A high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface

Abstract

The application provides a high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface, relates to the technical field of laser three-dimensional nanolithography, and comprises a light path modulation module, a multiplexed metasurface, a sample clamping module and an image observation module on the same axis, the light path modulation module is used for modulating excitation light emitted by an excitation light laser into circularly polarized light, modulating loss light emitted by a loss light laser into linearly polarized light, and modulating the deflection directions of the excitation light and the loss light, the multiplexed metasurface is used for focusing the excitation light and the loss light, so that the excitation light and the loss light correspondingly generate tight focusing focal points and three-dimensional hollow light fields at the same focal point, the sample clamping module is used for translating and fixing a sample, so that the sample is located in the irradiation area of the excitation light and the loss light, and three-dimensional micro-nano structure processing is performed on the sample, and the image observation module is used for observing and recording the three-dimensional micro-nano structure processing process of the sample. The application helps to improve the lithography resolution.

Description

Technical Field

[0001] This invention relates to the field of laser three-dimensional nanolithography technology, and in particular to a high-precision laser three-dimensional nanolithography system based on a reusable metasurface. Background Technology

[0002] Laser 3D nanolithography, as an advanced manufacturing method, is widely recognized for its true 3D manufacturing capabilities and high printing resolution exceeding the optical diffraction limit, enabling the high-precision fabrication of metamaterials, sensors, microrobots, and micro / nano optical devices. However, limited by factors such as photoresist properties, excitation wavelength, and the numerical aperture (NA) of the objective lens, the feature size of laser 3D nanolithography is typically confined to the hundreds of nanometers scale, making it difficult to meet the growing demand for nanoscale structure manufacturing.

[0003] Chinese Patent CN114924466A discloses a high-precision maskless laser projection lithography system and method. The method includes designing a light source module to obtain a linearly polarized laser beam; adjusting the phase and amplitude using a spatial light modulator and a 4f system to obtain a collimated and filtered first-order diffracted beam capable of imaging the target; and shaping the beam by controlling the grayscale matrix of the target template within the sample to obtain different spot shapes. A control module modulates the size of the laser beam in pixels; a light fabrication module switches the pixel displacement of the axis according to instructions from the spot correction module; and, combined with Fresnel's law, efficiently self-assembles the required template. A projection lens images the emitted light onto the silicon wafer surface. However, the above scheme results in inconsistent responses of the target template within the sample to different wavelengths, and the combination of multiple components easily generates dispersion and off-axis aberrations, thus affecting the lithography resolution. Therefore, providing a high-precision laser three-dimensional nanolithography system based on a reusable metasurface is essential to improve lithography resolution. Summary of the Invention

[0004] In view of this, the present invention proposes a high-precision laser three-dimensional nanolithography system based on a reusable metasurface.

[0005] This invention provides a high-precision laser three-dimensional nanolithography system based on a reusable metasurface, comprising an optical path modulation module, a reusable metasurface, a sample clamping module, and an image observation module located on the same axis, wherein...

[0006] The optical path modulation module is used to modulate the excitation light emitted by the excitation laser in the optical path modulation module into circularly polarized light, modulate the loss light emitted by the loss laser in the optical path modulation module into linearly polarized light, and modulate the deflection directions of the excitation light and the loss light.

[0007] The reusable metasurface is used to focus the excitation light and the loss light, so that the excitation light and the loss light respectively generate a tightly focused focal point and a three-dimensional hollow light field at the same focal point;

[0008] The sample clamping module is used to translate and fix the sample so that the sample is placed in the irradiation area of ​​the excitation light and the loss light, and to perform three-dimensional micro-nano structure processing on the sample;

[0009] The image observation module is used to observe and record the fabrication process of the three-dimensional micro / nano structure of the sample.

[0010] Based on the above technical solutions, preferably, the optical path modulation module further includes a first polarization modulator, a second polarization modulator, a dichroic mirror, and a beam scanning unit. The transmission surface of the dichroic mirror is located on the pulsed laser output light path of the excitation laser, and the reflection surface of the dichroic mirror is located on the pulsed laser output light path of the loss laser. The first polarization modulator is disposed between the excitation laser and the dichroic mirror, and the second polarization modulator is disposed between the loss laser and the dichroic mirror.

[0011] Based on the above technical solutions, preferably, the reusable metasurface includes multiple first unit structures and multiple second unit structures. The first unit structure performs uniform multi-level modulation on the excitation light in the 0-2π phase range, and the transmittance of the excitation light is above 90%. The second unit structure performs uniform multi-level modulation on the loss light in the 0-2π cross-polarization transmission phase range, and the polarization conversion efficiency of the loss light is above 70%.

[0012] More preferably, the sample clamping module includes a three-dimensional displacement stage and an immersion varnish, a sample substrate, and a photoresist located on the same axis and in close contact. The immersion varnish is coated on the side of the reusable metasurface away from the optical path modulation module. The three-dimensional displacement stage is fixedly connected to the sample substrate and is used to adjust the position of the sample substrate and the photoresist.

[0013] More preferably, the image observation module includes an objective lens, a tube lens, and an image sensor located on the same axis. The objective lens receives the fluorescence signal generated by the photoresist during the photopolymerization process initiated by the excitation light, and the tube lens transmits the fluorescence signal to the image sensor so that the image sensor can perform polymerization imaging.

[0014] More preferably, the three-dimensional hollow light field includes a superimposed annular light field and a bottle-shaped light field. The phase distribution functions corresponding to the annular light field and the bottle-shaped light field, and the focusing phase functions superimposed on the annular light field and the bottle-shaped light field during encoding to focus the three-dimensional hollow light field, are respectively expressed as follows:

[0015]

[0016]

[0017]

[0018] in, φ Dou ( ) represents the spiral phase distribution function of the annular light field. l Indicates the topological load value. α This represents the angular coordinates of the reusable metasurface. φ Bot ( ) represents the phase distribution function corresponding to the bottle-shaped light field. r This represents the radial coordinates of the reusable metasurface. k Represents a constant. D This indicates the diameter of the reusable metasurface. φ Foc ( ) represents the focused phase distribution function. x 0 represents the x-coordinate position of the focal point at the focal plane. y 0 represents the ordinate position of the focal point at the focal plane. f This indicates the focal length of the reusable metasurface. x Indicates the x-coordinate position of the reusable metasurface. y This indicates the ordinate position of the reusable metasurface. λ Indicates the wavelength of the incident light. n Indicates the refractive index of the environment.

[0019] More preferably, the multiplexed metasurface combines the excitation light modulation region and the loss light modulation region using a spatial multiplexing method. The spatial multiplexing method includes any one of checkerboard multiplexing, random matrix multiplexing, strip segmentation multiplexing, sector staggered multiplexing, crescent segmentation multiplexing, multi-aperture metasurface multiplexing, and multilayer metasurface multiplexing.

[0020] More preferably, the first polarization modulator includes a linear polarizer and a quarter-wave plate located on the same axis, and the second polarization modulator is a linear polarizer.

[0021] More preferably, the excitation laser is a laser capable of exciting photopolymerization, and the loss laser is a laser capable of suppressing photopolymerization.

[0022] More preferably, the first unit structure and the second unit structure are both cylindrical, annular, cuboid, regular polygonal prism, elliptical prism, X-shaped cube, C-shaped cube, cross cube, and one or more of the above-mentioned Babiné structures. The materials of the first unit structure and the second unit structure include one or more of silicon nitride, gallium nitride, gallium arsenide, titanium dioxide, monocrystalline silicon, polycrystalline silicon, amorphous silicon, IP-Dip polymer, IP-L polymer, IP-n162 polymer, IP-S polymer, silicon dioxide, zinc oxide, germanium, silicon carbide, tellurium, gallium antimonide, hafnium oxide, niobium dioxide, niobium pentoxide, gold, aluminum, silver, and copper.

[0023] The high-precision laser three-dimensional nanolithography system based on a reusable metasurface provided by this invention has the following advantages over existing technologies:

[0024] (1) By using the first and second polarization modulators in conjunction with the dichroic mirror, the deflection directions of the excitation light and the loss light can be independently controlled. The reusable metasurface focuses two beams of light on the same optical axis, forming a tight focal point and a three-dimensional hollow light field respectively, ensuring the best overlap between the two in space and depth. The loss light generates a suppressive light-gathering effect around the excitation light. Furthermore, the optical path modulation, the reusable metasurface, the sample clamping and imaging observation are coaxially integrated, eliminating the need for large-volume lens groups and multi-level relay imaging systems. This makes the high-precision laser three-dimensional nanolithography system smaller in size and with higher optical path stability. It can also reduce the dependence on precise alignment and dynamic correction, significantly compress the voxel size, and improve the lithography resolution. The beam scanning unit, in conjunction with the sample precision translation platform, realizes a fast and programmable three-dimensional writing path. The real-time image observation module can monitor the nanostructure formation process online, provide timely feedback and optimize the processing parameters. The reusable metasurface can be mass-produced and different wavelengths or functions of micro-nano structures can be customized as needed, greatly simplifying the procurement and maintenance costs of traditional multi-optical-path, high numerical aperture lenses.

[0025] (2) The first unit structure achieves multi-level uniform phase modulation of the excitation light, covering the range of 0 to 2π. With a transmittance of over 90%, the beam shape and focal position can be precisely controlled without significant energy loss. The second unit structure also modulates the light that should be lost in the range of 0 to 2π with multi-level uniform modulation and achieves a polarization conversion efficiency of ≥70%, fully recovering and utilizing the lost light energy and significantly improving the overall efficiency. The two types of unit structures independently control light of different polarizations / wavelengths, which can simultaneously carry multi-band and multi-polarization light field information, greatly enhancing the functional density and information bandwidth of the metasurface. High transmittance and high polarization conversion efficiency reduce the energy loss of the system. The multi-level phase modulation capability provides fine and controllable wavefront modulation for applications such as super-resolution imaging, optical communication, and photolithography. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a high-precision laser three-dimensional nanolithography system provided in an embodiment of the present invention;

[0028] Figure 2 A perspective view of the first unit structure and the second unit structure provided in the embodiments of the present invention;

[0029] Figure 3 A schematic diagram of the transmittance and phase as a function of radius for a unit structure provided in an embodiment of the present invention;

[0030] Figure 4 A schematic diagram illustrating the variation of cross-polarization transmission phase and polarization conversion efficiency with the lengths of the major and minor axes of a unit structure provided in an embodiment of the present invention;

[0031] Figure 5 A schematic diagram illustrating a polarization multiplexing method for a reusable metasurface provided in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram illustrating a spatial reuse method of a reusable metasurface provided in an embodiment of the present invention;

[0033] Figure 7 This is a schematic diagram of the phase distribution and its corresponding random matrix provided in an embodiment of the present invention;

[0034] Figure 8 A partial layout of a reusable metasurface provided in an embodiment of the present invention;

[0035] Figure 9 This is a simulated focusing characteristic diagram of a reusable metasurface provided in an embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures: 1. Excitation laser; 2. First polarization modulator; 3. Loss laser; 4. Second polarization modulator; 5. Dichroic mirror; 6. Beam scanning unit; 7. Multiplexed metasurface; 8. Illuminating oil; 9. Three-dimensional displacement stage; 10. Sample substrate; 11. Photoresist; 12. Objective lens; 13. Tube lens; 14. Image sensor. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0039] refer to Figure 1 This invention provides a high-precision laser three-dimensional nanolithography system based on a reusable metasurface, comprising an optical path modulation module, a reusable metasurface 7, a sample clamping module, and an image observation module located on the same axis, wherein...

[0040] The optical path modulation module includes an excitation laser 1, a first polarization modulator 2, a loss laser 3, a second polarization modulator 4, a dichroic mirror 5, and a beam scanning unit 6. The transmission surface of the dichroic mirror 5 is located on the pulsed laser output path of the excitation laser 1, and the reflection surface of the dichroic mirror 5 is located on the pulsed laser output path of the loss laser 3. The first polarization modulator 2 is disposed between the excitation laser 1 and the dichroic mirror 5, and the second polarization modulator 4 is disposed between the loss laser 3 and the dichroic mirror 5. The optical path modulation module is used to modulate the excitation light emitted by the excitation laser 1 into circularly polarized light, modulate the loss light emitted by the loss laser 3 into linearly polarized light, and modulate the deflection directions of the excitation light and the loss light.

[0041] Furthermore, the first polarization modulator 2 includes a linear polarizer and a quarter-wave plate located on the same axis, and the second polarization modulator 4 is a linear polarizer. The excitation laser 1 is a laser capable of exciting optical aggregation, and the loss laser 3 is a laser capable of suppressing optical aggregation. The excitation laser 1 is used to output a femtosecond laser that can induce a two-photon aggregation effect. The wavelength of the excitation laser 1 is 780 nm, the repetition frequency of the excitation laser 1 is 80 MHz, and the pulse width of the excitation laser 1 is 100 fs. The loss laser 3 is used to output a continuous-wave laser that can suppress the two-photon aggregation effect. The wavelength of the loss laser 3 is 532 nm. The beam scanning unit 6 is a scanning galvanometer.

[0042] In one example, excitation laser 1 outputs laser light that can induce photopolymerization, while loss laser 3 outputs laser light that suppresses photopolymerization. An optical path modulation system modulates the polarization state and deflection direction of the excitation and loss beams. When the optical path modulation module is operational, the first polarization modulator 2 in the excitation beam path modulates the polarization state of the excitation beam into circularly polarized light, and the second polarization modulator 4 in the loss beam path modulates the polarization state of the loss beam into linearly polarized light. A dichroic mirror 5 combines the excitation and loss beams. A beam scanning unit 6 enables high-speed scanning deflection of the excitation and loss beams in the X and Y directions.

[0043] Circularly polarized excitation light uniformly excites the photosensitive material at the focal point, while linearly polarized loss light precisely suppresses polymerization around the focal point, forming a sub-diffraction-limited "solid + hollow" high-contrast focal spot. The beam scanning unit 6 performs high-speed deflection scanning in the X and Y directions, allowing continuous writing along a preset path without point-by-point stops. The scanning speed is synchronized with the alternating control of polymerization / suppression, significantly improving processing throughput and efficiency. A dichroic mirror 5 combines the two beams on the same optical axis without chromatic aberration, ensuring that the excitation and loss fields always coincide without offset. The polarization state, scanning trajectory, and power ratio can be adjusted in real time to achieve the writing of three-dimensional nanostructures of arbitrary shapes and layers.

[0044] The multiplexed metasurface 7 is used to focus the excitation and loss beams, so that the excitation and loss beams generate a tightly focused focal point and a three-dimensional hollow light field respectively at the same focal point. When the multiplexed metasurface 7 is working, the excitation and loss beams are incident on the entrance pupil of the multiplexed metasurface 7, modulated, and tightly focused into the photoresist 11, generating two light fields at the same focal length: one is a three-dimensional hollow light field used to suppress photopolymerization; the other is a tightly focused focal point used to excite photopolymerization. The NA of the multiplexed metasurface 7 is maximized to generate a smaller spot size and achieve high-precision processing. The multiplexed metasurface 7 operates under two different light source conditions, and crosstalk issues caused by potentially different light source wavelengths must be considered; simultaneously, the excitation beam may be an ultrafast laser with a certain spectral bandwidth, therefore the multiplexed metasurface 7 needs to have an achromatic function. The design of the multiplexed metasurface 7 needs to consider off-axis aberrations caused by beam scanning incident conditions, such as coma and field curvature, therefore the multiplexed metasurface 7 needs to have aberration correction capabilities.

[0045] In one example, the NA of the reusable metasurface 7 can be 1.1.

[0046] The reusable metasurface 7 includes multiple first unit structures and multiple second unit structures. The first unit structure performs uniform multi-level modulation of the excitation light in the 0-2π phase range, and the transmittance of the excitation light is above 90%. The second unit structure performs uniform multi-level modulation of the loss light in the 0-2π cross-polarization transmission phase range, and the polarization conversion efficiency of the loss light is above 70%.

[0047] In one example, titanium dioxide is used as the unit structural material and silicon dioxide is used as the substrate material.

[0048] The first and second unit structures are both cylindrical, toroidal, cuboid, regular polygonal prism, elliptical cylinder, X-shaped cube, C-shaped cube, cross cube, and one or more of the above-mentioned Babiné structures. The materials of the first and second unit structures include one or more of silicon nitride, gallium nitride, gallium arsenide, titanium dioxide, monocrystalline silicon, polycrystalline silicon, amorphous silicon, IP-Dip polymer, IP-L polymer, IP-n162 polymer, IP-S polymer, silicon dioxide, zinc oxide, germanium, silicon carbide, tellurium, gallium antimonide, hafnium oxide, niobium dioxide, niobium pentoxide, gold, aluminum, silver, and copper.

[0049] In one example, the reusable metasurface 7 is designed based on both polarization multiplexing and spatial multiplexing principles. It utilizes polarization multiplexing to generate a three-dimensional hollow light field, uses the equal optical path principle to generate a tightly focused focal point, and uses spatial multiplexing to simultaneously encode both the three-dimensional hollow light field and the tightly focused focal point onto a single metasurface. Its design and manufacturing methods include:

[0050] S1. Design of the unit structure and its substrate: The unit structure is based on the principle of pure phase modulation or complex amplitude modulation. Its shape can be one or more of the following: cylinder, toroidal cylinder, cuboid, regular polygonal prism, elliptical cylinder, X-shaped cube, C-shaped cube, cross cube, and Babinet structures of the above shapes. Its material can be one or more of the following: silicon nitride, gallium nitride, gallium arsenide, titanium dioxide, single-crystal silicon, polycrystalline silicon, amorphous silicon, IP-Dip polymer, IP-L polymer, IP-n162 polymer, IP-S polymer, silicon dioxide, zinc oxide, germanium, silicon carbide, tellurium, gallium antimonyide, hafnium oxide, niobium pentoxide, gold, aluminum, silver, and copper. The substrate is made of a laser-transparent material, such as quartz, silicon dioxide, or sapphire.

[0051] S2, design the phase distribution for both excitation and loss light: For the excitation light, calculate the focused phase distribution based on the required focal position, focal length, and optical path principle of the lens. Focal position ( x 0, y 0, f () represents the position of any point in space after the beam passes through the multiplexed metasurface 7. Focal length f denoted as axial distance between the focal point and the reusable metasurface 7.

[0052] The principle of equal optical path length in lenses states that if the coordinates of the focal point at the focal plane are ( x 0, y 0, f Then the focused phase distribution should satisfy:

[0053]

[0054] in, φ Foc ( ) represents the focusing phase distribution function of the closely focused focal point. x 0 represents the x-coordinate position of the focal point at the focal plane. y 0 represents the ordinate position of the focal point at the focal plane. f This indicates the focal length of the reusable metasurface 7. x The x-coordinate position of the reusable metasurface 7 is indicated. y The ordinate position of the reusable metasurface 7 is indicated. λ Indicates the wavelength of the incident light. n Indicates the refractive index of the environment.

[0055] For lossy light, it is necessary to superimpose a ring-shaped light field and a bottle-shaped light field to generate a three-dimensional hollow light field.

[0056] The phase distribution corresponding to the ring-shaped light field is a spiral phase, which must satisfy:

[0057]

[0058] in, φ Dou ( ) represents the spiral phase distribution function of the ring-shaped light field. l Indicates the topological load value. α The angular coordinates represent the reusable metasurface 7. Beams with topological charges are considered to carry orbital angular momentum. ,in, is Planck's constant.

[0059] The phase distribution corresponding to the bottle-shaped light field is a 0-π ring phase, satisfying:

[0060]

[0061] in, φ Bot ( ) represents the phase distribution function corresponding to the bottle-shaped light field. r Indicates the radial coordinates of the reusable metasurface 7. k Represents a constant. k Used to control the area ratio of the 0-phase delay region and the π-phase delay region. D This indicates the diameter of the reusable metasurface 7.

[0062] In one example, k is 0.707, meaning the areas of the 0-phase delay region and the π-phase delay region are equal, and the diameter D of the reusable metasurface 7 is 990 μm.

[0063] To focus the three-dimensional hollow light field, a focusing phase is superimposed on the annular light field and the bottle-shaped light field during encoding. φ Foc ( ). The superposition of the ring-shaped and bottle-shaped light fields is based on the principle of polarization multiplexing. Anisotropic unit structures can usually convert part of the incident circularly polarized light into orthogonal circularly polarized light components. In this process, there are simultaneous transmission phase modulation and geometric phase modulation. The former is related to the geometric dimensions of the unit structure and has polarization insensitivity; while the latter is related to the orientation angle of the unit structure and has polarization correlation. Based on this, the two phase distributions (spiral phase and 0-π ring phase) can be independently controlled. When the incident light is linearly polarized, it can be regarded as a linear superposition of left-handed and right-handed circularly polarized light, thus simultaneously generating a ring-shaped and bottle-shaped light field in the target region. The two superimpose in space to form a three-dimensional hollow light field.

[0064] S3. Combining the electromagnetic response characteristics of the unit structure in step S1 and the phase distribution in S2, the multiplexed metasurface 7 uses a spatial multiplexing method to combine the excitation light modulation region and the loss light modulation region. The spatial multiplexing method includes any one of checkerboard multiplexing, random matrix multiplexing, strip segmentation multiplexing, sector staggered multiplexing, crescent segmentation multiplexing, multi-aperture metasurface multiplexing, and multilayer metasurface multiplexing.

[0065] Similarly, chromatic aberration can be achieved using methods such as dispersion engineering, multilayer metasurface stacking, and spatial reuse. Off-axis aberrations can also be eliminated by using monolithic metasurface designs with hyperbolic or quadratic phase distributions, monolithic metasurface designs with aperture stops, and multilayer metasurface stacking.

[0066] S4. Combine the model file from step S3 and process it using micro-nano manufacturing technology.

[0067] The sample clamping module is used to translate and fix the sample so that it is placed in the irradiation area of ​​the excitation light and the depletion light, and to perform three-dimensional micro / nano structure fabrication on the sample. The sample clamping module includes a three-dimensional displacement stage 9 and an immersion varnish 8, a sample substrate 10, and a photoresist 11 located on the same axis and in close contact. The immersion varnish 8 is coated on the side of the reusable metasurface 7 away from the optical path modulation module. The three-dimensional displacement stage 9 is fixedly connected to the sample substrate 10 and is used to adjust the position of the sample substrate 10 and the photoresist 11.

[0068] In one example, immersion varnish 8 is uniformly coated on the back of a reusable metasurface 7 substrate. A sample substrate 10 is placed above the immersion varnish 8, and photoresist 11 is placed above the sample substrate 10. A three-dimensional displacement stage 9 controls the movement of the sample substrate 10 and the photoresist 11, enabling the fabrication of arbitrary three-dimensional micro / nano structures. Furthermore, the sample clamping system needs to consider the refractive index matching of the multilayer dielectric environment. The refractive indices of the immersion varnish 8, sample substrate 10, and photoresist 11 should be kept as consistent as possible to improve processing accuracy. The photoresist 11 initiates a photopolymerization process under excitation light irradiation, while suppressing the photopolymerization process under depletion light irradiation.

[0069] In this embodiment, by using the first and second polarization modulators 4 in conjunction with the dichroic mirror 5, independent control of the deflection directions of the excitation and loss beams is achieved. The reusable metasurface 7 simultaneously focuses two beams on the same optical axis, forming a tightly focused focal point and a three-dimensional hollow light field, respectively, ensuring optimal overlap between the two in space and depth. The loss beam generates a suppression of light-gathering effect around the excitation beam. Furthermore, the optical path modulation, reusable metasurface, sample clamping, and imaging observation are coaxially integrated, eliminating the need for large-volume lens groups and multi-level relay imaging systems. This results in a smaller size and higher optical path stability for the high-precision laser three-dimensional nanolithography system. It also reduces the dependence on precise alignment and dynamic correction, significantly compressing voxel size to improve lithography resolution. The beam scanning unit 6, in conjunction with the sample precision translation platform, enables a fast and programmable three-dimensional writing path. The real-time image observation module can monitor the nanostructure formation process online, providing timely feedback and optimizing processing parameters. The reusable metasurface 7 can be mass-produced and customized with different wavelengths or functions as needed, greatly simplifying the procurement and maintenance costs of traditional multi-optical-path, high numerical aperture lenses.

[0070] Furthermore, the immersion oil 8 can be Cargille Type HF, the sample substrate 10 can be Schott D263, and the photoresist 11 can initiate the photopolymerization process under excitation light irradiation and suppress the photopolymerization process under depletion light irradiation. The photoresist 11 can be Yuzhiquan MPP-1.52S.

[0071] The image observation module is used to observe and record the fabrication process of the three-dimensional micro / nano structure of the sample. The image observation module includes an objective lens 12, a tube lens 13, and an image sensor 14, all located on the same axis. The objective lens 12 receives the fluorescence signal generated during the photopolymerization process initiated by the photoresist 11 under excitation light. The tube lens 13 transmits the fluorescence signal to the image sensor 14, enabling the image sensor 14 to create an image. The objective lens 12 is a 10x objective lens, and the image sensor 14 is a CCD image sensor.

[0072] Please see Figure 2 , Figure 2 Two unit cell structures constituting the reusable metasurface 7 are shown. Figure 2 In (a) of the image, the cylinder is used to modulate the excitation light. Figure 2 In (b), the elliptical cylinder is used as the modulation loss light. The height H of both unit structures is the same, and both are 700 nm. The period P1 of the cylindrical unit structure is 450 nm, and the period P2 of the elliptical cylinder unit structure is 300 nm.

[0073] Please see Figure 3 , Figure 3 This is a schematic diagram of the transmittance and phase as a function of radius for a unit structure that modulates excitation light, wherein the unit structure is a titanium dioxide cylinder and the substrate is silicon dioxide. Figure 3 The unit cell structure can uniformly cover the 0-2π phase range, as shown by the six solid triangles marked in the figure. Notably, the transmittance of this sixth-order unit cell structure is greater than 90%, as shown by the six solid squares marked in the figure, which ensures the high efficiency of the reusable metasurface 7.

[0074] Please see Figure 4 , Figure 4 This is a schematic diagram showing the cross-polarization transmission phase and polarization conversion efficiency of a unit structure for modulating lossy light as a function of the lengths of the major and minor axes. The unit structure is a titanium dioxide elliptical cylinder, and the substrate is silicon dioxide. Figure 4 The unit cell structure can uniformly cover the 0-2π cross-polarization transmission phase range, such as Figure 4 As shown in the six solid circles marked in (a) above. It is worth noting that the polarization conversion efficiency of this sixth-order unit cell structure is greater than 70%, as... Figure 4As shown in (b) of the diagram, the six solid circles indicate that this ensures the high efficiency of the reusable metasurface 7.

[0075] like Figure 5 As shown, Figure 5 A polarization multiplexing method for multiplexed metasurface 7. The elliptical cylinder that modulates the lossy light also exhibits transmission phase modulation. and geometric phase modulation The former is related to the geometric dimensions of the unit structure and exhibits polarization insensitivity; while the latter is related to the orientation angle of the unit structure and exhibits polarization dependence. When the incident light is left-handed circularly polarized light, the phase modulation of the elliptical cylinder is: Used to encode the 0-π annular phase corresponding to the bottle-shaped light field; when the incident light is right-handed circularly polarized light, the phase modulation amount of the elliptical cylinder is This is used to encode the spiral phase corresponding to the annular optical field. Furthermore, the loss modulation region of the multiplexed metasurface 7 needs to generate the transmission phase quantity. Geometric phase quantity Therefore, by combining the transmission phase and the geometric phase, two independent phase distributions can be encoded. When the incident light is linearly polarized, it can be regarded as a linear superposition of left-handed and right-handed circularly polarized light, thereby simultaneously generating a ring-shaped light field and a bottle-shaped light field in the target region. The two superimpose in space to form a three-dimensional hollow light field.

[0076] like Figure 6 As shown, Figure 6 This describes a spatial multiplexing method for the reusable metasurface 7. A random matrix multiplexing method is used to achieve spatial multiplexing of the excitation modulation region and the loss modulation region. Given that the period P1 of the excitation unit structure is 450 nm and the period P2 of the loss unit structure is 300 nm, a square with a period of 900 nm is considered as a large pixel. Each large pixel contains either 2×2 excitation unit structures or 3×3 loss unit structures. Using the large pixel as the basic unit, a binary matrix A is randomly generated, where the probability of "0" appearing is 50% and the probability of "1" appearing is 50%. Multiplying matrix A by the excitation coding distribution yields the Hadamard product A1; subtracting matrix A from an all-one matrix yields matrix B, which is then multiplied by the loss coding distribution to obtain the Hadamard product B1. The linear superposition of these two Hadamard products yields the arrangement of the reusable metasurface 7.

[0077] like Figure 7 As shown, Figure 7This represents the phase distribution and its corresponding random matrix. Since the spiral phase corresponding to the annular light field and the 0-π annular phase corresponding to the bottle-shaped light field cannot be directly focused at the target position, they need to be multiplied by the focusing phase to obtain the phase distribution of the focused annular beam and the phase distribution of the focused bottle-shaped beam, respectively. Multiplying these two by the loss light random matrix yields the Hadamard product, which is then used... Figure 5 The loss modulation region of the multiplexed metasurface 7 is obtained by superimposing the polarization multiplexing method. At the same time, the excitation modulation region of the multiplexed metasurface 7 is obtained by multiplying the focusing phase with the excitation light random matrix.

[0078] like Figure 8 As shown, Figure 8 This is a partial layout of the reusable metasurface 7. The unit structure is combined with the excitation light modulation region and the loss light modulation region respectively, and cylindrical or elliptical cylinders with appropriate geometric dimensions and orientation angles are filled in according to the required phase to generate the layout of the reusable metasurface 7.

[0079] like Figure 9 As shown, Figure 9 The simulated focusing characteristics of the reusable metasurface 7 are shown in the figure. Figure 9 In the diagram, (a) represents the lossy light field. Figure 9 (b) in the figure represents the excitation light field. Due to limitations in computing resources, a small-aperture reusable metasurface 7 with the same NA was simulated using the electromagnetic simulation software Lumerical FDTD. The metasurface has a radius of 22.5 μm and a focal length of 21.11 μm. A back-immersion focusing method was used to improve the NA, and its value reached 1.1. Figure 9 It demonstrates that a three-dimensional hollow light field and an ellipsoidal focal point can be generated simultaneously at the same focal length, proving the design effectiveness and superiority of the reusable metasurface 7.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision laser three-dimensional nanolithography system based on a reusable metasurface, characterized in that, This includes an optical path modulation module, a multiplexed metasurface (7), a sample clamping module, and an image observation module, all located on the same axis. The optical path modulation module is used to modulate the excitation light emitted by the excitation laser (1) in the optical path modulation module into circularly polarized light, modulate the loss light emitted by the loss laser (3) in the optical path modulation module into linearly polarized light, and modulate the deflection directions of the excitation light and the loss light. The reusable metasurface (7) is used to focus the excitation light and the loss light so that the excitation light and the loss light generate a tightly focused focal point and a three-dimensional hollow light field respectively at the same focal point; The three-dimensional hollow light field includes a superimposed annular light field and a bottle-shaped light field. The phase distribution functions corresponding to the annular light field and the bottle-shaped light field, and the focusing phase functions superimposed on the annular light field and the bottle-shaped light field during encoding to focus the three-dimensional hollow light field, are respectively expressed as: ； ； ； in, φ Dou ( ) represents the spiral phase distribution function of the annular light field. l Indicates the topological load value. α This represents the angular coordinates of the reusable metasurface (7). φ Bot ( ) represents the phase distribution function corresponding to the bottle-shaped light field, and r represents the radial coordinate of the reusable metasurface (7). k Represents a constant. D This indicates the diameter of the reusable metasurface (7). φ Foc ( ) represents the focused phase distribution function. x 0 represents the x-coordinate position of the focal point at the focal plane. y 0 represents the ordinate position of the focal point at the focal plane. f Indicates the focal length of the reusable metasurface (7). x The x-coordinate position of the reusable metasurface (7) is indicated. y The ordinate position of the reusable metasurface (7) is indicated. λ Indicates the wavelength of the incident light. n Indicates the refractive index of the environment; The sample clamping module is used to translate and fix the sample so that the sample is placed in the irradiation area of ​​the excitation light and the loss light, and to perform three-dimensional micro-nano structure processing on the sample; The image observation module is used to observe and record the fabrication process of the three-dimensional micro / nano structure of the sample.

2. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 1, characterized in that, The optical path modulation module further includes a first polarization modulator (2), a second polarization modulator (4), a dichroic mirror (5), and a beam scanning unit (6). The transmission surface of the dichroic mirror (5) is located on the pulsed laser output path of the excitation laser (1), and the reflection surface of the dichroic mirror (5) is located on the pulsed laser output path of the loss laser (3). The first polarization modulator (2) is disposed between the excitation laser (1) and the dichroic mirror (5), and the second polarization modulator (4) is disposed between the loss laser (3) and the dichroic mirror (5).

3. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 1, characterized in that, The reusable metasurface (7) includes multiple first unit structures and multiple second unit structures. The first unit structure performs uniform multi-level modulation on the excitation light in the 0-2π phase range, and the transmittance of the excitation light is above 90%. The second unit structure performs uniform multi-level modulation on the loss light in the 0-2π cross-polarization transmission phase range, and the polarization conversion efficiency of the loss light is above 70%.

4. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 1, characterized in that, The sample clamping module includes a three-dimensional displacement stage (9) and an immersion varnish (8), a sample substrate (10), and a photoresist (11) located on the same axis and in close contact. The immersion varnish (8) is coated on the side of the reusable metasurface (7) away from the optical path modulation module. The three-dimensional displacement stage (9) is fixedly connected to the sample substrate (10). The three-dimensional displacement stage (9) is used to adjust the position of the sample substrate (10) and the photoresist (11).

5. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 4, characterized in that, The image observation module includes an objective lens (12), a tube lens (13), and an image sensor (14) located on the same axis. The objective lens (12) receives the fluorescence signal generated by the photoresist (11) during the photopolymerization process triggered by the excitation light. The tube lens (13) transmits the fluorescence signal to the image sensor (14) so ​​that the image sensor (14) can perform polymerization imaging.

6. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 3, characterized in that, The multiplexed metasurface (7) uses a spatial multiplexing method to combine the excitation light modulation region and the loss light modulation region. The spatial multiplexing method includes any one of checkerboard multiplexing, random matrix multiplexing, strip segmentation multiplexing, sector staggered multiplexing, crescent segmentation multiplexing, multi-aperture metasurface multiplexing, and multilayer metasurface multiplexing.

7. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 2, characterized in that, The first polarization modulator (2) includes a linear polarizer and a quarter-wave plate located on the same axis, and the second polarization modulator (4) is a linear polarizer.

8. The high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 1, characterized in that, The excitation laser (1) is a laser capable of exciting photopolymerization, and the loss laser (3) is a laser capable of suppressing photopolymerization.

9. A high-precision laser three-dimensional nanolithography system based on a reusable metasurface as described in claim 3, characterized in that, Both the first and second unit structures are cylindrical, annular, cuboid, regular polygonal prism, elliptical cylinder, X-shaped cube, C-shaped cube, cross cube, and one or more of the above-mentioned Babiné structures. The materials of the first and second unit structures include one or more of silicon nitride, gallium nitride, gallium arsenide, titanium dioxide, monocrystalline silicon, polycrystalline silicon, amorphous silicon, IP-Dip polymer, IP-L polymer, IP-n162 polymer, IP-S polymer, silicon dioxide, zinc oxide, germanium, silicon carbide, tellurium, gallium antimonide, hafnium oxide, niobium dioxide, niobium pentoxide, gold, aluminum, silver, and copper.

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