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We report the first observation, to our knowledge, of three-level laser oscillator operation in a crystal activated with Mn5+. The material is Mn:Ba3(VO4)2 which exhibited laser oscillation at room temperature under pulsed 592 nm excitation. The laser emission occurs at 1181 nm with a threshold of 0.3 J/cm2. Spectroscopy indicates that this material operates as a three-level system on the 1E to 3A2 transition of the Mn5+ ion with tetrahedral coordination. The strong, broad absorption bands and 0.43 ms room-temperature lifetime make this system very promising for flash lamp AlxGa1−xAs diode pumping.

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Laser action in chromium-doped forsterite (Cr:Mg2SiO4), pumped with a 1.064 μm Nd:YAG laser, was demonstrated for the first time. The free-running laser emission is centered at 1.221 μm and has a spectral width of 28 nm. An efficiency of 8% has been achieved with an uncoated crystal produced by the laser-heated-pedestal growth method. The available evidence suggests that the laser action is due to Cr4+ in tetrahedral sites.

Pr3+-doped SrAl12O19 has been investigated spectroscopically as a visible laser material. Its 3P0 fluorescence lifetime is rather long for an oxide, about 35 μs. This excited state exhibits only mild concentration and temperature quenching, so that concentrations high enough to give good ground state absorption into the 3P0 and 3P1 manifolds still give strong, long-lived emission. The ground state absorption spectra indicate that excited state absorption into the 4f5d configuration is less likely to be significant at laser wavelengths in this host than in Y3Al5O12. The stimulated emission cross sections of major emission lines have been estimated, and are quite realistic for laser operation. Laser pumped laser operation has been demonstrated in the red (3P0→3F2) at room temperature and in the blue-green (3P0→3H4) at cryogenic temperatures.