Nonlinear absorption in optical materials at a wavelength of 193 nm

The coefficients of two-photon absorption of 30- and 70-ns ArF laser pulses in high-purity CaF₂, BaF₂, and Al₂O₃ crystals are measured by the method of nonlinear transmission to be 2.2 ± 0.8, 2.3 ± 0.8, and 5.6 ± 2.2 cm GW^-1, respectively. The thresholds of the laser breakdown of the surface of crystals are determined.