Laser Irradiation Defects Repair In The Process Of Optical Device

The development of high-power laser system is the mainstream direction of laser technology application.As the damage of optical components limits the development of high power systems such as ICF laser driver,how to minimize the surface damage caused by laser irradiation is a problem that needs to be solved.Strong laser induced fused silica optical components because of its good physical properties and anti-damage ability,in the economic cost control and scientific and technological progress of continuous efforts,is in its development process to solve one after another technical problems.Now the main technology to repair surface damage and damage re-growth of optical materials,CO2 laser irradiation material surface technology is widely used.In this paper,a series of theoretical analysis and numerical calculation are carried out for this technique.The theoretical model of thermodynamics is established and analyzed.With heat absorption as the research start,the experimental results show that the laserThe characteristics of the temperature distribution,the residual stress and the real-time process of the melt flow will be discussed.The model will be established at the physical level using a wide range of optical materials.Then,the effects of various laser parameters on the morphology of the Gaussian pit Analysis,the main research content and results are as follows:1.Simulated fused silica elements are irradiated by different laser Gaussian circles with a temperature distribution and a change in the process.When the laser irradiates the surface of the damaged fused silica element,the center temperature of the surface of the optical element is high,and then the temperature of the surrounding material decreases in the order of decreasing the temperature gradient from the center of the laser irradiation damage pits along the horizontal plane,The surface of the component points to the inside of the component with a large temperature gradient.The surface temperature rise and decrease of the laser irradiating optical element showed rapid change in the early stage,and the change of the surface temperature around the edge of the spot was very slow.2.In this paper,the two-dimensional melt flow modeling of the surface of the optical element under CO2 laser irradiation is modeled by the coupling of heat conduction and melt flow.The reconstructed morphological features of the surface damage of fused silica were described by the combination of theory and experiment.The effects of three driving forces on the melt flow process were analyzed.It is found that the surface tension of the molten silica element is the main driving force of the flow,and under its influence,the flow of the surface material of the optical element is significantly changed.The special form of the annular protrusion near the damage pit is consistent with the conclusion.3.Two models were established,one for smooth damage and the other with bumps.In the simulation experiment,we used a two-dimensional melt flow model to simulate the process of laser repair damage.After simulation,we can conclude that the use of laser single point of repair of various damage,the surface of the element in the vicinity of the Gauss pit observation of the ring after the repair of the traces of the bulge.However,the greater the size of the original damage,the higher the difficulty of repairing the surface of the optical element.4.The effects of laser power,irradiation time and laser beam radius on the melt flow during laser irradiation were investigated.By observing the two-dimensional plot drawn from the experimental data,it can be found that the surface morphology formed after the repair is similar,regardless of the type of damage.In addition,the depth of damage to the damaged area is relatively large,because in the current calculation conditions and models difficult to make the damage to achieve the desired repair effect,that is,after the formation of the surrounding convex Gaussian pit,so as not to achieve the desired repair effect.In general,improving the output stability of the laser device,increasing the radius of the beam and controlling the irradiation time reasonably allows the surface to be repaired to be smoother.5.The effect of pulsed laser parameters emitted by the laser on the surface size of the optical element was analyzed.The experimental data show that the Gaussian pit is generally found in the evaporation and melting zone during CO2 laser repair,the laser output power,the length of the irradiation,the size of the spot size is more significant for the repairing size,especially the repair of the height of the damage surface of the optical element,While the laser beam pulse frequency and duty cycle on the size of the role of maintenance is relatively low.And the laser beam frequency of the laser increases,it is observed that the evaporation size starts to decrease,but the size of the melt does not change,thus restricting the evaporation and smoothing the surface of the optical element.