Lanthanide Doped Crystals for Tunable UV Lasers

摘要

Several Pr3+ doped fluoride and oxide crystals, most of them being grown in our laboratory, are investigated spectroscopically to examine their potential use for tunable UV laser systems. The study is both experimental and theoretical with emphasis on measurements of excited state absorption (ESA) spectra, in particular to evaluate the possibility to operate these laser systems after two step excitations using visible/near UV pump photons. The complex electronic structure (positions of the energy levels, polarizations of the transitions) of the first excited electronic configuration 4f5d for Pr3+ (the one giving rise to UV emission) is clearly demonstrated. Assuming negligible ESA in the emitting level, which is probably too optimistic, simulations based on ESA and fluorescence data show the possibility of 20% laser gain per pass using moderate pump energies. It is then concluded and recommended to address more specifically the crystal growth question to obtain better quality materials and also to investigate new types of crystals, either doped with Pr3+, but emitting at slightly longer wavelengths, between about 260 and 310 nm, to reduce ESA in the emitting State, or doped with Nd3+ to reach then UV emissions at shorter wavelengths.