Efficient three-dimensional spiral metamaterial optical device for chiral resolution of vortex beam

Abstract

The invention discloses an efficient three-dimensional spiral metamaterial optical device for chiral resolution of vortex beams, which comprises a substrate and a three-dimensional spiral metamaterial structure layer positioned on the surface of the substrate, and is characterized in that the structure layer comprises a spiral dielectric layer and a spiral metal layer and has preset inherent chirality; the chiral structure of the spiral structure is designed to be matched with the annular intensity distribution of a target topological charge vortex beam and the spiral wavefront in the spatial scale, when a vortex beam carrying an opposite topological charge is incident, the device can generate asymmetric scattering modulation based on the matching relationship between the geometric chirality and the light field wavefront chirality, and the optical field wavefront chirality of the vortex beam is matched with the optical field wavefront chirality of the vortex beam carrying the opposite topological charge. Therefore, a remarkable vortex dichroism effect is shown on the scattering intensity. The three-dimensional spiral metamaterial optical device has the advantages of being high in detection response, clear in physical mechanism, simple in structure, excellent in performance and the like, and is suitable for the fields of high-capacity optical communication, optical manipulation, quantum information processing and the like.

Description

Technical Field

[0001] This invention relates to the field of micro-nano photonics technology, and in particular to a highly efficient three-dimensional helical metamaterial optical device for chiral resolution of vortex beams. Background Technology

[0002] Vortex beams, as a special type of optical field carrying orbital angular momentum (OAM), exhibit a spiral wavefront distribution and possess unique phase singularities and a central dark spot structure. Unlike spin angular momentum (SAM), which has only two eigenstates (corresponding to left- and right-hand circular polarization), OAM theoretically provides an infinite number of orthogonal states, opening up new dimensions for high-capacity optical communication, optical micromanipulation, and quantum information processing. When a vortex beam interacts with matter, its spiral wavefront can couple with the chirality of the structure, thus triggering a novel optical response that transcends traditional circular dichroism—vortex dichroism (VD). Vortex dichroism characterizes the different optical responses (such as scattering differences) exhibited by structures to vortex beams with opposite topological charge signs (i.e., opposite rotation directions). This provides a completely new technical approach for detecting and resolving chiral information in the phase dimension, possessing significant fundamental research value and application potential.

[0003] However, achieving strong vortex dichroism presents significant challenges. Natural chiral molecules exhibit extremely weak interactions due to a severe scale mismatch between their size (nanometer-scale) and the toroidal field distribution of optical vortices (micrometer-scale), resulting in negligible vortex dichroism responses. To enhance the interaction between light and chiral matter, artificial chiral metamaterials have been extensively studied. However, most reported chiral metamaterials generally produce weak vortex dichroism responses [C.-Y. Ji, et al., Observation of Magnetic Quadrupole Endowed Helical Dichroism in Artificial Propeller Meta-Molecules. Adv. Optical Mater. 2024,12, 2302795.]. This is mainly due to the low spatial coupling efficiency between their geometry and the toroidal field distribution of optical vortices, failing to fully utilize the helical phase characteristics of OAM beams, thus limiting their application in sensitive detection and high-efficiency devices.

[0004] To overcome the core bottleneck of weak vortex dichroism response in existing technologies and achieve high-efficiency vortex chiral detection, developing new enhanced coupling mechanisms is crucial. Three-dimensional helical metamaterials, due to their natural morphological fit between their geometric chirality and the wavefront of vortex beams, provide a highly promising platform for enhancing the chiral interaction between light and matter. These structures can utilize their inherent helical properties to achieve efficient coupling with vortex beams of different topological charges, thereby significantly improving the sensitivity and efficiency of chiral resolution. Therefore, developing high-response vortex chiral detection devices based on such structures and elucidating the physical mechanisms of their efficient coupling are of vital importance for advancing chiral photonics and developing advanced optical applications. Summary of the Invention

[0005] To address the problems of weak vortex dichroism response and low chiral detection response in existing technologies, this invention aims to provide a highly efficient three-dimensional helical metamaterial optical device for chiral resolution of vortex beams. Through its unique three-dimensional helical structure, this device can generate a high-response light-matter interaction with the vortex beam, thereby achieving high-response detection of the chiral signal of the vortex beam.

[0006] The present invention is achieved by at least one of the following technical solutions.

[0007] A highly efficient three-dimensional helical metamaterial optical device for chiral resolution of vortex beams includes a substrate and a three-dimensional helical metamaterial structure layer located on the surface of the substrate. The three-dimensional helical metamaterial structure layer includes a helical dielectric layer and a helical metal layer, with the helical metal layer located on the helical dielectric layer and the helical dielectric layer located on the substrate. The helical metamaterial structure of the three-dimensional helical metamaterial structure layer has a predetermined intrinsic geometric chirality. The helical profile of the three-dimensional helical metamaterial structure layer is adapted to the annular intensity distribution and helical wavefront of the target topological charge vortex beam in spatial scale. When a vortex beam carrying the opposite topological charge is incident, based on the matching relationship between geometric chirality and the chirality of the optical field wavefront, asymmetric scattering modulation is generated on the beam, thereby exhibiting a significant vortex dichroism effect in the scattering intensity.

[0008] Furthermore, the length and width of the substrate are... L The range of values ​​is L > λ ,in λ The wavelength of the light beam to be detected is... λ It is in the near-infrared band.

[0009] Furthermore, the radius of the helical unit in the three-dimensional helical metamaterial structure layer R The range of values ​​is R < L / 2, L The length and width of the substrate.

[0010] Furthermore, the spiral profile of the spiral metal layer is adapted to the annular intensity distribution of the incident vortex beam.

[0011] Furthermore, the three-dimensional helical metamaterial structure consists of two types of three-dimensional helical units: left-handed and right-handed.

[0012] Furthermore, the geometric profile of the three-dimensional helical metamaterial structure layer is defined by the following parametric equations: (1) in, For rotation angle, R Where is the helix radius. P For pitch, N The number of turns of the helix. x ( θ ), y ( θ )and z ( θ () represents the three-dimensional coordinates of a point on a three-dimensional helical metamaterial.

[0013] Furthermore, the spiral radius and pitch of the three-dimensional spiral metamaterial structure layer enable the three-dimensional spiral metamaterial to achieve optimal spatial mode matching with the topological charge vortex beam, thereby maximizing the vortex dichroism response.

[0014] Furthermore, both the substrate and the spiral dielectric layer are made of optically transparent materials.

[0015] Furthermore, the material of the spiral metal layer includes gold, silver, or aluminum.

[0016] Furthermore, the pre-defined inherent geometric chiral structure is a single-turn helix, with the direction of rotation being either left-handed or right-handed.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) High detection response: This invention utilizes the inherent morphological fit between the three-dimensional spiral structure and the optical vortex to achieve efficient chiral coupling, generating a vortex dichroism value as high as 0.69, laying the foundation for high-sensitivity chiral detection; (2) Clear physical mechanism: Through near-field distribution analysis, it was clarified that the high efficiency of chirality resolution is due to the chirality-dependent electromagnetic energy localization effect, that is, the chirality-dependent spatial mode coupling mechanism, which provides a clear physical picture for guiding device optimization; (3) Simple structure and superior performance: The device has a simple structure, consisting of only a single continuous spiral. It does not require complex multi-layer stacking or pattern design, and can achieve excellent chiral resolution performance far exceeding that of existing complex structures, making it easy to prepare and apply. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the principle of vortex dichroism effect generated by a three-dimensional spiral metamaterial optical device under vortex beam illumination, as an example.

[0019] Figure 2 The scattering intensity spectrum and vortex dichroism spectrum of the three-dimensional spiral metamaterial optical device are shown in the example.

[0020] Figure 3 The image shows the near-field electric field intensity distribution of the three-dimensional spiral metamaterial optical device in the example.

[0021] Figure 4 This is an analysis diagram showing the influence of the geometric parameters of the three-dimensional helical metamaterial optical device on the vortex dichroism in the embodiment. Detailed Implementation

[0022] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0023] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0024] To make the content of this invention easier to understand, it will be described in detail below with reference to the accompanying drawings and specific embodiments. The listed embodiments are only some embodiments of this invention, and other combinations are possible without departing from this invention.

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] This invention provides a highly efficient three-dimensional helical metamaterial optical device for chiral resolution of vortex beams, comprising a substrate and a three-dimensional helical metamaterial structure layer located on the surface of the substrate. The three-dimensional helical metamaterial structure layer includes a three-dimensional helical dielectric layer and a three-dimensional helical metal layer. The three-dimensional helical metamaterial structure layer has a predetermined inherent geometrical chiral structure, and its helical structure is spatially adapted to the annular intensity distribution and helical wavefront of the target topological charge vortex beam. The three-dimensional helical structure of the three-dimensional helical metamaterial structure layer is configured such that when a vortex beam carrying an opposite topological charge is incident, based on the matching relationship between its geometrical chirality and the chirality of the optical field wavefront, it generates asymmetric scattering modulation on the beam, thereby exhibiting a significant vortex dichroism effect in the scattering intensity.

[0027] In one embodiment of the present invention, the preset inherent geometrical chiral structure is a single-turn helix with a clearly defined left-handed or right-handed rotation.

[0028] Specifically, the three-dimensional helical metamaterial structure layer consists of two types of three-dimensional helical units: left-handed and right-handed. Its geometric profile is defined by the following parametric equations: (1) Among them, rotation angle spiral radius R =7μm, pitch P =5μm, number of spiral turns N =1, x ( θ ), y ( θ )and z ( θ () represents the three-dimensional coordinates of a point on the three-dimensional helical metamaterial. The top of the three-dimensional helical metamaterial structure layer has a thickness of... H t A three-dimensional spiral metal layer with a diameter of 0.5 μm 3.

[0029] The vortex dichroism effect originates from a chirality-dependent spatial mode coupling and energy path modulation mechanism: when the topological chirality of the incident vortex beam is opposite to the geometric chirality of the three-dimensional spiral unit (mismatch), the spatial mode mismatch prevents energy from being effectively coupled into the spiral channel, resulting in energy being strongly localized in the interface region and producing strong backscattering; when the chirality of the two is the same (match), the spatial mode matching allows energy to be efficiently coupled into the guiding mode of the spiral channel and propagate along it, and the energy is relatively uniformly distributed in the dielectric layer, resulting in a significant reduction in scattering intensity.

[0030] This embodiment of the three-dimensional helical metamaterial optical device includes a substrate 1 and a three-dimensional helical metamaterial structure layer, wherein the three-dimensional helical metamaterial structure layer includes a three-dimensional helical dielectric layer 2 and a three-dimensional helical metal layer 3. The three-dimensional helical metal layer 3 is located above the three-dimensional helical dielectric layer 2, and the three-dimensional helical dielectric layer 2 is located above the substrate 1. As one embodiment, the metacellular unit layer material of the three-dimensional helical metal layer 3 can be gold, silver, or aluminum; the materials of the three-dimensional helical dielectric layer 2 and the substrate 1 are both optically transparent materials, including MgF2, SiO2, and Si; the three-dimensional helical dielectric layer 2 and the substrate 1 serve as a refractive index matching layer between the three-dimensional helical metal layer 3 and low-refractive-index air, and can be specifically designed according to the operating wavelength of the device. As one embodiment, the operating wavelength can be a single wavelength in the near-infrared range. In this embodiment, the operating wavelength is selected as 0.8 μm, the substrate and the three-dimensional helical dielectric layer 2 are made of SiO2, the substrate 1 is 1 μm thick, and the material of the three-dimensional helical metal layer 3 is gold (Au). The helical radius of the three-dimensional helical metamaterial structure layer is... R Its range of values R < L / 2 , LThe dimensions of substrate 1 are shown. The three-dimensional spiral metamaterial optical device in this embodiment is simulated using FDTD (Finite-Difference Time-Domain) software to optimize the device.

[0031] Specifically, Figure 1 The core physical phenomenon of asymmetric scattering response generated when left-handed and right-handed helical structures interact with vortex beams with opposite topological charges is clearly demonstrated: when the topological charge chirality of the vortex beam is opposite to the geometric chirality of the helical structure (such as a three-dimensional left-handed helical structure with a right-handed vortex beam or a three-dimensional right-handed helical structure with a left-handed vortex beam), extremely strong scattering is produced; while when the chirality of the two is the same (such as a three-dimensional left-handed helical structure with a left-handed vortex beam or a three-dimensional right-handed helical structure with a right-handed vortex beam), the scattering is significantly weakened.

[0032] Wherein, the length and width of substrate 1 are L Its value range is L >λ, where λ is the wavelength of the beam to be detected, and the wavelength λ of the beam to be detected is located in the near-infrared band. The vortex beam uses a Laguerre-Gaussian (LG) beam as the incident vortex beam, and its electric field distribution is... Described by the following formula: (2) in, C It is a normalization constant, independent of l and R , w 0 = 1.1 μm is the beam waist. r And φ are polar coordinates, i For imaginary units, topological load l Scan from -50 to +50. Incident beam is x A linearly polarized vortex beam is simulated with perfectly matched layer boundary conditions in all three directions of the simulation area. The scattering intensity distribution of the vortex beam is shown. for: (3) Two OAM states (+ l and l The asymmetric scattering intensity between the two scattering points constitutes the essence of the vortex dichroism (VD) effect, which can be quantitatively evaluated by the following formula: (4) in, I +l It is the topological load number l The scattering intensity when it is a positive value, I -l It is the topological load number l The scattering intensity when it is negative.

[0033] Specifically, Figure 2 The scattering intensity spectra of left-handed, right-handed, and chiral three-dimensional helical structures under illumination by vortex beams with opposite topological charges, and their corresponding vortex dichroism spectra, are presented. In the simulation, a Laguerre-Gaussian vortex beam was used as the light source, with a working wavelength of 800 nm, and the topological charge... l Scan from -50 to +50. From Figure 2 A and B represent the scattering intensity spectra of the left-handed spiral structure and the right-handed spiral structure under illumination by vortex beams with different topological charges, respectively. It can be seen that the three-dimensional left-handed and right-handed spiral structures exhibit mirror-symmetric scattering responses. The three-dimensional left-handed spiral structure shows a greater scattering intensity response to the right-handed spiral vortex wavefront (+). l The scattering intensity response is stronger, and the three-dimensional right-handed helical structure responds more strongly to the left-handed vortex wavefront (- l The scattering intensity response is stronger. Figure 2 C and D are the scattering intensity spectra of the non-chiral structure and the vortex dichroism spectra of the three structures. Figure 2 The C-shaped structure shows a non-chiral structure against + l and- l The scattering intensity response is exactly the same. Figure 2 The vortex dichroism spectra of D show that the vortex dichroism responses of the three-dimensional left-handed helical structure and the three-dimensional right-handed helical structure are completely opposite, in | l When |=9, the vortex dichroism response reaches 0.69, while the vortex dichroism response of non-chiral structures is close to zero.

[0034] The following explanation is based on the analysis of the chiral resolution and electric field distribution of the vortex beam with high response at opposite topological charges of the aforementioned three-dimensional spiral metamaterial optical device.

[0035] Specifically, Figure 3 Showing | l The near-field electric field distribution (|E|) of the three three-dimensional spiral structures when |=9 reveals the physical origin of vortex dichroism. Figure 3 A, C, and E are schematic diagrams of the three-dimensional left-handed spiral structure, the three-dimensional right-handed spiral structure, the non-chiral structure, and the electric field section positions (P1~P3), respectively. Figure 3 B1 and B2 show that for a three-dimensional left-handed spiral, under the condition of anti-handed matching (right-handed spiral vortex wavefront), l =+9 irradiation), due to spatial mode mismatch, electromagnetic energy cannot be effectively coupled into the helical channel. The energy is localized on one side of the dielectric layer, forming an asymmetric field distribution and producing strong backscattering; while under the same chirality condition (left-handed helical vortex wavefront), l =-9 irradiation), the vortex light field can penetrate and propagate along the spiral path, and the energy is evenly distributed in the spiral dielectric layer, resulting in weak scattering. Figure 3 The D1 and D2 displays show that the three-dimensional right-handed spiral exhibits completely opposite characteristics: strong localization and scattering are produced under the illumination of the left-handed spiral vortex wavefront, while uniform transmission is achieved under the illumination of the right-handed spiral vortex wavefront. Figure 3 F1 and F2 show that the chiral structure produces almost the same electric field distribution under the illumination of the two helical vortex wavefronts, with energy symmetric localization in the dielectric layer and no obvious directional constraint. Figure 3 The near-field distribution clearly reveals the physical origin of vortex dichroism. The above near-field analysis clarifies the physical origin of the vortex dichroism effect. In order to further study how to optimize device performance through structural design, the influence of key geometric parameters on the vortex dichroism effect was analyzed.

[0036] Figure 4 The spiral radius was systematically studied. R and the thickness of the metal layer at the top of the three-dimensional spiral structure H t The influence of these two key geometric parameters on vortex dichroism performance provides clear guidance for device optimization design.

[0037] Figure 4 A and B show the helix radius. R The influence of the helix radius on the vortex dichroism effect was investigated. A significant change occurred in the vortex dichroism spectrum as the helix radius increased from 5 μm to 9 μm. From... Figure 4 As can be seen from A, with R As the vortex dichroism increases, the topological charge number corresponding to the peak value shifts to higher orders, indicating that larger helical dimensions and higher-order vortex beams with larger ring diameters can achieve more effective spatial mode matching. Figure 4 B further quantitatively demonstrates this trend: when R At a depth of 7 μm, the vortex dichroism peak reaches its maximum value of 0.69; while when R When deviating from this optimal value, whether decreasing to 5 μm or increasing to 9 μm, the peak value of the vortex dichroism response decreases significantly. This phenomenon can be explained by the variation in the annular intensity distribution of the vortex beam and the spatial overlap of the helical structure: when the helical radius and the characteristic size of the vortex beam with a specific topological charge reach optimal matching, the chiral coupling response is the highest, thus producing the strongest vortex dichroism response.

[0038] Figure 4 C and D investigated the thickness of the metal layer at the top of the three-dimensional helical structure. H t The effect on vortex dichroism properties. From... Figure 4 As can be seen from C, with H tAs the vortex dichroism increases from 0.5 μm to 2.5 μm, the overall amplitude gradually decreases, while the peak position shifts towards higher topological charges. l Slight movement. Figure 4 Quantitative analysis of D showed that when H t The vortex dichroism peak is largest at a thickness of 0.5 μm; as the thickness increases, the peak value shows a monotonically decreasing trend. This phenomenon is because a thicker metal layer suppresses electromagnetic field penetration, weakening the chiral coupling response between the optical vortex and the helical channel. Especially... H t Beyond 1.0 μm, the vortex dichroism performance decreases more significantly, indicating that the thickness of the metal layer needs to be strictly controlled in device design to balance the mechanical strength and optical performance of the structure.

[0039] These parameter studies not only validated the chirality-dependent energy localization mechanism proposed in this invention, but also provided important theoretical basis and design guidelines for the customized design of three-dimensional helical metamaterial optical devices for different application requirements. By precisely controlling the helical radius and the thickness of the metal layer, high-response chiral resolution of vortex beams with different topological charge ranges can be achieved, further expanding the flexibility of this invention in practical applications.

[0040] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0041] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams, characterized in that, The system includes a substrate and a three-dimensional spiral metamaterial structure layer located on the substrate surface. The three-dimensional spiral metamaterial structure layer includes a spiral dielectric layer and a spiral metal layer, with the spiral metal layer located on the spiral dielectric layer and the spiral dielectric layer located on the substrate. The spiral metamaterial structure of the three-dimensional spiral metamaterial structure layer has a predetermined intrinsic geometric chirality. The spiral profile of the three-dimensional spiral metamaterial structure layer is adapted to the annular intensity distribution and spiral wavefront of the target topological charge vortex beam in spatial scale. When a vortex beam carrying the opposite topological charge is incident, based on the matching relationship between the geometric chirality and the wavefront chirality of the optical field, the beam is asymmetrically scattered and modulated, thus exhibiting a significant vortex dichroism effect in the scattering intensity.

2. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The length and width of the substrate are L The range of values ​​is L > λ ,in λ The wavelength of the light beam to be detected is... λ It is in the near-infrared band.

3. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The radius of the spiral unit in the three-dimensional spiral metamaterial structure layer R The range of values ​​is R < L / 2, L The length and width of the substrate.

4. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The spiral profile of the spiral metal layer is adapted to the annular intensity distribution of the incident vortex beam.

5. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The three-dimensional helical metamaterial structure consists of two types of three-dimensional helical units: left-handed and right-handed.

6. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The geometric profile of the three-dimensional helical metamaterial structure layer is defined by the following parametric equations: （1） in, For rotation angle, R Where is the helix radius. P For pitch, N The number of turns of the helix. x ( θ ), y ( θ )and z ( θ () represents the three-dimensional coordinates of a point on a three-dimensional helical metamaterial.

7. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The spiral radius and pitch of the three-dimensional spiral metamaterial structure layer enable the three-dimensional spiral metamaterial to achieve optimal spatial mode matching with the topological charge vortex beam, thereby maximizing the vortex dichroism response.

8. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, Both the substrate and the spiral dielectric layer are made of optically transparent materials.

9. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The material of the spiral metal layer includes gold, silver, or aluminum.

10. The high-efficiency three-dimensional helical metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The pre-defined inherent geometric chiral structure is a single-turn helix, with either left-handed or right-handed rotation.

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