One of the promising active ions giving the possibility of laser radiation generation in 4 - 5 μm region is trivalent
dysprosium in lead thiogallate crystal. On the basis of our previous Dy3+:PbGa2S4 laser study, this work is showing a
several wavelengths generation possibility. The laser was working at the room temperature and it was in-band pumped
by the Er:YLF laser radiation with the wavelength 1.73 μm. The investigated crystal Dy3+:PbGa2S4 was synthesized
using Bridgman technique from the melt. Dimension of the sample was 16 mm long and 19 mm in diameter and the
nominal Dy3+ ion concentration was ~ 0.7 at. %. The laser operation was tested with three resonator configurations. The
first was the non-selective resonator with the length 41 mm. To perform the wavelength tuning, in the second case the
MgF2 Lyot filter was inserted under Brewster angle inside the resonator which length was 100 mm. In both these cases
the laser resonator was formed by the incoupling flat dichroic mirror with low reflectivity at pumping wavelength (T =
90%@1.73 μm) and high reflectivity (R~100%) within the 3.5 - 4.5 μm spectral range, and by an out-coupling concave
(r = 500 mm) mirror with reflectivity of 95 % or 98 % in the same region of wavelengths. For the third case the selective
mirrors supporting the 3.0 - 4.0 μm spectral region were chosen. The generation possibility on three lines 4 μm, 4.3 μm,
and 4.6 μm were found without continuous tuning between them.
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