Local polarization enhanced nonlinear ionization nanometer inscribing system and method

Abstract

The invention relates to a local polarization enhanced nonlinear ionization nanometer inscribing system and method, and belongs to the technical field of femtosecond laser processing. The nanometer inscribing method has the large-area machining capacity, a large-area nanometer hole array can be machined in a material in a flying dotting mode, and the distance between adjacent points in the nanometer hole array can be controlled by controlling the speed of a high-precision displacement table and the repetition frequency of femtosecond laser pulses; the size of the nanopore can be controlled by controlling the pulse energy; the characteristic line width of the nanowire can be controlled by controlling the pulse energy and the speed of the high-precision displacement table; patterns are designed, and a high-precision displacement table is introduced, so that patterning processing of nanowires can be realized.

Description

Technical Field

[0001] The invention relates to a local polarization enhanced nonlinear ionization nano-writing system and method, belonging to the technical field of femtosecond laser processing. Background Art

[0002] With the development trend of high integration, multifunctionality and miniaturization of microelectronic products, higher requirements are put forward for micro-nano manufacturing technology. At present, the main micro-nano processing technologies in the field of microelectronics include photolithography, focused ion beam, electron beam etching and nanoimprinting. Photolithography is the most common technology in microelectronics processing. It can realize structure and pattern processing with nanometer resolution, but the photolithography process is extremely complex, the cost of photolithography machine and mask is high, and it is difficult to achieve cross-scale processing from micrometer to nanometer. Focused ion beam focuses high-energy ion flow on the surface of target material to achieve precision cutting, etching and other operations. It has high processing accuracy, can adapt to a variety of complex processing requirements, and has the characteristics of high flexibility and high repeatability. However, focused ion beam needs to work in a high vacuum environment, has high maintenance cost and relatively low processing efficiency. Electron beam etching is a micro-nano processing technology that uses electron beam as a mask to expose photosensitive materials. This technology has extremely high resolution, does not need to replace the mask, and has high flexibility. However, electron beam etching also requires a high vacuum environment and has high maintenance costs. Compared with other micro-nano processing technologies, electron beam etching uses point-by-point scanning for processing, and the processing efficiency is relatively low. It is difficult to achieve etching processing of complex pattern structures. In addition, the proximity effect is very easy to cause during electron beam etching, which greatly affects the processing accuracy and quality. Nanoimprinting is a processing technology based on template pattern transfer. It has high precision and can achieve mass production. Through precisely designed templates, it can even achieve the preparation of quasi-three-dimensional structures. However, nanoimprinting technology requires complex preparation processes when manufacturing templates, and faces a series of challenges in actual use, such as template cost and life, structural consistency, and structural defects. In order to adapt to the rapid development of the field of microelectronics, it is urgent to develop a micro-nano processing technology with simple process, low cost, and strong adaptability.

[0003] Femtosecond laser processing technology is a new type of nano-processing method that has developed rapidly in recent years. With its femtosecond pulse duration and ultra-high peak power, it has shown unparalleled advantages in the field of precision processing, especially suitable for high-precision drilling, cutting, welding and other processing scenarios. Compared with traditional micro-nano processing technology, femtosecond laser processing technology does not require a high vacuum environment, has the characteristics of "cold processing" and has a wide range of material applicability. In addition, femtosecond laser also has the unique ability of "true three-dimensional" processing. It can focus on the inside of transparent materials and accurately process the inside without damaging the surface of the material. Although femtosecond laser has many advantages in high-precision processing, the existence of diffraction limit limits the processing accuracy of femtosecond laser. A cylindrical vector beam is a type of beam whose polarization state changes along the radial or azimuthal direction. When it is focused by a high numerical aperture (NA) lens, the beam will form a longitudinal field along the propagation direction in the focusing area, forming a more compact spot in space than the scalar light field, and even break the diffraction limit. Longitudinal light fields have some unique properties. They can accelerate electrons and produce a strong localized effect on a smaller spatial scale. At the same time, longitudinal light fields can more effectively excite longitudinal dipoles and induce unique optical responses of materials. At present, the technology of super-resolution processing using vector beams has attracted widespread attention.

[0004] The disadvantages of the prior art are:

[0005] Traditional micro-nano processing technology generally requires a high vacuum environment, complex process flow, high cost, and poor technical flexibility, and cannot adapt to the rapid development of the microelectronics field.

[0006] The processing accuracy of traditional femtosecond laser processing technology is limited by the optical diffraction limit, and the processing accuracy is difficult to improve. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and to propose a nonlinear ionization nano-writing system and method with local polarization enhancement.

[0008] The technical solution of the present invention is:

[0009] A local polarization enhanced nonlinear ionization nano-writing system, the writing system comprises a titanium sapphire femtosecond laser 1, an energy control module 2, a radial polarization converter 3, a frequency doubling module 4, a conical lens 5, a first dichroic mirror 6, a plano-convex lens 7, an annular phase filter 8, a focusing objective lens 9, a culture dish 10, a high-precision translation stage 11, a second dichroic mirror 12, an illumination light source 13, and a CCD imaging unit 14;

[0010] The titanium sapphire femtosecond laser 1 is used to emit femtosecond laser to the energy control module 2. The femtosecond laser is a horizontally polarized femtosecond laser, the light intensity in space is Gaussian distribution, and the wavelength is 800nm;

[0011] The energy control module 2 is used to adjust the pulse energy of the femtosecond laser and transmit the femtosecond laser after the pulse energy adjustment to the radial polarization converter 3;

[0012] The radial polarization converter 3 is used to receive the femtosecond laser after pulse energy adjustment, and convert the received femtosecond laser into radially polarized femtosecond laser and transmit it to the frequency doubling module 4;

[0013] The frequency doubling module 4 is used to receive radially polarized femtosecond laser light, and convert the received radially polarized femtosecond laser light into frequency doubling light with a wavelength of 400nm and then transmit it to the axicon 5;

[0014] The axicon 5 is used to receive the doubled frequency light of 400nm wavelength, and spatially shape the received doubled frequency light of 400nm wavelength into a primary Bessel-Gaussian beam, and then transmit it to the first dichroic mirror 6 for reflection, the plano-convex lens 7 for transmission, the annular phase filter 8 for filtering, and the focusing lens 9 for focusing to obtain a focused beam, the full width at half maximum (FWHM) of the focused beam is much lower than the diffraction limit, and the focused beam irradiates the quartz sample fixed in the culture dish 10, and performs nano-writing operation on the quartz sample in the oil immersion environment;

[0015] The illumination light emitted by the illumination light source 13 passes through the second dichroic mirror 12, the first dichroic mirror 6, the plano-convex lens 7, the annular phase filter 8, and the focusing objective lens 9 in sequence, and then irradiates the quartz sample. After being reflected by the surface of the quartz sample, it returns along the original path and is reflected by the second dichroic mirror 12 to the CCD imaging unit 14, so as to dynamically monitor the entire processing process.

[0016] The high-precision translation stage 11 can translate at high speed in the XYZ directions, driving the quartz sample to move along a set trajectory.

[0017] The femtosecond laser emitted by the titanium sapphire femtosecond laser 1 is transmitted to the radial polarization converter 3 after the pulse energy is adjusted by the energy control module 2. The radial polarization converter 3 converts the horizontally polarized femtosecond laser into radial polarization. The radially polarized femtosecond laser is transmitted to the frequency doubling module 4 and becomes a frequency doubling light with a wavelength of 400nm. The frequency doubling light with a wavelength of 400nm is transmitted to the aconic lens 5. The aconic lens 5 spatially shapes the femtosecond laser with Gaussian energy distribution into a primary Bessel-Gaussian beam. The primary Bessel-Gaussian beam is reflected by the first dichroic mirror 6 and transmitted to the 4f beam reduction system composed of a plano-convex lens 7 and a focusing lens 9 for beam reduction to obtain a secondary Bessel-Gaussian beam. The annular phase filter 8 placed in front of the focusing lens 9 performs phase modulation on the incident light, and finally obtains a focused beam after the focusing lens 9. The full width at half maximum (FWHM) of the focused beam spot is much lower than the diffraction limit. The focused beam irradiates the quartz sample fixed in the culture dish 10, and performs nano-writing operation on the quartz sample in an oil immersion environment. The illumination light emitted by the illumination light source 13 passes through the second dichroic mirror 12, the first dichroic mirror 6, the plano-convex lens 7, the annular phase filter 8, and the focusing objective lens 9, and then irradiates the quartz. After being reflected by the quartz surface, it returns along the original path and is reflected by the second dichroic mirror 12 to the CCD imaging unit 14, so as to dynamically monitor the entire processing process. The present invention performs nano-writing on the material by using a sub-diffraction limit focused beam created by a nonlinear ionization controllable nano-writing system enhanced by local polarization.

[0018] The titanium sapphire femtosecond laser emits a laser with a central wavelength of 800nm, a pulse width of 50fs, an adjustable repetition frequency of 1kHz, a maximum energy of 3mJ per single pulse, a Gaussian light intensity spatial distribution, and horizontal linear polarization;

[0019] The energy control module is composed of a half-wave plate and a polarizing plate. The pulse energy of the incident femtosecond laser is adjusted by rotating the half-wave plate or the polarizing plate and changing the relative angle between the half-wave plate and the polarizing plate.

[0020] The radial polarization converter can convert linearly polarized femtosecond laser light into radially polarized femtosecond laser light.

[0021] The frequency doubling module is composed of a BBO crystal and a filter, and can double the frequency of an 800nm ​​femtosecond laser to a 400nm femtosecond laser;

[0022] The cone base angle of the aconic lens is 1°, the focal length of the plano-convex lens is f=175 mm, and the focusing objective lens is a 100-fold oil immersion objective lens (NA=1.4).

[0023] The annular phase filter is a 5-ring phase filter, consisting of 5 concentric rings, and the radii of the concentric rings from the inside to the outside are r1=75μm, r2=117μm, r3=214μm, r4=238μm, and r5=250μm. The material of the annular phase filter is fused quartz with a thickness of 500μm. The concentric circle structure is prepared by photolithography, and the area to be etched is the annular area between r1-r2 and r3-r4, which is prepared by three rounds of photolithography, and the height of each step d is 106nm.

[0024] The sample is fixed in a culture dish filled with immersion oil and placed on a high-precision translation stage.

[0025] The intensity distribution of the focused light beam in the focus area is determined by the Richards–Wolf vector diffraction theory, and its expression in the cylindrical coordinate system is shown as (1):

[0026]

[0027] Among them, E r and E z Represent the radial and longitudinal components of the total light intensity, respectively. B is the amplitude constant, which can be set to 1. α is the maximum convergence angle determined by the numerical aperture NA of the objective lens. is the apodization function of the focusing lens, J i is the i-th order Bessel function, θ1 and θ2 are the incident angle before the immersion oil-quartz interface and the refraction angle after the immersion oil-quartz interface, respectively. The relationship between the two angles can be calculated by Snell's law as follows:

[0028] n1sin(θ1)=n2sin(θ2)(2)

[0029] Where n1 and n2 are the refractive indices of immersion oil and quartz, respectively.

[0030] t p It represents the Fresnel coefficient at the immersion oil-quartz interface and is calculated as follows:

[0031]

[0032] l0(θ1) is the primary Bessel-Gaussian beam light field expression, which is expressed as follows:

[0033]

[0034] Among them, β0 is the truncation parameter, which represents the ratio of the pupil radius to the beam waist radius.

[0035] T(θ1) is the transmittance function of the annular phase filter, expressed as:

[0036]

[0037] Among them, φ i The angle between the edge of each ring of the annular phase filter and the optical axis can be expressed by r i = sinφ i / NA confirmed, r i is the radius of each ring zone of the annular phase filter.

[0038] k0, k1 and k2 are the wave vectors of the focused beam in vacuum, immersion oil and quartz, expressed as:

[0039]

[0040] λ is the wavelength of the light beam incident on the focusing objective.

[0041] ψ represents the aberration function caused by the refractive index mismatch and is defined as:

[0042] ψ=d(n2cosθ2-n1cosθ1)(7)

[0043] The present invention also provides a local polarization enhanced nonlinear ionization nano-writing method based on the above system, and the nano-writing method has two processing modes, which are as follows:

[0044] Mode 1: One-dimensional processing mode, specifically nano-hole processing mode, has the following steps:

[0045] Step 1: clean the quartz with ethanol and deionized water for ten minutes respectively under ultrasonic environment, and dry;

[0046] Step 2: Use the local polarization enhanced nonlinear ionization controllable nano-writing system to create a sub-diffraction limit focused beam, focus the beam on the quartz surface, adjust the light output mode of the titanium sapphire femtosecond laser 1 to a single pulse mode, and adjust the incident femtosecond laser pulse energy by adjusting the energy control module 2;

[0047] Step 3: In the single pulse light mode, the strong longitudinal field of the sub-diffraction limit focused beam is used to induce local polarization in the quartz to trigger the redistribution of the electric dipole moment inside the material, thereby enhancing and regulating the nonlinear ionization process of the material, and then processing the nanopore structure on the sample surface;

[0048] Step 4: Soak the quartz processed by femtosecond laser in a 5% hydrofluoric acid solution for chemical etching post-treatment. After soaking for three minutes, take it out and wash it with ethanol and deionized water for ten minutes respectively to remove the splashes and recast layer during the femtosecond laser processing, and obtain a nanopore structure with a clean surface and clear structure.

[0049] Mode 2: Two-dimensional processing mode, specifically nanowire processing mode, has the following steps:

[0050] Step 1: Clean the quartz with ethanol and deionized water for ten minutes respectively in an ultrasonic environment, and then dry it.

[0051] Step 2: Adjust the light emission mode of the titanium sapphire femtosecond laser to a multi-pulse mode, and use the sub-diffraction limit focused beam created by the local polarization enhanced nonlinear ionization controllable nano-writing system to process the nano-hole structure on the quartz;

[0052] Step 3: Using the nanohole processed in step 2 as the initial nanocavity, the subsequently incident focused light beam interferes with the nanocavity and forms a local enhanced field at the edge of the nanocavity. The local enhanced field causes the distribution of the electric dipole moment inside the material to be concentrated at the edge of the nanocavity, resulting in enhanced optical response in the vicinity of the nanocavity. By moving the position of the high-precision translation stage and injecting energy below the threshold, the nanocavity will gradually expand into a nanowire structure on a two-dimensional plane. The formation direction of the nanowire is controlled by controlling the moving direction of the high-precision translation stage 11.

[0053] Step 4: Soak the quartz processed by femtosecond laser in a 5% hydrofluoric acid solution for chemical etching post-treatment. After soaking for three minutes, take it out and wash it with ethanol and deionized water for ten minutes respectively to remove the splashes and recast layer during the femtosecond laser processing to obtain a nanowire structure.

[0054] Beneficial Effects

[0055] 1. The micro-nano processing technology proposed in the present invention does not require a vacuum environment, is simple to operate, does not require cumbersome process steps, has low cost, and has extremely strong stability and wide material applicability, and can achieve ultra-high-precision nano-writing on a variety of hard, brittle and transparent materials.

[0056] 2. The local polarization enhanced nonlinear ionization controllable nano-writing method involved in the present invention has two writing modes, namely one-dimensional (nanohole) and two-dimensional (nanowire) processing modes. The processing accuracy in both modes reaches sub-5nm scale.

[0057] 3. The nano-writing method involved in the present invention triggers the rearrangement of the electric dipole moment inside the material through the local polarization effect induced by the strong longitudinal field of the sub-diffraction limit focused light beam, enhances and regulates the nonlinear ionization process of the material, and thus realizes ultra-high precision processing. Furthermore, the two-dimensional processing mode is realized based on the redistribution of the electric dipole moment inside the material induced by the local enhanced field of the radially polarized light beam. The formation of this local enhanced field does not depend on the polarization direction, but is only related to the scanning direction. This feature enables the two-dimensional processing mode to have a higher degree of processing freedom, and it is possible to create nanowire structures of arbitrary lengths in any direction in a two-dimensional plane. In addition, due to its symmetrical polarization and intensity distribution characteristics, the radially polarized light beam effectively avoids the phenomenon of uneven energy deposition of the light beam during the material removal process, which is conducive to the processing and preparation of high-quality nanostructures.

[0058] 4. The full width at half maximum (FWHM) of the focused spot inside the material created by the focused beam using the local polarization enhanced nonlinear ionization nano-writing system is only 0.28λ, which is far below the Abbe diffraction limit (0.5λ / NA). The energy distribution of the beam is more concentrated, which limits the nonlinear interaction area between the femtosecond laser and the material to a very small spatial range, making the physical processes of the material such as nonlinear ionization, lattice heat transfer, and phase change spatially controllable.

[0059] 5. The nano-engraving method involved in the present invention has the ability to process large areas. Through the "flying dot" method, a large-area nanohole array can be processed on the material. By controlling the speed of the high-precision displacement stage and the repetition frequency of the femtosecond laser pulse, the distance between adjacent points in the nanohole array can be controlled; by controlling the pulse energy, the size of the nanohole can be controlled; by controlling the pulse energy and the speed of the high-precision displacement stage, the characteristic line width of the nanowire can be controlled; by designing the pattern and introducing the high-precision displacement stage, the patterned processing of the nanowire can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Schematic diagram of the optical path of the local polarization enhanced nonlinear ionization nanowriting system;

[0061] Figure 2 It is a schematic diagram of the structure of the annular phase filter and a schematic diagram of the steps generated when the annular phase filter ring structure is prepared using photolithography technology;

[0062] Figure 3 The subdiffraction-limited focused beam created for the local polarization-enhanced nonlinear ionization nanowriting system is focused in the xy plane ( Figure 3 a) and yz plane ( Figure 3 b) intensity distribution;

[0063] Figure 4 Schematic diagram of chemical etching of a sample processed by a focused beam;

[0064] Figure 5 The SEM images of the nanopore structure obtained on quartz in the one-dimensional processing mode of the nonlinear ionization controllable nanowriting method enhanced by local polarization and the SEM images of the nanopore array obtained on quartz in the "flying dot" mode;

[0065] Figure 6 Scanning electron microscope images and deep optical microscope images of the surface morphology of the nanopore structure processed on quartz in the one-dimensional processing mode of the local polarization enhanced nonlinear ionization controllable nanowriting method;

[0066] Figure 7 Schematic diagram of the local enhanced field formed by the focused beam at the edge of the quartz nanohole in the two-dimensional processing mode of the simulated local polarization enhanced nonlinear ionization controllable nanowriting method;

[0067] Figure 8 Scanning electron microscope image of a nanowire structure fabricated on quartz in a two-dimensional processing mode using a nonlinear ionization-controlled nanowriting method enhanced by local polarization;

[0068] Fig. 9 The scanning electron microscope image of the patterned nanowire structure prepared on quartz in the two-dimensional processing mode of the local polarization enhanced nonlinear ionization controllable nanowriting method. The inset is the optical microscope image of the patterned nanowire structure.

[0069] Fig.10 Scanning electron microscope images of nanohole and nanowire structures created on sapphire, YAG, and LiNbO3 using the local polarization enhanced nonlinear ionization controllable nanowriting method. The scale bars in the figures are 200nm.

[0070] Among them, 1-titanium sapphire femtosecond laser, 2-energy control module, 3-radial polarization converter, 4-frequency doubling module, 5-conical lens, 6-first dichroic mirror, 7-plano-convex lens, 8-annular phase filter, 9-focusing objective lens, 10-culture dish, 11-high-precision translation stage, 12-second dichroic mirror, 13-illumination light source, 14-CCD imaging unit. DETAILED DESCRIPTION

[0071] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the technical solution of the present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods.

[0072] The present invention provides a local polarization enhanced nonlinear ionization controllable nano-writing system and method. The system and method use an annular phase filter to phase modulate a tightly focused radially polarized Bessel-Gaussian beam, and shape a traditional Gaussian-distributed femtosecond laser into a sub-diffraction-limited focused beam with a high-purity longitudinal component. The full width at half maximum (FWHM) of the focused beam spot is only 0.28λ, which is much smaller than the optical diffraction limit (Abbe diffraction limit: 0.5λ / NA). The local polarization effect of the strong longitudinal field of the sub-diffraction-limited focused beam is used to induce the redistribution of the electric dipole moment inside the material, thereby significantly enhancing and regulating the nonlinear interaction between the femtosecond laser and the material, thereby achieving high-precision processing. In a two-dimensional processing mode, the initial nanocavity prepared by the focused beam interferes with the subsequent incident beam, resulting in the redistribution of the light field intensity near the nanocavity and the formation of a local enhanced field. The local enhanced field causes the electric dipole moment in the material to be concentrated at the edge of the nanocavity, so that the optical response of the edge region of the nanocavity is enhanced. During this process, by moving the position of the high-precision translation stage and injecting energy below the threshold into the material, the nanocavity will gradually expand into a nanowire structure on the two-dimensional plane.

[0073] refer to Figure 1As shown, the local polarization enhanced nonlinear ionization controllable nano-writing system provided by the present invention includes a titanium sapphire femtosecond laser 1, an energy control module 2, a radial polarization converter 3, a frequency doubling module 4, a conical lens 5, a first dichroic mirror 6, a plano-convex lens 7, an annular phase filter 8, a focusing objective lens 9, a culture dish 10, a high-precision translation stage 11, a second dichroic mirror 12, an illumination light source 13, and a CCD imaging unit 14. The femtosecond laser emitted by the titanium sapphire femtosecond laser 1 is transmitted to the radial polarization converter 3 after the pulse energy is adjusted by the energy control module 2. The radial polarization converter 3 converts the horizontally polarized femtosecond laser into a radially polarized femtosecond laser. The radially polarized femtosecond laser is transmitted to the frequency doubling module 4 and becomes a frequency doubling light with a wavelength of 400nm. The frequency doubling light with a wavelength of 400nm is transmitted to the aconic lens 5. The aconic lens 5 spatially shapes the Gaussian-distributed femtosecond laser into a primary Bessel-Gaussian beam. The primary Bessel-Gaussian beam is reflected by the first dichroic mirror 6 and transmitted to the 4f beam reduction system composed of a plano-convex lens 7 and a focusing lens 9 for beam reduction to obtain a secondary Bessel-Gaussian beam. The annular phase filter 8 placed in front of the focusing lens 9 performs phase modulation on the beam incident in front of the focusing lens 9, and finally obtains a focused beam after the focusing lens 9. The focused beam irradiates the quartz sample fixed in the culture dish 10, and performs nano-writing operation on the quartz sample in an oil immersion environment. The illumination light emitted by the illumination light source 13 passes through the second dichroic mirror 12, the first dichroic mirror 6, the plano-convex lens 7, the annular phase filter 8, and the focusing objective lens 9, and then irradiates the quartz. After being reflected by the quartz surface, it returns along the original path and is reflected by the second dichroic mirror 12 to the CCD imaging unit 14, so as to dynamically monitor the entire processing process. The present invention performs nano-writing on the sample by using a sub-diffraction limit focused beam created by a local polarization enhanced nonlinear ionization controllable nano-writing system.

[0074] The annular phase filter 8 is a 5-ring phase filter, which consists of 5 concentric rings, and the concentric rings are r1=75μm, r2=117μm, r3=214μm, r4=238μm, r5=250μm from the inside to the outside. Figure 2 a). The material of the annular phase filter is fused quartz with a thickness of 500 μm. The concentric circle structure on the annular phase filter is prepared by photolithography, where the area to be etched is the annular area between r1-r2 and r3-r4, which is prepared by three rounds of photolithography. The height of each step d is 106 nm ( Figure 2 b).

[0075] With the support of the above-mentioned local polarization enhanced nonlinear ionization controllable nano-writing system, the present invention also proposes a local polarization enhanced nonlinear ionization controllable nano-writing method, which has two processing modes, one-dimensional and two-dimensional, as follows:

[0076] One-dimensional processing mode: sub-diffraction-limited focused beams are obtained through a local polarization-enhanced nonlinear ionization controllable nano-writing system ( Figure 3 ), the beam has an extremely high purity longitudinal field, and the spot size full width at half maximum (FWHM) inside the material is only 0.28λ. After the focused beam is irradiated on the sample surface, the strong longitudinal field of the beam will induce local polarization of the sample, which will then cause the electric dipole moment inside the material to rearrange, enhance and regulate the nonlinear ionization process of the material, and use this mechanism to process nanopore structures on the sample.

[0077] Two-dimensional processing mode: The nanohole processed by the sub-diffraction-limited focused beam is used as the initial nanocavity. The subsequent incident focused beam interferes with the nanocavity and forms a local enhanced field at the edge of the nanocavity ( Figure 7 ), the local enhanced field enhances and regulates the distribution density of the electric dipole moment at the edge of the nanocavity. By moving the position of the high-precision displacement stage and injecting energy below the threshold into the material, the nanopore will gradually expand in the two-dimensional plane and form a nanowire structure.

[0078] Example 1

[0079] A method for processing quartz nanopores with local polarization enhanced nonlinear ionization controllable preparation, the specific steps are as follows:

[0080] Step 1: Clean the quartz with ethanol and deionized water for ten minutes respectively under ultrasonic environment, dry the sample and place it in a culture dish filled with immersion oil;

[0081] Step 2: Adjust the optical path collimation of the local polarization enhanced nonlinear ionization controllable nano-writing system to create a sub-diffraction limit focused beam. The parameters of the titanium sapphire femtosecond laser 1 used in the experiment are as follows: the femtosecond laser system uses a laser produced by Spectrum Physics, Inc., with a laser center wavelength of 800nm, a pulse width of 50fs, an adjustable repetition frequency of 1kHz, a maximum single pulse energy of 3mJ, a Gaussian light intensity spatial distribution, and linear polarization; the sample to be processed in the experiment is a Z-cut quartz crystal with a size of 10mm×10mm×0.5mm.

[0082] Step 3: Adjust the position of the high-precision translation stage 11 so that the image of the quartz formed in the CCD imaging unit 14 is clearly visible;

[0083] Step 4: Change the light emission mode of the titanium sapphire femtosecond laser 1 to a single pulse light emission mode, adjust the pulse incident energy of the femtosecond laser through the energy control module 2, process the nanopore structure on the quartz sample, and control the aperture of the nanopore by adjusting the incident pulse energy until the aperture meets the requirements;

[0084] Step 5: The femtosecond laser processed quartz sample was cleaned with ethanol and deionized water in an ultrasonic environment for ten minutes respectively, and then placed in a 5% hydrofluoric acid solution for chemical etching after drying. After etching for three minutes at room temperature ( Figure 4 ), take out the quartz and clean it with ethanol and deionized water in an ultrasonic environment for ten minutes respectively, and dry it;

[0085] Step 6: Use a scanning electron microscope to characterize the nanoholes processed by the focused beam, and use an optical microscope to characterize the depth of the nanoholes. Figure 5 a shows the surface morphology of the nanopore structure with a diameter of 4.83 nm. Figure 6 a shows the surface morphology of a nanopore with a diameter of 13.6 nm. Figure 6 b shows the corresponding depth of the nanopore (3.3 μm), and the calculated aspect ratio of the nanopore is 243:1.

[0086] Example 2

[0087] The same as Example 1, except that in step 4, the repetition frequency of the titanium sapphire femtosecond laser 1 is adjusted to 100 Hz, the movement speed of the high-precision translation stage 11 is adjusted to 600 μm / s, the nanopore array structure is processed on the quartz by the "flying dot" method, and the nanopore array processed by the femtosecond laser is characterized by a scanning electron microscope. Figure 5 b shows the surface morphology of the nanohole array, where the distance between two adjacent nanoholes is 6 μm.

[0088] Example 3

[0089] A method for processing quartz nanowires with local polarization enhanced nonlinear ionization controllable preparation, the specific steps are as follows:

[0090] Step 1: Clean the quartz with ethanol and deionized water for ten minutes respectively in an ultrasonic environment, dry the sample and place it in a culture dish filled with immersion oil. The sample to be processed is a Z-cut quartz crystal with a size of 10 mm × 10 mm × 0.5 mm.

[0091] Step 2: Adjust the optical path alignment of the local polarization enhanced nonlinear ionization controllable nano-writing system to create a sub-diffraction limit focused beam, adjust the repetition frequency of the titanium sapphire femtosecond laser 1 to 1 kHz, use the energy control module 2 to adjust the incident laser pulse energy, set the speed of the high-precision translation stage 11 to 100 μm / s, and drive the quartz sample to move in a directional manner through the high-precision translation stage 11;

[0092] Step 3: Use a sub-diffraction-limited focused beam to machine the initial nanocavity on quartz. The subsequent focused beam incident on the edge of the nanocavity forms a Figure 7The local enhanced field shown is processed by moving the position of the high-precision translation stage 11 on quartz to form a single nanowire structure;

[0093] Step 4: The quartz sample processed by the focused beam is cleaned with ethanol and deionized water for ten minutes respectively in an ultrasonic environment, and after drying, it is placed in a 5% hydrofluoric acid solution for chemical etching post-treatment. After etching for three minutes at room temperature, the quartz is taken out and cleaned with ethanol and deionized water for ten minutes respectively in an ultrasonic environment, and dried;

[0094] Step 5: Use a scanning electron microscope to characterize the single nanowire structure prepared by the focused beam. Figure 8 The surface morphology of a single nanowire structure with a line width of 4.86 nm is demonstrated.

[0095] Example 4

[0096] The same as Example 3, except that in step 3, a trajectory is set in the high-precision translation stage 11, a patterned nanowire structure is processed on quartz, and the prepared patterned nanowire structure is characterized using a scanning electron microscope and an optical microscope. Fig. 9 The surface morphology of the patterned nanowire structure is shown. Fig. 9 The inset shows an optical microscope image of the patterned nanowire structure.

[0097] Example 5

[0098] The same as Example 1, except that the processed samples in Example 1 are replaced with sapphire, YAG, and LiNbO3, respectively, and nanopores are prepared on the material surface using a local polarization enhanced nonlinear ionization controllable nano-writing system. The prepared nanopore structure is characterized using a scanning electron microscope. Fig.10 a, 10b, and 10c are scanning electron microscope images of nanopore structures prepared on sapphire, YAG, and LiNbO3, respectively.

[0099] Example 6

[0100] The same as Example 3, except that the processed samples in Example 3 are replaced with sapphire, YAG, and LiNbO3, respectively, and nanowires are prepared on the material surface using a local polarization enhanced nonlinear ionization controllable nanowriting system, and the prepared nanowire structure is characterized using a scanning electron microscope. Fig.10 d, 10e, and 10f are scanning electron microscope images of nanowire structures prepared by focusing the beam on sapphire, YAG, and LiNbO3, respectively.

[0101] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of 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 local polarization enhanced nonlinear ionization nanowriting system, characterized in that: The writing system includes a titanium sapphire femtosecond laser, an energy control module, a radial polarization converter, a frequency doubling module, a conical lens, a first dichroic mirror, a plano-convex lens, an annular phase filter, a focusing objective lens, a culture dish, a high-precision translation stage, a second dichroic mirror, an illumination light source, and a CCD imaging unit; The titanium sapphire femtosecond laser is used to emit femtosecond laser to the energy control module. The femtosecond laser is a horizontally polarized femtosecond laser, the light intensity in space is Gaussian distribution, and the wavelength is 800nm; The energy control module is used to adjust the pulse energy of the femtosecond laser and transmit the femtosecond laser after the pulse energy adjustment to the radial polarization converter; The radial polarization converter is used to receive the femtosecond laser after the pulse energy is adjusted, and convert the received femtosecond laser into radially polarized femtosecond laser and then transmit it to the frequency doubling module; The frequency doubling module is used to receive radially polarized femtosecond laser light, and convert the received radially polarized femtosecond laser light into frequency-doubled light with a wavelength of 400nm and then transmit it to the axicon; The axicon is used to receive the doubled frequency light of 400nm wavelength, and spatially shape the received doubled frequency light of 400nm wavelength into a primary Bessel-Gaussian beam, which is then transmitted to the first dichroic mirror for reflection, the plano-convex lens for transmission, the annular phase filter for filtering, and the focusing lens for focusing to obtain a focused beam, which irradiates the quartz sample fixed in the culture dish and performs nano-writing operation on the quartz sample in an oil immersion environment; The illumination light emitted by the illumination light source passes through the second dichroic mirror, the first dichroic mirror, the plano-convex lens, the annular phase filter, and the focusing objective lens in sequence, and then irradiates the quartz sample. After being reflected by the surface of the quartz sample, it returns along the original path and is reflected by the second dichroic mirror to the CCD imaging unit, so as to dynamically monitor the entire processing process.

2. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The high-precision translation stage can translate at high speed in the XYZ directions, driving the quartz sample to move along a set trajectory.

3. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The titanium sapphire femtosecond laser emits a laser with a central wavelength of 800 nm, a pulse width of 50 fs, an adjustable repetition frequency of 1 kHz, a maximum energy of 3 mJ for a single pulse, a Gaussian light intensity spatial distribution, and horizontal linear polarization.

4. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The energy control module is composed of a half-wave plate and a polarizing plate. The pulse energy of the incident femtosecond laser is adjusted by rotating the half-wave plate or the polarizing plate and changing the relative angle between the half-wave plate and the polarizing plate.

5. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The radial polarization converter is used for converting linearly polarized femtosecond laser into radially polarized femtosecond laser.

6. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The frequency doubling module is composed of a BBO crystal and a filter, and is used for doubling the frequency of 800nm ​​femtosecond laser to 400nm femtosecond laser.

7. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The cone base angle of the aconic lens is 1°, the focal length of the plano-convex lens 7 is f=175 mm, and the focusing objective lens is a 100x oil immersion objective lens with NA=1.

4.

8. The local polarization enhanced nonlinear ionization nanowriting system according to claim 1, characterized in that: The annular phase filter is a 5-ring phase filter, which is composed of 5 concentric rings. The radii of the rings from inside to outside are r1=75μm, r2=117μm, r3=214μm, r4=238μm, and r5=250μm respectively. The material of the annular phase filter is fused quartz with a thickness of 500μm. The concentric circle structure is prepared by a photolithography process, wherein the area to be etched is the annular area between r1-r2 and r3-r4, which is prepared by three rounds of photolithography process, and the height of each step d is 106nm.

9. A local polarization enhanced nonlinear ionization nanowriting method, characterized in that: Step 1: Clean the quartz sample with ethanol and deionized water respectively under ultrasonic environment and dry it; Step 2: Use the nano-writing system described in claim 1 to create a sub-diffraction limit focused beam, focus the beam on the quartz surface, adjust the light output mode of the titanium sapphire femtosecond laser to a single pulse mode, and adjust the energy of the incident femtosecond laser pulse by adjusting the energy control module; Step 3, in a single pulse light emission mode, using the strong longitudinal field of the created sub-diffraction-limited focused beam to process a nano-hole structure on the quartz surface; Step 4: chemically etch and clean the quartz processed by femtosecond laser to obtain a nanopore structure.

10. A local polarization enhanced nonlinear ionization nanowriting method, characterized in that: Step 1: clean the quartz with ethanol and deionized water respectively in an ultrasonic environment and dry it. Step 2: adjusting the light emission mode of the titanium sapphire femtosecond laser to a multi-pulse mode, and using the writing system described in claim 1 to create a sub-diffraction limit focused beam to process a nanopore structure on quartz; Step 3: Using the nanohole processed in step 2 as the initial nanocavity, the nanocavity is gradually expanded into a nanowire structure on a two-dimensional plane by moving the position of the high-precision translation stage and injecting energy below the threshold, and the formation direction of the nanowire is controlled by controlling the moving direction of the high-precision translation stage; Step 4: chemically etch and clean the quartz processed by femtosecond laser to obtain a nanowire structure.

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