Spectroscopic and laser classification of chromium(2+) in II-VI chalcogenides

A highly efficient stimulated Raman conversion of Nd: YAG radiation in H2 and D2 cells was realized while preserving the beam quality and temporal profile of the input beam. This approach provided a pump source at 1560 and 1907nm for spectroscopic and laser characterization of Cr2+ doped II-VI crystals.; Chromium was successfully introduced into ZnS, ZnSe and CdS. The crystals surfaces were coated with chromium via pulsed laser deposition within a vacuum chamber. The chromium was then thermally diffused into the materials.; Spectroscopic characterizations were performed on Cr doped ZnS and ZnSe crystals. Kinetics of fluorescence measurements revealed room temperature quantum efficiencies of 70% for ZnS and 100% for ZnSe. These quantum efficiencies would indicate both materials as promising laser media in the middle infrared spectral range. Absorption and emission cross-sections were also found for both materials. Saturation experiments on Cr2+: ZnS were performed under 1.56mum excitation. The absorption cross-section determined by fitting experimental results with Frantz-Nodvik equation was 0.8x1018cm 2, which is in agreement with spectroscopic measurements.; Laser experiments were successfully conducted on the Cr2+: ZnS and ZnSe crystals. Successful demonstration of CW Cr2+: ZnS and ZnSe microchip lasers with maximum output powers of 150mW and 500mW at ∼2400nm and slope efficiency of up to 50% under direct Er-fiber laser excitation was achieved. In free-running oscillation approximately 100 and roughly 50 axial modes were created in ZnSe and ZnS respectively. The addition of an external mirror within a coupled cavity configuration was effective at providing mode control. In both crystals the number of modes produced was reduced to approximately 20.; A gain-switched Cr2+: ZnSe microchip laser was realized with a maximum slope efficiency of 6.5% and maximum output energy of 1mJ. These results were obtained for a microchip without mirrors, utilizing only Fresnel reflections.; In external cavity configuration a compact Er-fiber laser pumped broadly tunable between 2200nm and 2650nm CW room temperature Cr2+: ZnSe laser was realized, yielding up to 90 mW at ∼40% slope efficiency and a 0.5nm linewidth.