Laser‐induced breakdown by impact ionization in SiO2 with pulse widths from 7 ns to 150 fs

Abstract

Results of laser‐induced breakdown experiments in fused silica (SiO2) employing 150 fs–7 ns, 780 nm laser pulses are reported. The avalanche ionization mechanism is found to dominate over the entire pulse‐width range. Fluence breakdown threshold does not follow the scaling of Fth∼ √τp, when pulses are shorter than 10 ps. The impact ionization coefficient of SiO2 is measured up to ∼3×108 V/cm. The relative role of photoionization in breakdown for ultrashort pulses is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69530/2/APPLAB-64-23-3071-1.pd