Spectroscopic investigation of the visible and infrared emission in Tm, Ho-doped YAG and YLF crystals

Abstract

Thulium-sensitized holmium lasers have proved to be very attractive, efficient infrared radiation sources in eye-safe spectral regions. Following to Tm 3H4 excitation of interest for optical pumping with commercially available diode-laser, transfer of energy to the Ho 5I7 upper laser level competes with a variety of interactions that may cause energy loss. The relative importance of the various processes is not very often considered, and still needs to be carefully analyzed. In this paper we describe our results of spectroscopic measurements carried out after Tm 3H4 excitation, in order to identify and evaluate the main de-excitation mechanisms.