Laser performance of Cr2+ doped ZnS

Laser properties and spectroscopic characterization of diffusion doped Cr2+: ZnS crystals synthesized by chemical transport reaction from gas phase are reported. Lasing was realized with a threshold of 170 muJ and slope efficiency of 9.5 % with respect to the 1.5607 mum pump energy, in a hemispherical cavity. Low doped samples (3-4 cm(-1) at 1.7 mum) of 1.7 mm thickness were utilized. The 1.5607 mum excitation was realized with a D-2 Raman cell pumped in a backscattering geometry by the 1.064 mum radiation of the single frequency Nd:YAG laser. Maximum output energy reached 100 muJ Lasing in the hemispherical cavity was achieved with output couplers R-2.36 mum=80 % and 90 % and radius of curvature 20 cm. Absorption cross section was estimated from spectroscopic measurements and was in a good agreement with saturation data (sigma (abs.) = 0.80x10(-18) cm(2)) calculated with the modified Frantz-Nodvik equation for a four level slow absorber. Findlay Clay losses were found to be about 14%. Selective cavity experiments were performed in a hemispherical cavity with a CaF2 prism as the dispersive element. A tuning range of 2.05-2.40 mum was realized, limited by the spectral range of the output coupler of the selective laser cavity.