阅读说明：本技术 一种利用飞秒激光加工金属氧化物纳米光栅的方法及系统 (Method and system for processing metal oxide nano grating by femtosecond laser ) 是由 姜澜 闫剑锋 乔明 于 2021-08-17 设计创作，主要内容包括：本发明属于飞秒激光加工技术领域,具体而言,涉及一种利用飞秒激光加工金属氧化物纳米光栅的方法及系统。本发明利用高重频飞秒激光作用下金属的局部氧化实现金属氧化物纳米光栅的单线直写,依赖于已生成金属氧化物纳米线对后续光场的局域化效应实现相邻纳米线间隙小于光的衍射极限,进一步实现周期小于衍射极限的金属氧化物纳米光栅加工。本方法确定了加工金属氧化物纳米光栅所用飞秒激光的波长、重复频率、脉冲宽度、激光脉冲能量通量以及扫描速度和扫描间隙的范围。本发明方法与现有的加工方法相比可实现超衍射极限、光栅周期在纳米级范围内的灵活可调的纳米光栅加工。(The invention belongs to the technical field of femtosecond laser processing, and particularly relates to a method and a system for processing a metal oxide nano grating by using femtosecond laser. The invention realizes the single-line direct writing of the metal oxide nano-grating by utilizing the local oxidation of metal under the action of high repetition frequency femtosecond laser, realizes the gap between adjacent nanowires to be smaller than the diffraction limit of light by depending on the localization effect of the generated metal oxide nano-grating on a subsequent light field, and further realizes the processing of the metal oxide nano-grating with the period smaller than the diffraction limit. The method determines the wavelength, repetition frequency, pulse width, laser pulse energy flux, scanning speed and scanning gap range of femtosecond laser used for processing the metal oxide nanometer grating. Compared with the existing processing method, the method can realize the flexible and adjustable processing of the nano-grating with super diffraction limit and grating period in the nano-scale range.)

1. A metal oxide nano grating is characterized in that the nano grating is of a convex structure.

2. A system for processing a metal oxide nanograting as in claim 1, comprising:

an illumination system for illuminating the machining location;

an imaging system for imaging the process onto a computer display;

the processing light path is used for focusing the femtosecond laser pulse on the surface of the metal sheet to be processed;

the processing light path and the illumination system are overlapped after passing through the ultrafast laser reflector, and the imaging system and the illumination system are overlapped between the metal sheet to be processed and the semi-transparent semi-reflective mirror;

the control system is used for controlling the movement of the two-dimensional scanning galvanometer in the processing light path in the processing process to realize the processing of the nano grating; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through data lines, and the external control card and the precise electric control translation table are connected with a computer through data lines to form a control system.

3. The system for processing the metal oxide nano-gratings according to claim 2, wherein in the illumination system, illumination light emitted by the illumination light source sequentially passes through the half-transmitting mirror, the ultrafast laser mirror, the two-dimensional scanning galvanometer and the high power objective lens and then irradiates the surface of the metal sheet to be processed to form the illumination system.

4. The system for processing metal oxide nano-gratings according to claim 2, wherein in the imaging system, the illumination light reflected by the surface of the metal sheet to be processed passes through the high power objective lens, the two-dimensional scanning galvanometer, the ultrafast laser reflector, the half mirror and the imaging lens in sequence, then is irradiated onto the camera, and finally is imaged onto a computer display through the data line to form the imaging system.

5. The system for processing a metal oxide nano-grating according to claim 2, wherein in the processing optical path, the femtosecond laser pulse emitted from the high repetition frequency femtosecond laser sequentially passes through the neutral density attenuator, the electrically controlled shutter, the ultrafast laser reflector, the two-dimensional scanning galvanometer and the high power objective lens and then is focused on the surface of the metal sheet to be processed to form the processing optical path.

6. A method of fabricating a metal oxide nanograting device according to claim 1, comprising:

the processing system of the metal oxide nanometer grating is built according to claim 1, in the system, illumination light emitted by an illumination light source sequentially passes through a semi-transparent semi-reflecting mirror, an ultrafast laser reflecting mirror, a two-dimensional scanning galvanometer and a high-power objective lens and then irradiates the surface of a metal sheet to be processed to form an illumination system; illuminating light reflected by the surface of the metal sheet to be processed sequentially passes through the high-power objective lens, the two-dimensional scanning galvanometer, the ultrafast laser reflector, the semi-transparent semi-reflecting mirror and the imaging lens, then is irradiated onto the camera, and finally is imaged on a display of a computer through a data line to form an imaging system; the femtosecond laser pulse emitted by the high-repetition-frequency femtosecond laser sequentially passes through a neutral density attenuation sheet, an electric control shutter, an ultrafast laser reflector, a two-dimensional scanning galvanometer and a high-power objective lens and then is focused on the surface of a metal sheet to be processed to form a processing light path; the processing light path and the illumination system are overlapped after passing through the ultrafast laser reflector, and the imaging system and the illumination system are overlapped between the metal sheet to be processed and the semi-transparent semi-reflective mirror; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through a data line, and the external control card and the precise electric control translation table are connected with a computer through the data line to form a control system;

mounting a metal sheet to be processed on a precise electric control translation table of the control system;

turning on an illumination light source of the illumination system, so that illumination light emitted by the illumination light source sequentially passes through the illumination system consisting of a semi-transparent and semi-reflective mirror, an ultrafast laser reflector, a two-dimensional scanning galvanometer and a high power objective lens to be irradiated on the surface of the metal sheet to be processed;

adjusting the height of a precise electric control translation table of the control system, and utilizing the imaging system to enable the illumination light reflected by the surface of the metal sheet to be processed to sequentially pass through a high power objective lens, a two-dimensional scanning galvanometer, an ultrafast laser reflector, a semi-transmitting semi-reflecting mirror and an imaging lens and then irradiate a camera, and finally the image is imaged on a display of a computer through a data line, the image is clear, and focusing is realized;

the high repetition frequency femtosecond laser is started, femtosecond laser pulses emitted by the high repetition frequency femtosecond laser sequentially pass through the neutral density attenuation sheet, the electric control shutter, the ultrafast laser reflector, the two-dimensional scanning galvanometer and the high-power objective lens and then are focused on the surface of a metal sheet to be processed, the control system controls the two-dimensional scanning galvanometer to move, line-by-line scanning of focusing light spots is achieved, and therefore machining of the nano grating is achieved.

7. The method as claimed in claim 6, wherein the femtosecond laser is linearly polarized light.

8. The method of claim 6, wherein the femtosecond laser has a wavelength of 800nm to 1064nm, a repetition frequency of 25kHz to 80MHz, and a pulse width of 50fs to 350 fs.

9. The method of claim 6, wherein the femtosecond laser has a laser pulse energy flux of 0.25-0.5J/cm²。

10. The method for processing the metal oxide nano-grating according to claim 6, wherein the line-by-line scanning of the focused light spot is as follows: the motion direction of the focusing light spot is consistent with the polarization direction of the femtosecond laser, the scanning speed of the focusing light spot is 0.1-10 mm/s, and the scanning gap l is 300 nm-1 μm.

Technical Field

The invention belongs to the technical field of femtosecond laser processing, and particularly relates to a method and a system for processing a metal oxide nano grating by using femtosecond laser.

Background

The grating is the core device of many precision optical instruments and is composed of a large number of parallel equal-width equidistant slits (scribed lines). Is commonly used to implement a dispersive splitting function. In recent years, the role of gratings is no longer limited to the field of spectroscopy, and many fields such as astronomy, quantum optics, optical communication and the like require the participation of gratings. These new applications also place higher demands on the precision and flexibility of the gratings, and in particular the processing of nano-gratings becomes more and more important. The traditional nanometer grating processing method comprises mechanical scribing, holographic lithography and the like, but the method has the defects of complex process, difficult control and the like.

Disclosure of Invention

The invention aims to solve the technical problems to at least a certain extent, and based on the discovery and the recognition of some facts and problems of the inventor, the femtosecond laser is a micro-nano processing method with wide application prospect, and can directly process the surfaces of almost all materials with high precision. The grating structure can be obtained by using a femtosecond laser direct ablation processing technology, but two adjacent lines are easy to overlap due to the diffraction limit of light, so that the grating structure cannot be used for processing the nano grating.

The invention aims to provide a method and a system for processing a metal oxide nano grating by using femtosecond laser, which realize single-line direct writing of the metal oxide nano grating by using local oxidation of metal in air under the action of the femtosecond laser. And then processing parallel metal oxide nanostructures beside the generated metal oxide nanostructures, wherein the gaps between the parallel metal oxide nanostructures can be smaller than the diffraction limit of light depending on the localization effect of the generated metal oxide nanostructures on the subsequent light field, and further processing of the metal oxide nano-grating with the period smaller than the diffraction limit of light is realized.

In a first aspect of the present invention, a metal oxide nano-grating is provided, wherein the nano-grating has a convex structure.

In a second aspect of the present invention, a system for processing a metal oxide nano-grating is provided, which includes:

an illumination system for illuminating the machining location;

an imaging system for imaging the process onto a computer display;

the processing light path is used for focusing the femtosecond laser pulse on the surface of the metal sheet to be processed;

the processing light path and the illumination system are overlapped after passing through the ultrafast laser reflector, and the imaging system and the illumination system are overlapped between the metal sheet to be processed and the semi-transparent semi-reflective mirror; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through a data line;

the control system is used for controlling the movement of the two-dimensional scanning galvanometer in the processing light path in the processing process to realize the processing of the nano grating; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through data lines, and the external control card and the precise electric control translation table are connected with a computer through data lines to form a control system.

The femtosecond laser is a micro-nano processing method with wide application prospect, and can directly carry out high-precision processing on the surfaces of almost all materials. The system for processing the metal oxide nano-grating by using the femtosecond laser can realize the precise adjustment of laser energy flux by using the neutral density attenuation sheet, and can realize the rapid and precise movement of a focusing light spot while realizing the high focusing of the laser by using the combination of the two-dimensional scanning galvanometer and the high-power objective lens. In addition, the system has the functions of illumination and imaging, and can realize the real-time monitoring of the processing process.

In one embodiment, in the illumination system, illumination light emitted by an illumination light source sequentially passes through a half-transmitting mirror, a ultrafast laser mirror, a two-dimensional scanning galvanometer and a high-power objective lens and then irradiates the surface of a metal sheet to be processed to form the illumination system.

In one embodiment, in the imaging system, the illumination light reflected by the surface of the metal sheet to be processed sequentially passes through the high power objective lens, the two-dimensional scanning galvanometer, the ultrafast laser reflector, the half-mirror and the imaging lens, then is irradiated onto the camera, and finally is imaged on a display of a computer through a data line, so as to form the imaging system.

In one embodiment, in the processing optical path, the femtosecond laser pulses emitted by the high repetition frequency femtosecond laser sequentially pass through the neutral density attenuation sheet, the electronic control shutter, the ultrafast laser reflector, the two-dimensional scanning galvanometer and the high power objective lens and then are focused on the surface of the metal sheet to be processed, so as to form the processing optical path.

In a third aspect of the present invention, a method for processing a metal oxide nanograting is provided, which includes:

(1) the processing system of the metal oxide nanometer grating is built according to claim 1, in the system, illumination light emitted by an illumination light source sequentially passes through a semi-transparent semi-reflecting mirror, an ultrafast laser reflecting mirror, a two-dimensional scanning galvanometer and a high-power objective lens and then irradiates the surface of a metal sheet to be processed to form an illumination system; illuminating light reflected by the surface of the metal sheet to be processed sequentially passes through the high-power objective lens, the two-dimensional scanning galvanometer, the ultrafast laser reflector, the semi-transparent semi-reflecting mirror and the imaging lens, then is irradiated onto the camera, and finally is imaged on a display of a computer through a data line to form an imaging system; the femtosecond laser pulse emitted by the high-repetition-frequency femtosecond laser sequentially passes through a neutral density attenuation sheet, an electric control shutter, an ultrafast laser reflector, a two-dimensional scanning galvanometer and a high-power objective lens and then is focused on the surface of a metal sheet to be processed to form a processing light path; the processing light path and the illumination system are overlapped after passing through the ultrafast laser reflector, and the imaging system and the illumination system are overlapped between the metal sheet to be processed and the semi-transparent semi-reflective mirror; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through a data line, and the external control card and the precise electric control translation table are connected with a computer through the data line to form a control system;

(2) mounting a metal sheet to be processed on a precise electric control translation table of the control system;

(3) turning on an illumination light source of the illumination system, so that illumination light emitted by the illumination light source sequentially passes through the illumination system consisting of a semi-transparent and semi-reflective mirror, an ultrafast laser reflector, a two-dimensional scanning galvanometer and a high power objective lens to be irradiated on the surface of the metal sheet to be processed;

(4) adjusting the height of a precise electric control translation table of the control system, and utilizing the imaging system to enable the illumination light reflected by the surface of the metal sheet to be processed to sequentially pass through a high power objective lens, a two-dimensional scanning galvanometer, an ultrafast laser reflector, a semi-transmitting semi-reflecting mirror and an imaging lens and then irradiate a camera, and finally the image is imaged on a display of a computer through a data line, the image is clear, and focusing is realized;

(5) the high repetition frequency femtosecond laser is started, femtosecond laser pulses emitted by the high repetition frequency femtosecond laser sequentially pass through the neutral density attenuation sheet, the electric control shutter, the ultrafast laser reflector, the two-dimensional scanning galvanometer and the high-power objective lens and then are focused on the surface of a metal sheet to be processed, the control system controls the two-dimensional scanning galvanometer to move, line-by-line scanning of focusing light spots is achieved, and therefore machining of the nano grating is achieved.

The grating structure can be obtained by using a femtosecond laser direct ablation processing technology, but two adjacent lines of the processed grating are easy to overlap due to the diffraction limit of light. The method for processing the metal oxide nano grating by utilizing the femtosecond laser realizes the processing of the nano grating with the grating period smaller than the laser diffraction limit by depending on the localization effect of the generated metal oxide nano structure on a subsequent light field, and can also realize the flexible adjustment of the grating period in a nano-scale range compared with the traditional interference method and the laser induced periodic surface structure method.

In some embodiments, the femtosecond laser is linearly polarized light.

In some embodiments, the femtosecond laser has a wavelength of 800nm to 1064nm, a repetition frequency of 25kHz to 80MHz, and a pulse width of 50fs to 350 fs.

In some embodiments, the femtosecond laser has a laser pulse energy flux of 0.25-0.5J/cm²。

In some embodiments, the line-by-line scanning of the focused spots is: the motion direction of the focusing light spot is consistent with the polarization direction of the femtosecond laser, the scanning speed of the focusing light spot is 0.1-10 mm/s, and the scanning gap l is 300 nm-1 μm.

According to the embodiment of the invention, the metal oxide nano grating obtained by femtosecond laser processing has the following advantages:

1. femtosecond laser is a micro-nano processing method with wide application prospect, and can directly process the surfaces of all materials with high precision almost, but because of the diffraction limit of light, two adjacent lines are easy to overlap, so that the femtosecond laser cannot be used for processing the nano grating. The method provided by the invention realizes the processing of the nano grating with the grating period less than the laser diffraction limit by depending on the localization effect of the generated metal oxide nano structure on the subsequent light field.

2. Compared with the traditional interference method and the laser-induced periodic surface structure method, the method can realize the flexible adjustment of the grating period in the nano-scale range.

3. The invention provides a special system for processing metal oxide nano-gratings on metal, which can realize flexible and rapid preparation of the metal oxide nano-gratings.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

Fig. 1 is a schematic diagram of a system for processing a metal oxide nanograting using a femtosecond laser according to an embodiment of the present invention.

In the figure 1, 1 is a high repetition frequency femtosecond laser, 2 is a neutral density attenuation sheet, 3 is an electric control shutter, 4 is an ultrafast laser reflector, 5 is a two-dimensional scanning galvanometer, 6 is a high power objective lens, 7 is a metal sheet to be processed, 8 is a precise electric control translation table, 9 is an external control card, 10 is a computer, 11 is a half-lens, 12 is an illumination light source, 13 is an imaging lens, and 14 is a camera.

Fig. 2 is a schematic view of a metal oxide nanograting processed in example 1 of the invention and a process for processing the same.

In FIG. 2, 15 is the femtosecond laser pulse, 16 is the laser spot scanning path, 17-21 are the metal oxide nano-gratings with different gaps, l represents the laser scanning gap, and Λ represents the grating period.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

One embodiment of the invention provides a metal oxide nano-grating, which is a convex structure.

One embodiment of the present invention provides a system for processing a metal oxide nanograting, a schematic diagram of which is shown in fig. 1, including:

an illumination system for illuminating the machining location; illuminating light emitted by an illuminating light source 12 sequentially passes through a semi-transparent semi-reflecting mirror 11, an ultrafast laser reflecting mirror 4, a two-dimensional scanning vibrating mirror 5 and a high-power objective lens 6 and then irradiates the surface of a metal sheet 7 to be processed to form an illuminating system;

an imaging system for imaging the process onto a computer display; the illumination light reflected by the surface of the metal sheet 7 to be processed sequentially passes through the high power objective 6, the two-dimensional scanning galvanometer 5, the ultrafast laser reflector 4, the semi-transparent semi-reflecting mirror 11 and the imaging lens 13 and then irradiates the camera 14, and finally is imaged on a display of a computer through a data line to form an imaging system;

the processing light path is used for focusing the femtosecond laser pulse on the surface of the metal sheet to be processed; the femtosecond laser pulse emitted by the high repetition frequency femtosecond laser 1 sequentially passes through a neutral density attenuation sheet 2, an electric control shutter 3, an ultrafast laser reflector 4, a two-dimensional scanning galvanometer 5 and a high-power objective lens 6 and then is focused on the surface of a metal sheet 7 to be processed to form a processing light path;

the processing light path and the illumination system are overlapped after passing through the ultrafast laser reflector, and the imaging system and the illumination system are overlapped between the metal sheet to be processed and the semi-transparent semi-reflective mirror; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through a data line;

the control system is used for controlling the movement of the two-dimensional scanning galvanometer in the processing light path in the processing process to realize the processing of the nano grating; the two-dimensional scanning galvanometer and the electric control shutter are connected with an external control card through data lines, and the external control card and the precise electric control translation table are connected with a computer through data lines to form a control system.

The femtosecond laser is a micro-nano processing method with wide application prospect, and can directly carry out high-precision processing on the surfaces of almost all materials. The system for processing the metal oxide nano-grating by using the femtosecond laser can realize the precise adjustment of laser energy flux by using the neutral density attenuation sheet, and can realize the rapid and precise movement of a focusing light spot while realizing the high focusing of the laser by using the combination of the two-dimensional scanning galvanometer and the high-power objective lens. In addition, the system has the functions of illumination and imaging, and can realize the real-time monitoring of the processing process.

One embodiment of the present invention provides a method for processing a metal oxide nanograting, which comprises:

firstly, a processing system as shown in fig. 1 is constructed, and the processing system comprises a high repetition frequency femtosecond laser 1, a neutral density attenuation sheet 2, an electric control shutter 3, an ultrafast laser reflector 4, a two-dimensional scanning galvanometer 5, a high-power objective lens 6, a metal sheet 7 to be processed, a precise electric control translation table 8, an external control card 9, a computer 10, a half-transmitting and half-reflecting mirror 11, an illumination light source 12, an imaging lens 13 and a camera 14. The metal sheet 7 to be processed is arranged on the precise electric control translation table 8; the illumination light emitted by the illumination light source 12 sequentially passes through the semi-transparent semi-reflecting mirror 11, the ultrafast laser reflecting mirror 4, the two-dimensional scanning vibrating mirror 5 and the high power objective lens 6 and then irradiates the surface of the metal sheet 7 to be processed to form an illumination system; the illumination light reflected by the surface of the metal sheet 7 to be processed sequentially passes through the high power objective 6, the two-dimensional scanning galvanometer 5, the ultrafast laser reflector 4, the semi-transparent semi-reflecting mirror 11 and the imaging lens 13 and then irradiates the camera 14, and finally is imaged on a display of a computer 10 through a data line to form an imaging system; the femtosecond laser pulse emitted by the high repetition frequency femtosecond laser 1 sequentially passes through a neutral density attenuation sheet 2, an electric control shutter 3, an ultrafast laser reflector 4, a two-dimensional scanning galvanometer 5 and a high-power objective lens 6 and then is focused on the surface of a metal sheet 7 to be processed to form a processing light path; the processing light path and the lighting system are superposed after passing through the ultrafast laser reflector 4, and the imaging system and the lighting system are superposed between the metal sheet 7 to be processed and the semi-transparent semi-reflective mirror 11; the two-dimensional scanning galvanometer 5 and the electric control shutter 3 are connected with an external control card 9 through data lines, and the external control card 9 and the precise electric control translation table 8 are connected with a computer 10 through data lines to form a control system.

The following operations are performed on the system shown in fig. 1:

(1) installation of the sample:

(1-1) mounting a metal sheet 7 to be processed on a precise electric control translation table 8;

(1-2) turning on an illumination light source 12, so that illumination light emitted by the illumination light source 12 irradiates the surface of a metal sheet 7 to be processed through an illumination system consisting of a semi-transparent semi-reflecting mirror 11, an ultrafast laser reflecting mirror 4, a two-dimensional scanning galvanometer 5 and a high-power objective lens 6, and by adjusting the height of a precise electrically controlled translation stage 8, the illumination light reflected by the surface of the metal sheet 7 to be processed irradiates a camera 14 after passing through the high-power objective lens 6, the two-dimensional scanning galvanometer 5, the ultrafast laser reflecting mirror 4, the semi-transparent semi-reflecting mirror 11 and an imaging lens 13 in sequence, and is finally imaged on a display of a computer 10 through a data line, and the image is clear, so that focusing is realized;

(2) processing the metal oxide nano grating:

(2-1) opening the high repetition frequency femtosecond laser 1, wherein femtosecond laser pulses emitted by the high repetition frequency femtosecond laser 1 sequentially pass through a neutral density attenuation sheet 2, an electric control shutter 3, an ultrafast laser reflector 4, a two-dimensional scanning galvanometer 5 and a high-power objective lens 6 and then are focused on the surface of a metal sheet 7 to be processed; the wavelength of the high repetition frequency femtosecond laser is 800 nm-1064 nm, and the repetition frequency is highThe complex frequency is 25 kHz-80 MHz, the pulse width is 50 fs-350 fs, and the laser is linearly polarized light; the neutral density attenuation sheet 2 is adjusted to ensure that the energy flux of the laser pulse is 0.25-0.5J/cm²；

(2-2) controlling the two-dimensional scanning galvanometer 5 by the control system to carry out progressive scanning processing, wherein the motion direction of a focusing light spot is consistent with the polarization direction of laser during scanning, the scanning speed is 0.1-10 mm/s, and the range of a scanning gap l is 300-1 mu m, so that the processing of the metal oxide nano grating is realized, and the metal oxide nano grating is of a convex structure.

The invention realizes the single-line direct writing of the metal oxide nano-grating by utilizing the local oxidation of metal under the action of high repetition frequency femtosecond laser, realizes the gap between adjacent nanowires to be smaller than the diffraction limit of light by depending on the localization effect of the generated metal oxide nano-grating on a subsequent light field, and further realizes the processing of the metal oxide nano-grating with the period smaller than the diffraction limit. The method determines the wavelength, repetition frequency, pulse width, laser pulse energy flux, scanning speed and scanning gap range of femtosecond laser used for processing the metal oxide nanometer grating. Compared with the existing processing method, the method can realize the flexible and adjustable processing of the nano-grating with super diffraction limit and grating period in the nano-scale range.

The grating structure can be obtained by using a femtosecond laser direct ablation processing technology, but two adjacent lines of the processed grating are easy to overlap due to the diffraction limit of light. The method for processing the metal oxide nano grating by utilizing the femtosecond laser realizes the processing of the nano grating with the grating period smaller than the laser diffraction limit by depending on the localization effect of the generated metal oxide nano structure on a subsequent light field, and can also realize the flexible adjustment of the grating period in a nano-scale range compared with the traditional interference method and the laser induced periodic surface structure method.

The invention is further described with reference to the following figures and examples.

Example 1

In this embodiment, the metal sheet 7 is specifically a metal titanium sheet, and the obtained metal oxide nano-grating is specifically a titanium dioxide nano-grating.

Firstly, a system for processing the metal oxide nano grating by using femtosecond laser as shown in figure 1 is built;

the following operations are performed on the system shown in fig. 1:

(1) installation of the sample:

(1-1) mounting a metal titanium sheet 7 to be processed on a precise electric control translation table 8;

(1-2) turning on an illumination light source 12, so that illumination light emitted by the illumination light source 12 irradiates the surface of a metal titanium sheet 7 to be processed through an illumination system consisting of a semi-transparent semi-reflecting mirror 11, an ultrafast laser reflecting mirror 4, a two-dimensional scanning vibrating mirror 5 and a high-power objective lens 6, and by adjusting the height of a precise electrically controlled translation stage 8, the illumination light reflected by the surface of the metal titanium sheet 7 to be processed sequentially passes through the high-power objective lens 6, the two-dimensional scanning vibrating mirror 5, the ultrafast laser reflecting mirror 4, the semi-transparent semi-reflecting mirror 11 and an imaging lens 13 and irradiates a camera 14, and finally is imaged on a display of a computer 10 through a data line, and the image is clear, so that focusing is realized;

(2) processing the titanium dioxide nano grating:

(2-1) opening the high repetition frequency femtosecond laser 1, and focusing the femtosecond laser pulse 15 emitted by the high repetition frequency femtosecond laser 1 on the surface of a metal titanium sheet 7 to be processed after sequentially passing through a neutral density attenuation sheet 2, an electric control shutter 3, an ultrafast laser reflector 4, a two-dimensional scanning galvanometer 5 and a high-power objective lens 6; the high repetition frequency femtosecond laser adopted in the embodiment has the wavelength of 800nm, the repetition frequency of 80MHz and the pulse width of 50fs, and the laser is linearly polarized light; the energy flux of the laser pulse is 0.3J/cm by adjusting the neutral density attenuation sheet 2²；

And (2-2) controlling the two-dimensional scanning galvanometer 5 by the control system to carry out progressive scanning processing, wherein the motion direction of a focusing light spot is consistent with the polarization direction of laser during scanning, and the scanning speed is 5 mm/s. The scanning gaps l in the regions 17-21 are respectively set to be 300nm, 500nm, 900nm, 800nm and 700nm, so that the processing of the titanium dioxide nanometer grating with different grating periods lambada is realized, the grating period lambada is consistent with the set scanning gaps l, and the titanium dioxide nanometer grating is of a convex structure.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.