Damage growth characteristics of different initial damage sites of fused silica under 355 nm small laser beam irradiation

• The influence of initial damage sites on the subsequent growth is investigated.
• The fixed and ramp-up fluence tests are performed to obtain the growth behaviors.
• The growth trends can be well fitted by exponential formulas.
• The growth rates of the lateral size, crater and crack depth are given.
• As the main features of growth, the cracks are categorized into three main types.

Growth behaviors of initial damage sites are important in investigating laser-induced damage mechanisms of optical materials and in evaluating the lifetime of optical components. The characteristics of the initial damage sites initiated by different fluences were investigated to determine the effects of the initial conditions on damage growth. Two kinds of experiments, fixed and ramp-up fluences, were conducted under a 355 nm small laser beam to obtain the growth behaviors in terms of morphology, lateral size, as well as crater and crack depth. Preliminary statistical results revealed the relationship between the growth trends and initiating and subsequent laser fluences. As the main features of damage growth, visible cracks are categorized into three main types, which are associated with the laser irradiation.