Abstract

We report direct measurements of nonlinear transmission prior to laser-induced breakdown in a wide band gap dielectric. Various workers have suggested that bulk laser-induced breakdown is due to avalanche breakdown induced by multiphoton absorption. A detailed quantitative description of the generation of the initial conduction band electrons and the dynamics of the breakdown process is not yet available. A major obstacle to the development of a quantitative description of the damage process has been the inability of researchers to measure the onset of nonlinear absorption (e.g., multiphoton absorption) which initiates the avalanche process. In this work we observe pronounced, reversible nonlinear transmission prior to bulk breakdown. The sample studied was cubic zirconia (ZrO₂) stabilized with yttria (Y₂O₃) which has an UV transmission cutoff at 330 nm. Our measurements were made at 532 nm which is within the range where two-photon absorption is possible. The observed nonlinear transmission prior to breakdown is consistent with the interpretation that damage in this material is due to two-photon absorption-induced avalanche breakdown.

© 1986 Optical Society of America