Polarization conversion metasurface structure light super-resolution microscopic chip and imaging system and method

Abstract

The application discloses a polarization conversion super surface structure light super resolution microscopic chip and an imaging system and method, the chip is based on a light transparent substrate with two parallel surfaces, the two surfaces of the substrate are polished, one of the surfaces is used as a light field modulation surface, a super surface light field modulation structure is prepared on the surface of a waveguide, and the polarization control of coupled light fields and the improvement of coupling efficiency can be realized by using the free and flexible control characteristics of the super surface on electromagnetic fields. Since a traditional polarization rotating device is not needed, compared with a previously proposed structure light super resolution microscopic chip, the structure light super resolution microscopic chip based on the super surface can realize higher integration, faster imaging speed and higher energy utilization.

Description

Technical Field

[0001] This invention relates to the technical field of super-resolution microscopy, specifically to a polarization-conversion metasurface structured light super-resolution microscopy chip, imaging system, and method. Background Technology

[0002] Traditional optical systems are limited by the Abbe diffraction limit, restricting microscope resolution to only half the illumination wavelength. To overcome this diffraction limit, a series of fluorescent and non-fluorescent labeling methods have been developed. Among these, frequency-shifting techniques can overcome the bandwidth limitations of traditional imaging and detection devices, offering significant advantages in terms of large field of view and high speed. Structured illumination microscopy (SIM) is a frequency-shifting technique, characterized by its fast imaging speed and relatively low excitation light intensity (W / cm²). 2 With its advantages such as non-specific requirements for fluorescent dyes, it has become one of the mainstream super-resolution imaging technologies and is widely used in biological imaging.

[0003] The principle of structured light illumination super-resolution microscopy is to encode the high-frequency spatial structure information of an object into the bandwidth of the microscopic system through spatial frequency mixing, thereby achieving resolution that breaks the diffraction limit. This is achieved by illuminating the sample with sinusoidal fringe structured light of spatial frequency f1, which produces low-frequency moiré fringes of spatial frequency fm = |f - f1|. The moiré fringes are actually the beat frequency signal between the sample and the structured light, containing high-frequency information f that allows for super-diffraction resolution. mWhen f0, Moiré fringes can be observed under a microscope objective. Then, the super-resolution information of the sample can be extracted through decoding, and further, a high-resolution image of the sample can be reconstructed. To ensure the isotropy of the imaging resolution of the structured illumination microscopy system, it is necessary to rotate the illumination light field to symmetrically illuminate the sample in multiple directions during the experiment. Usually, 3 positions are rotated in each imaging plane, with an included angle of 60° between each two. From the frequency domain perspective, structured light illumination expands the OTF radius of the microscopy system from f0 to f0 + f1. Therefore, the larger f1 is, that is, the smaller the period of the illumination light field is, the higher the spatial resolution of SIM imaging is. However, the spatial frequency f1 of the structured illumination light field is also limited by the diffraction limit. Ordinary structured illumination microscopy techniques use an objective lens to couple two beams to generate interference fringes as the modulated light field illumination, and the fringe period depends on the effective numerical aperture of the objective lens, that is, f1 ≤ f0. So, linear SIM microscopy techniques can at most double the spatial resolution of the optical microscopy system. To obtain higher resolution in the experiment, the most direct method is to increase the effective numerical aperture of the objective lens. However, the design of an objective lens with a higher NA is more complex, which ultimately limits the resolution of this super-resolution method. In addition, increasing the effective numerical aperture will also lead to a reduction in the imaging field area and a shortening of the working distance of the microscope.

[0004] The idea to solve this contradiction is to separate the illumination system and the receiving system. Among them, the illumination system can use a chip with a high refractive index to provide structured light illumination with a smaller period, and the receiving system uses an objective lens with a smaller numerical aperture. Therefore, a larger imaging field and a higher resolution can be obtained simultaneously. In addition, this super-resolution method that uses chip illumination to generate structured light illumination combined with a small-NA objective lens has the advantages of light weight and integration, and is expected to realize a low-cost and miniaturized super-resolution microscopy system, which can be applied to scenarios such as medical examinations in remote areas, scientific expeditions, and space experiments where there are limitations on the weight, volume, or cost of the instrument.

[0005] In addition, SIM needs to be reconstructed through algorithms, and the fringe contrast affects the measurement accuracy of the reconstruction parameters and the signal-to-noise ratio of the high-frequency information, which in turn affects the quality of the final reconstructed image. Therefore, high fringe contrast is a necessary condition for obtaining high-quality images. In the traditional structured light microscopy optical path, in order to achieve high-contrast interference fringes, it is necessary to rotate the polarization directions of the two beams in each direction to achieve the unity of the polarization directions. There are two ways to achieve this polarization rotation. One is to use a mechanical rotation of a quarter-wave plate or a liquid crystal polarization rotator (CN 111610621A) to achieve it. Its disadvantage is that the mechanical rotation speed or the modulation speed of the liquid crystal is limited, which limits the final imaging speed. The other is The pizza polarizer method, proposed by [names of individuals], first converts a linearly polarized beam into circularly polarized light by passing it through a quarter-wave plate, and then passes it through a specially processed pizza polarizer. This polarizer consists of 12 small sector polarizers, each with its polarization direction perpendicular to the radial direction. The polarizers are then bonded together with optical adhesive. This method is beneficial for improving imaging speed, but the incident circularly polarized light loses 50% of its light energy after passing through the sector polarizers. Furthermore, neither of these two methods can achieve true integration.

[0006] In the field of structured light illumination chips, CN 111024664A proposes a scheme for fabricating structured light illumination super-resolution microchips using bulk optical waveguide materials. A grating is used to couple free-space laser light to a high transverse wave vector evanescent field. Interference fringes are achieved using the ±1st order diffraction beams of a pair of gratings. However, the polarization direction of the two free beams still needs to be adjusted using the two traditional methods mentioned above to optimize the interference contrast of the evanescent wave. Furthermore, this structured light illumination chip uses a conventional one-dimensional rectangular grating to control the wave vector, and its diffraction energy is mainly distributed to the zeroth order and the second order diffraction beams. Therefore, the coupling efficiency of the first order diffraction beam of the grating is relatively low, reaching a maximum of only about 40%. In summary, due to the limited degrees of freedom in controlling the optical field using a conventional rectangular grating, new micro / nano structures are needed to achieve higher evanescent field coupling efficiency and optimized polarization.

[0007] Metasurfaces are artificial metamaterials composed of multiple artificial unit structures with wavelengths much smaller than electromagnetic waves, arranged according to certain rules. Similar to atoms or molecules in natural materials, they allow for flexible control of electromagnetic waves through the autonomous design of unit structures, resulting in novel electromagnetic properties. Therefore, utilizing the free and flexible control of electromagnetic waves by metasurfaces holds promise for improving evanescent wave coupling efficiency and polarization conversion of incident light at corresponding positions. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing structured light illumination super-resolution microscopy technology by proposing a structured light illumination super-resolution microscopy chip based on metasurfaces, and combining it with corresponding excitation and imaging optical paths to achieve super-resolution imaging.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A polarization-conversion metasurface structured light super-resolution microchip includes two parallel, light-transparent substrates, both of which are polished. One side serves as a light field modulation surface, with metasurface light field modulation structures distributed on its surface. These structures couple two collimated free-space beams into the chip, where they meet and interfere at the center of the other side of the chip, generating illumination interference fringes. Except for the locations of the metasurface light field modulation structures, the light field modulation surface is also equipped with light-shielding structures. The other side of the light-transparent substrate serves as a sample surface, with a sample placement area in the central region and light-shielding structures in the remaining areas.

[0011] Preferably, the chip further includes a dielectric film located between the light field modulation surface and the light-shielding structure of the surface.

[0012] Preferably, the metasurface optical field modulation structure is a periodic structure, and its period determines the angle of incident light deflection.

[0013] Preferably, each cycle of the metasurface optical field modulation structure consists of multiple micro / nanostructures, each of which is a cuboid. The length, width, and thickness of each micro / nanostructure determine the phase delay, and the phase delay formed by the micro / nanostructures within one cycle uniformly covers 2π. This gradient phase delay can couple the required first-order diffracted light to the chip substrate for total internal reflection illumination with maximum efficiency.

[0014] Preferably, the long sides of the micro / nano structures of a single period of the metasurface optical field modulation structure point to the same angle, and their direction determines the axis of symmetry of polarization conversion, which is used to mirror the polarization direction of the outgoing light along the axis of symmetry and the polarization direction of the incident light.

[0015] Preferably, the metasurface optical field modulation structure is composed of two materials with unequal refractive indices alternating laterally.

[0016] Preferably, the light-shielding structure is an opaque metal film used to block unwanted stray light and illumination light that has not been modulated by the metasurface.

[0017] Preferably, the optically transparent substrate includes one or more of Si3N4, SiO2, Al2O3, SiC, GaP, TiO2, GaN, and Polymer.

[0018] Preferably, the light field modulation surface is fabricated using micro / nano fabrication methods such as EBL, FIB, photolithography, or nanoimprinting to create a metasurface light field modulation structure.

[0019] This invention also provides an optical system, including a light source, a beam adjustment and filtering system, a light field modulation system, a mirror, a sample stage, an imaging system, a computer, and a structured light super-resolution microchip based on a polarization conversion metasurface. The chip is mounted on the sample stage. Parallel light emitted from the light source passes through the beam adjustment and filtering system and the light field modulation system successively, and is modulated into two parallel beams. Then, the two beams are reflected by the mirror and perpendicularly enter the light field modulation surface of the chip. After coupling, they meet at the sample on the other side of the chip and excite the fluorescent sample. After that, the image is formed by the imaging system and sent to the computer for processing.

[0020] The present invention also provides an imaging method comprising the following steps:

[0021] Step 1: Two coherent beams are generated using an optical field modulation system and respectively strike a pair of metasurface optical field modulation structures. After passing through the pair of metasurface optical field modulation structures, first-order diffraction occurs and the beams are coupled into the substrate. The two first-order diffracted beams interfere on the sample surface of the chip and excite the fluorescent sample.

[0022] Step 2: Adjust the optical path difference between the two coherent beams using an optical field modulation system, causing the structured light generated after interference to undergo two translations, and then collect the modulated fluorescence distribution maps.

[0023] Step 3: Switch the two coherent beams to paired metasurface light field modulation structures with different directions and periods, repeat steps 1 and 2, and obtain the fluorescence distribution map of the sample modulated under structured light illumination with different directions and periods.

[0024] Step 4: For all the modulated fluorescence distribution maps obtained in Step 3, the phase and frequency shift are solved using the structured light illumination super-resolution imaging algorithm, and iterative stitching is performed in the frequency domain to obtain the expanded spectrum. Finally, inverse Fourier transform is performed to reconstruct the super-resolution sample image.

[0025] This invention utilizes bulk high-refractive-index optical waveguide materials to fabricate metasurface optical field modulation structures on the waveguide surface. By leveraging the free and flexible control characteristics of the metasurface over the electromagnetic field, polarization control of the coupled optical field can be achieved, improving coupling efficiency. Since traditional polarization rotation devices are not required, compared to previously proposed structured light super-resolution microscopy chips, this metasurface-based structured light super-resolution microscopy chip can achieve higher integration, faster imaging speed, and higher energy utilization efficiency. This invention offers the following advantages:

[0026] (1) Compared to objective-coupled structured light illumination, high-refractive-index waveguides can generate higher-frequency structured light, thus achieving higher resolution than objective-coupled methods. In addition, it can be used with low-magnification objectives to achieve large field-of-view super-resolution capabilities.

[0027] (2) Compared with the structured light illumination chip coupled by a rectangular grating, the present invention can achieve higher light field coupling efficiency by utilizing the metasurface to flexibly control the light field.

[0028] (3) Compared with the polarization adjustment methods of structured light illumination with objective lens coupling and rectangular grating coupling, structured light illumination based on metasurface can realize real-time conversion of the polarization of incident light at the corresponding position without the need for additional devices to convert the polarization of incident light, thus having higher integration and faster imaging speed. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the structured light super-resolution microchip based on polarization conversion metasurface of the present invention;

[0030] Figure 2 This is a schematic diagram of the optical system of the present invention;

[0031] Figure 3 This is a planar distribution diagram of the metasurface optical field modulation structure of the present invention;

[0032] Figure 4 This is a planar distribution diagram and a corresponding polarization conversion diagram of the metasurface optical field modulation structure of the present invention;

[0033] Figure 5 This is a planar distribution diagram and corresponding polarization conversion diagram of another metasurface optical field modulation structure of the present invention;

[0034] Figure 6 This is a schematic diagram of the metasurface optical field modulation planar structure and polarization conversion of the present invention;

[0035] Figure 7 yes Figure 6 The corresponding metasurface optical field modulation structure achieves high-efficiency coupling and polarization conversion using FDTD simulation. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to embodiments and accompanying drawings.

[0037] like Figure 1As shown in (a), a polarization-conversion metasurface structured light super-resolution microchip of the present invention includes a two-sided, light-transparent substrate 102. Both sides of the light-transparent substrate 102 are polished. One side serves as a light field modulation surface, with a metasurface light field modulation structure 101 distributed on its surface. The metasurface light field modulation structure 101 is used to couple two collimated free-space beams into the chip, where they meet and interfere at the center of the other side of the chip, generating illumination interference fringes. The metasurface light field modulation structure 101 can simultaneously change the polarization direction of the corresponding incident light to maximize interference contrast. Except for the metasurface light field modulation structure 101, the light field modulation surface is provided with light-shielding structures 103. The other side of the light-transparent substrate 102 serves as a sample surface. A sample placement area 105 is provided in the central region of the sample surface, and light-shielding structures 103 are provided in the remaining areas. The sample placement area 105 is used to place the sample 106 to be observed. The metasurface light field modulation structure 101 is composed of two materials with unequal refractive indices alternating laterally. The light-shielding structure 103 is an opaque metal film used to block unwanted stray light and illumination light not modulated by the metasurface. The light-transparent substrate 102 includes one or more of Si3N4, SiO2, Al2O3, SiC, GaP, TiO2, and polymer. The light field modulation surface is fabricated using micro / nano fabrication methods such as EBL, FIB, photolithography, or nanoimprinting to create the metasurface light field modulation structure.

[0038] like Figure 1 As shown in (b), a polarization conversion metasurface structure light super-resolution microchip of the present invention further includes a dielectric film 104, which is located between the light field modulation surface and the light-shielding structure 103 of the surface.

[0039] The metasurface optical field modulation structure 101 is a periodic structure, and its period L determines the angle of incident light deflection. Each period of the metasurface optical field modulation structure 101 consists of multiple micro / nano structures. Each micro / nano structure is a cuboid, and its length, width, and thickness determine the phase delay. The phase delay formed by the micro / nano structures within one period needs to uniformly cover 2π. This gradient phase delay can couple the required first-order diffracted light to the chip substrate for total internal reflection illumination with maximum efficiency. The long sides of the micro / nano structures within a single period point to the same angle, and their orientation determines the axis of symmetry for polarization conversion, which can mirror the polarization direction of the outgoing light along this axis of symmetry and the polarization direction of the incident light.

[0040] The other surface of substrate 102 is a sample plane, used to place sample 106. The imaging plane of the chip is polished to improve the efficiency of total internal reflection and the uniformity of the evanescent field. The imaging region of the sample plane is located at the center of the metasurface optical field modulation structure ring on the functional surface. The spacing between a set of identical metasurface optical field modulation structures 101 satisfies:

[0041]

[0042] Where T is the thickness of the substrate material, λ is the wavelength of the illumination light used, n is the refractive index of the substrate material, and L... m φ is the period of the metasurface optical field modulation structure, and φ is the angle between the incident light and the waveguide normal.

[0043] The distribution of the metasurface optical field modulation structure 101 is as follows Figure 3 As shown, the structure is divided into multiple rings; each ring has a different period, with the innermost ring having the longest period, and the periods gradually decreasing from the inside out. Each ring of metasurface optical field modulation structure is responsible for illumination in different directions, the direction of which is determined by the periodic direction and points towards the center of the chip.

[0044] The optical system of the present invention, such as Figure 2 As shown, the optical system includes a light source 201, a beam adjustment and filtering system 202, a light field modulation system 203, a mirror 204, a sample stage 205, an imaging system, a computer 211, and a structured light super-resolution microscopy chip 1 based on a polarization conversion metasurface. The chip is mounted on the sample stage 205. Parallel light emitted from the light source 201 is modulated into two parallel beams by the beam adjustment and filtering system 202 and the light field modulation system 203. The two beams are then reflected by the mirror 204 and perpendicularly incident on the light field modulation surface of the chip. After coupling, they meet at the sample 106 on the other side of the chip and excite the fluorescent sample 106. The image is then formed by the imaging system and sent to the computer 211 for processing. The imaging system includes a microscope objective 207, a filter 208, a lens 209, and an optical camera 210.

[0045] The light source 201 is a coherent light source. The beam adjustment and filtering system 202 is used to reduce or expand the parallel light emitted by the light source 201 and to filter it, generating an incident light spot suitable for the size of the metasurface light field modulation structure. The core of the light field modulation system 203 is a spatial light modulator, which is used to generate two beams with coherent characteristics and can adjust the phase difference between the two beams. The two coherent beams are reflected by the mirror 204 onto the light field modulation surface of the chip 1. The microscope objective 207 is located outside the sample surface on the chip and is used to collect the imaging signal of the interaction between the illumination light on the chip surface and the sample. The filter 208 is used to block the excitation light and only allow the emission fluorescence of the sample to pass through. The emission fluorescence of the sample is then focused by the lens 209 to the optical camera 210, captured, and sent to the computer 211. The computer 211 is used to record, store, and process the imaging signal and uses a structured light illumination super-resolution algorithm to recover the super-resolution image.

[0046] The specific implementation method of super-resolution imaging using this invention is as follows:

[0047] Step 1: Two coherent light beams are generated using the optical field modulation system 203 and incident on the paired metasurface optical field modulation structures 101 respectively; the light field undergoes first-order diffraction after passing through the paired metasurface optical field modulation structures, diffracting at a certain angle θ. m Coupled to substrate 102;

[0048]

[0049] Where λ is the wavelength of light used, n is the refractive index of the material, and L... m φ is the period of the metasurface optical field modulation structure, and φ is the angle between the incident light and the waveguide normal. The innermost ring of the metasurface optical field modulation structure has the largest period, and the period of the metasurface optical field modulation structure gradually decreases from the inside to the outside.

[0050] Two beams of light coupled into the substrate 102 undergo total internal reflection at the imaging plane. The resulting evanescent fields meet and interfere at the center of the imaging region. The structured light generated after the interference illuminates the sample, producing a modulated fluorescence distribution map, which is then photographed using a conventional microscope. The period of the structured light is related to the period of the metasurface light field modulation structure 101.

[0051] Step 2: The optical path difference between the two coherent beams is adjusted using the optical field modulation system 203, causing the structured light generated after interference to undergo two translations, and the modulated fluorescence distribution maps are acquired separately. The three modulated fluorescence distribution maps obtained in Step 1 and Step 2 are used to demodulate the phase of the spatial spectrum of the sample under structured light illumination of the corresponding direction and period during reconstruction.

[0052] Step 3: Switch the two coherent beams to paired metasurface light field modulation structures 101 with different directions and periods, and repeat steps 1 and 2 to obtain the fluorescence distribution map of the sample under structured light illumination with different directions and periods.

[0053] Step 4: For all the modulated fluorescence distribution maps obtained in Step 3, the phase and frequency shift are solved using the structured light super-resolution imaging algorithm, and iterative stitching is performed in the frequency domain to obtain the expanded spectrum. Finally, inverse Fourier transform is performed to reconstruct the super-resolution sample image.

[0054] Example 1

[0055] Take six lighting directions per circle as an example. Figure 4 , Figure 5 Planar distribution diagrams of the metasurface optical field modulation structures corresponding to two different incident light polarization directions, and their corresponding polarization conversion diagrams. (Left) Figure 6Metasurface micro / nanostructures are distributed at the center of the edges of the polygon. The right figure corresponds to the metasurface micro / nanostructure units in the respective regions, with numbers representing region numbers. The period of each metasurface micro / nanostructure unit is L, and the period direction points towards the center of the chip. The polarization conversion direction is determined by the length direction of the metasurface microcube, and the polarization conversion of the outgoing light is a mirror image of that of the incident light along the length direction of the metasurface microcube.

[0056] Figure 4 The incident light, polarized at 90 degrees, is represented by an arrow in the central region corresponding to the polarization direction of the outgoing light. The metasurface optical field modulation structures at positions 1, 4, 2, 5, 3, and 6 deflect the polarization direction of the light field by 90 degrees, 30 degrees, and -30 degrees, respectively. This ensures that the 90-degree perpendicularly polarized incident light, after passing through a pair of metasurface optical field modulation structures, has the same polarization direction, maximizing the interference contrast. To achieve this polarization conversion, the long sides of the microcubes in the metasurface structural units at positions 1, 4, 2, 5, 3, and 6 point to 135 degrees, 105 degrees, and 75 degrees, respectively.

[0057] Figure 5 The incident light has a polarization direction of 0 degrees, and the arrow in the central region corresponds to the polarization direction of the outgoing light. The metasurface optical field modulation structures at positions 1, 4, 2, 5, 3, and 6 respectively deflect the polarization direction of the light field to 0 degrees, -60 degrees, and 60 degrees. This ensures that the polarization direction of the 90-degree perpendicularly polarized incident light is consistent after passing through a pair of metasurface optical field modulation structures, maximizing the interference contrast. To achieve this polarization conversion, the long sides of the microcubic prisms of the metasurface structural units at positions 1, 4, 2, 5, 3, and 6 point to 0 degrees, 150 degrees, and 30 degrees, respectively.

[0058] Within a single period, there are three metasurface microcubic blocks, achieving phase delays of 0, 2π / 3, and 4π / 3 respectively, to maximize the diffraction efficiency of a certain order of optical field. To illustrate this, we use... Figure 6 The above example is a metasurface optical field modulation structure. Figure 6 The metasurface optical field modulation unit consists of three microcubic blocks with a period L of 600 nm, a width of 200 nm, and a height of 500 nm. The microcubic blocks are made of Si, and the substrate material is SiO2. The long side of the microcubic block is oriented at a 45-degree angle to the polarization direction of the incident light. After modulation by the metasurface optical field modulation unit, the polarization direction of the outgoing light changes to 90 degrees. Figure 7 (a) is the spatial angular distribution of the diffraction orders after the light field passes through a periodic metasurface light field modulation unit. Figure 6 Coupling efficiencies and deflection angles at each stage of the structure. The first-order diffracted light exits at an angle of 46 degrees, satisfying the diffraction equation: The energy of the first-order diffraction accounts for 68% of the incident light, indicating that the energy of the outgoing light is mainly distributed in the first diffraction order. Figure 7 (b) Corresponding Figure 6 The phase diagram of the Ey electric field component of the outgoing light field of the structure verifies that the outgoing light is mainly first-order diffraction and achieves a 90-degree polarization conversion.

[0059] The above two cases are merely preferred embodiments of the present invention. In reality, the metasurface optical field modulation structure may not be limited to 6 directions, and the number of metasurface microcubes in one period is not limited to 3.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification to the structure, change in proportion or adjustment of size, without affecting the effects and objectives of the present invention, shall still fall within the scope of the technology disclosed in the present invention.

Claims

1. A polarization-conversion metasurface structured light super-resolution microchip, comprising two parallel, light-transparent substrates, characterized in that: The optically transparent substrate is polished on both sides, with one side serving as the light field modulation surface. A metasurface light field modulation structure is distributed on the surface of this surface. This structure couples two collimated free-space beams into the chip and changes their polarization direction, causing the two coupled beams to meet and interfere at the center of the other side of the chip, producing illumination interference fringes with maximum contrast. Except for the metasurface light field modulation structure, the light field modulation surface is also equipped with light-shielding structures. The other side of the optically transparent substrate serves as the sample surface, with a sample placement area in the central region and light-shielding structures in the remaining areas. The aforementioned metasurface optical field modulation structure is a periodic structure, and its period determines the angle of incident light deflection. Each cycle of the metasurface optical field modulation structure is composed of multiple micro-nano structures. Each micro-nano structure is a cuboid, and its length, width and thickness determine the phase delay. The phase delay formed by the micro-nano structures within one cycle uniformly covers 2π. The long sides of the single-period micro / nano structure of the metasurface optical field modulation structure point to the same angle, and its direction determines the symmetry axis of polarization conversion, which is used to mirror the polarization direction of the outgoing light along the symmetry axis and the polarization direction of the incident light. The metasurface optical field modulation structure is composed of two materials with unequal refractive indices alternating laterally.

2. The polarization-conversion metasurface structured light super-resolution microchip according to claim 1, characterized in that: It also includes a dielectric film, which is located between the light field modulation surface and the light-shielding structure of the surface; wherein the surface is the light field modulation surface.

3. The polarization-conversion metasurface structured light super-resolution microchip according to claim 1, characterized in that: The light-shielding structure is an opaque metal film.

4. The polarization-conversion metasurface structured light super-resolution microchip according to claim 1, characterized in that: The optically transparent substrate includes one or more of Si3N4, SiO2, Al2O3, SiC, GaP, TiO2, GaN, and Polymer.

5. An optical system, comprising a light source, a beam adjustment and filtering system, a light field modulation system, a mirror, a sample stage, an imaging system, and a computer, characterized in that: It also includes the chip according to any one of claims 1-4, wherein the chip is mounted on a sample stage, and the parallel light emitted by the light source passes through a beam adjustment and filtering system and a light field modulation system in succession, and is modulated into two parallel beams of light. Then, the two beams of light are reflected by a mirror and perpendicularly enter the light field modulation surface of the chip. After coupling, they meet at the sample on the other side of the chip and illuminate the sample. After that, the image is formed by an imaging system and sent to a computer for processing.

6. The imaging method according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Two coherent beams are generated using an optical field modulation system and respectively strike a pair of metasurface optical field modulation structures. After passing through the pair of metasurface optical field modulation structures, first-order diffraction occurs and the beams are coupled into the substrate. The two first-order diffracted beams interfere on the sample surface of the chip and excite the fluorescent sample. Step 2: Adjust the optical path difference between the two coherent beams using an optical field modulation system, causing the structured light generated after interference to undergo two translations, and then collect the modulated fluorescence distribution maps. Step 3: Switch the two coherent beams to paired metasurface light field modulation structures with different directions and periods, repeat steps 1 and 2, and obtain fluorescence distribution images of the sample under structured light illumination with different directions and periods. Step 4: For all the modulated fluorescence distribution maps obtained in Step 3, the phase and frequency shift are solved using the structured light super-resolution imaging algorithm, and iterative stitching is performed in the frequency domain to obtain the expanded spectrum. Finally, inverse Fourier transform is performed to reconstruct the super-resolution sample image.

Images