Energy deposition at front and rear surfaces during picosecond laser interaction with fused silica

The difference between front-surface and rear-surface energy deposition of a 35 ps laser pulse (lambda = 1064 nm) in fused silica was investigated usi ng shadowgraphic and laser-deflection techniques. Shock waves were observed in the glass and in air. Shock waves generated in air at the front surface are stronger than at the rear surface. Less than 35% of the energy inciden t on the surface drives the air shock waves at the rear surface. Up to 90% of the incident energy drives the air shock waves at the front surface. Las er-plasma interaction is responsible for this difference and for limiting t he amount of energy deposited inside the sample during front-surface ablati on. Energy deposition at the rear surface is mostly limited by self-focusin g inside the material. (C) 2001 American Institute of Physics.