Super surface light field three-dimensional modulation device based on fabry-perot cavity, light field modulation method and optical device

Abstract

The application discloses a kind of super surface devices of F-P cavity combination, its structure includes: upper reflection layer, super surface layer and lower reflection layer, wherein upper and lower two high reflection layers constitute micro-nano F-P cavity, the super surface layer of middle is formed by anisotropic medium nano column array.Based on the wavelength selection principle of F-P cavity, narrow-band filtering can be realized;Based on the geometric phase principle, the phase control and amplitude control can be realized by arranging the medium nano column with specific shape, size and azimuth angle.The geometric phase super surface is embedded in the micro-nano F-P cavity, and the wavelength, phase and amplitude of the light field can be simultaneously and independently modulated.The application has the advantages of flexible design, compact structure, strong control ability and high control freedom, and has high application prospect in various practical applications such as light field control, color printing and holographic display, information storage, optical anti-counterfeiting, etc.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optical metasurface technology, and particularly relates to a three-dimensional optical field manipulation device, optical field manipulation method, and optical apparatus based on a Fabry-Perot (FP) cavity. This device achieves three-dimensional joint manipulation of the wavelength, phase, and amplitude of the optical field by embedding a geometrically phased metasurface into a micro-nano FP cavity, and can be widely used in fields such as optical field manipulation, color holographic display, optical anti-counterfeiting, and information storage. Background Technology

[0002] Optical field manipulation is the process of arbitrarily modulating the fundamental parameters of light, such as wavelength, phase, amplitude, and polarization, and plays a crucial role in various applied optics fields. With the development of information technology, the demand for multi-dimensional free manipulation of optical fields is increasing. However, traditional optical field manipulation devices have limited modulation capabilities and a single modulation dimension.

[0003] Metasurfaces are a new type of material composed of subwavelength structures. These materials can achieve spatial control of electromagnetic waves by utilizing the strong interaction between the subwavelength structures and electromagnetic waves, and flexibly manipulate the basic properties of light, such as amplitude, phase, polarization and spectral response.

[0004] In recent years, researchers have attempted to combine metasurfaces with optical resonators to enhance controllability. Fabry-Perot (FP) cavities have become important candidates due to their narrowband filtering characteristics and high-field enhancement effect. However, current techniques for combining FP cavities with metasurfaces mostly focus on single functions (such as wavelength selection or phase modulation), failing to achieve independent joint control of wavelength, phase, and amplitude. Furthermore, the coupling between the cavity structure and the metasurface in traditional designs often restricts the degrees of freedom of control or introduces complex multilayer structures, sacrificing device compactness. Summary of the Invention

[0005] To address the limitations of existing technologies, such as limited control dimensions, high crosstalk, and low integration, this invention provides a three-dimensional optical field manipulation device, method, and optical apparatus based on a Fabry-Perot cavity metasurface. This aims to overcome the limitations of current metasurface devices, which can only individually control the complex amplitude or wavelength of the optical field. The metasurface device provided by this invention can achieve three-dimensional joint control of wavelength, phase, and amplitude without sacrificing integration, enhancing the controllability of metasurfaces and enabling applications in fields such as optical field manipulation, color holography, and displays.

[0006] The technical solution of the present invention is as follows:

[0007] A three-dimensional optical field manipulation device based on a Fabry-Perot cavity on a metasurface is characterized by comprising:

[0008] An upper reflective layer and a lower reflective layer, which together constitute a micro / nano FP cavity;

[0009] A metasurface layer, located between the upper and lower reflective layers, is composed of an array of anisotropic dielectric nanopillars arranged in a subwavelength periodic pattern; wherein,

[0010] The metasurface layer independently controls the wavelength, phase, and amplitude of the light field by adjusting the major and minor axis dimensions and azimuth angle of the dielectric nanopillars;

[0011] The resonant wavelength of the micro / nano FP cavity is determined by the equivalent refractive index of the dielectric nanopillar and the height of the FP cavity, and the phase of the metasurface layer... Modulation, satisfying the relation Where θ is the azimuth angle of the dielectric nanopillar.

[0012] Furthermore, the amplitude modulation of the metasurface layer is related to the cross-polarization efficiency of the dielectric nanopillars, which is achieved by changing the shape of the dielectric nanopillars.

[0013] Furthermore, the remaining part of the micro / nano FP cavity formed by the upper and lower reflective layers is filled with a low refractive index material (or air). The greater the difference in refractive index between the filling material and the metasurface material, the better. The difference in refractive index between the two materials determines the range of control of the device's resonant wavelength.

[0014] The aforementioned metasurface layer is based on the geometric phase principle. The periodic dimensions of the metasurface are at the subwavelength level, and it is composed of anisotropic dielectric nanopillars, possessing phase modulation and amplitude modulation capabilities. Designing a dielectric nanopillar array with specific shape, size, and azimuth angle allows for independent modulation of the phase and amplitude of the optical field. According to the geometric phase principle, when incident right-handed (left-handed) circularly polarized light passes through the anisotropic dielectric nanopillars, it will become left-handed (right-handed) circularly polarized light, carrying a phase that is twice the azimuth angle of the nanopillars. Assuming the azimuth angle of the nanopillars is θ, the transmission coefficient of the left-handed light generated by right-handed light incident on the metasurface can be expressed as:

[0015]

[0016] Where t xx , t yy , Representing the transmission amplitude and phase in the x-polarization direction and the y-polarization direction, respectively, t +- The phase factor carried in the nanopillar is the geometric phase, and the magnitude of the geometric phase depends only on the azimuth angle of the nanopillar. The relationship between and the azimuth angle θ satisfies t +- The preceding coefficients determine the cross-polarization efficiency, i.e., the transmission amplitude, which can be adjusted by changing the shape of the dielectric nanopillars.xx , t yy , Specifically, amplitude modulation is achieved by changing the lengths of the long and short axes of the nanopillars. The greater the difference between the long and short axes of the dielectric nanopillars, the greater the transmission amplitude. Based on this design method, amplitude modulation and phase modulation can be achieved independently.

[0017] The upper and lower reflective layers are broadband high-reflectivity layers, composed of a metal thin film or a dielectric / semiconductor distributed Bragg reflector. These two layers form a micro / nano FP cavity, capable of precisely filtering out the designed wavelength from broadband light waves. Light reflects back and forth between the two high-reflectivity surfaces. At a specific wavelength, the repeatedly reflected light waves form a peak signal, while other wavelengths cancel each other out. A narrow-band high-Q resonance peak appears in the transmission spectrum, with the resonance condition being:

[0018] λ=2n eff l cavity cosβ / m (2)

[0019] Where λ is the resonant wavelength, n eff It is the equivalent refractive index of the FP cavity, l cavity Where β is the height of the FP cavity, m is the incident angle, and m is the order, m = 1, 2, 3... From formula (2), it can be seen that changing the height and refractive index of the FP cavity will change the resonant wavelength. This invention adopts the method of changing the equivalent refractive index n of the FP cavity. eff The resonant wavelength can be tuned by changing the size of the dielectric nanopillars embedded in the FP cavity. eff This allows for wavelength modulation. The wavelength adjustment range is Δλ = 2Δn. eff l cavity / m, where Δn eff The wavelength range that can be adjusted is determined by the difference in refractive index between the metasurface material and the remaining space material of the FP cavity. The greater the difference in refractive index between the two materials, the larger the range of adjustable wavelengths.

[0020] Embedding a geometrically phased metasurface into a photonic field (FP) cavity enables three-dimensional joint control of the wavelength, amplitude, and phase of the optical field. The structural design of the metasurface device described in this invention involves selecting appropriate materials as the upper and lower reflective layers based on the device's designed operating wavelength, forming the FP cavity, and optimizing the height of the FP cavity and the size of the nanopillars to achieve a narrow-band resonance peak within the designed operating wavelength. Then, adjusting the size of the nanopillars controls the resonance wavelength, while adjusting the azimuth and shape of the nanopillars controls the phase and amplitude. Based on the desired metasurface device function, the phase and amplitude distributions are calculated, and then nanopillars of appropriate size, azimuth, and shape are arranged to simultaneously control the device's spectral response and shape an arbitrary wavefront.

[0021] This invention also provides a method for controlling the optical field, employing the aforementioned three-dimensional optical field control device based on a Fabry-Perot cavity metasurface, characterized by comprising the following steps:

[0022] ① Based on the target resonance wavelength λ, the equivalent refractive index n of the FP cavity is changed by adjusting the major and minor axis dimensions of the dielectric nanopillars. eff And combined with the height l of the FP cavity cavity , such that λ = 2n eff l cavity cosβ / m, where β is the angle of incidence and m is the order, m=1,2,3...;

[0023] ② By rotating the dielectric nanopillar at the azimuth angle θ, a phase distribution of 0-2π is applied according to the geometric phase principle to satisfy...

[0024] ③ By adjusting the difference Δ(lw) between the long axis and short axis of the dielectric nanopillar, the cross-polarization efficiency can be controlled, thereby achieving independent modulation of the transmission amplitude;

[0025] By combining independent modulation of wavelength, phase, and amplitude, a light field with a specific spectral response and wavefront distribution can be generated.

[0026] Furthermore, when the metasurface device is used for multi-wavelength holographic display, it is divided into multiple independent control regions, each region corresponding to a nanopillar array with different resonant wavelengths, and the azimuth angle and major axis / minor axis difference of the nanopillars in each region are arranged according to the phase and amplitude distribution of the hologram to achieve multi-channel color holographic synthesis.

[0027] Third, the present invention also provides an optical device comprising the above-mentioned three-dimensional control device for the metasurface optical field based on a Fabry-Perot cavity, characterized in that the device is any one of the following:

[0028] Color printing devices generate micro-nano structured color pixels through multi-wavelength nanopillar arrays;

[0029] A color holographic display system utilizes a multi-wavelength nanopillar array and its phase and amplitude modulation to achieve color holographic projection;

[0030] Optical anti-counterfeiting labels utilize three-dimensional joint control characteristics to generate unreplicable optical features;

[0031] High-density information storage devices achieve multi-dimensional optical information storage through wavelength-phase-amplitude encoding.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] Without sacrificing integration density, this device achieves three-dimensional joint modulation of wavelength, phase, and amplitude of an optical field using a single metasurface. It can independently control the spectral response while shaping wavefronts with arbitrary functions. Compared to some traditional technologies, this device offers independent modulation of spectral response and complex amplitude, providing advantages such as high degree of control freedom and strong controllability. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the three-dimensional optical field manipulation device based on a FP cavity of the present invention.

[0035] Figure 2 This is a schematic diagram of the unit structure parameters of an embodiment of the present invention.

[0036] Figure 3 This is the transmittance curve of the metasurface for the orthogonal polarization conversion of right-handed circularly polarized light in an embodiment of the present invention.

[0037] Figure 4 This illustrates the modulation relationship between the azimuth angle θ of the metasurface nanopillars and the phase and amplitude in this embodiment of the invention.

[0038] Figure 5 The amplitude curves of metasurface nanopillars with different major and minor axis structural parameters in the embodiments of the present invention are shown.

[0039] Figure 6 The relationship between the major and minor axis differences of the metasurface nanopillars in this embodiment of the invention and the modulation of amplitude. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the various embodiments of the present invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0041] Figure 1 The figure shows a schematic diagram of the three-dimensional optical field control device based on the FP cavity of the present invention. As shown in the figure, from top to bottom, it includes an upper reflective layer, a metasurface layer and a lower reflective layer. The upper reflective layer and the lower reflective layer constitute a micro-nano FP cavity, and the middle metasurface layer is composed of an anisotropic dielectric nanopillar array.

[0042] In this embodiment, the upper reflective layer is an Ag thin film with a thickness of d, which has high reflectivity (>95%) in the visible light band (400-700nm), effectively limiting multiple reflections of the light field within the FP cavity. The metasurface layer is composed of an array of elliptical cylindrical dielectric nanopillars of different shapes, made of silicon, with the remainder of the FP cavity filled with air. The dielectric nanopillars have a period of p, a height of h, a major axis of l, a minor axis of w, and an azimuth angle of θ. A silicon dioxide spacer layer of thickness g exists between the dielectric nanopillars and the Ag thin film to reduce plasma coupling and maintain cavity mode purity. The lower reflective layer, symmetrical to the upper reflective layer, is an Ag thin film of the same thickness d, and together with the upper reflective layer, constitutes the micro / nano FP cavity.

[0043] Figure 2 This is a schematic diagram of the unit structure parameters in an embodiment of the present invention. Using the CST STUDIO SUITE electromagnetic simulation tool, the structural parameters were optimized to form a narrow-band transmission peak in the visible light band. Simultaneously, by optimizing the long axis length l and short axis length w of the nanopillars, the transmission peak can be designed to be located at the desired wavelength, such as... Figure 3 The transmittance curve of the metasurface for the orthogonal polarization conversion of right-handed circularly polarized light in this embodiment of the invention is shown in Table 1. By adjusting only the l and w parameters, the resonant wavelengths were achieved at 450 nm, 532 nm and 650 nm, respectively, corresponding to blue light, green light and red light. The specific parameters are shown in Table 1.

[0044] Table 1 Specific parameters of the unit structure in the embodiments of the present invention

[0045]

[0046] By changing the azimuth angle of the nanopillars, arbitrary phase modulation can be achieved. Taking blue nanopillars as an example... Figure 4 The modulation relationship between the azimuth angle θ of the nanopillar and the phase and amplitude, where phase... As the azimuth angle changes from 0 to 180°, the phase completely covers 0 to 2π, and the azimuth angle change of the nanopillar has no effect on the wavelength and amplitude. The phase modulation is independent of the amplitude modulation and wavelength modulation.

[0047] The amplitude can be modulated by adjusting the l and w parameters of the nanopillar. To ensure that amplitude modulation and wavelength modulation are independent of each other, the equivalent refractive index n of the micro / nano FP cavity is required. eff The product of l and w remains constant. Empirically, when the product of l and w is constant, the resonant wavelength remains constant. Under this premise, the amplitude is modulated by changing the difference between l and w; the smaller the difference between l and w, the smaller the amplitude. Taking a blue nanopillar with a resonant wavelength of 450nm as an example... Figure 5The figure shows the amplitude curves of nanopillars with different long and short axis structural parameters. As can be seen from the figure, by selecting appropriate long axis l and short axis w of the nanopillar, the resonant wavelength can be fixed at 450 nm while achieving amplitude modulation of different magnitudes. Figure 6 The figure shows the modulation relationship between the difference between the long and short axes of the nanopillar, lw, and the amplitude. The amplitude increases with the increase of the difference between l and w. The amplitude modulation and wavelength modulation are also independent of each other.

[0048] Based on the designed device function, the required wavelength, phase, and amplitude distribution are calculated. Combined with the optimized nanopillar structure parameters, the corresponding nanopillars are arranged at each pixel location to obtain the target spectral response and wavefront function.

[0049] This embodiment achieves three-dimensional joint control of the wavelength, phase, and amplitude of the optical field without sacrificing integration. While independently controlling spectral information, it can shape wavefronts with arbitrary functions. This invention has advantages such as flexible design, compact structure, strong control capability, and high degree of freedom in control.

[0050] The embodiments described above do not constitute a limitation on the scope of protection of this invention. Any other corresponding changes and modifications made based on the technical concept of this invention should be included within the scope of protection of the claims of this invention.

Claims

1. A metasurface light field three-dimensional modulation device based on Fabry-Perot cavity, characterized in that, Comprise: Upper and lower reflective layers, which constitute a micro-nano F-P cavity; A metasurface layer between the upper and lower reflective layers, which is composed of an anisotropic elliptical cylindrical dielectric nanorod array arranged in a subwavelength period; wherein, The metasurface layer independently regulates the wavelength, phase and amplitude of the light field by adjusting the major axis, minor axis size and azimuth angle of the dielectric nanorod; The resonance wavelength of the micro-nano F-P cavity is determined by the equivalent refractive index of the F-P cavity and the F-P cavity height, and the phase of the super surface layer Modulation, satisfying the relationship Wherein, θ is the azimuth angle of the medium nanometer column; The filling material of the micro-nano F-P cavity is air or a low refractive index medium with a refractive index less than 1.5, And the refractive index difference with the dielectric nanorod material is greater than 1.5; The regulation range of the resonance wavelength λ satisfies the following conditions: λ = 2n eff l cavity cosβ / m where n eff is the equivalent refractive index of the F-P cavity, l cavity is the height of the F-P cavity, β is the incidence angle, and m is the order m = 1, 2, 3...

2. The metasurface light field three-dimensional modulation device based on Fabry-Perot cavity according to claim 1, wherein, The upper and lower reflective layers are broadband high reflective layers composed of metal thin films or dielectric / semiconductor distributed Bragg reflectors, with a reflectivity greater than 95% in the target waveband.

3. The metasurface light field three-dimensional modulation device based on Fabry-Perot cavity according to claim 1, wherein, The material of the dielectric nanorod is one of silicon, silicon nitride or titanium dioxide, with a period of 100-300 nm and a height of 50-150 nm; the difference between the major axis and the minor axis of the dielectric nanorod is 10-50 nm, and the transmission amplitude increases with the increase of the difference.

4. The metasurface light field three-dimensional modulation device based on Fabry-Perot cavity according to claim 1, wherein, The azimuthal coverage of the medium nano-pillar is 0° to 180°, the phase modulation range is 0 to 2π, and the phase modulation is not coupled with the resonance wavelength and the amplitude modulation; the resonance wavelengths of the medium nano-pillars are the same, the product of the long axis and the short axis of the medium nano-pillar remains constant, so as to ensure that the F-P cavity equivalent refractive index n eff is unchanged, so as to realize independent regulation of the amplitude and the wavelength.

5. A method for light field manipulation, using the super- surface light field three-dimensional manipulation device based on Fabry-Perot cavity according to any one of claims 1-4, characterized in that, Comprise the following steps: ① According to the target resonance wavelength λ, by adjusting the long axis and short axis size of the medium nano column, the equivalent refractive index n of the F-P cavity is changed eff , and the height l of the F-P cavity is combined cavity , So λ = 2n eff l cavity cosβ / m, wherein β is the incidence angle, m is the order, m = 1, 2, 3...; ii. By rotating the azimuth angle θ of the medium nano-pillar, a phase distribution of 0-2π is loaded according to the geometric phase principle, which satisfies ③ By adjusting the difference Δ(l-w) between the major axis l and the minor axis w of the dielectric nanorod, the cross-polarization efficiency is controlled to realize independent modulation of the transmission amplitude; Combine the independent regulation of wavelength, phase and amplitude to generate a light field with specific spectral response and wavefront distribution.

6. The method of claim 5, wherein, When the metasurface device is used for multi-wavelength holographic display, it is divided into multiple independent regulation regions, each region corresponds to a nanorod array of different resonance wavelengths, and the azimuth angle and the difference between the major axis and the minor axis of the nanorod in each region are arranged according to the phase and amplitude distribution of the hologram, realizing multi-channel color holographic synthesis.

7. An optical device comprising the metasurface light field three-dimensional modulation device based on Fabry-Perot cavity according to any one of claims 1-4, characterized in that, The device is any of the following: Color printing device, which generates micro-nano structure color pixels through multi-wavelength nanorod array; Color holographic display system, which realizes color holographic projection by using multi-wavelength nanorod array and its phase and amplitude regulation; Optical anti-counterfeiting label, which generates non-reproducible optical features by three-dimensional joint regulation characteristics; High-density information storage device, which realizes multi-dimensional optical information storage by wavelength-phase-amplitude coding.

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