Laser-Induced Breakdown Mechanisms and Damage Threshold Investigations in Optical Materials

Laser induced damage investigations using single and multiple pulse lasers are carried out on borosilicate glasses. Experiments are conducted on the surface and the bulk of materials utilizing nanosecond (ns) and sub-nanosecond (sub-ns) laser pulses at a wavelength of 1064 and 532 nm, employing precise and dependable measuring methods. Confinement geometry target assemblies play a crucial role in investigating the behavior of the materials under laser-shock compression and laser shock peening. The shock pressure in confinement geometry is contingent upon the intensity of the incoming laser and is primarily constrained by the occurrence of dielectric breakdown in the transparent materials employed for confinement. Therefore, it is essential to investigate the damage processes caused by laser pulses in optical materials. Our study focused on examining the damage threshold of the front and back surfaces of BK-7 glass, which is a dielectric material. We also analyzed how this damage threshold is influenced by various laser parameters. An analysis of the laser induced damage width, geometry, microstructure modifications and damage crater morphology are conducted using an optical microscope and scanning electron microscope. The findings indicate that symmetrical damages occur at low energy, and the width of these damages rises non-linearly with laser intensity. Most of the experimental data unambiguously demonstrates thermal effects throughout a wide range of pulse durations.