Patent ID: 11914165
Assignee: JILIN UNIVERSITY
Field: Machine tools (Mechanical engineering)
Classification: CPC G  B  H | IPC B  G  H

Claim 0:
1. A method using femtosecond laser for nano precision preparation, comprising the following steps:
(1) leveling of a sample;
comprising: firstly fixing the sample to be processed to a motion stage with an adjustment device; then turning on an optical shutter in a processing optical path, focusing the laser by an objective lens, and focusing the femtosecond laser on the surface of the sample to be processed by adjusting the height of the motion stage; then controlling the motion stage to move horizontally along the long axis of a sample sheet by 2 cm, adjusting the adjustment device of the motion stage, such that when the motion stage moves, the laser focus is always focused on the interface between the surface of the sample and the air without relative movement and the morphology of a light spot in a processing real-time monitoring device remains unchanged; controlling the motion stage to move horizontally along the short axis of the sample piece by 2 cm, and adjusting the adjustment device of the motion stage, such that when the motion stage moves, the focus of the laser is always focused on the interface without relative movement, and the morphology of the light spot in the processing real-time monitoring device remains unchanged, and at this time, a sample table to be processed has been leveled;
(2) generation of an initial seed structure;
comprising: firstly the femtosecond laser emitted from the laser device is subjected to light spot beam expansion by a beam expander consisting of a concave lens L1 and a first convex lens L2, then passes through an energy modulation system consisting of a first half-wave plate H1 and a first Glan prism P1, and afterwards passes through a first total-reflection mirror M1 and a polarization control system consisting of a second Glan prism P1 and a second half-wave plate H2 sequentially, and a light beam is enabled to vertically enter a galvanometer; then the light beam reflected by the galvanometer passes a 4f system consisting of a second convex lens L3 and a third convex lens L4, and a light spot entering the galvanometer is projected onto a front of a processing objective lens in a ratio of 1:1, and finally is focused on the surface of the sample to be processed; and the single pulse energy of the laser is selected to be within the range of 100% and 110% of a material damage threshold Fth, and the exposure time is accurately controlled, such that two pulses are deposited on the surface of the sample to complete the preparation of the seed structure;
(3) relaxation and stabilization of the seed structure;
comprising: after completing the generation of the initial seed structure according to the step (2), rotating the angle of the first half-wave plate H1 relative to the first Glan prism P1 in the energy modulation system, such that the energy of subsequent pulses from a third pulse is reduced to 60%-110% of the material damage threshold Fth so as to homogenize the near-field energy distribution near the structure; and then, keeping the pulse energy at this level, and continuously depositing 4 to 16 pulses on the seed structure by controlling the exposure time, such that the morphology of the seed structure is continuously relaxed in the process of interacting with the laser and finally is stabilized, that is, the morphology of the seed does not change any more; and
(4) laser direct writing of high-precision two-dimensional patterns;
comprising: after completing the relaxation and stabilization of the seed structure according to the step (3), rotating the second half-wave plate H2 in the polarization control system to adjust the polarization of the laser entering the objective lens, thereby changing the direction of the near-field enhancement generated at the seed structure; controlling the movement of a focused light spot and the rotation of the laser polarization jointly by a computer to enable the pulse polarization to be always and locally perpendicular to a pre-designed geometric structure, such that the dynamic near-field enhancement can be realized, and then the laser direct writing of the far-field high resolution of any given two-dimensional pattern is realized; at this time, the movement of the light spot of the laser and the trajectory of the pattern coincide; meanwhile, adjusting the pulse energy of the laser to be within the range of 60% to 110% of the damage threshold Fth, adjusting a relative position of the focused light spot and an ablation front by adjusting the scanning speed of the light spot of the laser to change within the range of 2 μm/s to 50 μm/s, and then adjusting the width of a near-field light spot to achieve different direct writing linewidths from 18 nm to 200 nm; and
(5) laser printing of high-precision periodic nano grooves:
comprising: reducing the energy of the laser pulse to be within the range of 60% to 110% of the material damage threshold, preferably within the range of 60% to 100%, and enabling the light spot to perform grating scanning in a periodic direction of a seed array, meanwhile constantly changing the polarization of the laser pulse by using the polarization control system according to the morphology of the preset nano grooves, such that the laser polarization at each scanning is exactly perpendicular to tangent lines of the preset nano grooves, and thus, large-area periodic nano groove structures can be quickly prepared.