CN109709630B - A method for generating subwavelength vortex beam arrays based on metal nanometasurfaces - Google Patents

Abstract

The invention proposes a method for generating a subwavelength vortex beam array based on a metal nanometer metasurface, which firstly prepares a specific metal nanometer metasurface structure composed of a metal nanorod array, and then vertically irradiates the specific metal nanometer with circularly polarized light Metasurface structure, thereby converting circularly polarized light into a subwavelength vortex beam array, the present invention also prepares a specific metal nanometer supersurface capable of generating a subwavelength vortex beam array by rationally designing the size and arrangement of the metal nanorods. Surface structure, compared with other vortex beam generation methods, the method used in the present invention has the advantages of simple structure, easy integration, uniform light intensity distribution, etc., and the vortex beam array generated by this method can not only enhance information in information transmission and storage Safety and capacity, a large number of particles can be captured at one time in particle capture, and the motion characteristics of different objects can be detected at the same time, which expands the application field of vortex beams.

Description

A method for generating subwavelength vortex beam arrays based on metal nanometasurfaces

technical field

The invention relates to the field of novel light field regulation in micro-nano optics, in particular to a method for generating a subwavelength vortex beam array based on a metal nanometer metasurface.

Background technique

λ表示入射光的波长。由于不同的拓扑荷数，每个光子携带的轨道角动量

不同。涡旋光束的中心为一个微米级的暗斑，且对微纳粒子操控时无热损耗效应，这使得涡旋光束在微纳操控领域有着广泛的应用，同时涡旋光束对粒子囚禁时，会通过轨道角动量让粒子发生旋转，因此也被称为“光学扳手”。涡旋光束在长距离传输时稳定性强，且理论上具有无限正交状态，同轴传输的不同方位角的涡旋光束之间是相互正交的，光束之间的串扰最小，所以光束可以有效地复用和解复用，这使得涡旋光束在保密通信领域有着巨大的应用前景。另外，涡旋光束还在生物医学、微观力学、天文学、量子信息处理等领域有着巨大的应用潜力。A vortex beam, also known as an optical vortex, is a light field with an isolated singularity. The phase singularity is called a phase vortex beam (Orbital Angular Momentum, OAM). The wave vector of the phase vortex beam has an azimuth term. , and rotates around the center of the vortex, there is a phase factor exp(ilθ) in the optical expression μ ₀ (r,θ,z)=μ ₀ (r,z)exp(ilθ)exp(-ikz), where r is the displacement vector at the distance from the origin, μ ₀ represents the amplitude, θ represents the azimuth angle, z represents the propagation distance, l is its topological charge number, k is the wave number, and the magnitude is

λ represents the wavelength of incident light. The orbital angular momentum carried by each photon due to the different topological charge numbers

different. The center of the vortex beam is a micron-scale dark spot, and there is no heat loss effect when manipulating micro-nano particles, which makes the vortex beam have a wide range of applications in the field of micro-nano manipulation. At the same time, when the vortex beam traps the particles, it will Particles are rotated by orbital angular momentum, hence the name "optical wrench". Vortex beams have strong stability during long-distance transmission, and theoretically have an infinite orthogonal state. Effectively multiplexing and demultiplexing, this makes vortex beams have great application prospects in the field of secure communications. In addition, vortex beams also have great application potential in biomedicine, micromechanics, astronomy, quantum information processing and other fields.

At present, the methods for generating vortex beams mainly include: helical phase plate method, geometric mode conversion method, spatial light modulator method and computational holography method. The helical phase plate method is to add a helical phase to the light through the period of the helical phase, and the geometric mode change is to change the mode of the incident light through optical devices. The essence of these two methods is to modulate the optical path of the incident light. How can different positions have different phases, but the accumulation of optical paths makes the device must have a certain physical size, which has also become an important factor limiting its development to miniaturization and integration; spatial light modulator method and computational holography The method is to reproduce the vortex beam through the holographic principle. This method can generate multiple vortex beams, but the light energy distribution of the beams is not uniform, and the beams of different orders will overlap, so it is difficult to separate a single topological charge from them. Vortex beam. Although there are many ways to generate vortex beams, they all have some drawbacks and limited application scenarios. Therefore, it is of great significance in the field of micro-nano optics to develop a subwavelength-scale vortex beam array generator that can produce uniform light energy distribution without high-order diffraction effects.

In 1984, British Professor Berry first proposed the concept of geometric phase. Berry's research found that when an adiabatic physical system evolves from the initial state along a certain path (in a certain parameter space or state space) for a period and returns to the initial state, its final state is not equivalent to the initial state, but needs to be Add an extra phase factor (Quantal phasefactors accom panying adiabatic changes, M.V.Berry, Proceedings of the Royal Society A:Mathematical,Physical and Engineering Sciences, Vol.392, No.1802, pages 45–57, 08March 1984); 1956, Professor Pancharatnam of the Indian Institute of Raman Research found that the electromagnetic wave will generate an additional phase during the transformation of the polarization state (Generalized theory of interference and its applications, Pancharatnam S., Proceedings of the Indian Academy of Sciences-Section A, Vol.44, No. .5, pages 247–262, 30 October 1956). The electromagnetic wave of a certain polarization state evolves along a certain path on the surface of the Poincaré sphere and returns to the initial state. half. Based on these theories, related researchers have proposed the concept of geometric phase-type metasurfaces. The electromagnetic wave phase parameters are controlled by the geometric curvature of the subwavelength metal or dielectric structure in the two-dimensional plane, so as to construct the desired wavefront, and then obtain a plane imaging lens, a directional surface wave coupler, a superoscillating lens, and a vortex beam. A series of complex planar optics including generators, vortex beam splitters. The invention obtains a subwavelength vortex beam array generation method based on the research of the geometric phase type metasurface.

In the above-mentioned background technologies, vortex beam generating methods such as the spiral phase plate method, the geometric mode conversion method, the spatial light modulator method, and the computational holography method all have some defects and have limited application scenarios. The invention researches and designs a method for generating a subwavelength vortex beam array based on a metal nanometer metasurface, which can not only enhance information security and capacity in information transmission and storage, but also capture and manipulate a large number of particles in micro-nano manipulation. At the same time, the motion characteristics of different objects are detected, which expands the application field of vortex beams.

SUMMARY OF THE INVENTION

The purpose of the invention is to convert the amplitude and phase of the vortex beam array into the size and rotation angle of the metal nanorods, and realize the simultaneous regulation of the amplitude and phase of the incident beam by reasonably designing the size and rotation angle of the metal nanorods. Electron beam etching method prepares metal nanorod arrays with periodic distribution, thereby forming metal nanometer metasurface structure. Under the normal incidence of circularly polarized light from the bottom of metal nanometer metasurface structure, the transmission area formed by metal nanometer metasurface structure generates light energy A vortex beam array with a uniform distribution of sub-wavelength scales is used to solve the problems existing in the background art. Compared with other vortex beam generation methods, the method for generating a subwavelength vortex beam array based on a metal nano-metasurface of the present invention has the advantages of simple structure, easy integration and the like.

The method for generating a subwavelength vortex beam array based on a metal nanometer metasurface of the present invention includes: firstly preparing a specific metal nanometer metasurface structure composed of a metal nanorod array and a quartz glass substrate, which is in the shape of a cuboid as a whole, the metal nanorods The array includes n metal nanorods, where n is a positive integer and n>4, the metal nanorods are periodically arranged on the upper surface of the quartz glass substrate, and the upper surface of the metal nanorod array is in the plane Any point is the origin, starting from this origin, the length and width directions of the specific metal nano-metasurface structure are the X-axis and the Y-axis respectively, and the opposite direction of the thickness of the specific metal nano-metasurface structure is the Z-axis; then the wavelength The circularly polarized light of 532 nm is vertically irradiated to a specific metal nano-metasurface structure from the region of Z < 0. After the circularly polarized light interacts with any metal nanorod, a phase factor 2θ is added to the light wave phase, where θ is any The angle between the long axis of a metal nanorod and the X axis, because the long axis of each metal nanorod is different from the angle θ between the long axis and the X axis, the circularly polarized light transmitted from the XY plane with Z=0 is transmitted at Z>0. Different positions of the region present different phases, and the four adjacent metal nanorods in the X and Y axes generate a vortex beam with a diameter of 180 nm. Due to the effect of the metal nanorod array, in Z The transmission region > 0 produces a subwavelength-scale vortex beam array with uniform light energy distribution and phase helical distribution.

Wherein, the specific method of preparing specific metal nanometer metasurface structure comprises the following steps:

S1) Spin-coating photoresist on quartz glass substrate

S11) Cleaning the quartz glass substrate

Place the original quartz glass substrate in the shape of a cuboid in a HCl solution with a concentration of 0.5 mol/L and a temperature of 35°C to 50°C. After standing for 10 minutes, place the quartz glass substrate in pure water at about 50°C for 5 minutes. minutes, take out the quartz glass substrate and perform secondary cleaning with pure water at about 50°C to complete the chemical cleaning of the quartz glass substrate;

S12) drying the quartz glass substrate

Place the quartz glass substrate processed in step S11) on the cleaning basket, and pass high-clean air or nitrogen gas with a temperature of about 80°C into the cleaning basket for 10 to 20 minutes, until the quartz glass substrate and the cleaning basket are fully dried. After that, the drying of the quartz glass substrate is completed;

S13) Spin coating photoresist

The quartz glass substrate processed in step S12) is adsorbed on the vacuum chuck, the rotation speed of the vacuum chuck is adjusted to 500rpm, and photoresist is dripped into the center of the upper surface of the quartz glass substrate. After 5 seconds, the rotation speed of the vacuum chuck is increased to 500 rpm. 3000 ~ 7000rpm, sling for 30 seconds to form a photoresist coating with a thickness of 140nm;

S14) Soft-bake the quartz glass substrate after sizing

After the photoresist is evenly coated on the upper surface of the quartz glass substrate, the quartz glass substrate processed in step S13) is placed on a vacuum hot plate at 80° C. for soft baking for 2 to 5 minutes;

S2) Electron beam exposure to obtain a pattern

S21) Focused electron beam exposure

Use an electron beam vector exposure machine with an accelerating voltage of 30KV, a spot size of 30nm, and an exposure dose of 25 μc/cm ² to expose the quartz glass substrate processed in step S1), and use a preset program to control the electron beam vector exposure machine. The photoresist nanorod array pattern obtained on the upper surface of the quartz glass substrate has a rod length of 90 nm, a rod width of 30 nm, and a thickness of 140-150 nm. The photoresist nanorods in the row and each column are arranged at an angle of 45° and -45° respectively with the X axis, and the distance between the geometric centers of any two adjacent photoresist nanorods is 180 nm;

S22) drying the quartz glass substrate after exposure

Place the quartz glass substrate processed in step S21) in an oven at 150°C to 170°C, bake for 90 minutes, and stand for 30 minutes in a normal temperature environment;

S3) Development

S31) developing, fixing

The quartz glass substrate processed in step S2) is immersed in a developing solution with a temperature of 21±0.2° C. for 60 to 120 seconds, and then placed in an isopropanol solution for 30 to 40 seconds to complete the fixing, and obtain a solution on the quartz glass substrate. The nanorod array pattern on the surface;

S32) drying the substrate after fixing

Take out the quartz glass substrate processed in step S31) and place it on a vacuum hot plate at 80° C. for soft baking for 2 to 5 minutes to obtain a dried nanorod array pattern on the upper surface of the quartz glass substrate;

S33) Pattern inspection, evaporating metal film

The dried nanorod array pattern on the upper surface of the quartz glass substrate processed in step S32) is inspected by scanning electron microscopic observation technology. After confirming that the dried nanorod array pattern is qualified, the quartz glass substrate is subjected to a thermal evaporation table. Evaporating metal gold (Au), wherein the thickness of gold (Au) is 20nm-30nm;

S34) remove the photoresist to obtain the metal pattern

Acetone peeling is performed on the quartz glass substrate treated in step S33), the residual electron beam photoresist and metal gold are removed, and a gold nanorod array is obtained on the upper surface of the quartz glass substrate, wherein the gold nanorods in the gold nanorod array are The rods are all 90nm long, 30nm wide, and 25nm thick. The gold nanorods in each row and column of the gold nanorod array are arranged at an angle of 45° and -45° with the X axis, respectively, and any two of them are in phase. The distances between the geometric centers of adjacent gold nanorods are all 180 nm, thereby obtaining a specific metal nano-metasurface structure.

The present invention prepares a periodic metal nanorod metasurface capable of generating subwavelength vortex beam arrays by rationally designing the size and arrangement of the metal nanorods and using electron beam etching, a relatively mature micro-nano processing method. Compared with other vortex beam generating methods, the method used in the present invention has the advantages of simple structure, easy integration, uniform light intensity distribution, and the like. In addition, the vortex beam array generated by this method can not only enhance information security and capacity in information transmission and storage, capture a large number of particles at one time in particle capture, but also detect the motion characteristics of different objects at the same time, expanding the application of vortex beams. field.

Description of drawings

Fig. 1 is the schematic diagram of the metal nanometer metasurface structure of the present invention

Figure 2 is a phase distribution diagram of a single vortex beam at a distance of 100 nm from the gold nanorod array along the Z axis in the transmission region (Z>0 region) obtained by finite difference time domain simulation;

Figure 3 shows the simulation results obtained by finite difference time domain: (a) the light intensity distribution in the transmission region (Z>0 region) along the Z axis at a distance of 100 nm from the gold nanorod array; (b) the transmission region (Z>0 region) ) phase distribution at 100 nm from the gold nanorod array along the Z axis

Figure 4 is a scanning electron microscope photograph of gold nanorod arrays obtained by electron beam etching

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings.

The method for generating a subwavelength vortex beam array based on a metal nanometer metasurface of the present invention firstly prepares a specific metal nanometer metasurface structure. A gold nanorod array with periodic arrangement is prepared on the surface, and the gold nanorod array includes n gold nanorods, wherein, n is a positive integer and n>4, and any point in the plane where the upper surface of the gold nanorod array is located As the origin, starting from this origin, the length and width directions of the specific metal nano-metasurface structure are the X axis and the Y axis, respectively, and the opposite direction of the thickness of the specific metal nano-metasurface structure is the Z axis, that is, the gold nanorod array. The upper surface is located on the XY plane at Z=0, and the size of the gold nanorods is 90nm×30nm×25nm, and they are staggered at an angle of 45° and -45° in the transverse direction, the longitudinal direction and the X axis, respectively, that is, gold The nanorods are arranged at a periodic interval of 360nm±10nm, because in every row and every column of the gold nanorod array, the gold nanorods are arranged at an interval of 180nm, and are arranged at an angle of 45° and -45° respectively with the X axis. , there is an interval of 360nm from a gold nanorod arranged at an angle of 45° to the X axis to the next gold nanorod arranged at an angle of 45° to the X axis in this row or column, plus the allowable Therefore, the gold nanorods in the gold nanorod array are arranged at periodic intervals of 360 nm ± 10 nm; then circularly polarized light with a wavelength of 532 nm is irradiated vertically from the region of Z < 0 to the specific metal nano-metasurface structure. After the circularly polarized light interacts with any gold nanorod, the phase of its light wave is added with a phase factor 2θ, where θ is the angle between the long axis of any gold nanorod and the X axis, because the long axis of each gold nanorod and X The included angle θ of the axes is different, and the circularly polarized light transmitted from the XY plane at Z=0 presents different phases at different positions in the transmission area of Z>0. The nanorods generate a vortex beam with a diameter of 180nm, that is, the diameter of the vortex beam is smaller than the wavelength of the incident circularly polarized light, so under the action of the gold nanorod array, light is generated in the transmission region of Z>0 A subwavelength-scale vortex beam array with uniform distribution and phase helical distribution.

The specific method for preparing the specific metal nanometer metasurface structure in the present invention comprises the following steps:

S1) Spin-coating photoresist on quartz glass substrate

S11) Cleaning the quartz glass substrate

A high-purity quartz glass substrate with a refractive index of 90%, a maximum temperature resistance of 1500°C, a thickness of 3mm, and a length and width of 800nm was placed in a HCl solution with a concentration of 0.5mol/L and a temperature of 45°C. , after standing for 10 minutes, soak the quartz glass substrate in pure water at about 50 °C for 5 minutes, take out the quartz glass substrate and then use pure water at about 50 °C for secondary cleaning to complete the chemical cleaning of the quartz glass substrate;

S12) drying the quartz glass substrate

Place the quartz glass substrate processed in step S11) on the cleaning basket, and pass high-clean air or nitrogen gas with a temperature of about 80°C into the cleaning basket for 10 to 20 minutes, until the quartz glass substrate and the cleaning basket are fully dried. After that, the drying of the quartz glass substrate is completed;

S13) Spin coating photoresist

The quartz glass substrate processed in step S12) is adsorbed on the vacuum chuck, the rotation speed of the vacuum chuck is adjusted to 500 rpm, and polymethyl methacrylate (PMMA) with a concentration of 5% is dripped into the center of the upper surface of the quartz glass substrate. ) photoresist, after 5 seconds, the speed of the vacuum chuck is increased to 3000-7000rpm, and the glue is spun for 30 seconds to form a photoresist coating with a thickness of 140nm;

S14) Soft-bake the quartz glass substrate after sizing

After the photoresist is evenly coated on the upper surface of the quartz glass substrate, the quartz glass substrate processed in step S13) is placed on a vacuum hot plate at 80° C. for soft baking for 2 to 5 minutes;

S2) Electron beam exposure to obtain a pattern

S21) Focused electron beam exposure

Use a Raith 150 electron beam vector exposure machine with a spot size of 30nm, an acceleration voltage of 30KV, and an exposure dose of 25μc/cm ² to perform vector exposure on the quartz glass substrate processed in step S1), and use a preset program to control the electron beam. The vector exposure machine is used to obtain photoresist nanorod array patterns with photoresist nanorods on the upper surface of the quartz glass substrate. The rod length is 90 nm, the rod width is 30 nm, and the thickness is 150 nm. The photoresist nanorod array pattern is The photoresist nanorods in each row and column are arranged at an angle of 45° and -45° respectively with the X axis, and the distance between the geometric centers of any two adjacent photoresist nanorods is 180nm.

S22) drying the quartz glass substrate after exposure

Place the quartz glass substrate processed in step S21) in an oven at 170°C, bake for 90 minutes, and stand for 30 minutes in a normal temperature environment;

S3) Development

S31) developing, fixing

Immerse the quartz glass substrate processed in step S2) in a developing solution in which tetramethyldipentanone (MIBK) and isopropanol (IPA) are mixed at a temperature of 21±0.2° C. in a ratio of 1:3 for 100 seconds, Then put it into the isopropanol solution for 40 seconds to complete the fixing to obtain the nanorod array pattern on the upper surface of the quartz glass substrate;

S32) drying the substrate after fixing

Take out the quartz glass substrate processed in step S31) and place it on a vacuum hot plate at 80° C. for soft baking for 2 to 5 minutes to obtain a dried nanorod array pattern on the upper surface of the quartz glass substrate;

S33) Pattern inspection, evaporating metal film

Scanning electron microscopy (SEM) observation technology is used to inspect the dried nanorod array pattern on the upper surface of the quartz glass substrate after step S32), and after confirming that the dried nanorod array pattern is qualified, a thermal evaporation table is used to inspect the pattern. A layer of metal gold (Au) with a thickness of 25 nm was evaporated from a quartz glass substrate;

S34) remove the photoresist to obtain the metal pattern

Acetone peeling is performed on the quartz glass substrate treated in step S33), the residual electron beam photoresist and metal gold are removed, and a gold nanorod array is obtained on the upper surface of the quartz glass substrate, wherein the gold nanorods in the gold nanorod array are The rods are all 90nm long, 30nm wide, and 25nm thick. The gold nanorods in each row and column of the gold nanorod array are arranged at an angle of 45° and -45° with the X axis, respectively, and any two of them are in phase. The distances between the geometric centers of adjacent gold nanorods are all 180 nm, thereby obtaining a specific metal nano-metasurface structure. Fig. 4 is a scanning electron microscope (SEM) photograph thereof, and 100 nm in Fig. 4 is only used as a scale.

Figures 2 to 3 show the effect of subwavelength periodic vortex beam generation of the above-mentioned specific metal nano-metasurface structure composed of metal nanorod arrays by using the finite difference time domain method:

First, set 25 gold nanorod arrays arranged at 45° and -45° angles in the horizontal, vertical, and X-axis, respectively, and all of them are arranged at 360 nm periodic intervals, as shown in Figure 1. Among them, 25 gold nanorods The lengths are 90nm, the widths are 30nm, and the thicknesses are 25nm, as shown in Figure 1; then the simulation area is set to 400nm × 400nm × 2000nm, and the left-handed circularly polarized light with a wavelength of 532nm is set from the specific metal nano-metasurface The bottom of the structure is irradiated vertically into the gold nanorod array of the specific metal nanometasurface structure; then in the transmission region (Z>0 region) along the Z axis from the upper surface of the gold nanorod array 20nm, 50nm, 100nm, 500nm, 1000nm , a field monitor is set up at 2000nm to monitor the electric field and magnetic field at the location of each monitor respectively; finally, the electric field intensity distribution and field vector phase distribution of each position in the transmission area are obtained through simulation calculation. Figure 3(a) shows the electric field intensity distribution in the transmission region of the specific metal nano-metasurface structure at a distance of 100 nm from the nanorod array along the Z axis, and its light energy is relatively concentrated and periodically distributed; Figure 3(b) shows the specific metal nano-metasurface The phase distribution of the transmission area of the structure along the Z axis at a distance of 100 nm from the nanorod array, it can be seen that the phase is centered on the center of each helix (ie, the strongest point of light intensity) in Figure 3(a), and the phase is -π ~ π Spiral distribution. The above simulation results show that after a beam of circularly polarized light is vertically irradiated to the specific metal nano-metasurface structure prepared by the present invention, the circularly polarized light transmitted from the XY plane of Z=0 is transformed into a subwavelength vortex beam array; Fig. 2 is the result of separately extracting the data of a single vortex beam in Fig. 3(b) and redrawing it, so as to obtain a more obvious helical effect.

The present invention prepares a periodic metal nanorod metasurface capable of generating subwavelength vortex beam arrays by rationally designing the size and arrangement of the metal nanorods and using electron beam etching, a relatively mature micro-nano processing method. Compared with other vortex beam generating methods, the method used in the present invention has the advantages of simple structure, easy integration, uniform light intensity distribution, and the like. In addition, the vortex beam array generated by this method can not only enhance information security and capacity in information transmission and storage, capture a large number of particles at one time in particle capture, but also detect the motion characteristics of different objects at the same time, expanding the application of vortex beams. field.

While illustrative specific embodiments of the present invention have been described above to facilitate understanding of the invention by those skilled in the art, it should be clear that the invention is not limited in scope to specific real-time implementations. Where equivalent replacements or equivalent replacements are adopted, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are included in the protection list.

Claims (9)

1. A method for generating a sub-wavelength vortex beam array based on a metal nano super surface is characterized by comprising the steps of firstly preparing a specific metal nano super surface structure which is formed by a metal nanorod array and a quartz glass substrate and is integrally in a cuboid shape, wherein the metal nanorod array comprises n metal nanorods, n is a positive integer and is greater than 4, the metal nanorods are periodically distributed on the upper surface of the quartz glass substrate, the specific metal nano super surface structure is emitted from an original point which is any point in a plane where the upper surface of the metal nanorod array is located, the length and width directions of the specific metal nano super surface structure are respectively an X axis and a Y axis, and the reverse direction of the thickness of the specific metal nano super surface structure is a Z axis; then, circularly polarized light with the wavelength of 532nm is vertically irradiated to the specific metal nano super-surface structure from a region with the Z being less than 0, after the circularly polarized light acts with any one metal nanorod, a phase factor 2 theta is added to the light wave phase, wherein theta is the included angle between the long axis of any one metal nanorod and the X axis, because the included angle theta between the long axis of each metal nanorod and the X axis is different, the circularly polarized light transmitted from the XY plane at the position with the Z being 0 presents different phases at different positions of a transmission region with the Z being more than 0, 4 metal nanorods adjacent in the two directions of the X axis and the Y axis generate a vortex light beam, the diameter of the vortex light beam is 180nm, and due to the action of the metal nanorod array, a vortex light beam array with the sub-wavelength scale with uniform light energy distribution and spiral phase distribution is generated in the transmission region with the Z being more than;

wherein, the preparation method of the specific metal nano super surface structure comprises the following steps:

s1) spin-coating photoresist on a quartz glass substrate

S11) cleaning the silica glass substrate

Placing an original quartz glass substrate in a cuboid shape in HCl solution with the concentration of 0.5mol/L and the temperature of 35-50 ℃, standing for 10 minutes, placing the quartz glass substrate in pure water with the temperature of about 50 ℃ for soaking for 5 minutes, taking out the quartz glass substrate, and then carrying out secondary cleaning by using the pure water with the temperature of about 50 ℃ to complete the chemical cleaning of the quartz glass substrate;

s12) drying the quartz glass substrate

Placing the quartz glass substrate treated in the step S11) on a cleaning basket, introducing high-clean air or nitrogen at the temperature of about 80 ℃ into the cleaning basket for 10-20 minutes, and drying the quartz glass substrate after the quartz glass substrate and the cleaning basket are fully dried;

s13) spin-on resist

Adsorbing the quartz glass substrate treated in the step S12) on a vacuum chuck, adjusting the rotating speed of the vacuum chuck to 500rpm, dripping photoresist into the center of the upper surface of the quartz glass substrate, and after 5 seconds, increasing the rotating speed of the vacuum chuck to 3000-7000 rpm, and spinning the photoresist for 30 seconds to form a photoresist coating with the thickness of 140 nm;

s14) soft baking of quartz glass substrate after glue homogenizing

After the photoresist is uniformly coated on the upper surface of the quartz glass substrate, placing the quartz glass substrate treated in the step S13) on a vacuum hot plate at 80 ℃ for soft baking for 2-5 minutes;

s2) exposing with electron beam to obtain pattern

S21) focused electron beam exposure

Accelerating voltage of 30KV, light spot size of 30nm, and exposure dose of 25 μ c/cm²Exposing the quartz glass substrate processed in the step S1), and controlling the electron beam vector exposure machine by using a preset program to obtain a photoresist nanorod array pattern with the length of each nanorod being 90nm, the width of each nanorod being 30nm and the thickness of each nanorod being 140-150 nm on the upper surface of the quartz glass substrate, wherein the photoresist nanorods of each row and each column in the photoresist nanorod array pattern are respectively arranged at intervals at an included angle of 45 degrees to 45 degrees with the X axis, and the distance between the geometric centers of any two adjacent photoresist nanorods is 180 nm;

s22) baking the quartz glass substrate after exposure

Placing the quartz glass substrate treated in the step S21) in an oven at 150-170 ℃, baking for 90 minutes, and standing and cooling for 30 minutes in a normal temperature environment;

s3) development

S31) developing and fixing

Immersing the quartz glass substrate processed in the step S2) in a developing solution at the temperature of 21 +/-0.2 ℃ for 60-120 seconds, and then putting the quartz glass substrate in an isopropanol solution for 30-40 seconds to complete fixation, so as to obtain a nanorod array pattern on the upper surface of the quartz glass substrate;

s32) post-fixing baking substrate

Taking out the quartz glass substrate treated in the step S31), and placing the quartz glass substrate on a vacuum hot plate at 80 ℃ for soft drying for 2-5 minutes to obtain a dried nanorod array pattern on the upper surface of the quartz glass substrate;

s33) pattern inspection, evaporating the metal film

Inspecting the dried nanorod array pattern on the upper surface of the quartz glass substrate treated in the step S32) by using a scanning electron microscopy observation technology, and evaporating metal gold (Au) on the quartz glass substrate by using a thermal evaporation table after determining that the dried nanorod array pattern is qualified, wherein the thickness of the gold (Au) is 20-30 nm;

s34) removing the photoresist to obtain a metal pattern

And (2) stripping the quartz glass substrate treated in the step S33) with acetone to remove residual electron beam photoresist and metal gold, and obtaining a gold nanorod array on the upper surface of the quartz glass substrate, wherein the sizes of the gold nanorods in the gold nanorod array are all 90nm long, 30nm wide and 25nm thick, every 1 row and every 1 column of the gold nanorods in the gold nanorod array are respectively arranged at intervals with an included angle of 45 degrees to 45 degrees with the X axis, and the distance between the geometric centers of any two adjacent gold nanorods is 180nm, so that the specific metal nano super-surface structure is obtained.

2. The method for generating a sub-wavelength vortex beam array based on metal nano-super surface according to claim 1, wherein the original quartz glass substrate in the step S11) is high-purity quartz glass with a thickness of 3mm, a length and a width of 800nm, a light transmittance of more than 90% and a maximum temperature resistance of 1500 ℃.

3. The method for generating the sub-wavelength vortex beam array based on the metal nano-super surface according to claim 2, wherein the photoresist in the step S13) is polymethyl methacrylate (PMMA) with a concentration of 5%.

4. The method as claimed in claim 3, wherein the developing solution of step S31) is a mixture of tetramethylcyclopentanone (MIBK) and isopropyl alcohol (IPA) at a ratio of 1: 3.

5. The method for generating the sub-wavelength vortex beam array based on the metal nano-super surface according to claim 3, wherein the temperature of the HCl solution in the step S11) is 45 ℃.

6. The method for generating the sub-wavelength vortex beam array based on the metal nano-super surface according to claim 4, wherein the oven temperature in the step S22) is 170 ℃.

7. The method for generating the sub-wavelength vortex beam array based on the metal nano-super surface according to claim 5, wherein the quartz glass substrate is immersed in the developing solution for 100 seconds and placed in the isopropanol solution for 40 seconds in the step S31).

8. The method for generating the sub-wavelength vortex beam array based on the metal nano-super surface according to claim 5, wherein the thickness of the gold (Au) in the step S33) is 25 nm.

9. The method for generating the sub-wavelength vortex beam array based on the metal nano-super surface according to any one of claims 1 to 8, wherein the circularly polarized light is left-handed circularly polarized light.

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