Chalcogenide glasses doped with rare-earth elements provide an opportunity to obtain fluorescence, and possibly laser action, at longer wavelengths than presently available from oxide and fluoride vitreous hosts. Present silica-based solid state lasers are operational only from the visible out to less than 3 /xm since the intrinsic phonon absorption bands extend from long wavelengths into the mid-infrared region [1]. Heavy metal fluoride glasses have also been investigated, but their high multipho-non absorption in the 6-7 jum wavelength region competes with the desired emission which reduces the efficiency for fluorescence in the mid-infrared region [2].
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