Alexandrite spectroscopic and laser characteristic investigation within a 78–400 K temperature range

We report on the influence of temperature on the spectroscopic and lasing properties of alexandrite ($C{r}^{3+}:BeA{l}_2{O}_4$) crystal. The fluorescence lifetime, polarization-resolved absorption and emission spectra, and laser characteristics at  ∼750 nm are described in detail within a 78–400 K temperature range. As a pumping source, a 3.5 W InGaN blue laser-diode operating at a wavelength of 444 nm was used. The best results achieved were at a crystal temperature of  ∼353 K with 326 mW of continuous output power at a wavelength of 750 nm with a slope efficiency near 20% (related to absorbed pump power). At cryogenic temperatures, alexandrite laser generation at the so-called R-line, i.e. not in the vibronic mode, has been observed. (paper)