CN-122016246-A - On-chip angular momentum detection method based on slit ring structure

Abstract

The application provides an on-chip angular momentum detection method based on a slit ring structure, which can simultaneously distinguish SAM and OAM. When backlit, the etched slits in the ring create Surface Plasmon Polariton (SPP) waves that centrally form SAM and OAM related interference patterns. The different interference patterns can directly identify SAM and OAM by a single measurement. The proposed on-chip detector is easy to manufacture and can be extended for broadband applications. Based on the technical scheme of the application, the angular momentum of terahertz vortex rotation can be conveniently detected, a novel method for detecting the angular momentum of vortex light is provided for the fields of free space optical communication and particle manipulation, and the method has a great application value.

Inventors

• YANG YUANJIE
• CHENG YIHANG
• Bai yihua
• Zeng Jiongchao

Assignees

• 电子科技大学

Dates

Publication Date

20260512

Application Date

20260118

Claims (8)

1. 1. An on-chip angular momentum detection method based on a slit ring structure is used for simultaneously detecting the orbit and spin angular momentum of incident light in a terahertz wave band and is characterized in that a surface plasma laser wave is excited when vortex light is incident through a multi-section spin Hall slit structure, an interference pattern of spin and orbit angular momentum of the incident light is generated at the center of a slit ring, each slit ring comprises m pairs of slits, the slits are rectangular slits with the length of w 0 mm and the width of d 0 mm, and the polar coordinates of the j pairs of slits of the i-th slit row are respectively represented by the following formula: ; where r 0 is the slit ring center radius, Is the wavelength of the plasma laser wave, Is the polar coordinate of the slit of the outer ring, Is the polar coordinate of the slit of the inner ring.
2. 2. The method for on-chip angular momentum detection based on a slit ring structure according to claim 1, wherein, For a forward slit column, the angle α between the slit and the x-axis is expressed as ; For the reverse slit column, the angle α between the slit and the x-axis is expressed as ; Is the included angle between the slit of the inner ring and the x axis, An included angle between the outer ring slit and the x axis; when the slit resonator is surrounded into a circular ring, the polar coordinates of the slit resonator are And the included angle between the slit and the x-axis is The point surface plasmon with a distance l on the line connecting the slit resonators is: ; Wherein the method comprises the steps of Is the unit vector of the excitation direction of the slit resonator.
3. 3. The method of on-chip angular momentum detection based on slit ring structure according to claim 1, wherein for calculating an interference image of slit ring at the center of the ring, each slit resonator is used as a source to calculate the superposition of their excitation at any point, at any incident light The superimposed electric field at point o for all of the following slot resonators can be calculated as: ; Wherein, the Is a unit vector in the surface plasmon excitation direction of the mth slit resonator, Is a vector pointing from the center of the mth slot resonator to the point o, Is a vector And Included angle between them in the equation The term is determined by the orbital angular momentum of the incident light.
4. 4. The method for detecting angular momentum on-chip based on a slit ring structure according to claim 1, wherein the slit ring center radius r 0 e [1.8mm,3mm ].
5. 5. The method for on-chip angular momentum detection based on a slit ring structure according to claim 1, wherein w 0 e [70 μm,120 μm ].
6. 6. The method for on-chip angular momentum detection based on a slit ring structure according to claim 1, wherein d 0 e [10 μm,30 μm ].
7. 7. The method for detecting angular momentum on a chip based on a slit ring structure according to claim 1, wherein the number of columns n=10 of spin hall slits, and the number of pairs of slits included in each column m=9.
8. 8. The method for detecting angular momentum on-chip based on slit ring structure according to claim 1, wherein when terahertz eddy current is perpendicularly incident from one side of a substrate, a surface plasmon wave excited along an annular integrated spin Hall slit forms an interference pattern at the center of the slit ring, the interference pattern is highly sensitive to SAM and OAM of incident light, and spin and orbital angular momentum of the eddy current is obtained by one measurement by comparing the interference pattern generated by the incident light with a standard pattern obtained by simulation.

Description

On-chip angular momentum detection method based on slit ring structure Technical Field The invention relates to the technical field of light field regulation, in particular to an on-chip angular momentum detection method based on a slit ring structure. Background Light has not only energy but also momentum, including linear and angular momentum. Among them, orbital Angular Momentum (OAM) has been widely used in quantum information processing, large-capacity optical communication realized by multiplexing, and three-dimensional holographic imaging using circular polarization. In order to expand the practical application of vortex beams, especially in integrated photonics and quantum photonics, compact and efficient methods for accurately measuring angular momentum of light must be developed. Traditionally, measurement of Spin Angular Momentum (SAM) is performed using polarizers and waveplates, whereas OAM is determined by interferometry [ Phys. Rev. Lett., vol. 92, no. 1, p. 013601, jan. 2004] or multi-pinhole interferometry [ photon. Res., vol. 8, no. 5, p. 745, may 2020 ]. However, these methods typically require bulky devices and expensive optical components, limiting their integration and scalability. With the rapid development of integrated photonics technologies, on-chip detection schemes for SAM and OAM have received attention for their potential for compact structure, no alignment operations, and large scale integration. The pioneering studies of Zayats [ Science, vol. 340, no. 6130, pp. 328-330, apr. 2013] and Lee [ Phys. Rev. Lett., vol. 108, no. 21, p. 213907, may 2012] et al showed that plasma excitation on metal slit structures was related to SAM. Subsequent studies explored the chip detection of OAM using various mechanisms including orbital photocoupling effects, spin-hall couplers, photodetectors, and surface wave nanostructures. In the existing angular momentum detection method based on surface plasmons, the orbital angular momentum of the SPPs is generally judged according to the propagation angle or the spacing distance of the SPPs, the identification of the SPPs needs additional calculation, meanwhile, the angle difference of the SPPs excited by incident light of adjacent topological charges is small, the spacing distance is nano-scale, and the SPPs are difficult to directly distinguish in space. Here, we propose a convenient and novel on-chip angular momentum detection method, which can simply and rapidly detect the orbital angular momentum and the spin angular momentum of the vortex rotation at the same time, so as to enrich the schemes of optical communication field and particle manipulation field for angular momentum detection. Disclosure of Invention The application provides an on-chip angular momentum detection method based on a slit ring structure, which can simultaneously distinguish SAM and OAM. When backlit, the etched slits in the ring create Surface Plasmon Polariton (SPP) waves that centrally form SAM and OAM related interference patterns. The different interference patterns can directly identify SAM and OAM by a single measurement. The proposed on-chip detector is easy to manufacture and can be extended for broadband applications. According to the invention, a metal surface plasmon is utilized, and a super-surface structure based on a self-selected Hall slit under specific parameters is designed to generate a surface plasmon field on the surface of the structure. The surface plasmon field is highly sensitive to spin and orbital angular motion of incident light in a space structure, and has important application value in the field of vortex light detection. An on-chip angular momentum detector based on a spin Hall slit ring is used for simultaneously detecting the orbit and spin angular momentum of incident light in a terahertz wave band. The device is characterized in that through a multi-section spin Hall slit structure, surface plasma laser waves are excited when vortex light is incident, and an interference pattern of spin and orbital angular momentum of the incident light is generated at the center of a slit ring. For a slit ring composed of n slit columns, each slit column contains m pairs of slits, the slits are of length w 0 mm and width d 0 mm Is provided. Wherein the polar coordinates (r, phi) of the j-th pair of slits of the i-th slit row are represented by the following formulas, respectively: where r 0 is the slit ring center radius, Is the wavelength of the plasma laser wave,Is the polar coordinate of the slit of the outer ring,Is the polar coordinate of the slit of the inner ring. For a forward slit column, the angle α between the slit and the x-axis is expressed as; For the reverse slit column, the angle α between the slit and the x-axis is expressed as; Is the included angle between the slit of the inner ring and the x axis,An included angle between the outer ring slit and the x axis; when the slit resonator is surrounded into a circular ring, the polar coordi