Comparison of Gain-switched Operated Cr2+ and Fe3+ Ions Co-doped Zn1-xMnxSe (x ≈ 0.3) Lasers in Mid-IR under Different Excitation Wavelengths

Two different mid-infrared (mid-IR) crystalline laser active media of Zn1-xMnxSe and Zn1-xMgxSe with similar manganese or magnesium ions amount of x approximate to 0.3 co-doped by divalent chromium (Cr2+) and iron (Fe2+) ions were investigated at cryogenic temperatures and compared for different excitation wavelengths used. Both single crystals were synthesized by high pressure Bridgman method and their thickness were 2.6 mm and 5 mm, respectively. Crystals were investigated under three excitation wavelengths of the Q-switched Er3+:YLF laser at similar to 1.73 mu m, Q-switched Er3+:YAG laser at similar to 2.94 mu m, and the gain-switched Fe2+:ZnSe laser operated at liquid nitrogen temperature of 78 K at a wavelength of similar to 4.05 mu m. Spectroscopic and laser output characteristics were measured: absorption and fluorescence spectra, laser output pulse duration, mean output energy, and laser oscillation spectra. Both laser systems were able to generate radiation by Cr2+ or by Fe2+ ions under direct excitation, or by Fe2+ ions via the Cr2+ -> Fe2+ energy transfer depending on the excitation wavelength and the output coupler conditions. Fe2+ ions in Cr2+, Fe2+:Zn1-xMnxSe and Cr2+,Fe2+:Zn1-xMgxSe (x approximate to 0.3) laser systems at 78 K pumped by Er3+:YLF laser radiation at similar to 1.73 mu m via the energy transfer mechanism generated laser radiation at the wavelengths of similar to 4.4 mu m and similar to 4.8 mu m at 78 K, respectively. Obtained results have shown a possibility of developing novel coherent laser systems in mid-IR region (similar to 2.3 - 2.5 mu m and similar to 4.4 - 4.9 mu m) based on A(II)B(VI) matrices. Thus, possibility to excite the Fe2+ active ions in both samples directly by similar to 2.94 mu m as well as similar to 4.05 mu m radiation or eventually in a compact way through the Cr2+ -> Fe2+ ions energy transfer-based mechanism by similar to 1.73 mu m radiation was demonstrated.