Laser-Induced Damage Initiation and Growth of Optical Materials

Abstract

The lifetime of optical components is determined by the combination of laser-induced damage initiation probability and damage propagation rate during subsequent laser shots. This paper reviews both theoretical and experimental investigations on laser-induced damage initiation and growth at the surface of optics. The damage mechanism is generally considered as thermal absorption and electron avalanche, which play dominant roles for the different laser pulse durations. The typical damage morphology in the surface of components observed in experiments is also closely related to the damage mechanism. The damage crater in thermal absorption process, which can be estimated by thermal diffusion model, is typical distortion, melting, and ablation debris often with an elevated rim caused by melted material flow and resolidification. However, damage initiated by electron avalanche is often accompanied by generation of plasma, crush, and fracture, which can be explained by thermal explosion model. Damage growth at rear surface of components is extremely severe which can be explained by several models, such as fireball growth, impact crater, brittle fracture, and electric field enhancement. All the physical effects are not independent but mutually coupling. Developing theoretical models of multiphysics coupling are an important trend for future theoretical research. Meanwhile, more attention should be paid to integrated analysis both in theory and experiment.

Indentation hardness and scratch tests for thin layers manufactured by sol-gel process

“…The aim is to study films with elastic properties that could absorb shocks induced by the power laser beam absorption. Indeed, these shockwaves can increase the size of previously produced laser damage [3]. The absorption processes due to laser beams by a thin film are numerous and complex.…”

Focused Nanosecond Pulsed Laser‐Induced Homogeneous Nucleation in Undercooled Oxide Melts

“…Part of the energy was released electrons from the lattice in the form of ionization, such as hot electron emission or photoelectric effect. [37,38] Another portion was converted into heat energy of the material through the interaction of electrons with the lattice or ions. As the relaxation time for the electron to absorb energy is much shorter than that for the exchange energy between electron and lattice or ion, ionization of clusters will first occur within the skin depth of undercooled sample.…”

Dark-field line confocal imaging with point confocality and extended line field for bulk defects detection

“…Three-dimensional (3D) macroscopic defects, referred to as the bulk defects including cracks, pores, or inclusions, are inevitably introduced into an optical component during refinement from its raw state or during fabrication processes. Bulk defect is one of the origins of laser-induced damage when exposed to high-energy irradiation, as it is likely to cause photothermal absorption [1,2] , light intensification [3,4] , plasma generation [5] , and shock-wave propagation [6] . Hence, detection of bulk defects is an indispensable step in fabrication of high-quality optics.…”