High-efficiency three-dimensional double-helix metamaterial optical device for chiral discrimination of optical vortex beams

Abstract

The application discloses a high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams, comprising a substrate and a three-dimensional double-helix metamaterial structure layer arranged on the substrate, wherein the structure layer comprises a double-helix dielectric layer and a metal coating layer wrapped around the periphery of the dielectric layer; the spiral structure of the double-helix dielectric layer enables the device to have a significant geometric chiral feature, and has a higher design freedom and chiral response efficiency compared with a single-helix structure. Under the condition of incident of vortex beams with opposite topological charges, based on the synergistic effect between geometric chirality and light field wavefront chirality, the device can induce an asymmetric light scattering response, thereby generating a significant vortex dichroism effect, and realizing high-resolution discrimination of chiral states. The device has a compact structure and stable performance, is suitable for high-capacity optical communication, optical micro-manipulation and quantum information processing, can be extended to integrated light field regulation and high-resolution optical sensing, and provides an effective solution for the next generation of small-sized intelligent optical systems.

Description

Technical Field

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

[0002] A vortex beam is a special type of optical field carrying orbital angular momentum (OAM). Its spiral wavefront endows it with a unique phase singularity and central dark spot structure. Compared to traditional optical chirality detection, which mainly relies on the interaction between photon spin angular momentum (SAM), which has only two degrees of freedom, and chiral matter to produce circular dichroism (CD) spectra, orbital angular momentum (OAM) theoretically possesses an infinite number of distinguishable orthogonal states, exhibiting greater degrees of freedom and potential application advantages. When a vortex beam interacts with matter, its spiral wavefront can couple with the chirality of the structure. This manifests as a significantly different optical response characteristic of the chiral structure to vortex beams with opposite topological charge signs, i.e., opposite rotation directions. This novel response is called vortex dichroism (VD), which opens up a completely new control space in the phase dimension for the interaction between chiral light and matter, containing rich fundamental physical implications and application prospects.

[0003] However, achieving strong vortex dichroism faces significant challenges. The interaction between nanoscale natural chiral molecules and micrometer-scale vortex light ring field distributions is extremely weak due to scale mismatch. For example, Brullot et al. first experimentally attempted to detect chiral molecules using vortex light (Resolving enantiomers using the optical angular moment of twisted light), but they had to rely on complex nanoparticle aggregates as a medium to generate a local electric quadrupole moment. The resulting helical dichroism signal asymmetry factor was only about 0.6%, far below the requirements for practical applications, clearly demonstrating the severe inadequacy of direct detection schemes in terms of signal strength. Although artificial chiral metamaterials have been extensively studied, the existing structures have low coupling efficiency with the ring field of vortex light due to their geometry, failing to fully utilize the helical phase characteristics of OAM, thus resulting in generally weak vortex dichroism responses. For example, the PhotonicOrbital Angular Momentum Dichroism on Three-Dimensional Chiral Oligomers designed by Cao et al. in 2023, while extending the response to the OAM dimension and achieving approximately 23% helical dichroism, still suffers from mode mismatch between its discrete spherical ligand configuration and the spatial distribution of the continuous helical phase wavefront of vortex light, limiting further improvements in coupling efficiency. This clearly demonstrates that to fully utilize the helical phase information of photonic OAM, it is necessary to explore chiral geometric configurations that can achieve better spatial mode matching with vortex light fields.

[0004] To this end, the three-dimensional double-helix metamaterial structure proposed in this invention achieves more efficient light-matter coupling through its continuous, symmetrical geometric features that highly match the distribution of the vortex light ring field, thereby obtaining a significantly enhanced vortex dichroism response. Furthermore, compared to the single-helix structure, the double-helix geometry can generate stronger local field enhancement and more efficient chiral light-matter interaction through near-field coupling and synergistic effects between the two helical arms, thus achieving a higher chiral resolution efficiency than the single-helix structure under vortex light excitation. Based on this, conducting research on three-dimensional double-helix metamaterial devices for high-performance vortex chiral detection and deeply revealing the physical mechanisms of its efficient coupling and synergistic enhancement of the two arms is of significant scientific and strategic value for promoting the development of chiral photonics and expanding advanced photonics applications. Summary of the Invention

[0005] To address the technical bottlenecks of weak vortex dichroism response signals and low chiral detection sensitivity in existing technologies, this invention proposes a high-performance three-dimensional double-helix metamaterial optical element for chiral identification of vortex beams. This element, with its unique three-dimensional double-helix geometry, can significantly enhance the interaction between the vortex beam and matter, thereby achieving high-sensitivity detection and resolution of chiral signals.

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

[0007] A highly efficient three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams includes a substrate and a three-dimensional double-helix metamaterial structure layer disposed on the substrate. The three-dimensional double-helix metamaterial structure layer includes a double-helix dielectric layer and a metal cladding covering the outer periphery of the double-helix dielectric layer. The overall configuration of the three-dimensional double-helix metamaterial structure layer possesses intrinsic geometric chirality. The optical field interaction region of the three-dimensional double-helix metamaterial structure layer is adapted to the annular intensity profile and helical wavefront of the vortex beam under test in terms of spatial scale. Under the incident condition of vortex beams with opposite topological charges, based on the synergistic effect between geometric chirality and optical field wavefront chirality, an asymmetric light scattering response is induced, thereby generating a significant vortex dichroism effect and achieving high-resolution discrimination of chiral states.

[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 double-helix dielectric layer comprises two single-helix structures with the same direction of rotation, wherein both single-helix structures are either left-handed or both are right-handed.

[0010] Furthermore, the radius of the single helix structure R The value range is 0 < R < L / 2, L The edge length of the substrate.

[0011] Furthermore, the spiral profile of the metallic cladding is adapted to the annular intensity distribution of the incident vortex beam.

[0012] Furthermore, if the helical radius of the three-dimensional double-helix metamaterial structure layer is from the bottom radius... b Linear change to top radius a The helical radius of the three-dimensional double-helix metamaterial structure layer is... The formula is defined as: (1) The rotation angle at the starting point. The rotation angle at the end.

[0013] Furthermore, the central geometric path of the three-dimensional double-helix metamaterial structure layer is defined by the following parametric equation: (2) in, For rotation angle, Where is the helix radius. H 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 double-helix metamaterial.

[0014] Furthermore, the spiral radius and pitch of the three-dimensional double-helix metamaterial structure layer enable the three-dimensional double-helix metamaterial to achieve optimal spatial mode matching with the topological charge vortex beam, thereby maximizing the vortex dichroism response.

[0015] Furthermore, both the substrate and the spiral dielectric layer are made of optically transparent materials.

[0016] Furthermore, the material of the metal cladding includes gold, silver, or aluminum.

[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 double helix structure and the optical vortex to achieve efficient chiral coupling, generating a vortex dichroism value as high as 121.6%, 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) Dual-element synergistic effect: Compared with a single helix, the geometric synergistic effect of the double helix structure can be more effectively coupled with the vortex beam, which greatly improves the efficiency of chiral optical response. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the principle of vortex dichroism effect generated by a three-dimensional double-helix 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 double-helix 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 double-helix metamaterial optical device in the example.

[0021] Figure 4 This is an analysis diagram showing the influence of geometric parameters on vortex dichroism of the three-dimensional double-helix metamaterial optical device 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 embodiment discloses a high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams, comprising a substrate 1 and a three-dimensional double-helix metamaterial structure layer disposed on the substrate 1. The three-dimensional double-helix metamaterial structure layer includes a double-helix dielectric layer 2 and a metal cladding layer 3 covering the outer periphery of the double-helix dielectric layer. The overall configuration of the three-dimensional double-helix metamaterial structure layer has a pre-defined intrinsic geometric chirality, and its unique double-helix configuration has higher design freedom and chiral response efficiency compared to a single-helix structure. The optical field interaction region of the double-helix dielectric layer 2 is adapted to the annular intensity profile and helical wavefront of the vortex beam under test in terms of spatial scale. Under the condition of incident vortex beams with opposite topological charges, based on the synergistic effect between geometric chirality and optical field wavefront chirality, the device can induce an asymmetric light scattering response, thereby generating a significant vortex dichroism effect.

[0027] In one embodiment of the present invention, the intrinsic geometric chirality of the double-helical dielectric layer 2 is determined by two single-turn single-helical structures with the same direction of rotation but different starting angles, namely helical units (first helical coils). A Second helical coil B） The structure consists of two single helical structures, either both left-handed or both right-handed.

[0028] Specifically, if the helical radius of the double-helix dielectric layer 2 is increased from the bottom radius... b Linear change to top radius a Let the initial rotation angle be... Rotation angle at the end , For the rotation angle, the helix radius is... The formula is defined as: (1) The central geometric path of the double-helix dielectric layer 2 is defined by the following parametric equation: (2) in , This represents the three-dimensional coordinates of a point on the three-dimensional double-helix metamaterial. In this invention, the parameter is set to the number of helix turns. N =1, pitch H =25μm, bottom radius b =20μm, top radius a =10μm, starting angle =0°, then the first spiral coil A The specific parametric equations are as follows: (4) With the first helical coil A Around z The second helical coil is mirror-symmetric on the axis. B The parametric equations are as follows: (5) The physical essence of the vortex dichroism effect can be attributed to a chirality-dependent spatial mode coupling and energy path modulation mechanism. Specifically, when the topological chirality of the incident vortex beam is opposite to the geometric chirality of the three-dimensional double-helix unit (i.e., a "mismatch"), the spatial mode mismatch between the two hinders the effective coupling of energy into the helical channel. The energy is thus strongly localized in the interface region, making it difficult to propagate deeper and triggering significant backscattering, resulting in a strong response signal. Conversely, when the chirality is the same (i.e., a "match"), the synergy of the spatial modes allows energy to efficiently couple into the guiding mode of the helical channel and propagate smoothly along its path. In this case, the energy exhibits a relatively uniform distribution in the dielectric layer, the scattering intensity is significantly reduced, and the overall system response tends to be a weak signal. Therefore, based on chirality matching, the device can achieve high-contrast resolution of chiral signals.

[0029] As one embodiment, the materials of the substrate 1 and the double-helix dielectric layer 2 can be optically transparent materials, such as... , , SiThe outer metal cladding 3 is made of a highly conductive metal such as gold, silver, or aluminum. The substrate 1 and the double-helix dielectric layer 2 act as refractive index matching layers, used to match the optical properties between the three-dimensional double-helix metal layer 3 and the low-refractive-index air layer. The material and thickness of the substrate 1 can be optimized according to the operating wavelength of the device; for example, the operating wavelength can be selected from a specific wavelength in the near-infrared band. In this embodiment, 0.8 μm is used as the operating wavelength. The substrate 1 is selected from... The thickness is 3μm; the dielectric layer 2 also uses... The thickness of the metal coating has a certain impact on device performance, but the sensitivity is low. It is not strictly limited within the scope of this invention; in this embodiment, it is taken as 1.7 μm for structural illustration. The material of the metal coating 3 is gold (…). Au) The thickness is 0.5 μm. It should be noted that the thickness of both the metal layer and the dielectric layer are not key sensitive parameters of this invention, and their values ​​within a reasonable range have limited impact on the main conclusions. The radius of the helical structure in the double-helix dielectric layer 2... R Satisfying condition 0 < R < L / 2, where L Let be the side length of substrate 1. To verify the structural performance, this embodiment uses the finite-difference time-domain (FDTD) method to simulate the device, and optimizes the geometric and material parameters of the three-dimensional double-helix metamaterial structure based on the simulation results to improve its optical response characteristics.

[0030] 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 double helix structure (such as a three-dimensional left-handed double helix structure with a right-handed vortex beam or a three-dimensional right-handed double helix 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 double helix structure with a left-handed vortex beam or a three-dimensional right-handed double helix structure with a right-handed vortex beam), the scattering is significantly weakened.

[0031] Wherein, the side length of substrate 1 is L Its value range is L>λ ,in λ The wavelength of the light beam to be detected is... λ 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... Described by the following formula: (6) in, C It is a normalization constant, independent of l and R , w0 = 2.3 μm is the beam waist. r and φ In polar coordinates, i For imaginary units, topological load l Scan from -60 to +60. 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: (7) The helical radius and pitch of the double-helix dielectric layer 2 enable optimal spatial mode matching between the three-dimensional double-helix metamaterial and the topological charge vortex beam, thereby maximizing the vortex dichroism response. Two OAM states (+ l and l The asymmetric scattering intensity between the two ions constitutes the essence of the vortex dichroism (VD) effect, which can be quantitatively evaluated by the following formula: (3) 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.

[0032] Specifically, Figure 2 The scattering intensity spectrum of a right-handed three-dimensional double-helix structure under illumination by a vortex beam with opposite topological charges is shown, along with the vortex dichroism spectra corresponding to the left-handed, right-handed, and chiral structures. The simulation uses a Laguerre-Gaussian vortex beam as the light source, with a working wavelength of 0.8 μm and a topological charge number of... |l| Scan from -60 to +60. Figure 2 (a) shows the scattering intensity spectrum of the right-handed helical structure under excitation by vortex beams with different topological charges. The results indicate that the three-dimensional right-handed double helical structure has a left-handed helical wavefront (- l The vortex beam exhibits a stronger scattering response, while the corresponding three-dimensional left-handed spiral structure exhibits a stronger scattering response to the right-handed spiral wavefront (+). l The vortex beam scattering is stronger. Figure 2 (b) compares the vortex dichroism spectra of the three chiral characteristic structures. It can be seen that the vortex dichroism responses of the three-dimensional left-handed spiral structure and the right-handed spiral structure are completely opposite. |l| When the vortex dichroism is 15, the vortex dichroism response reaches 0.46; while the vortex dichroism response of the non-chiral structure is almost zero.

[0033] 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 double-helix metamaterial optical device.

[0034] Specifically, Figure 3 (a) shows a comparison of the vortex dichroism of the right-handed three-dimensional double helix structure and the right-handed three-dimensional single helix structure in the range of topological charge from -60 to +60. Simulation results show that the peak value of the vortex dichroism response of the double helix structure is as high as 121.5%, which is significantly better than the efficiency value of about 57% of the single helix structure, demonstrating excellent topological response characteristics.

[0035] Figure 3 (b) and (c) demonstrate |l| = 15, the near-field electric field distribution (|E|) of the right-handed three-dimensional double helix and single helix structures reveals the physical origin of vortex dichroism and the difference in electric field intensity between the two structures. It can be seen that for the right-handed double helix structure, compared with the right-handed helix wavefront ( l=+15 A vortex beam, when the incident vortex beam is a left-handed spiral wavefront ( l =-15 When the transmitted field strength is weaker, the corresponding scattered electric field strength is stronger: this is due to spatial mode mismatch, electromagnetic energy cannot be effectively coupled into the spiral channel, most of the incident energy is converted into a local field on the surface of the structure and absorbed or confined by the material, very little energy can be reflected back along the original path, so the scattering rate is very low from the detector's perspective; when the direction of light rotation and topological charge match the double helix structure, the vortex light field can penetrate and propagate along the spiral path, the incident energy is efficiently coupled into the near-field region between the two spiral arms, forming a strong surface mode resonance, the energy is "trapped" on the surface of the structure, resulting in suppressed scattering. Secondly, comparing the scattered electric field strength of single and double helix structures, it can be seen that when | l After irradiation with vortex light of |=15, the electric field intensity difference of the double-helix structure is significantly greater than that of the single-helix structure. This is because the high-density chiral geometry formed by the double arms of the double-helix structure results in stronger mode matching and resonant coupling with the helical phase of the vortex light. In contrast, the single-helix structure lacks this resonant cavity structure with coordinated double arms, and its response to the two directions of light is simply a matter of efficiency. Therefore, its vortex dichroism response is much smaller than that of the double-helix structure. The above near-field analysis clarifies the physical origin of the vortex dichroism effect. To further investigate how to optimize device performance through structural design, the influence of key geometric parameters on the vortex dichroism effect was analyzed.

[0036] Figure 4 (a) and (b) investigated the pitch K The ratio of the top and bottom radii of the three-dimensional double helix structure ρThe influence of these two key geometric parameters on vortex dichroism performance provides clear guidance for device optimization design. (Pitch) K When the value increased from 21 μm to 29 μm, K The value reaches its maximum of approximately 121.6% at a thickness of 25 μm. |l| = 15. The top radius of the double-helix microstructure was then investigated. a and bottom radius b proportion ρ = a / b Increased from 2 / 1 to 2 / 5. Figure 4 (b) shows when ρ = 2 / 4, meaning that when the top radius is 10μm and the bottom radius is 20μm, the percentage of vortex dichroism reaches its maximum value. It can also be seen that the efficiency of the conical spiral structure with asymmetrical upper and lower radii is better than that of the cylindrical spiral structure.

[0037] 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 double-helix metamaterial optical devices for different application requirements. By precisely controlling the helix 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.

[0038] 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.

[0039] 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 highly efficient three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams, characterized in that, The material includes a substrate (1) and a three-dimensional double-helix metamaterial structure layer disposed on the substrate (1). The three-dimensional double-helix metamaterial structure layer includes a double-helix dielectric layer (2) and a metal cladding layer (3) covering the outer periphery of the double-helix dielectric layer. The overall configuration of the three-dimensional double-helix metamaterial structure layer has intrinsic geometric chirality. The optical field interaction region of the three-dimensional double-helix metamaterial structure layer is adapted to the annular intensity profile and helical wavefront of the vortex beam to be measured in space. Under the condition of incident vortex beams with opposite topological charges, based on the synergistic effect between geometric chirality and optical field wavefront chirality, an asymmetric light scattering response is induced, thereby generating a significant vortex dichroism effect and achieving high-resolution discrimination of chiral states.

2. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The length and width of the substrate (1) 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 double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The double-helix dielectric layer (2) includes two single-helix structures with the same direction of rotation, wherein both single-helix structures are either left-handed or right-handed.

4. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 3, characterized in that, The radius of the single helix structure R The value range is 0 < R < L / 2, L Let be the side length of the substrate (1).

5. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The spiral profile of the metal cladding (3) is adapted to the annular intensity distribution of the incident vortex beam.

6. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, If the helical radius of the three-dimensional double-helix metamaterial structure layer is from the bottom radius b Linear change to top radius a The helical radius of the three-dimensional double-helix metamaterial structure layer is... The formula is defined as: （1） The rotation angle at the starting point. The rotation angle at the end.

7. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 6, characterized in that, The central geometric path of the three-dimensional double-helix metamaterial structure layer is defined by the following parametric equation: （2） in, For rotation angle, Where is the helix radius. H 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 double-helix metamaterial.

8. The high-efficiency three-dimensional double-helix 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 double-helix metamaterial structure enable the three-dimensional double-helix metamaterial to achieve optimal spatial mode matching with the topological charge vortex beam, thereby maximizing the vortex dichroism response.

9. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, Both the substrate and the spiral dielectric layer (2) are made of optically transparent materials.

10. The high-efficiency three-dimensional double-helix metamaterial optical device for chiral resolution of vortex beams according to claim 1, characterized in that, The material of the metal cladding (3) includes gold, silver or aluminum.

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