OPTICAL-BREAKDOWN IN ALKALI-HALIDES

Damage thresholds in NaCl are calculated for photon energies between 2 and 8 eV with pulse lengths in the nanosecond and picosecond regimes using our polaron model. It is assumed that breakdown can occur either at the temporal center of a (clipped Gaussian) pulse or at its end. We conclude that changes in the refractive index (negative lensing effects) while much smaller at the end than at the center are still not negligible and must, like self-focusing effects, be carefully considered in threshold studies. © 1979 The American Physical Society.