On-chip angular momentum detection method based on slit ring structure
By employing a spin Hall slit ring detection method with a slit ring structure and utilizing surface plasmon wave interferometry patterns, the problems of complexity and low integration in existing optical angular momentum detection technologies are solved, achieving compact and efficient angular momentum detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-01-18
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies for optical angular momentum detection require large devices and expensive optical components, which limits integration and scalability. Furthermore, they are difficult to directly distinguish angular differences at the nanometer level, resulting in complex and inefficient detection methods.
An on-chip detection method based on a slit ring structure is adopted. By designing a spin Hall slit ring structure on a metal surface, the interference pattern generated at the center of the slit ring by surface plasmon waves is utilized to achieve simultaneous detection of spin and orbital angular momentum.
It achieves simple and fast angular momentum detection, has a compact structure, is easy to manufacture, is suitable for broadband applications, has high integration, can simultaneously identify the trajectory and spin angular momentum of vortex light, and is not limited by traditional multi-aperture interferometry.
Smart Images
Figure CN122016246A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical field manipulation technology, and in particular to an on-chip angular momentum detection method based on a slit ring structure. Background Technology
[0002] Light possesses not only energy but also momentum, including linear and angular momentum. Orbital angular momentum (OAM) has been widely applied in quantum information processing, high-capacity optical communication via multiplexing, and three-dimensional holographic imaging utilizing circular polarization. To expand the practical applications of vortex beams, especially in integrated photonics and quantum photonics, it is essential to develop compact and efficient methods for accurately measuring optical angular momentum. Traditionally, spin angular momentum (SAM) measurements have used polarizers and waveplates, while OAM has been determined using 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 equipment and expensive optics, limiting their integration and scalability.
[0003] With the rapid development of integrated photonics technology, on-chip detection schemes for SAM and OAM have attracted much attention due to their compact structure, lack of alignment operations, and potential for large-scale integration. The pioneering research by 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. demonstrated the association of plasmonic excitation on metallic slit structures with SAM. Subsequent studies have explored chip detection of OAM using various mechanisms, including orbital photoelectric coupling, spin-Hall couplers, photodetectors, and surface wave nanostructures.
[0004] Existing angular momentum detection methods based on surface plasmons (SPPs) typically determine the orbital angular momentum of SPPs based on their propagation angle or spacing. This identification requires additional computation, and the angular differences and nanometer-scale spacing between SPPs excited by incident light from adjacent topological charges are small, making direct spatial differentiation difficult. Here, we propose a convenient and novel on-chip angular momentum detection method that can quickly and easily detect both the orbital and spin angular momentum of vortex light, enriching the angular momentum detection solutions in optical communication and particle manipulation fields. Summary of the Invention
[0005] This application proposes an on-chip angular momentum detection method based on a slit ring structure, capable of simultaneously resolving SAM and OAM. Under back illumination, the etched slits within the ring generate surface plasmon polariton (SPP) waves, forming interference patterns associated with both SAM and OAM at the center. Different interference modes can be directly identified between SAM and OAM through a single measurement. The proposed on-chip detector is easy to fabricate and can be extended for broadband applications.
[0006] This invention utilizes surface plasmons on metal surfaces to generate a surface plasmon field on the surface of a metasurface structure based on a self-selected Hall slit, designed with specific parameters. This surface plasmon field is highly sensitive to the spin and orbital angular momentum of incident light in its spatial structure, and has significant application value in the field of vortex light detection.
[0007] An on-chip angular momentum detector based on a spin Hall slit ring is disclosed for simultaneously detecting the orbital and spin angular momentum of incident light in the terahertz band. Its key feature is that a multi-segment spin Hall slit structure excites surface plasmon waves upon the incidence of vortex light, generating an interference pattern at the center of the slit ring with the spin and orbital angular momentum of the incident light. For a slit ring composed of n slit segments, each segment contains m pairs of slits, with each slit having a length w0 mm and a width d0 mm. A rectangular slit. Among them, the first... i The first of the narrow slits j The polar coordinates (r, φ) of the slit are expressed by the following formulas:
[0008] Where r0 is the center radius of the slit ring. The wavelength of the plasmon wave, Let be the polar coordinates of the outer slit. These are the polar coordinates of the inner slit.
[0009] For a positive slit array, the angle α between the slit and the x-axis is expressed as: ; For a reverse slit array, the angle α between the slit and the x-axis is expressed as: ; Let be the angle between the inner slit and the x-axis. The angle between the outer slit and the x-axis; When the slit resonator is arranged in a circular ring, the polar coordinates of the slit resonator are: The angle between the slit and the x-axis is... The distance on the line connecting the slit resonators is l The point surface plasmons are: ; in It is the unit vector of the excitation direction of the slit resonator.
[0010] To calculate the interference pattern formed by the slit ring at its center, it is necessary to calculate the superposition of their excitations at any point, using each slit resonator as a source. Under arbitrary incident light... The superimposed electric field of all the slit resonators at point o can be calculated as follows: ;
[0011] in, It is the unit vector along the surface plasmon excitation direction of the m-th slit resonator. It is the vector pointing from the center of the m-th slit resonator to point o. It is a vector and The included angle between them. In the equation The term is determined by the orbital angular momentum of the incident light, and thus we can detect the orbital angular momentum of the incident light based on the distribution of the plasmon field.
[0012] In one implementation, the initial radius r0 ∈ [1.8 mm, 3 mm].
[0013] In one implementation, w0 ∈ [70 μm, 120 μm].
[0014] In one implementation, d0 ∈ [10 μm, 30 μm].
[0015] In one implementation, the number of columns of the spin Hall slits is n=10, and the number of slit pairs in each column is m=9.
[0016] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.
[0017] This invention regulates the generation of a plasmonic field sensitive to the angular momentum of incident light by adjusting the structural parameters of the slit ring and the number of slits in the slit ring; the slit distribution can be represented by the following function:
[0018] Where r0 is the center radius of the slit ring. Let be the polar coordinates of the outer slit. Let n be the polar coordinates of the inner slit ring, n be the number of slit columns in the slit ring, and m be the total number of slits contained in the slit column.
[0019] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved.
[0020] The present invention provides a method for detecting the angular momentum of a spin Hall slit ring, which, compared with the prior art, has at least the following advantages: 1. The slit ring has a simple structure, is easy to manufacture, and its structural parameters are robust to the recognition effect, with minimal impact from manufacturing errors. This means that this metasurface detector is simple to manufacture and has strong anti-interference capabilities.
[0021] 2. Metasurface detectors are highly integrated, compact, and expandable, making them easy to integrate as small devices in various systems.
[0022] 3. In free space, when the number of topological charges is greater than half the number of mask apertures, the pattern corresponding to the traditional multi-aperture interferometry will exhibit periodic repetition, and it is only suitable for measuring vortex light with low orbital angular momentum. For the on-chip detector proposed in this invention, even if the number of topological charges is greater than the number of ring arc segments, the light intensity distribution of near-field surface plasmons still exhibits significantly different interference patterns, and therefore it is not limited by the traditional multi-aperture interferometry.
[0023] 4. Unlike most plasmonic devices, this simple geometric structure has broadband characteristics, making it suitable for incident light of different wavelengths. The longer the incident light wavelength, the longer the generated plasmonic wavelength, and therefore the larger the obtained interference pattern. Thus, a single structural design can achieve the measurement of the topological charge of vortex beams of different wavelengths.
[0024] In summary, the angular momentum detection method proposed in this invention has unique advantages in simultaneously detecting the spin and orbital angular momentum of vortex light. Attached Figure Description
[0025] The invention will now be described in more detail with reference to embodiments and the accompanying drawings. Figure 1 This indicates the structural design of the slit ring on the chip; Figure 2 To design an on-chip detector for simultaneously measuring spin and orbital angular momentum; Figure 3 The detection principles of optical SAM and OAM; Figure 4 LCP and simulated near-field interferogram at incidence. Detailed Implementation
[0026] An on-chip angular momentum detection method based on a slit ring structure is disclosed for simultaneously detecting the orbital and spin angular momentum of incident light in the terahertz band. Its key feature is that a multi-segment spin Hall slit structure is used to excite surface plasmon waves when vortex light is incident, generating an interference pattern at the center of the slit ring with the spin and orbital angular momentum of the incident light. Figure 1As shown, for a slit ring composed of n slit segments, each slit ring contains m pairs of slits, and each slit is a rectangular slit with a length of w0 mm and a width of d0 mm. Wherein... i The first of the narrow slits j The polar coordinates (r, φ) of the slit are expressed by the following formulas: Where r0 is the center radius of the slit ring. Let be the polar coordinates of the outer slit. These are the polar coordinates of the inner slit.
[0027] For a positive slit array, the angle α between the slit and the x-axis is expressed as:
[0028] For a reverse slit array, the angle α between the slit and the x-axis is expressed as:
[0029] Let be the angle between the inner slit and the x-axis. The angle between the outer slit and the x-axis; The vortex light detection method designed in this invention detects the angular momentum of vortex light by using the surface plasmon field generated when terahertz vortex light is perpendicularly incident on an on-chip detector. Only one detection of the plasmon field is needed, and by comparing it with a standard field pattern, both the orbital angular momentum and spin angular momentum of the vortex light can be obtained simultaneously.
[0030] Figure 2 (a) Excitation of the detector and device; (b) Scanning electron microscopy (SEM) image of the fabricated on-chip detector; (c) Structural parameters of the slit pair in the on-chip detector; (d) The slit ring consists of ten annular arcs, including five left-handed and five right-handed arcs. Utilizing Figure 2 The on-chip detector shown detects vortex light, and the steps are as follows: Step 1: The terahertz vortex light to be detected is incident perpendicularly from one side of the SiO2 substrate to excite a surface plasmon field on the aluminum film surface.
[0031] Step 2: Detect the plasmonic field generated on the surface of the aluminum film to obtain its field distribution.
[0032] Step 3: Compare the detected field distribution with the standard results, and determine the orbital angular momentum and spin angular momentum of the vortex light through its pattern.
[0033] Figure 3(a) A single slit as an antenna-excited SPP wave; (b, c) Two pairs of orthogonally arranged slits with LCP or RCP incident unidirectional transmission; (d) SPP waves propagating in opposite directions to different SAMs via the spin Hall effect, with the m-th and m+1-th slits using opposite hand directions; (eg) Slits sampling the incident light phase to detect OAM, with the topological charge of the vortex phase l = -1,2. Figure 4 The topological charge ranges from -1 to 2.
[0034] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.
Claims
1. An on-chip angular momentum detection method based on a slit ring structure, used to simultaneously detect the trajectory and spin angular momentum of incident light in the terahertz band; characterized in that: A multi-segment spin Hall slit structure is used to excite surface plasmon waves when vortex light is incident, generating an interference pattern with the spin and orbital angular momentum of the incident light at the center of the slit ring. For a slit ring composed of n slit segments, each segment contains m pairs of slits, and the slits are rectangular slits with a length of w0 mm and a width of d0 mm; where the... i The first of the narrow slits j The polar coordinates of the slit are expressed by the following formulas: ； Where r0 is the center radius of the slit ring. The wavelength of the plasmon wave, Let be the polar coordinates of the outer slit. These are the polar coordinates of the inner slit.
2. The on-chip angular momentum detection method based on a slit ring structure according to claim 1, characterized in that, For a positive slit array, the angle α between the slit and the x-axis is expressed as: ; For a reverse slit array, the angle α between the slit and the x-axis is expressed as: ; Let be the angle between the inner slit and the x-axis. The angle between the outer slit and the x-axis; When the slit resonator is arranged in a circular ring, the polar coordinates of the slit resonator are: The angle between the slit and the x-axis is... The distance on the line connecting the slit resonators is l The point surface plasmons are: ; in It is the unit vector of the excitation direction of the slit resonator.
3. The on-chip angular momentum detection method based on a slit ring structure according to claim 1, characterized in that, To calculate the interference pattern formed by the slit ring at its center, it is necessary to calculate the superposition of their excitations at any point, using each slit resonator as a source; under arbitrary incident light... The superimposed electric field of all the slit resonators at point o can be calculated as follows: ; in, It is the unit vector along the surface plasmon excitation direction of the m-th slit resonator. It is the vector pointing from the center of the m-th slit resonator to point o. It is a vector and The included angle between them; in the equation The term is determined by the orbital angular momentum of the incident light.
4. The on-chip angular momentum detection method based on a slit ring structure according to claim 1, characterized in that, The center radius of the slit ring is r0 ∈ [1.8 mm, 3 mm].
5. The on-chip angular momentum detection method based on a slit ring structure according to claim 1, characterized in that, w0∈[70μm,120μm].
6. The on-chip angular momentum detection method based on a slit ring structure according to claim 1, characterized in that, d0∈[10μm,30μm].
7. The on-chip angular momentum detection method based on a slit ring structure according to claim 1, characterized in that, The number of columns of the spin Hall slits is n=10, and the number of slit pairs in each column is m=9.
8. The angular momentum detection method based on the on-chip angular momentum detection method of the slit ring structure according to claim 1, characterized in that: When terahertz vortex light is incident perpendicularly from one side of the substrate, the surface plasmon waves excited along the ring-integrated spin Hall slit will form an interference pattern at the center of the slit ring. The interference pattern is highly sensitive to both the SAM and OAM of the incident light. By comparing the interference pattern generated by the incident light with the standard pattern obtained through simulation, the spin and orbital angular momentum of the vortex light can be obtained through a single measurement.