A fused silica polishing method based on metal vaporization reaction force

Abstract

This invention belongs to the field of optical component polishing, specifically relating to a polishing method for fused silica based on the reaction force of metal vaporization. It includes the following steps: Step (1): Depositing a 100-300 μm thick nickel film on the surface of a fused silica sample; Step (2): Irradiating the nickel film with a high-energy-density laser, adjusting the laser parameters to cause the nickel to ablate and evaporate. The downward force generated on the fused silica surface by the ablation and evaporation of the nickel achieves polishing of the fused silica surface. This invention utilizes the reaction force generated during the ablation and vaporization of the nickel film to polish the fused silica surface, achieving efficient, high-precision, and defect-free polishing.

Description

Technical Field

[0001] This invention belongs to the field of optical component polishing, and specifically relates to a fused silica polishing method based on the metal vaporization reaction force. Background Technology

[0002] Fused silica (amorphous SiO2) has stable chemical properties, a low coefficient of thermal expansion, high hardness, and good light transmittance. In inertial confinement fusion, fused silica has become an indispensable optical component in laser ignition devices due to its excellent optical and mechanical properties.

[0003] Fused silica is a typical hard and brittle material. During traditional mechanical grinding and polishing, numerous structural defects, such as microcracks, pits, and scratches, inevitably occur on the surface and subsurface of fused silica. Under high-power laser irradiation, these surface and subsurface defects cause the laser-induced damage threshold of optical components to be much lower than their intrinsic value, resulting in a significant reduction in their optical performance and service life. There is an urgent need to develop a non-contact, non-destructive polishing method for fused silica. High-energy-density laser polishing, as an advanced manufacturing technology, is widely used in the processing of fused silica optical devices. Compared to traditional mechanical polishing, the high-energy-density laser polishing process reduces surface defects through localized high-temperature melting and removes deposits from the fused silica surface, thereby improving the surface quality and damage threshold of the fused silica.

[0004] During the laser polishing process of fused silica, the localized and continuous heating of the laser causes large residual stress on the surface of the fused silica. When the residual stress reaches the fracture limit of the fused silica material, cracks will appear on its surface. Summary of the Invention

[0005] The purpose of this invention is to provide a polishing method for fused silica based on the reaction force of metal vaporization, which reduces surface thermal stress and suppresses the generation of surface cracks in fused silica. This method first deposits a 100-300 μm nickel film on the surface of the fused silica, and then performs high-energy-density laser polishing. The reaction force generated during the ablation and vaporization of the nickel film is used to polish the fused silica surface, achieving efficient, high-precision, and defect-free polishing.

[0006] The technical solution to achieve the objective of this invention is: a fused silica polishing method based on metal vaporization reaction force, comprising the following steps:

[0007] Step (1): Deposit a 100-300 μm thick nickel film on the surface of the fused silica sample;

[0008] Step (2): High energy density laser is used to irradiate the nickel film. The laser parameters are adjusted to ablate and evaporate the nickel. The downward force generated on the surface of the fused silica by the ablation and evaporation of the nickel is used to polish the surface of the fused silica.

[0009] Furthermore, step (1) specifically includes the following steps:

[0010] Step (11): Ultrasonically clean the fused silica sample for 20-30 minutes, then remove it and air dry it at room temperature;

[0011] Step (12): Apply a nickel film with a thickness of 100-300 μm to the surface of the fused silica sample using chemical plating.

[0012] Step (13): In a cleanroom, repeat step (11) to clean the sample again with ultrasonic cleaning and then dry it at room temperature.

[0013] Furthermore, the cleaning solution used for ultrasonic cleaning in steps (11) and (13) is acetone or anhydrous ethanol.

[0014] Furthermore, step (12) specifically includes the following steps:

[0015] Step (121): Roughen the surface of the fused silica;

[0016] Step (122): Activate the surface of the roughened fused silica sample by spraying an activation solution;

[0017] Step (123): Electroless nickel plating is performed on the surface of the activated fused silica sample.

[0018] Furthermore, the activation solution in step (122) contains NiSO4 at a concentration of 130-160 g / L and NaH2PO2 at a concentration of 200-250 g / L.

[0019] Furthermore, the metal film on the surface of the fused silica sample can also be copper, gold, or silver.

[0020] Furthermore, in step (2), the laser irradiation of the nickel film makes the surface temperature of the sample 1600℃-2700℃.

[0021] Furthermore, the specific parameters of laser irradiation in step (2) are as follows: laser power is 20-50W, frequency is 10-20kHz, laser spot diameter is 0.5-1mm, defocusing amount is 5-10mm, and scanning speed is 100-150mm / s.

[0022] Furthermore, the laser irradiation polishing path is a bidirectional single channel.

[0023] A fused silica polishing apparatus includes a laser, an acousto-optic modulator, a continuous attenuator, a mirror I, an aperture I, an aperture II, a mirror II, a beam expander collimator, an aperture III, a half-wave plate, a PBS prism, an aperture IV (12), a galvanometer system control mirror, a galvanometer system, a mirror III, a field mirror, a fused silica sample, a three-dimensional precision displacement stage, and a control center.

[0024] The fused silica sample is placed on a three-dimensional precision displacement stage. Then, the control center is turned on and the laser is activated. The laser is adjusted to the required high energy density by an acousto-optic modulator and a continuous attenuator. The adjusted laser then passes sequentially through mirror I, aperture I, aperture II, mirror II, beam expander collimator, aperture III, half-wave plate, PBS prism, aperture IV, galvanometer system, mirror III, and field mirror, irradiating the surface of the fused silica sample.

[0025] Compared with the prior art, the significant advantages of this invention are:

[0026] Compared with ordinary laser polishing, after coating the surface of fused silica with a nickel film, the polishing power required is smaller, and the surface temperature of fused silica does not need to reach above its melting point, which can avoid the phenomenon of ablation of fused silica surface due to high temperature.

[0027] Compared with traditional mechanical polishing, fused silica high-energy-density laser polishing, as a non-contact polishing method, can effectively avoid the impact of polishing fluid on surface quality during mechanical polishing.

[0028] By depositing a micron-sized nickel film on the surface of fused silica, the laser spot can be prevented from directly contacting the fused silica surface. This can effectively reduce the absorption of laser heat by the fused silica surface and prevent cracks from appearing on the surface due to large residual stress.

[0029] The fused silica laser polishing test is conducted in a cleanroom environment, which can effectively avoid secondary contamination of optical components by the environment.

[0030] The method of using a limiting and fixing optical element is easy to operate and does not generate a holding force.

[0031] The laser polishing scanning motion trajectory is bidirectional and single-channel, which avoids the accumulation of laser heat at the edge of the fused silica surface and can effectively improve the phenomenon of uneven heat distribution on the fused silica surface. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the laser processing system of the present invention.

[0033] Figure 2 This is a schematic diagram of nickel plating on the fused silica surface according to the present invention.

[0034] Figure 3 This is a schematic diagram of the laser polishing motion trajectory of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1-Laser, 2-Acousto-optic modulator, 3-Continuous attenuator, 4-Mirror I, 5-Aperture I, 6-Aperture II, 7-Mirror II, 8-Beam expander collimator, 9-Aperture III, 10-Half-wave plate, 11-PBS prism, 12-Aperture IV, 13-Galvanometer system control mirror, 14-Galvanometer system, 15-Mirror III, 16-Field mirror, 17-Fused silica sample, 18-Three-dimensional precision displacement stage, 19-Control center. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings.

[0038] The principle and basis of this invention are as follows: Fused silica has a high absorption rate for laser light. When the surface temperature of fused silica exceeds its melting temperature (2700℃), the viscosity of the fused silica decreases. Under the influence of surface tension and other forces, the melted fused silica flows from the peaks to the troughs, thus reducing surface roughness. However, during high-energy-density laser polishing of fused silica, the laser spot directly irradiates the fused silica surface, and the high temperature easily causes ablation. Simultaneously, the localized and continuous heating by the high-power, high-energy-density laser leads to significant residual stress on the surface. When this residual stress concentration reaches the fracture limit of the fused silica material, cracks will appear on the surface. To solve the problems caused by direct laser irradiation, a layer of metal can be plated onto the fused silica surface to isolate the laser energy. Nickel has a certain absorption rate for high-energy-density laser light, especially when the material surface is heated to a certain temperature, its absorption rate increases significantly. Therefore, nickel is chosen as the coating material for the fused silica surface. When the surface temperature of fused silica is heated to its softening temperature (around 1600℃), the surface viscosity of the fused silica decreases, and metallic nickel (evaporation temperature around 1444℃) evaporates. The ablation and evaporation of metallic nickel exerts a downward force on the fused silica surface, causing the fused silica from the crests to the troughs, thereby reducing surface roughness. Since the surface temperature of the fused silica is near its softening temperature, far below its melting temperature, the thermal stress generated on its surface is also much lower than that during polishing without a nickel film, thus suppressing the formation of surface cracks. A fused silica polishing method based on the reaction force of metal vaporization can both reduce the surface roughness of fused silica and suppress the formation of surface cracks.

[0039] This invention Figure 1 The optical path diagram of the high-energy-density laser processing system in this embodiment is shown. The high-energy-density laser polishing process of fused silica is as follows: the fused silica sample 17 is placed on the three-dimensional precision displacement stage 18, then the control center 19 is turned on, the laser 1 is turned on, and the laser beam travels along... Figure 1The optical path diagram shown is used for transmission. The laser is adjusted to the required high energy density laser by the acousto-optic modulator 2 and the continuous attenuator 3. The adjusted laser then passes sequentially through the reflector 4, aperture 5, aperture 6, reflector 7, beam expander collimator 8, aperture 9, half-wave plate 10, PBS prism 11, aperture 12, galvanometer system 14, reflector 15, and field lens 16, irradiating the surface of the fused silica sample.

[0040] Example 1

[0041] A chemical nickel plating film was applied to the surface of the fused silica sample. The fused silica sample was placed in an ultrasonic cleaner for 30 minutes to remove surface impurities; after cleaning, it was dried with a hair dryer at room temperature. The nickel plating process on the fused silica sample surface consisted of three steps. The first step was roughening, where the surface of the fused silica sample was roughened. The second step was activation, where an activation solution was sprayed onto the roughened fused silica sample surface, and the activation solution was quickly dried with a hair dryer after spraying. The activation solution contained NiSO4 and NaH2PO2, with the NiSO4 concentration being 130-160 g / L and the NaH2PO2 concentration being 200-250 g / L. The third step was chemical nickel plating, where nickel was chemically plated onto the activated fused silica sample surface.

[0042] High-energy-density laser polishing was performed on fused silica samples with a nickel-plated surface. The high-energy-density laser polishing experiment was conducted in a cleanroom laboratory. First, the fused silica sample was placed in an ultrasonic cleaner for surface cleaning. After cleaning, the fused silica was removed and dried at room temperature with a blower. Then, the fused silica sample was placed on a three-dimensional precision displacement stage 18. The control center 19 was opened, laser 1 was turned on, and the laser parameters were set as follows: laser power 20W, frequency 20kHz, laser spot diameter 0.5μm, defocusing amount 5mm, scanning speed 100mm / s. Figure 3 Following the laser's trajectory, the window of the laser polishing device is closed to polish the fused silica.

[0043] The above experimental steps use a polishing method based on metal vaporization reaction force of the present invention to polish fused silica elements. No other impurities are introduced during the processing, and the fused silica sample is finally polished with high efficiency, high precision and no defects.

Claims

1. A fused quartz polishing method based on metal vaporization reaction force, characterized by, The polishing method for a crystal optical element with a plane, a spherical surface, a cylindrical surface, a non-rotational surface or a non-spherical surface comprises the following steps: Step (1): coating a metal nickel film with a thickness of 100-300 μm on the surface of a fused quartz sample; specifically comprising the following steps: roughening the surface of the fused quartz; activating the roughened surface of the fused quartz sample by spraying an activation solution; and electroless plating nickel on the activated surface of the fused quartz sample, wherein the activation solution contains 130-160 g / L of NiSO4 and 200-250 g / L of NaH2PO2; Step (2): irradiating the metal nickel film with high-energy-density laser, adjusting the laser parameters to make the metal nickel ablate and evaporate, and polishing the surface of the fused quartz by the downward force generated by the ablation and evaporation of the metal nickel; In step (2), the temperature of the surface of the sample is 1600-2700 ℃; in step (2), the specific parameters of the laser irradiation are as follows: the laser power is 20-50 W, the frequency is 10-20 kHz, the laser spot diameter is 0.5-1 mm, the defocusing amount is 5-10 mm, the scanning speed is 100-150 mm / s, and the polishing path of the laser irradiation is a two-way single channel.

2. The method of claim 1, wherein, Step (1) specifically comprises the following steps: Step (11): ultrasonic cleaning the fused quartz sample for 20-30 min, and then taking out and drying at room temperature; Step (12): coating a nickel film with a thickness of 100-300 μm on the surface of the fused quartz sample by electroless plating; Step (13): repeating step (11) in a dust-free room, and then taking out and drying at room temperature after ultrasonic cleaning the sample again.

3. The method of claim 2, wherein, The cleaning solution for the ultrasonic cleaning in steps (11) and (13) is acetone or anhydrous ethanol.

4. The method of claim 1, wherein, The metal film on the surface of the fused quartz sample can also be copper, gold or silver.

Images