Concentric ring damage on the front surface of fused silica induced by a nanosecond laser

Concentric rings are observed on the front surface when a laser pulse focuses on the rear surface of fused silica. The spatial distribution of concentric rings presents a certain regularity, and the width and depth of the ring gradually increase from inside to outside. These features of the concentric rings are affected by the laser wavelength and energy. Their formation mechanism is explored by means of combining a time-resolved pump-probe shadow graph and surface damage morphology. Concentric rings are formed during the irradiation process of one nanosecond pulses, whose radius and depth characteristics may record the relationship between the early stage of laser-induced damage structure and the evolution of early plasma. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement