Spectroscopic and laser investigations of Mn5+:Sr5(VO4)3F

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Abstract
Mn:Sr5(VO4)3F has been investigated as a laser material for operation near 1200 nm. Absorption and emission spectra are consistent with Mn5+ substitution into the distorted tetrahedral V5+ sites of this apatite crystal. Emission is almost entirely from the 1E state, resulting in a room‐temperature fluorescence lifetime of 475 μs. Together with a peak stimulated emission cross section of about 1×10−19 cm2 and strong, broad absorption bands, this is attractive for lamp‐ or diode‐pumped laser operation. However, the 1E emission makes Mn:Sr5(VO4)3F a three‐level system. Laser operation has been demonstrated at room temperature, but the efficiency is lower than expected. Single‐pass gain measurements and saturable absorption and fluorescence data indicate that the primary difficulty is excited‐state absorption at the pump wavelength. This absorption is very broad, and is probably due to 1T1 and 1T2 excited states.