Two-photon absorption measurements of deep UV transmissible materials at 213  nm

We report on two-photon absorption measurements at 213 nm of deep UV transmissible media, including LiF, MgF₂, CaF₂, BaF₂, sapphire (Al₂O₃), and high-purity grades of fused-silica (SiO₂). A high-stability 24 ps Nd:YAG laser operating at the 5th harmonic (213 nm) was used to generate a high-intensity, long-Rayleigh-length Gaussian focus inside the samples. The measurements of the fluoride crystals and sapphire indicate two-photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two-photon absorption; however, there are differences in linear losses associated with purity. A low two-photon absorption cross section is measured for MgF₂, making it an ideal material for the propagation of high-intensity deep UV lasers.