Three-level Nd:YLF Raman laser directly pumped by a beam shaped diode bar

Abstract

Low heat generation can be obtained when pumping Nd:YLF at wavelengths of 872 nm and 880 nm and emitting at the three-level transition of 908 nm. These transitions show very low quantum defect with efficiencies of 0.96 and 0.97, respectively. However, the low average absorption cross-section at these wavelengths makes efficient absorption even for longitudinal pump setups difficult. Using a beam-shaped pump diode instead of a fiber-coupled diode bar may be an effective means of increasing absorption because it can provide for π-polarized radiation which shows higher absorption cross section. In this work, a Nd:YLF was pumped at 872 nm by a diode bar using beam-shaping. Results were compared to pumping at 872 and 880 nm with non-polarized fiber-coupled diodes. Stimulated Raman scattering was also obtained with a KGW crystal generating first Stokes emissions at 990 nm and 976 nm.