The influence of Cr2+ to Fe2+ ions concentration ratio on the Cr,Fe:Zn(1-x)Mn(x)Se (x ≈ 0.15) laser properties excited via Cr2+ → Fe2+ energy transfer

Abstract

In this work the results of research of an optimal concentration ratio of Cr 2+ and Fe 2+ co-doped active ions for more efficient Cr 2+ → Fe 2+ ions energy transfer in a chosen Zn1-xMnxSe (x ≈ 0.15) host material are presented. Three cryogenically cooled Cr 2+ ,Fe 2+ :Zn1-xMnxSe (x ≈ 0.15) single crystals with the same thickness of ~2.7 mm and with different doping ratios of Cr 2+ and Fe 2+ ions of ~1:1, ~2:1, and ∼3:1 were investigated under Q-switched Er:YLF laser excitation (wavelength: ∼1.73 µm, pulse energy: ∼10 mJ, pulse duration: ∼150 ns). The temperature dependence of the absorption and fluorescence spectra, the fluorescence decay time as well as the laser output characteristics were measured. The Fe 2+ ions maximum laser output of ~50 µJ at the wavelength range of ~4.25-4.42 µm was obtained with the crystal sample for which the active ions ratio was ~2:1. A further increase of the chromium ions amount (Cr 2+ :Fe 2+ ≈ 3:1) led to worse results. Using appropriate resonator cavity mirrors, the samples were also able to generate the ~2.35-2.45 µm laser radiation from Cr 2+ ions. The laser output beam spatial profiles were close to Gaussian in all cases. In summary, an optimized compact source of mid-infrared ~4.25-4.42 µm (Fe 2+ ) and ~2.35-2.45 µm (Cr 2+ ) of Cr,Fe:Zn1-xMnxSe (x ≈ 0.15) crystal pumped via Cr 2+ ions by the ~1.73 µm radiation is described.