of light originates from the momentum conversion between spin angular momentum and orbital angular momentum as the light beam propagates in a medium with a refractive index gradient. Its ultimate manifestation is the lateral displacement of the perceived position of the interacting volume, which can be expressed as:

[0077] in, The third component of the Poynting vector of the scattered wave in spherical coordinates. Components in direction; P r Let r be the component of the Poynting vector of the scattered wave in the direction of the first component of the coordinate vector in spherical coordinates. The third component of the coordinate vector in spherical coordinate system The unit vector in the direction.

[0078] For example, constructing an optical spin Hall displacement Δ SH The expression for the mapping relationship between chiral parameters and chiral parameters is as follows:

[0079] Where θ is the second component of the coordinate vector in spherical coordinates, i.e., the scattering angle; Re(·) represents taking the real part of the value; This is the second scattering coefficient when m is 1; S1 is the associated Legendre polynomial when m is 1; S2 is the amplitude of the first scattering matrix; S3 is the amplitude of the second scattering matrix. This is the first scattering coefficient when m is 1; For the polynomial with regard to Legendre; (·) * This indicates that the numerical values ​​are conjugate.

[0080] [Corrected according to Rule 91, August 18, 2025] When light interacts with a medium, the conservation of angular momentum leads to coupling between the spin degree of freedom and orbital motion of the photon. This spin-orbit interaction is the source of the spin Hall shift. The Dirac form of Maxwell's equations can be used to describe the local spin and orbital momentum and their spin-orbit interaction, in the form:

[0081] [Corrected according to Rule 91, August 18, 2025] Where c is the speed of light in a vacuum; α and All are Dirac matrices; φ is the wave function of the electric and magnetic fields, expressed as... T represents the matrix transpose symbol; p is the momentum operator. V is the optical potential induced by the dielectric. Orbital momentum density p o Depend on This can be defined to characterize the trajectory of a photon, and its specific expression is:

[0082] Here, Im(·) represents the imaginary part of the numerical value. Furthermore, orbital momentum density can be used to characterize spin-orbit coupling in the near field.

[0083] Parameters such as dielectric constant, magnetic permeability, and particle radius can be theoretically calculated to obtain corresponding optical spin Hall shift values, and these shift values ​​have a clear mapping relationship with the chiral parameters of the particles. Based on this, a detailed mapping table can be constructed for the optical spin Hall shifts corresponding to different chiral parameters. In actual experiments, once the optical spin Hall shift of a particle is measured, its chiral parameters can be quickly and accurately deduced by consulting this mapping table. This method provides an efficient and reliable approach for the rapid identification and characterization of chiral particles in experiments.

[0084] Specifically, in step S3, when the chiral nanoparticle under test is irradiated with circularly polarized light and an optical spin Hall effect is generated, the wavelength of the incident light is adjusted until dual symmetry is satisfied to maximize the optical spin Hall displacement. The maximized optical spin Hall displacement is the optimal optical spin Hall displacement.

[0085] By adjusting the incident light wavelength to minimize the transfer function in step S2 to satisfy the dual symmetry condition, and then substituting the parameters and scattering coefficients at this point into the expression for the spin Hall displacement, we can obtain the optical spin Hall displacement under different chiral parameters.

[0086] Further, after adjusting the incident light wavelength in step S3 until dual symmetry is satisfied, the measurement of the optical spin Hall displacement of the chiral nanoparticle under test is also included. Since the optical spin Hall displacement is usually very weak, quantum weak measurement techniques are generally used to observe it. Weak measurement generally consists of three steps: pre-selection, weak coupling, and post-selection. The purpose of pre-selection is to adjust the polarization state of the incident beam to a specific initial state so that the optical spin Hall displacement can be effectively observed during the subsequent weak coupling process. Weak coupling causes a small lateral displacement of the beam through an air-glass interface or other non-uniform medium. The purpose of post-selection is to extract the scattered field characteristic values ​​related to the optical spin Hall displacement using a second polarizer. The specific steps for obtaining the optical spin Hall displacement through weak measurement are as follows:

[0087] First, the incident beam is passed through a first polarizer to achieve the pre-selected state. A high-precision, high-transmittance polarizer is selected to ensure the purity and stability of the incident beam's polarization state. By precisely adjusting the angle of the polarizer, the polarization direction of the incident beam is ensured to be consistent with the experimental design. For example, a half-wave plate or a quarter-wave plate can be used to precisely control the polarization state. By using a high-power laser source or optimizing the optical path design, the intensity of the incident beam is increased, thereby improving the signal-to-noise ratio of the measurement.

[0088] Secondly, weak coupling can be achieved through materials with high refractive index contrast. Specifically, materials with high refractive index contrast (such as air-glass interfaces) can be used to enhance the optical spin Hall shift. High refractive index contrast can increase the spin-orbit coupling strength of photons. By adjusting the angle of the incident beam, the optimal incident conditions can be found to maximize the optical spin Hall shift. Typically, incident conditions close to the critical angle can produce a large shift. Introducing micro / nano structures (such as gratings, nanopillars, etc.) at the interface can further enhance the optical spin Hall shift. These structures can amplify the shift through localized field enhancement effects.

[0089] Finally, the scattered field characteristic values ​​are obtained after using a second polarizer. Specifically, the projection directions of the two polarizers are precisely aligned to maximize the interference effect. This can be achieved using a high-precision optical adjustment platform. A high-sensitivity photodetector (such as a single-photon detector or a high-resolution camera) is selected to capture the weak scattered light signal. By repeating the measurement multiple times and averaging the results, noise can be effectively reduced and measurement accuracy improved. Advanced data analysis methods (such as Fourier transform and wavelet analysis) are employed to extract the characteristic values ​​of the optical spin Hall shift from the complex scattered field.

[0090] Using this method, optical spin Hall displacement can achieve measurable accuracy.

[0091] Specifically, in step S4, the chiral parameters of the chiral nanoparticle under the maximum optical spin Hall displacement are determined based on the mapping relationship between the optimal optical spin Hall displacement and the chiral parameters.

[0092] When dual symmetry is satisfied, the transfer function T has a magnitude of 0. In this embodiment of the invention, the relative permittivity is set to 3.55. 2 A silicon sphere with a permeability of 1 and a radius of 131 nm was used as the research object (the environmental medium was vacuum). When the chirality parameter was 0 (i.e., no chirality), the dual symmetry condition was satisfied when circularly polarized light with a wavelength of approximately 1068 nm (here, right-handed polarized light) was incident. At this time, the optical spin Hall shift peak reached its maximum, approximately 1.9 times the wavelength, as shown in Figure 4. In Figure 4(a), the spin Hall shift values ​​are all expressed in terms of the incident wavelength, i.e., Δ... SH / λ.

[0093] In Figure 4(a), the magnitude of the transfer function corresponding to the maximum value of the spin Hall displacement in the 1050nm to 1100nm band is obtained as the chiral parameter changes. The smaller the value, the closer it is to zero, and the closer the system is to dual symmetry.

[0094] Figure 4(b) shows the magnitude of the system's transfer function under different incident wavelengths and chiral parameters. It can be concluded that as the chiral parameter changes, the wavelength satisfying dual symmetry also changes, matching the parameter of the maximum peak value of the spin Hall shift in Figure 4(a). Observing the maximum peak value of the spin Hall shift under these dual symmetry conditions for different chiralities, it can be seen that chirality has a significant and somewhat linear influence on this peak value. When the chiral parameter is close to 1, the peak value of the spin Hall shift can reach 2.5 wavelengths, while for nanoparticles with the opposite chirality (i.e., when the chiral parameter is close to -1), this peak value can only reach about one wavelength. Therefore, nanoparticles with different chiralities can be distinguished by comparing the magnitude of the spin Hall shift peak value.

[0095] Simultaneously, the spin Hall displacement is also related to near-field spin-orbit coupling. When stronger spin-orbit coupling occurs near the particle, the corresponding peak value of the spin Hall displacement is larger. Orbital momentum density streamlines are a relatively intuitive way to observe this near-field spin-orbit interaction. After adding chirality, the streamlines and intensity distribution of orbital momentum density are also affected, as shown in Figure 5. When light enters a nanoparticle, the spin angular momentum of circularly polarized light is converted into orbital angular momentum. Therefore, the magnitude of the orbital momentum density and the degree of streamline distortion can, to some extent, intuitively reflect the strength of spin-orbit coupling. It was found that particles with larger chiral parameters, as shown in Figure 5(c), have higher orbital momentum density values ​​over a larger range near the particle, and a greater degree of streamline distortion. Conversely, particles with opposite chirality, as shown in Figure 5(b), have smaller orbital momentum density values ​​and a weaker degree of streamline distortion. Using orbital momentum density to reflect near-field spin-orbit coupling further reflects different near-field chiral information. Figure 5(a), (b), and (c) show the orbital momentum density streamlines and corresponding intensity distributions near the chiral nanoparticles when the chiral parameters are 0, -0.7, and 0.7, respectively (the incident wavelengths are 1068 nm, 1081 nm, and 1081 nm, which are the wavelengths that can satisfy dual symmetry under different chiral parameters, as shown in Figure 4(b)). The circles and squares in Figure 5 indicate the two corresponding singularities.

[0096] Figure 4(a) shows the optical spin Hall displacement for different chiral parameters in the wavelength range of 1050 nm to 1100 nm. It's important to note that the optical spin Hall displacement is related to the observation angle. Step S2 should yield a curve showing the spin Hall displacement as a function of the scattering angle θ, but the truly valuable information is its peak value. Therefore, Figure 4(a) displays the peak values ​​of the spin Hall displacement for different parameters. In actual measurement, this embodiment does not require plotting the spin Hall displacement curves for each set of parameters to record the corresponding maximum values. The transfer function value calculated in step S2 yields the result shown in Figure 4, allowing us to find parameters that satisfy dual symmetry. Only the spin Hall displacement curves for these parameter sets need to be plotted. This embodiment allows for a direct determination of the chiral parameters of chiral nanoparticles from the peak values ​​of the spin Hall displacement.

[0097] This invention provides a method for detecting chiral parameters using optical spin Hall displacement. The spin Hall displacement is highly sensitive to the dielectric constant, magnetic permeability, and particle radius of chiral nanoparticles, offering the advantage of high sensitivity in chiral detection. The method determines the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions, establishing a mapping relationship between the optical spin Hall displacement and chiral parameters. This allows for a direct assessment of the chiral parameters of the chiral nanoparticles based on the peak value of the spin Hall displacement.

[0098] Example 2

[0099] Based on the same inventive concept, this embodiment provides a chiral parameter detection system based on optical spin Hall displacement. The principle of solving the problem is similar to that of the chiral parameter detection method based on optical spin Hall displacement provided in Embodiment 1, and the repeated parts will not be described again.

[0100] This embodiment provides a chiral parameter detection system based on optical spin Hall displacement, including:

[0101] The acquisition module is used to acquire the dielectric constant, magnetic permeability, and particle radius of the chiral nanoparticles to be tested.

[0102] The comparison mapping relationship acquisition module is used to determine the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on dielectric constant, magnetic permeability and particle radius, and to obtain the comparison mapping relationship between optical spin Hall displacement and different chiral parameters.

[0103] The adjustment module is used to irradiate the chiral nanoparticle under test with circularly polarized light to generate the optical spin Hall effect; under the condition of generating the optical spin Hall effect, the wavelength of the incident light is adjusted until dual symmetry is satisfied to obtain the optimal optical spin Hall shift.

[0104] The determination module is used to determine the chiral parameters of the chiral nanoparticles to be tested based on the optimal optical spin Hall shift and the reference mapping relationship.

[0105] Example 3

[0106] This embodiment provides a chiral molecule detection device, including the chiral parameter detection system based on optical spin Hall shift as described in Embodiment 2.

[0107] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0108] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more flowchart illustrations and / or one or more block diagrams.

[0109] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0110] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0111] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for detecting chiral parameters based on optical spin Hall shift, characterized in that, include: S1. Obtain the dielectric constant, magnetic permeability, and particle radius of the chiral nanoparticles to be tested; S2. Determine the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on the dielectric constant, the magnetic permeability and the particle radius, and obtain the comparison mapping relationship between the optical spin Hall displacement and different chiral parameters. S3. Irradiate the chiral nanoparticle under test with circularly polarized light to generate an optical spin Hall effect; under the condition that the optical spin Hall effect is generated, adjust the wavelength of the incident light until dual symmetry is satisfied to obtain the optimal optical spin Hall shift. S4. Determine the chiral parameters of the chiral nanoparticles to be tested based on the optimal optical spin Hall shift and the reference mapping relationship.

2. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 1, characterized in that, The step S2, which determines the optical spin Hall shift of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on the dielectric constant, the magnetic permeability, and the particle radius, is as follows: The constitutive relation of the chiral nanoparticle under test is obtained based on the dielectric constant, the magnetic permeability, and the particle radius. An incident field model and a scattered field model are constructed, and an expression for the optical spin Hall displacement is obtained based on the incident field model, the scattered field model, and the constitutive relation. Under dual symmetry conditions, the optical spin Hall displacement of chiral nanoparticles with different chiral parameters is determined according to the optical spin Hall displacement expression.

3. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 1, characterized in that, In step S2, the step of obtaining the mapping relationship between the optical spin Hall shift and different chiral parameters is as follows: An internal field model of chiral nanoparticles was constructed to obtain the first and second scattering coefficients. The amplitudes of the first and second scattering matrices are calculated based on the first and second scattering coefficients. Based on the amplitudes of the first and second scattering matrices, a mapping relationship between the optical spin Hall shift and different chiral parameters is obtained.

4. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 3, characterized in that, The steps for constructing the internal field model of chiral nanoparticles to obtain the first and second scattering coefficients are as follows: The optical field that enters any chiral medium is divided into a left-handed field component and a right-handed field component. Construct the first expansion coefficient and the first wavenumber of the left-handed field component; construct the second expansion coefficient and the second wavenumber of the right-handed field component; construct the internal field model of the chiral nanoparticles based on the first expansion coefficient, the first wavenumber, the second expansion coefficient, and the first wavenumber; Obtain the incident field model and the scattering field model, and calculate the first scattering coefficient and the second scattering coefficient based on the incident field model, the scattering field model and the internal field model.

5. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 1, characterized in that, The expression for the optical spin Hall displacement is: Where, Δ SH Let be the optical spin Hall displacement, k be the wavenumber in the surrounding medium, θ be the second component of the coordinate vector in spherical coordinates, Re(·) represent the real part of the numerical value, n be the first summation index, and i be the imaginary sign. The first scattering coefficient is the summation index of 1. This is the second scattering coefficient when the second summation index is 1. Let S1 be the associated Legendre polynomial when the second summation index is 1, and S2 be the amplitude of the first scattering matrix; S2 be the amplitude of the second scattering matrix. * This indicates that the numerical values ​​are conjugate.

6. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 1, characterized in that, In step S2, the process of determining the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on the dielectric constant, the magnetic permeability, and the particle radius also includes constructing a transfer function. By adjusting the incident light wavelength, the transfer function is made to reach its minimum value, thereby obtaining the dual symmetry condition.

7. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 6, characterized in that, The expression for the transfer function is: Where T is the transfer function and n is the first summation index. The first scattering coefficient is the summation index of 1. This is the second scattering coefficient when the second summation index is 1.

8. The method for detecting chiral parameters based on optical spin Hall displacement according to claim 1, characterized in that, In step S3, after adjusting the incident light wavelength until dual symmetry is satisfied, the measurement of the optical spin Hall displacement of the chiral nanoparticle under test is also included. The step of measuring the optical spin Hall displacement is as follows: The beam passes through the first polarizer to achieve the pre-selection state; Based on the preselected state, the beam is weakly coupled through a material with high refractive index contrast, resulting in lateral displacement. The scattered field feature values ​​related to the lateral displacement are extracted using a second polarizer; The first polarizer and the second polarizer have opposite projection directions.

9. A system for detecting chiral parameters based on optical spin Hall displacement, characterized in that, include: The acquisition module is used to acquire the dielectric constant, magnetic permeability, and particle radius of the chiral nanoparticles to be tested. The comparison mapping relationship acquisition module is used to determine the optical spin Hall displacement of chiral nanoparticles with different chiral parameters under dual symmetry conditions based on the dielectric constant, the magnetic permeability and the particle radius, and to obtain the comparison mapping relationship between the optical spin Hall displacement and different chiral parameters. An adjustment module is used to irradiate the chiral nanoparticle under test with circularly polarized light to generate an optical spin Hall effect; under the condition of generating the optical spin Hall effect, the wavelength of the incident light is adjusted until dual symmetry is satisfied to obtain the optimal optical spin Hall shift. The determination module is used to determine the chiral parameters of the chiral nanoparticle under test based on the optimal optical spin Hall shift and the control mapping relationship.

10. A chiral molecule detection device, characterized in that, This includes the chiral parameter detection system based on optical spin Hall displacement as described in claim 9.

Images