Fluorescent radiation vector wavefront control method based on metasurface

Abstract

The invention discloses a fluorescent radiation vector wavefront control method based on a super-structure surface, and the method comprises the steps: constructing the super-structure surface which is a unit periodic array of a nanometer brick-waveguide-substrate-fluorescent material; pumping light is irradiated to quantum dots on a waveguide layer of the super-structure surface to excite full-angle fluorescent light, and part of the fluorescent light is coupled into in-plane guided wave fluorescent light which is propagated transversely; determining a wave vector of guided wave fluorescence, and designing a super-structure surface to scatter the guided wave fluorescence into a free space so as to realize unidirectional radiation of the fluorescence; the radiation angle of fluorescent one-way radiation is controlled through the period of the coding super-structure surface, the linear polarization state of the fluorescent one-way radiation is controlled through the rotation angle of the coding nanometer brick, and the radiation intensity of the fluorescent one-way radiation is controlled through the three-dimensional size of the coding nanometer brick. According to the invention, independent control of any radiation angle, linear polarization state and radiation intensity of fluorescent unidirectional radiation can be realized, and four-channel polarization multiplexing fluorescent holography and nano printing display is realized based on the independent control.

Description

Technical Field

[0001] The present invention relates to the fields of micro-nano optics and fluorescence technology, and particularly relates to a method for controlling the fluorescence radiation vector wavefront based on a metasurface. Background Art

[0002] In modern optics, achieving complete control of light emission in a super-compact form, including its polarization state and wavefront, is an important research goal. As an emerging photonics platform, metasurfaces have attracted much attention due to their unparalleled ability to manipulate light fields, driving significant progress in light-emitting devices. For example, integrating metasurfaces into laser cavities can also achieve various functions such as frequency tuning, vortex laser generation, holographic mode design, and laser mode locking.

[0003] Compared with the control of coherent laser light, how to manipulate the radiation characteristics of incoherent light (such as fluorescence) to achieve specific wavefronts and polarization states remains a huge challenge. This is mainly because the emission of incoherent light has characteristics such as omnidirectionality, non-polarization, and phase randomness. In recent years, some breakthroughs have been made in the research on this challenge. For example, integrating single quantum radiation sources with holographic metasurfaces can achieve quantum radiation with directivity and tunable polarization states. In addition, phenomena such as the photon Rashba effect and various optical resonances (including Mie resonances and BICs) have also been proven to be able to achieve directional emission with diverse polarization states and fluorescence enhancement. At the same time, guiding fluorescence as a guided-mode fluorescence propagating in a horizontal waveguide and modulating it with a metasurface can achieve functions such as fluorescence focusing, dynamic unidirectional emission, and fluorescence / pump light multiplexing.

[0004] However, current fluorescence manipulation techniques based on metasurface enhancement still have limitations, especially in achieving complex wavefront and vectorized emission control. For example, the photon Rashba effect can only generate multi-beam radiation with orthogonal polarizations at symmetric angles, while holographic metasurfaces integrated with single radiation sources are limited to generating circularly polarized light or s- / p-polarized light. For the fluorescence wavefront encoding required for complex functions, existing technologies are still limited by their limited coherence and the lack of corresponding complex amplitude wavefront modulation methods. Currently, how to enhance the coherence of fluorescence (incoherent light) and achieve vector complex amplitude wavefront control to realize more complex vector fluorescence manipulation, such as unidirectional emission of fluorescence with arbitrary diffraction angles and linear polarization states and vector fluorescence holography, remains to be further explored. Summary of the Invention

[0005] In view of the above technical deficiencies, the present invention provides a method for controlling the vector wavefront of fluorescence radiation based on a metasurface, which realizes that when the pump light irradiates the fluorescence light source integrated on the metasurface, the guided-mode fluorescence generated can achieve the function of unidirectional radiation of vector fluorescence with arbitrary radiation angles, linear polarization and radiation intensity after being modulated by the metasurface, and can further encode its complex amplitude wavefront to realize the functions of polarization multiplexed fluorescence holography and nano-printing display.

[0006] In the first aspect of the present invention, a method for controlling the vector wavefront of fluorescence radiation based on a metasurface is provided, and the method includes:

[0007] Construct a metasurface, and the structure of the metasurface is a unit periodic array of nano-bricks - waveguides - substrates - fluorescent materials;

[0008] Irradiate the quantum dots on the waveguide layer of the metasurface with pump light to excite fluorescence at all angles, and part of the fluorescence is coupled into laterally propagating in-plane guided-wave fluorescence;

[0009] Determine the wave vector of the guided-wave fluorescence, and design the metasurface to scatter the guided-wave fluorescence into free space to achieve unidirectional fluorescence radiation;

[0010] Control the radiation angle of the unidirectional fluorescence radiation by encoding the period of the metasurface, control the linear polarization state of the unidirectional fluorescence radiation by encoding the rotation angle of the nano-bricks, and control the radiation intensity of the unidirectional fluorescence radiation by encoding the three-dimensional size of the nano-bricks.

[0011] In some embodiments, determining the wave vector of the guided-wave fluorescence and designing the metasurface to scatter the guided-wave fluorescence into free space to achieve unidirectional fluorescence radiation includes:

[0012] Determine the wave vector k of the guided-wave fluorescence PL ;

[0013] When the guided-wave fluorescence passes through the metasurface, it is modulated, and the wave vector after being modulated by the metasurface that can provide an additional wave vector k MS is k out = k PL+ k MS ; where k out is the wave vector of the guided-wave fluorescence after being modulated by the metasurface, and k MS is the additional wave vector provided by the metasurface for the guided-wave fluorescence;

[0014] Design the metasurface so that |k PL+ k MS | / k0 < 1, and at this time the guided-wave fluorescence is deflected into free space to form unidirectional radiation; where the free space wave number k0 = 2π / λ, and λ is the wavelength.

[0015] In some embodiments, the period is P, the rotation angle is The additional wave vector provided by a rectangular nanobrick with length, width, and height of L, W, and H respectively is k MS = 2πm / P = mk0λ / P, where m is the grating order number.

[0016] In some of these embodiments, the fluorescence scattered into free space is linearly polarized light with a polarization vibration direction parallel to the long axis of the nanobrick.

[0017] In some of these embodiments, the three-dimensional dimensions of the nanobrick include length, width, and height.

[0018] According to the second aspect of the present invention, a metasurface is provided. The metasurface is designed by using the method for controlling the fluorescence radiation vector wavefront based on the metasurface described in any one of the first aspects, so as to realize independent manipulation of any radiation angle, linear polarization state, and radiation intensity of the fluorescence unidirectional radiation.

[0019] In some of these embodiments, the substrate of the metasurface is a glass substrate, the waveguide is a silicon nitride waveguide, the metasurface is a layer of silicon nitride waveguide and silicon nanobricks with specific size parameters covered on the glass substrate, and CdSe / ZnS quantum dots are randomly scattered above the waveguide layer.

[0020] According to the third aspect of the present invention, a polarization multiplexing fluorescence holography and nano-printing display method based on vector fluorescence complex amplitude wavefront encoding is provided. The method includes:

[0021] Designing a metasurface, each unit structure of the metasurface includes two nanobricks with equal sizes, independent lateral displacements, and orthogonal rotations to encode a set of orthogonal linear polarization channels;

[0022] Modulating the fluorescence radiation intensity of the metasurface by the presence or absence or geometric size of the nanobricks, and regulating the phase modulation of the metasurface by using the encoding principle of the detour phase to realize the control of the fluorescence radiation vector complex amplitude wavefront;

[0023] Realizing four-channel polarization multiplexing fluorescence holography and nano-printing display based on the control of the fluorescence radiation vector complex amplitude wavefront; among them, the display of the first fluorescence holographic image and the first fluorescence near-field image is realized based on one of the orthogonal linear polarization channels, and the display of the second fluorescence holographic image and the second fluorescence near-field image is realized based on the other of the orthogonal linear polarization channels.

[0024] In some of these embodiments, the design principle of the metasurface is as follows:

[0025] During the propagation of the guided-wave fluorescence in the waveguide layer of the metasurface, the phase accumulates continuously, so that the phase of the light scattered by the nanobrick is different according to its position; according to the encoding principle of the detour phase, the phase of the light extracted by the nanobrick is expressed as Φ n = Φ0 + kPL (nP + D n ), where n is the number of arrays of nanobricks along the propagation direction, Φ0 is a fixed initial phase, and D n is the displacement of the nanobrick along the light propagation direction, and k PL is the wave vector of the guided-wave fluorescence;

[0026] Design the metasurface period P such that k PL D n covers the phase range from 0 to 2π; encode the detour phase using the displacement of the nanobricks, and encode the fluorescence intensity using the presence or absence or geometric size of the nanobricks, thereby realizing the vector complex amplitude encoding of the fluorescence wavefront;

[0027] Use the angular spectrum diffraction method to calculate the Fresnel holographic image and optimize the phase distribution of the metasurface using the gradient descent algorithm, thereby finally designing the phase distributions corresponding to two vector Fresnel holograms and obtaining the exact positions of the nanobricks;

[0028] Encode the presence or absence or geometric size of the nanobricks according to the target near-field binary image to obtain the final metasurface design; obtain two independently encoded fluorescence near-field images by analyzing different linearly polarized light, and obtain two fluorescence holographic images with different polarizations by defocusing to the designed Fresnel holographic plane.

[0029] According to the fourth aspect of the present invention, there is provided a metasurface for realizing four-channel polarization multiplexed fluorescence holography and nanolithography display, which is designed by using the polarization multiplexed fluorescence holography and nanolithography display method based on vector fluorescence complex amplitude wavefront encoding described in any one of the third aspects, thereby realizing four-channel polarization multiplexed fluorescence holography and nanolithography display.

[0030] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0031] The present invention provides a method for controlling the vector wavefront of fluorescence radiation based on an on-chip metasurface. Using pump light to irradiate the in-plane guided-wave fluorescence with a specific wave vector generated by the fluorescence light source on the on-chip metasurface, different structural parameters of the metasurface can be designed to selectively couple the guided-wave fluorescence into free space to achieve the unidirectional radiation function, and independently control the radiation angle, linear polarization state, and radiation intensity of the unidirectional radiation. Furthermore, through holographic algorithm optimization and complex amplitude encoding of the guided-wave fluorescence, two independently encoded vector fluorescence nanolithography images and two independently encoded vector fluorescence holographic images can be displayed. Compared with the existing radiation control methods and components, the present invention has:

[0032] (1) The vector fluorescence unidirectional radiation function with independent control of the radiation angle, any linear polarization state, and radiation intensity can be realized by using a simple unit structure design.

[0033] (2) Based on the vector complex amplitude wavefront encoding ability of fluorescence radiation, the functions of polarization multiplexed fluorescence holography and nano-printing display are realized for the first time. Description of the Drawings

[0034] Figure 1 is a schematic diagram of the principle of unidirectional fluorescence radiation provided by an embodiment of the present application;

[0035] Figure 2 is a schematic diagram of the unit structure of a metasurface provided by an embodiment of the present application;

[0036] Figure 3 is a graph of the experimental results of the fluorescence spectrum of a quantum dot thin film provided by an embodiment of the present application;

[0037] Figure 4 is a graph of the experimental measurement results of the fluorescence angular spectrum and the fitting results of the guided-mode fluorescence wave vector at the central wavelength when the pump light irradiates the metasurface with different periods in the x direction provided by an embodiment of the present application;

[0038] Figure 5 is a graph of the experimental measurement results of the fluorescence angular spectrum when the pump light irradiates the metasurface with different periods in the +x direction provided by an embodiment of the present application;

[0039] Figure 6 is a graph of the experimental results of the change in fluorescence intensity when the linearly polarized analyzer rotates for a metasurface with different nano-brick rotation angles provided by an embodiment of the present application;

[0040] Figure 7 is a graph of the experimental results of the fluorescence spectrum of a metasurface with different nano-brick rotation angles under orthogonal linear polarization analysis provided by an embodiment of the present application;

[0041] Figure 8 is a graph of the experimental results of the fluorescence intensity of a metasurface with different nano-brick lengths provided by an embodiment of the present application;

[0042] Figure 9 is a schematic diagram of the encoding principle and unit structure of a polarization multiplexed metasurface for fluorescence nano-printing and holographic display provided by an embodiment of the present application;

[0043] Figure 10 is a graph of the experimental results of dual-channel polarization multiplexed nano-printing display generated by a metasurface provided by an embodiment of the present application;

[0044] Figure 11 is a graph of the Fresnel holographic optimization calculation results and experimental measurement results of dual-channel polarization multiplexed holographic display generated by a metasurface provided by an embodiment of the present application;

[0045] Figure 12It is a schematic diagram of four-channel display provided by an embodiment of the present application. Detailed implementation manners

[0046] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided in this application without creative efforts fall within the scope of protection of the present invention.

[0047] Obviously, the accompanying drawings in the following description are only some examples or embodiments of this application. For those of ordinary skill in the art, without creative efforts, this application can also be applied to other similar scenarios based on these drawings. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in this application, some design, manufacturing or production changes based on the technical content disclosed in this application are only conventional technical means and should not be understood as the content disclosed in this application being insufficient.

[0048] Referring to "embodiments" in this application means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments without conflict.

[0049] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the ordinary meanings understood by those with ordinary skills in the technical field to which this application belongs. The words such as "a", "an", "one kind", "the" and the like involved in this application do not indicate a limitation in quantity and may represent a singular or plural number. The terms "include", "comprise", "have" and any variations thereof involved in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may further include steps or units not listed, or may further include other steps or units inherent to these processes, methods, products or devices. The similar words such as "connect", "be connected", "couple" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "plurality" involved in this application means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the front and rear associated objects. The terms "first", "second", "third" and the like involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0050] This application provides a method for controlling the fluorescence radiation vector wavefront based on a metasurface. The metasurface structure from bottom to top is successively a substrate - waveguide - nanobrick array - fluorescent material, wherein the nanobrick array is composed of cuboid silicon nanobricks with different periods, rotation angles, sizes, and displacements arranged according to the phase distribution. When the pump light excites fluorescence, part of the fluorescence is coupled into the laterally propagating in-plane guided-wave fluorescence; since the generated guided-wave fluorescence has a specific wave vector, designing the metasurface can scatter the guided-wave fluorescence into free space to achieve unidirectional fluorescence radiation; by encoding parameters such as the period of the metasurface, the rotation angle of the nanobricks, and the length and width of the nanobricks, the radiation angle, linear polarization state, and radiation intensity of the unidirectional fluorescence radiation can be independently controlled. In addition, the fluorescence radiation intensity of the metasurface is modulated by the presence or absence or geometric size of the nanobricks, the radiation polarization state is controlled by the rotation angle of the nanobricks, and the phase modulation of the metasurface is regulated by the principle of the phase of detour, so as to realize the function of manipulating the complex amplitude of the vector wavefront of the fluorescence radiation, and further realize the four-channel polarization multiplexing nano-printing and holographic display functions based on the manipulation of the vector complex amplitude.

[0051] This application utilizes a simple unit structure to design the interaction between a metasurface and guided-mode fluorescence, and for the first time realizes the vector fluorescence unidirectional radiation function of independently controlling the radiation angle, arbitrary linear polarization state, and radiation intensity, as well as the polarization multiplexed fluorescence holography and nano-printing multi-dimensional display functions. The proposed strategy may open up new avenues for applications such as advanced lighting technologies, multiplexed optical displays, information storage, and next-generation wearable displays.

[0052] This application provides a method for controlling the wavefront of vector fluorescence directional radiation based on a metasurface, including: the structure of the metasurface is a unit periodic array of nano-bricks - waveguides - substrates - fluorescent materials; when the pump light excites fluorescence, part of the fluorescence is coupled into laterally propagating in-plane guided-wave fluorescence; due to the generated guided-wave fluorescence having a specific wave vector, designing the metasurface can scatter the guided-wave fluorescence into free space to achieve fluorescence unidirectional radiation; by encoding parameters such as the period of the metasurface, the rotation angle of the nano-bricks, and the length and width of the nano-bricks, the radiation angle, linear polarization state, and radiation intensity of the fluorescence unidirectional radiation can be independently controlled.

[0053] Furthermore, by controlling the presence or absence or geometric size of the nano-bricks to encode the radiation intensity, and using the principle of phase modulation of the detour phase encoding, the wavefront control of the complex amplitude of the fluorescence radiation vector can be achieved; finally, based on the wavefront control of the complex amplitude of the fluorescence radiation vector, a four-channel vector fluorescence nano-printing and holographic multi-dimensional display function is realized.

[0054] To this end, this application provides a polarization multiplexed fluorescence holography and nano-printing display method based on vector fluorescence complex amplitude wavefront encoding. The amplitude modulation of the metasurface is controlled by the presence or absence or geometric size of the nano-bricks; the phase modulation of the metasurface is obtained using the detour phase principle; the phase distribution of the metasurface for generating fluorescence holography is optimized according to the gradient descent algorithm, so as to realize four-channel polarization multiplexed fluorescence holography and nano-printing display.

[0055] Among them, the wave vector of the guided-wave fluorescence can be directly observed by using a microscope with a sufficient numerical aperture to observe the far-field distribution of the rear focal plane, or indirectly measured by using metasurface gratings with different periods according to the grating equation.

[0056] Specifically, as Figure 1 and Figure 2 shown, this application embodiment provides a method for vector fluorescence unidirectional radiation with independent encoding of arbitrary radiation angle, linear polarization state, and radiation intensity. The pump light irradiates the fluorescent material (quantum dots) on the waveguide layer to excite fluorescence at all angles. Among them, part of the fluorescence is coupled into a guided-wave mode with a wave vector of k PL whose angular spectrum is as Figure 1As shown in I therein. Here, light with k / k0 < 1 is light in free space, and light with k / k0 > 1 is light in the guided mode, where the free space wave number k0 = 2π / λ and λ is the wavelength. Part of the guided fluorescence propagating in the x direction will pass through the metasurface and be modulated, as Figure 1 shown in II therein, which is provided with an additional wave vector k MS after being modulated by the metasurface, and the wave vector is k out = k PL+ k MS . As Figure 1 shown in III therein, when designing |k PL+ k MS | / k0 < 1, the transverse wave vector propagating in the +x direction can be deflected into free space to form unidirectional radiation. As Figure 2 shown, with a period of P and a rotation angle of , the additional wave vector provided by a rectangular nanobrick with length, width, and height of L, W, and H respectively is k MS = 2πm / P = mk0λ / P, where m is the grating order. Its scattered light is linearly polarized light with the polarization vibration direction parallel to the long axis of the nanobrick, and the scattering intensity is related to its three-dimensional size. Thus, the angle of fluorescence unidirectional radiation can be determined by designing the period of the metasurface, the linear polarization state of radiation can be determined by designing the rotation angle of the nanobrick, and the radiation intensity can be controlled by designing the three-dimensional size of the nanobrick, so as to realize independent manipulation of any radiation angle, linear polarization state, and radiation intensity of fluorescence unidirectional radiation.

[0057] As Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 shown, the embodiments of the present application provide a group of metasurfaces for realizing the function of vector fluorescence unidirectional radiation. As Figure 3 shown, the fluorescence peak wavelength of the used CdSe / ZnS quantum dot film is 625 nm. The prepared metasurface structure is as Figure 1 and Figure 2 shown, which is a silicon nitride waveguide (190 nm thick) and silicon nanobricks with different size parameters covered on a glass substrate, with a height H = 360 nm, and CdSe / ZnS quantum dots randomly scattered above the waveguide layer. First, for a group of metasurfaces with L = 150 nm, W = 50 nm, P = 320 - 560 nm (a total of 7 periods, with a period interval of 40 nm), when the pump light irradiates on the -x side of the metasurface, the fluorescence angular spectrum of the fluorescence propagating in the +x direction excited and deflected into free space after passing through the metasurface is as Figure 4 shown, and its diffraction angle can cover an angular range from 7.6° to -43.4°. According to the grating equation, the wave vector k of the guided mode fluorescence can be fittedPL = k out -k MS ≈ 1.24k0. When the pump light irradiates the +x side of the metasurface and excites the fluorescence propagating in the -x direction, the measured fluorescence angular spectrum is as Figure 5 shown. The fluorescence unidirectional radiation angle satisfies symmetry, thus being opposite to that when exciting the fluorescence propagating in the +x direction (the diffraction angle covers -7.6° to 43.4°). Thus, the experiment proves that the manipulation of the fluorescence radiation angle can be achieved by changing the period parameter of the metasurface, and the experimental verification shows that the diffraction angle range of ±43.4° can be further expanded by changing the period.

[0058] For a group of metasurfaces with L = 150 nm, W = 50 nm, P = 560 nm, (a total of 6 angles, with an angular interval of 30°), when controlling the change of the analyzer angle ψ by clockwise rotating the linear polarizer, as Figure 6 shown, the fluorescence intensities generated by the metasurfaces with different rotation angles have different fluctuations, indicating that there are obvious differences in the fluorescence radiation polarization generated by them. Further measuring its fluorescence intensity under the orthogonal analyzer related to the rotation angle, as Figure 7 shown, the polarization component along the long axis of the nanobrick is significantly greater than the component perpendicular to the long axis, proving that the fluorescence extracted by the metasurface from free space is linearly polarized light, and the direction of its electric field vibration is parallel to the long axis, which is consistent with the theoretical design. For a group of metasurfaces with W = 40 nm, P = 500 nm, Figure 8 L = 80 - 200 nm (with a length interval of 20 nm), as

[0059] shown, the fluorescence extraction intensity of the metasurface is positively correlated with the length of the nanobrick, proving the regulation ability of the metasurface on the fluorescence radiation intensity.

[0059] As Figure 9 , Figure 10 , Figure 11 and Figure 12 shown, the embodiments of the present application provide a group of metasurfaces for realizing four-channel polarization multiplexed fluorescence nanolithography and holographic display. The design principle of the metasurface is as Figure 9 shown. During the propagation of the guided-mode fluorescence in the waveguide layer, the phase accumulates continuously, so that the phase of the light scattered by the nanobrick is different according to its position. According to the coding principle of the detour phase, the phase of the light extracted by the nanobrick can be expressed as Φ n = Φ0 + k PL (nP + D n ), where n is the number of nanobricks in the propagation direction, Φ0 is the fixed initial phase, and D n is the displacement of the nanobrick along the light propagation direction. Design the metasurface period P = 600 nm, such that kPL D n It can cover a phase range from 0 to 2π. Two nanobricks with equal sizes (L = 150 nm, W = 50 nm), independent lateral displacements, and rotation angles of ±45° are included in a unit structure to encode a set of orthogonal linear polarization channels. The displacement of the nanobricks is used to encode the roundabout phase, and the presence or absence of the nanobricks is used to encode the fluorescence intensity, so that the vector complex amplitude of the fluorescence wavefront can be encoded. The Fresnel holographic image is calculated by the angular spectrum diffraction method and the phase distribution of the metasurface is optimized by the gradient descent algorithm, so as to finally design the phase distributions corresponding to two vector Fresnel holograms and obtain the exact positions of the nanobricks. Further, the presence or absence of the nanobricks is encoded according to the target near-field binary image, so as to obtain the final metasurface design, realize the fluorescence nanolithography display function, and obtain the fluorescence near-field image. As Figure 10 shown, in the experiment, two independently encoded fluorescence near-field images were successfully obtained by analyzing different linearly polarized lights. As Figure 11 shown, by defocusing to the designed Fresnel holographic plane, two fluorescence holographic images with different polarizations were successfully captured in the experiment. As Figure 12 shown, the display of the first fluorescence holographic image and the first fluorescence near-field image is realized through the first polarization, and the display of the second fluorescence holographic image and the second fluorescence near-field image is realized based on the second polarization, where the fluorescence near-field image is displayed on the metasurface, and the fluorescence holographic image is displayed more than four hundred micrometers above the metasurface.

[0060] It should be noted that the technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. In addition, according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0061] Those skilled in the art can easily understand that the above-described embodiments only represent several implementation manners of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of the patent of this application should be subject to the appended claims.

Claims

1. A method for controlling fluorescence radiation vector wavefront based on metasurface, characterized in that: The method includes: Constructing a metasurface, wherein the structure of the metasurface is a unit periodic array of nanobricks-waveguide-substrate-fluorescent material; Irradiating the pump light to the quantum dots on the waveguide layer of the metasurface to excite fluorescence at all angles, wherein part of the fluorescence is coupled as in-plane guided wave fluorescence that propagates laterally; Determine the wave vector of the guided wave fluorescence, design the metasurface to scatter the guided wave fluorescence into free space, and realize unidirectional fluorescence radiation; The radiation angle of the fluorescent unidirectional radiation is controlled by encoding the period of the metasurface, the linear polarization state of the fluorescent unidirectional radiation is controlled by encoding the rotation angle of the nanobrick, and the radiation intensity of the fluorescent unidirectional radiation is controlled by encoding the three-dimensional size of the nanobrick.

2. The method for controlling fluorescence radiation vector wavefront based on metasurface according to claim 1, characterized in that: Determine the wave vector of the guided wave fluorescence, design the metasurface to scatter the guided wave fluorescence into free space, and realize unidirectional fluorescence radiation, including: Determine the wave vector k of guided wave fluorescence PL ; The guided wave fluorescence is modulated when passing through the metasurface, and its energy provides an additional wave vector k MS The wave vector after the metasurface is modulated is k out =k PL+ k MS ; where k out is the wave vector of the guided wave fluorescence modulated by the metasurface, k MS The additional wave vector provided by the metasurface for guided wave fluorescence; Designing metasurfaces to make |k PL+ k MS | / k0<1, at this time the guided wave fluorescence is deflected into the free space to form unidirectional radiation; where the free space wave number k0=2π / λ, λ is the wavelength.

3. The method for controlling the fluorescence radiation vector wavefront based on a metasurface according to claim 2, characterized in that: The additional wave vector k provided by a rectangular nanobrick with a period of P, a rotation angle of φ, and a length, width, and height of L, W, and H respectively is MS =2πm / P=mk0λ / P, where m is the grating order.

4. The method for controlling the fluorescence radiation vector wavefront based on a metasurface according to claim 1, characterized in that: The fluorescence scattered into free space is linearly polarized light with the polarization vibration direction parallel to the long axis of the nanobrick.

5. The method for controlling the fluorescence radiation vector wavefront based on a metasurface according to claim 1, characterized in that: The three-dimensional dimensions of the nanobrick include length, width and height.

6. A metasurface, characterized in that: The metasurface is designed using the metasurface-based fluorescence radiation vector wavefront control method described in any one of claims 1 to 5, thereby achieving independent control of any radiation angle, linear polarization state and radiation intensity of unidirectional fluorescence radiation.

7. The metasurface according to claim 6, characterized in that: The substrate of the metasurface is a glass substrate, and the waveguide is a silicon nitride waveguide. The metasurface is a glass substrate covered with a layer of silicon nitride waveguide and silicon nanobricks with specific size parameters, and CdSe / ZnS quantum dots are randomly scattered above the waveguide layer.

8. A polarization multiplexing fluorescence holographic and nano-printing display method based on vector fluorescence complex amplitude wavefront coding, characterized in that: The method includes: Designing a metasurface in which each unit structure consists of two nanobricks of equal size, independent lateral displacement, and orthogonal rotation angles to encode a set of orthogonal linear polarization channels; The fluorescence radiation intensity of the metasurface is modulated by the presence or absence of nanobricks or their geometric size, and the phase modulation of the metasurface is controlled by the encoding principle of the circuitous phase to achieve complex amplitude wavefront control of the fluorescence radiation vector. Four-channel polarization-multiplexed fluorescence holographic and nanoprinting display is realized based on the complex amplitude wavefront control of the fluorescence radiation vector; wherein, the display of the first fluorescence holographic image and the first fluorescence near-field image is realized based on one of the orthogonal linear polarization channels, and the display of the second fluorescence holographic image and the second fluorescence near-field image is realized based on the other one of the orthogonal linear polarization channels.

9. The polarization multiplexing fluorescence holography and nano-printing display method based on vector fluorescence complex amplitude wavefront coding according to claim 8, characterized in that: The design principles of the metasurface are as follows: During the propagation of guided fluorescence in the waveguide layer of the metasurface, the phase accumulates continuously, so that the phase of the light scattered by the nanobrick varies according to its position. According to the encoding principle of the circuitous phase, the phase of the light extracted by the nanobrick is expressed as Φ n =Φ0+k PL (nP+D n ), where n is the number of nanobrick arrays along the propagation direction, Φ0 is a fixed initial phase, and D n is the displacement of the nanobrick along the light propagation direction, k PL is the wave vector of guided wave fluorescence; Design the metasurface period P so that k PL D n Covering the phase range from 0 to 2π; using the displacement of nanobricks to encode the circuitous phase, and using the presence or absence or geometric size of nanobricks to encode the fluorescence intensity, thereby achieving vector complex amplitude encoding of the fluorescence wavefront; The angular spectrum diffraction method is used to calculate the Fresnel holographic image and the gradient descent algorithm is used to optimize the phase distribution of the metasurface, so that the phase distribution corresponding to the two vector Fresnel holograms is finally designed to obtain the exact position of the nanobricks. The final metasurface design is obtained by encoding the presence or absence of nanobricks or their geometric dimensions in the target near-field binary image. Two independently encoded fluorescence near-field images are acquired by analyzing different linear polarizations, and two fluorescence holographic images with different polarizations are obtained by defocusing to the designed Fresnel holographic plane.

10. A metasurface for realizing four-channel polarization multiplexing fluorescence holographic and nano-printing display, characterized in that: The metasurface is designed by using the polarization multiplexing fluorescence holography and nano-printing display method based on vector fluorescence complex amplitude wavefront coding as described in claim 8 or 9, thereby realizing four-channel polarization multiplexing fluorescence holography and nano-printing display.

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