Increasing the performance of an Fe: ZnSe laser using a hot isostatic press

A sample of Fe: ZnSe fabricated by post-growth thermal diffusion was purchased commercially. The sample was cooled to 80 K using liquid nitrogen and used as the gain element in a Watt-class continuous-wave laser with an output wavelength centered at 4050 nm. The sample was removed from the laser and treated using a hot isostatic press (HIP) technique. The crystal was then re-placed in the laser resonator. After the HIP treatment, and with no other changes to the laser resonator, the slope efficiency of the laser increased by 1.5x. The spectral output was red-shifted to 4122 nm and the output linewidth was narrowed by nearly two orders of magnitude, resulting in a 36x increase in power spectral density. The shift in wavelength and the increase in power scaling performance is consistent with the activation of previously inactive iron impurities in the sample by the HIP treatment.