A method for analyzing polarized Bessel vortex beam transmission in an anisotropic medium

Abstract

The invention belongs to the technical field of electromagnetism / light scattering and propagation of vortex beams carrying orbital angular momentum, and discloses a method for analyzing polarized Bessel vortex beam transmission in an anisotropic medium. The method comprises the steps of firstly establishing a global coordinate system and a local coordinate system; utilizing a spherical vector wavefunction to unfold the incident polarization Bessel vortex beam, and then utilizing a conversion relation between the spherical vector wave function and a cylindrical vector wave function to obtain acylindrical vector wave function unfold of the polarization Bessel vortex beam at any oblique incidence angle; obtaining cylindrical vector wave function expansion of the internal field of the mediumby utilizing an intrinsic plane angle spectrum method; establishing an expansion coefficient cascade expression of the multilayer anisotropic medium, and solving expansion coefficients of the reflection beam and the transmission beam; substituting the expansion coefficient into a corresponding field intensity expression to obtain the electric field intensity and the magnetic field intensity of any point reflection field and transmission field in the space. According to the method, the property change of the vortex beam during propagation in the multilayer anisotropic medium is calculated, thecalculation precision is higher, and the application range is wider.

Description

technical field [0001] The invention belongs to the technical field of electromagnetic / light scattering and propagation of vortex beams carrying orbital angular momentum, and in particular relates to an analytical method for transmission of polarized Bessel vortex beams in anisotropic media. Background technique [0002] At present, the existing technology commonly used in the industry is as follows: Polarized Bessel vortex beam is a kind of vortex beam, which is characterized by a circularly symmetrical annular distribution of intensity; the wavefront phase presents a spiral structure, and maintains from 0 to The cyclic gradient of 2π, the number of cycles is the topological charge of the beam, that is, the orbital angular momentum (OAM) state of the beam. Due to the non-diffraction and self-reconstruction characteristics of the polarized Bessel vortex beam itself, in practical applications, the energy loss of the beam in the propagation direction can be effectively reduced...

AI Technical Summary

Problems solved by technology

The former is mainly aimed at planar beams, by establishing a propagation matrix to solve the reflection coefficient and transmission coefficient, so as to solve the field intensity distribution of the reflection field and the transmission field, and it is applied to the physical beam with a certain angle between the wave vector direction and the propagation direction (polarized Bessel The vortex beam is a typical shaped beam) is more difficult, the reason is that for the shaped beam, the incident angles of the beam at different spatial positions are different, and there is a relationship between the wave vector polarization angle and the incident angle of the central axis of the beam Therefore, the reflection coefficient and transmission coefficient at different positions in space are different and difficult to solve; the latter can effectively analyze the transmission problem of the shaped beam by expanding the shaped beam into the superposition of planar wavelets, but for non- In the case of a homogeneous anisotropic medium (such as a multi-layer dielectric plate), since the transmission coefficient and reflection coefficient of each layer of plane wavelets need to be solved iteratively, the field strength of each wavelet is accumulated to obtain the final result , so the calculation process is difficult and inefficient

[0003] To sum up, the problems existing in the existing technology are: it is difficult to apply the existing beam-medium interaction method to the shaped beam whose wave vector direction and propagation direction have a certain angle; , can effectively analyze the transmission problem of the vortex beam, but for the case of inhomogeneous anisotropic media, the calculation is difficult and the efficiency is low

[0004] The difficulty and significance of solving the above technical problems: From the perspective of the application difficulty and limitations of existing technologies, for polarized Bessel vortex beams, there is a fixed angle (half cone angle) between the wave vector direction and the beam propagation direction, Therefore, the incident angles at the spatial positions are different, and the propagation matrix method cannot be used to solve the reflection coefficient and transmission coefficient on the surface of the medium; on the other hand, although the polarized Bessel vortex beam can be decomposed into plane The incidence of wavelets, thus transforming the problem into the case of plane wave incidence, but for inhomogeneous anisotropic media, it is necessary to use iterative method to find the reflection coefficient and transmission coefficient of each wavelet, which brings huge calculation to the calculation process Quantity and Calculation Difficulty

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