High-precision laser three-dimensional nanometer photoetching system based on multiplexing type metasurface

Abstract

The invention provides a high-precision laser three-dimensional nanometer photoetching system based on a multiplexing type metasurface, which relates to the technical field of laser three-dimensional nanometer photoetching and comprises a light path modulation module, the multiplexing type metasurface, a sample clamping module and an image observation module which are positioned on the same axis, the light path modulation module is used for modulating exciting light emitted by the exciting light laser into circularly polarized light, modulating loss light emitted by the loss light laser into linearly polarized light and modulating deflection directions of the exciting light and the loss light; the multiplexing metasurface is used for focusing the exciting light and the loss light, so that the exciting light and the loss light respectively and correspondingly generate a tight focusing focus and a three-dimensional hollow light field at the same focus; the sample clamping module is used for translating and fixing a sample, so that the sample is positioned in an irradiation area of exciting light and 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 processing process of the three-dimensional micro-nano structure of the sample. According to the invention, the photoetching resolution can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser three-dimensional nanolithography, and in particular to a high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface. Background Art

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

[0003] Chinese patent publication number CN114924466A discloses a high-precision maskless laser projection lithography system and method. The method includes designing a light source module to generate a linearly polarized laser beam, adjusting the phase and amplitude using a spatial light modulator and a 4f system to produce a collimated and filtered beam of first-order diffracted light. This beam can image the target, and the grayscale matrix of the target template within the sample is regulated to shape the beam to produce different spot shapes. A control module is used to modulate the size of the writing laser in units of pixels. An optical fabrication module switches the pixel displacement of the axis according to the instructions of the spot correction module. Incorporating Fresnel's law, the required template is efficiently self-assembled, and the projection objective images the output light onto the silicon wafer surface. However, the above scheme controls the target template within the sample to respond differently to different wavelengths, and the combination of multiple components is prone to dispersion and off-axis aberrations, which in turn affect the lithography resolution. Therefore, it is highly necessary to provide a high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface to help 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 multiplexed metasurface.

[0005] The present invention provides a high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface, comprising an optical path modulation module, a multiplexed metasurface, a sample clamping module, and an image observation module located on the same axis, wherein: The optical path modulation module is used to modulate the excitation light emitted by the excitation light laser in the optical path modulation module into circularly polarized light, modulate the loss light emitted by the loss light laser in the optical path modulation module into linearly polarized light, and modulate the deflection directions of the excitation light and the loss light; The multiplexed metasurface is used to focus the excitation light and the loss light so that the excitation light and the loss light respectively generate a tight focus and a three-dimensional hollow light field at the same focus; The sample holding module is used to translate and fix the sample so that the sample is 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 three-dimensional micro-nano structure processing process of the sample.

[0006] On the basis of the above technical solution, 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 pulse laser output optical path of the excitation light laser, the reflection surface of the dichroic mirror is located on the pulse laser output optical path of the loss light laser, the first polarization modulator is arranged between the excitation light laser and the dichroic mirror, and the second polarization modulator is arranged between the loss light laser and the dichroic mirror.

[0007] Based on the above technical solutions, preferably, the multiplexed metasurface includes multiple first unit structures and multiple second unit structures, the first unit structures perform uniform multi-order modulation on the excitation light within the phase range of 0-2π, and the transmittance of the excitation light is above 90%, and the second unit structures perform uniform multi-order modulation on the loss light within the cross-polarization transmission phase range of 0-2π, and the polarization conversion efficiency of the loss light is above 70%.

[0008] More preferably, the sample holding module includes a three-dimensional translation stage and immersion oil, a sample substrate, and a photoresist located on the same axis and tightly fitted together. The immersion oil is coated on a side of the multiplexed metasurface facing away from the optical path modulation module. The three-dimensional translation stage is fixedly connected to the sample substrate and is used to adjust the positions of the sample substrate and the photoresist.

[0009] Further 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 fluorescent signal generated by the photoresist during the photopolymerization process initiated by the excitation light, and the tube lens transmits the fluorescent signal to the image sensor to enable the image sensor to form a polymerized image.

[0010] More preferably, the three-dimensional hollow light field includes an annular light field and a bottle-shaped light field superimposed on each other, and the phase distribution functions corresponding to the annular light field and the bottle-shaped light field, and in order to focus the three-dimensional hollow light field, the focusing phase functions superimposed on the annular light field and the bottle-shaped light field during encoding are respectively expressed as

[0011]

[0012]

[0013] in, φ Dou ( ) represents the spiral phase distribution function of the annular light field, l represents the topological charge value, α represents the angular coordinates of the multiplexed metasurface, φ Bot ( ) represents the phase distribution function corresponding to the bottle-shaped light field, r represents the radial coordinate of the multiplexed metasurface, k represents a constant, D represents the diameter of the multiplexed metasurface, φ Foc ( ) represents the focusing phase distribution function, x 0 represents the horizontal coordinate position of the focus at the focal plane, y 0 represents the vertical coordinate position of the focus at the focal plane, f represents the focal length of the multiplexed metasurface, x represents the horizontal coordinate position of the multiplexed metasurface, y represents the ordinate position of the multiplexed metasurface, λ represents the wavelength of incident light, n Represents the ambient refractive index.

[0014] More preferably, the multiplexed metasurface adopts a spatial multiplexing method to combine the excitation light modulation area and the loss light modulation area, and the spatial multiplexing method includes any one of checkerboard multiplexing, random matrix multiplexing, strip segmentation multiplexing, sector interleaving multiplexing, crescent segmentation multiplexing, multi-aperture metasurface multiplexing and multi-layer metasurface multiplexing.

[0015] 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.

[0016] More preferably, the excitation light laser is a laser that can excite photopolymerization, and the loss light laser is a laser that can inhibit photopolymerization.

[0017] Further preferably, the shapes of the first unit structure and the second unit structure are one or more of a cylinder, a ring column, a cuboid, a regular polygonal prism, an elliptical cylinder, an X-cube, a C-cube, a cross cube and a Babinet structure of the above shapes, and the materials of the first unit structure and the second unit structure include 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 antimonide, hafnium oxide, chromium dioxide, niobium pentoxide, gold, aluminum, silver and copper. One or more.

[0018] The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface provided by the present invention has the following advantages over the prior art: (1) The first and second polarization modulators are combined with dichroic mirrors to achieve independent control of the deflection direction of the excitation light and the loss light. The multiplexed metasurface focuses two beams of light on the same optical axis at the same time, forming a tight focus and a three-dimensional hollow light field respectively, ensuring the best overlap between the two in space and depth. The loss light produces an inhibitory photopolymerization effect around the excitation light. In addition, the optical path modulation, multiplexed metasurface, sample clamping and imaging observation are coaxially integrated, eliminating the need for large-volume lens groups and multi-stage relay imaging systems, making the high-precision laser three-dimensional nanolithography system smaller in size and more stable in the optical path. 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 is combined with the sample precision translation platform to achieve 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 multiplexed metasurface can be prepared in batches, and micro-nanostructures with different wavelengths or functions can be customized as needed, greatly simplifying the procurement and maintenance costs of traditional multi-optical paths and high numerical aperture lenses.

[0019] (2) The first unit structure realizes multi-order uniform phase modulation of the excitation light, covering the range of 0 to 2π. With a transmittance of more than 90%, the beam shape and focal position can be precisely controlled without significant energy loss. The second unit structure uniformly modulates the light that should have been lost in the range of 0 to 2π in multiple orders, and achieves a polarization conversion efficiency of ≥70%, fully recycling and utilizing the lost light energy, and significantly improving the overall efficiency. The two types of unit structures independently regulate light of different polarizations / wavelengths, and 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 jointly reduce the energy loss of the system. The multi-order phase modulation capability provides finely controllable wavefront modulation for applications such as super-resolution imaging, optical communication, and lithography. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A schematic structural diagram of a high-precision laser three-dimensional nanolithography system provided by an embodiment of the present invention; Figure 2 A perspective view of a first unit structure and a second unit structure provided by an embodiment of the present invention; Figure 3 A schematic diagram of a function curve showing how the transmittance and phase of a unit structure vary with radius provided by an embodiment of the present invention; Figure 4 A schematic diagram showing how the cross-polarization transmission phase and polarization conversion efficiency of a unit structure vary with the lengths of the major axis and minor axis, provided in an embodiment of the present invention; Figure 5 A schematic diagram of a polarization multiplexing method of a multiplexed metasurface provided in an embodiment of the present invention; Figure 6 A schematic diagram of a spatial multiplexing method of a multiplexed metasurface provided in an embodiment of the present invention; Figure 7 A schematic diagram of the phase distribution and its corresponding random matrix provided in an embodiment of the present invention; Figure 8 A local layout of a multiplexed metasurface provided in an embodiment of the present invention; Figure 9 A simulated focusing characteristic diagram of a multiplexed metasurface provided in an embodiment of the present invention.

[0022] Explanation of the accompanying symbols: 1. Excitation light laser; 2. First polarization modulator; 3. Loss light laser; 4. Second polarization modulator; 5. Dichroic mirror; 6. Beam scanning unit; 7. Multiplexed metasurface; 8. Mirror oil; 9. Three-dimensional translation stage; 10. Sample substrate; 11. Photoresist; 12. Objective lens; 13. Tubular lens; 14. Image sensor. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "a" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0025] refer to Figure 1 The present invention provides a high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface, comprising an optical path modulation module, a multiplexed metasurface 7, a sample clamping module, and an image observation module located on the same axis, wherein: The optical path modulation module includes an excitation light laser 1, a first polarization modulator 2, a loss light 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 pulse laser output light path of the excitation light laser 1, and the reflection surface of the dichroic mirror 5 is located on the pulse laser output light path of the loss light laser 3. The first polarization modulator 2 is arranged between the excitation light laser 1 and the dichroic mirror 5, and the second polarization modulator 4 is arranged between the loss light laser 3 and the dichroic mirror 5. The optical path modulation module is used to modulate the excitation light emitted by the excitation light laser 1 into circularly polarized light, modulate the loss light emitted by the loss light laser 3 into linearly polarized light, and modulate the deflection directions of the excitation light and the loss light.

[0026] 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 light laser 1 is a laser that can excite photopolymerization, and the loss light laser 3 is a laser that can suppress photopolymerization. The excitation light laser 1 is used to output a femtosecond laser that can induce a two-photon polymerization effect. The wavelength of the excitation light laser 1 is 780 nm, the repetition frequency of the excitation light laser 1 is 80 MHz, and the pulse width of the excitation light laser 1 is 100 fs. The loss light laser 3 is used to output a continuous wave laser that can suppress the two-photon polymerization effect. The wavelength of the loss light laser 3 is 532 nm. The beam scanning unit 6 is a scanning galvanometer.

[0027] In one example, the excitation light laser 1 is used to output a laser that can induce a photopolymerization effect, and the loss light laser 3 is used to output a laser that can inhibit the photopolymerization effect. The optical path modulation system is used to modulate the polarization state and deflection direction of the excitation light and the loss light. When the optical path modulation module is working, the first polarization modulator 2 in the excitation light path modulates the polarization state of the excitation light into circularly polarized light, and the second polarization modulator 4 in the loss light path modulates the polarization state of the loss light into linearly polarized light. The dichroic mirror 5 combines the excitation light and the loss light. The beam scanning unit 6 enables high-speed scanning and deflection of the excitation light and the loss light in the X and Y directions.

[0028] Circularly polarized excitation light uniformly excites the photosensitive material at the focal point, while linearly polarized depletion 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, enabling continuous writing along a preset path without stopping at each point. Scanning speed is synchronized with alternating polymerization / inhibition control, 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 depletion fields always coincide and are not offset. The polarization state, scanning trajectory, and power ratio can be adjusted in real time to enable the writing of three-dimensional nanostructures of arbitrary shapes and levels.

[0029] The multiplexed metasurface 7 is used to focus the excitation light and the loss light so that the excitation light and the loss light generate a tight focus and a three-dimensional hollow light field at the same focal point. When the multiplexed metasurface 7 is in operation, the excitation light and the loss light are incident on the entrance pupil of the multiplexed metasurface 7. After modulation, they are tightly focused inside the photoresist 11, generating two light fields at the same focal length: one is a three-dimensional hollow light field, which is used to suppress photopolymerization; the other is a tight focus, which is used to stimulate photopolymerization. The NA of the multiplexed metasurface 7 is as large as possible to produce a smaller spot and achieve high-precision processing. When the multiplexed metasurface 7 operates under two different light source conditions, the crosstalk problem caused by the different wavelengths of the light sources must be considered. At the same time, the excitation light may be an ultrafast laser with a certain spectral bandwidth, so the multiplexed metasurface 7 needs to have an achromatic aberration function. The design of the multiplexed metasurface 7 needs to take into account the off-axis aberrations caused by the scanning incident light beam, such as coma and field curvature. Therefore, the multiplexed metasurface 7 needs to have an aberration correction function.

[0030] In one example, the NA of the multiplexed metasurface 7 may be 1.1.

[0031] The multiplexed metasurface 7 includes multiple first unit structures and multiple second unit structures. The first unit structure performs uniform multi-order modulation on the excitation light in the phase range of 0-2π, and the transmittance of the excitation light is above 90%. The second unit structure performs uniform multi-order modulation on the loss light in the cross-polarization transmission phase range of 0-2π, and the polarization conversion efficiency of the loss light is above 70%.

[0032] In one example, titanium dioxide is used as the unit structure material, and silicon dioxide is used as the base material.

[0033] The shapes of the first unit structure and the second unit structure are both one or more of a cylinder, a ring column, a cuboid, a regular polygonal prism, an elliptical cylinder, an X-cube, a C-cube, a cross cube and a Babinet structure of the above shapes. 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, 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 antimonide, hafnium oxide, chromium dioxide, niobium pentoxide, gold, aluminum, silver and copper.

[0034] In one example, a multiplexed metasurface 7 is designed based on both polarization multiplexing and spatial multiplexing principles. Polarization multiplexing is used to generate a three-dimensional hollow light field, and the equal optical path principle is used to generate a tight focus. Spatial multiplexing is used to simultaneously encode both the three-dimensional hollow light field and the tight focus on a single metasurface. The design and manufacturing methods include: S1. Design the unit structure and its substrate: The unit structure is based on the principles of pure phase modulation or complex amplitude modulation. Its shape can be one or more of a cylinder, an annular cylinder, a rectangular parallelepiped, a regular polygonal prism, an elliptical cylinder, an X-cube, a C-cube, a cross cube, or a Babinet structure of the above shapes. Its material can be one or more of 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 antimonide, hafnium oxide, halogenated oxide, niobium pentoxide, gold, aluminum, silver, and copper. The substrate is made of a laser-transparent material such as quartz, silicon dioxide, or sapphire.

[0035] S2, design the phase distribution for the excitation light and loss light respectively: for the excitation light, calculate the focusing phase distribution according to the required focal position, focal length and lens optical path principle. x 0, y 0, f ) is the position of any point in space after the light beam passes through the multiplexed metasurface 7. Focal length f is the axial distance between the focus and the multiplexed metasurface 7.

[0036] The lens equal optical path principle means that if the coordinate position of the focus on the focal plane is ( x 0, y 0, f ), the focusing phase distribution should satisfy:

[0037] in, φ Foc ( ) represents the focus phase distribution function of the tight focus, x 0 represents the horizontal coordinate position of the focus at the focal plane, y 0 represents the vertical coordinate position of the focus at the focal plane, f represents the focal length of the multiplexed metasurface 7, x represents the horizontal coordinate position of the multiplexed metasurface 7, y represents the ordinate position of the multiplexed metasurface 7, λ represents the wavelength of incident light, n Represents the ambient refractive index.

[0038] For loss light, it is necessary to superimpose the annular light field and the bottle-shaped light field to generate a three-dimensional hollow light field.

[0039] The phase distribution corresponding to the annular light field is a spiral phase, which must satisfy:

[0040] in, φ Dou ( ) represents the spiral phase distribution function of the annular light field, l represents the topological charge value, α represents the angular coordinates of the multiplexed metasurface 7. The light beam with topological charge is considered to carry orbital angular momentum ,in, is Planck's constant.

[0041] The phase distribution corresponding to the bottle-shaped light field is a 0-π annular phase, satisfying:

[0042] in, φ Bot ( ) represents the phase distribution function corresponding to the bottle-shaped light field, r represents the radial coordinate of the multiplexed 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 represents the diameter of the multiplexed metasurface 7.

[0043] In one example, k is 0.707, that is, the areas of the 0 phase delay region and the π phase delay region are equal, and the diameter D of the multiplexed metasurface 7 is 990 μm.

[0044] In order to focus the three-dimensional hollow light field, the focusing phase is superimposed on the annular light field and the bottle-shaped light field during encoding. φFoc ( ). The superposition of annular light fields 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, transmission phase modulation and geometric phase modulation exist simultaneously. The former is related to the geometric dimensions of the unit structure and has polarization-insensitive characteristics; while the latter is related to the orientation angle of the unit structure and has polarization-dependent characteristics. Based on this, the two phase distributions (spiral phase and 0-π annular phase) can be independently controlled. When the incident light is in a linear polarization state, it can be regarded as a linear superposition of left-handed circularly polarized light and right-handed circularly polarized light, thereby generating annular light fields and bottle-shaped light fields simultaneously in the target area. The two are superimposed in space to form a three-dimensional hollow light field.

[0045] S3, combining the electromagnetic response characteristics of the unit structure of step S1 and the phase distribution of S2, the multiplexed metasurface 7 adopts a spatial multiplexing method to combine the excitation light modulation area and the loss light modulation area. The spatial multiplexing method includes any one of checkerboard multiplexing, random matrix multiplexing, strip segmentation multiplexing, sector interleaving multiplexing, crescent segmentation multiplexing, multi-aperture metasurface multiplexing and multi-layer metasurface multiplexing.

[0046] Similarly, achromatic aberration can be achieved by using methods such as dispersion engineering, multi-layer metasurface superposition, and spatial multiplexing. Off-axis aberrations can also be eliminated by using methods such as monolithic metasurface designs with hyperbolic or quadratic phase distributions, monolithic metasurface designs with aperture stops, and multi-layer metasurface superposition.

[0047] S4, combining the model file of step S3 and processing using micro-nano manufacturing technology.

[0048] The sample holding module is used to translate and secure the sample, ensuring it is within the irradiation area of ​​the excitation and loss light, and to perform three-dimensional micro-nanostructuring on the sample. The sample holding module includes a three-dimensional translation stage 9, along with coaxially aligned and tightly fitted immersion oil 8, a sample substrate 10, and a photoresist 11. The immersion oil 8 is applied to the side of the multiplexed metasurface 7 facing away from the optical path modulation module. The three-dimensional translation 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.

[0049] In one example, immersion oil 8 is evenly coated on the back of the multiplexed metasurface 7 substrate. A sample substrate 10 is placed above the immersion oil 8, and a photoresist 11 is placed above the sample substrate 10. A three-dimensional translation stage 9 controls the movement of the sample substrate 10 and the photoresist 11 to achieve the processing of any three-dimensional micro-nanostructure. Furthermore, the sample clamping system needs to consider the refractive index matching of the multi-layer dielectric environment. The refractive indices of the immersion oil 8, sample substrate 10, and photoresist 11 should be kept as consistent as possible to improve processing accuracy. The photoresist 11 initiates the photopolymerization process under the irradiation of excitation light and can also inhibit the photopolymerization process under the irradiation of loss light.

[0050] In this embodiment, the first and second polarization modulators 4 are combined with the dichroic mirror 5 to achieve independent control of the deflection directions of the excitation light and the loss light. The multiplexed metasurface 7 simultaneously focuses two beams of light on the same optical axis, forming a tight focus and a three-dimensional hollow light field, respectively, to ensure optimal overlap between the two in space and depth. The loss light produces an inhibitory photopolymerization effect around the excitation light. In addition, the optical path modulation, multiplexing metasurface, sample clamping and imaging observation are coaxially integrated, eliminating the need for a large lens group and a multi-stage relay imaging system. This makes the high-precision laser three-dimensional nanolithography system smaller in size and has 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 6 is combined with the sample precision translation stage to achieve 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 multiplexed metasurface 7 can be mass-produced and customized micro-nanostructures with different wavelengths or functions as needed, greatly simplifying the procurement and maintenance costs of traditional multi-optical paths and high numerical aperture lenses.

[0051] Furthermore, the immersion oil 8 may be Cargille Type HF, the sample substrate 10 may be Schott D263, the photoresist 11 may initiate photopolymerization under the irradiation of excitation light and inhibit the photopolymerization under the irradiation of loss light, and the photoresist 11 may be Yuzhiquan MPP-1.52S.

[0052] The image observation module is used to observe and record the processing of the sample's three-dimensional micro-nanostructure. It consists of 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 fluorescent signal generated by the photoresist 11 during photopolymerization under excitation light. The tube lens 13 transmits the fluorescent signal to the image sensor 14, which then forms an image. The objective lens 12 is a 10x objective lens, and the image sensor 14 is a CCD image sensor.

[0053] See also Figure 2 , Figure 2 Two unit structures that constitute the multiplexed metasurface 7 are shown. Figure 2 The cylinder in (a) is used to modulate the excitation light. Figure 2 In (b), the elliptical cylinder is used to modulate the loss light. The height H of both unit structures is the same, 700 nm. The period P1 of the cylindrical unit structure is 450 nm, while the period P2 of the elliptical cylinder unit structure is 300 nm.

[0054] See also Figure 3 , Figure 3 Schematic diagram of the function curve of the transmittance and phase of the unit structure of modulated excitation light as a function of radius, where the unit structure is a titanium dioxide cylinder and the substrate is silicon dioxide. Figure 3 The unit structure can evenly cover the 0-2π phase range, as shown by the six solid triangles in the figure. It is worth noting that the transmittance of this six-order unit structure is greater than 90%, as shown by the six solid squares in the figure, which ensures the high efficiency of the multiplexed metasurface 7.

[0055] See also Figure 4 , Figure 4 Schematic diagram of the cross-polarization transmission phase and polarization conversion efficiency of the unit structure for modulating loss light as the major and minor axis lengths change, where the unit structure is a titanium dioxide elliptical cylinder and the substrate is silicon dioxide. Figure 4 The unit structure in can evenly cover the 0-2π cross-polarization transmission phase range, such as Figure 4 It is worth noting that the polarization conversion efficiency of the six-order unit structure is greater than 70%, as shown in the six solid circles marked in (a). Figure 4 As shown by the six solid circles marked in (b), this ensures the high efficiency characteristics of the multiplexed metasurface 7.

[0056] like Figure 5 As shown, Figure 5 This is a polarization multiplexing method for multiplexed metasurface 7. The elliptical cylinder that modulates the loss light also has transmission phase modulation. and geometric phase modulation The former is related to the geometric size of the unit structure and has polarization-insensitive characteristics; while the latter is related to the orientation angle of the unit structure and has polarization-dependent characteristics. When the incident light is left-handed circularly polarized light, the phase modulation amount of the elliptical cylinder is , used as the 0-π annular phase corresponding to the encoding bottle-shaped light field; when the incident light is right-handed circularly polarized light, the phase modulation amount of the elliptical cylinder is , used as the spiral phase corresponding to the encoded annular light field. Further, the loss light modulation area of ​​the multiplexed metasurface 7 needs to generate a transmission phase quantity , geometric phase quantity Therefore, combining the transmission phase and the geometric phase can encode two independent phase distributions. When the incident light is linearly polarized, it can be regarded as a linear superposition of left-handed circularly polarized light and right-handed circularly polarized light, thereby simultaneously generating a ring-shaped light field and a bottle-shaped light field in the target area. The two are superimposed in space to form a three-dimensional hollow light field.

[0057] like Figure 6 As shown, Figure 6 This is a spatial multiplexing method for multiplexed metasurface 7. A random matrix multiplexing method is used to achieve spatial multiplexing of the excitation light modulation area and the loss light modulation area. Given that the period P1 of the excitation light unit structure is 450 nm and the period P2 of the loss light unit structure is 300 nm, a square grid with a period of 900 nm is used as a large pixel. Each large pixel contains 2×2 excitation light unit structures or 3×3 loss light unit structures. Using the large pixel as the basic unit, a binary matrix A is randomly generated, in which the probability of "0" appearing is 50% and the probability of "1" appearing is 50%. Matrix A is multiplied by the excitation light coding distribution to obtain the Hadamard product A1. Matrix B is subtracted from the all-ones matrix to obtain matrix B, and matrix B is multiplied by the loss light coding distribution to obtain the Hadamard product B1. Linearly superimposing these two Hadamard product results yields the arrangement of multiplexed metasurface 7.

[0058] like Figure 7 As shown, Figure 7 is 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 on the target position, they need to be multiplied by the focusing phase to obtain the focused annular beam phase distribution and the focused bottle-shaped beam phase distribution. The Hadamard product is obtained by multiplying the two with the loss light random matrix, and then using Figure 5 The polarization multiplexing method in the above method is superimposed to obtain the loss light modulation area of ​​the multiplexed metasurface 7. At the same time, the Hadamard product is obtained by multiplying the focusing phase with the random matrix of the excitation light to obtain the excitation light modulation area of ​​the multiplexed metasurface 7.

[0059] like Figure 8 As shown, Figure 8 This is the local layout of the multiplexed metasurface 7. The unit structure is combined with the excitation light modulation area and the loss light modulation area respectively, and cylinders or elliptical cylinders with appropriate geometric dimensions and orientation angles are filled in according to the required phase to generate the layout of the multiplexed metasurface 7.

[0060] like Figure 9 As shown, Figure 9 is a simulated focusing characteristic diagram of the multiplexed metasurface 7, where Figure 9 (a) in the figure is the lossy light field. Figure 9(b) shows the excitation light field. Due to computational resource limitations, Lumerical FDTD simulation software was used to simulate a small-aperture multiplexed metasurface with the same NA (radius, 22.5 μm, focal length, 21.11 μm). Back-immersion focusing was used to increase the NA to 1.1. Figure 9 It was demonstrated that a three-dimensional hollow light field and an ellipsoidal focus can be generated simultaneously at the same focal length, proving the design effectiveness and superiority of the multiplexed metasurface 7.

[0061] 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 in the scope of protection of the present invention.

Claims

1. A high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface, characterized in that: It includes an optical path modulation module, a multiplexed metasurface (7), a sample clamping module, and an image observation module located on the same axis, wherein: The optical path modulation module is used to modulate the excitation light emitted by the excitation light laser (1) in the optical path modulation module into circularly polarized light, modulate the loss light emitted by the loss light 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 multiplexed metasurface (7) is used to focus the excitation light and the loss light, so that the excitation light and the loss light respectively generate a tight focus and a three-dimensional hollow light field at the same focus; The sample holding module is used to translate and fix the sample so that the sample is 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 three-dimensional micro-nano structure processing process of the sample.

2. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 1, characterized in that: The optical path modulation module further comprises a first polarization modulator (2), a second polarization modulator (4), a dichroic mirror (5) and a light beam scanning unit (6); the transmission surface of the dichroic mirror (5) is located on the pulse laser output optical path of the excitation light laser (1); the reflection surface of the dichroic mirror (5) is located on the pulse laser output optical path of the loss light laser (3); the first polarization modulator (2) is arranged between the excitation light laser (1) and the dichroic mirror (5); and the second polarization modulator (4) is arranged between the loss light laser (3) and the dichroic mirror (5).

3. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 1, characterized in that: The multiplexed metasurface (7) includes a plurality of first unit structures and a plurality of second unit structures, wherein the first unit structures perform uniform multi-order modulation on the excitation light within a phase range of 0-2π, and the transmittance of the excitation light is above 90%, and the second unit structures perform uniform multi-order modulation on the loss light within a cross-polarization transmission phase range of 0-2π, and the polarization conversion efficiency of the loss light is above 70%.

4. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 1, characterized in that: The sample holding module comprises a three-dimensional displacement stage (9) and immersion oil (8), a sample substrate (10) and a photoresist (11) located on the same axis and tightly fitted together. The immersion oil (8) is coated on the side of the multiplexed 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 positions of the sample substrate (10) and the photoresist (11).

5. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 4, characterized in that: The image observation module comprises an objective lens (12), a tube lens (13), and an image sensor (14) located on the same axis. The objective lens (12) receives a fluorescent signal generated by the photoresist (11) during the photopolymerization process initiated by the excitation light, and the tube lens (13) transmits the fluorescent signal to the image sensor (14) so ​​that the image sensor (14) forms a polymer image.

6. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 1, characterized in that: 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 in order to focus the three-dimensional hollow light field are respectively expressed as follows: in, φ Dou ( ) represents the spiral phase distribution function of the annular light field, l represents the topological charge value, α represents the angular coordinates of the multiplexed metasurface (7), φ Bot ( ) represents the phase distribution function corresponding to the bottle-shaped light field, r represents the radial coordinate of the multiplexed metasurface (7), k represents a constant, D represents the diameter of the multiplexed metasurface (7), φ Foc ( ) represents the focusing phase distribution function, x 0 represents the horizontal coordinate position of the focus at the focal plane, y 0 represents the vertical coordinate position of the focus at the focal plane, f represents the focal length of the multiplexed metasurface (7), x represents the horizontal coordinate position of the multiplexed metasurface (7), y represents the ordinate position of the multiplexed metasurface (7), λ represents the wavelength of incident light, n Represents the ambient refractive index.

7. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 3, characterized in that: The multiplexed metasurface (7) combines the excitation light modulation area and the loss light modulation area by using a spatial multiplexing method, wherein the spatial multiplexing method includes any one of checkerboard multiplexing, random matrix multiplexing, stripe segmentation multiplexing, sector interleaving multiplexing, crescent segmentation multiplexing, multi-aperture metasurface multiplexing and multi-layer metasurface multiplexing.

8. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 2, characterized in that: The first polarization modulator (2) comprises a linear polarizer and a quarter-wave plate located on the same axis, and the second polarization modulator (4) is a linear polarizer.

9. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 1, characterized in that: The excitation light laser (1) is a laser capable of exciting photopolymerization, and the loss light laser (3) is a laser capable of inhibiting photopolymerization.

10. The high-precision laser three-dimensional nanolithography system based on a multiplexed metasurface according to claim 3, characterized in that: The shapes of the first unit structure and the second unit structure are one or more of a cylinder, a ring column, a cuboid, a regular polygonal prism, an elliptical cylinder, an X-cube, a C-cube, a cross cube and a Babinet structure of the above shapes, and the materials of the first unit structure and the second unit structure include 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 antimonide, hafnium oxide, chromium dioxide, niobium pentoxide, gold, aluminum, silver and copper. One or more.

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