248 nm high fluence irradiation of CaF2 crystals

Abstract

Transmission, absorption and laser induced fluorescence (LIF) measurements were performed to reveal the applicability of different grade CaF2 for 248 nm laser applications. No emission from self-trapped excitions could be found in LIF measurements after irradiation with 100k pulses for all grades. Therefore, three-photon excitation could be excluded up to 1 J/cm2. Whereas emission at 420 nm and partially the double-peak at 313/333 nm could be found in LIF measurements. UV-VIS difference spectra did not show any absorption bands after 248 nm irradiation of the samples. Optical elements from CaF2 promise high life expectancy at 248 nm if a standard laser polish is used and hot spots are avoided.