Spectroscopic Investigation of Rare-Earth Doped CsCdCl3 Crystals for Potential Mid-Ir (3-5 Um) Laser Sources

The development of mid-IR lasers faces some unique challenges when striving to achieve the highest efficiency and power output. Most critical among these challenges is luminescence quenching of the relatively closely-spaced upper and lower laser levels, usually occurring through the process of multi-phonon relaxation. This quenching can be mitigated by using gain materials with small maximum phonon energies. In this work, mid-IR spectroscopic characterization of RE3+ doped cesium cadmium chloride (CsCdCl3) crystals was performed. The transition probabilities of RE3+ ions using Judd-Ofelt analysis as well as the multiphonon non-radiative transition rates in RE3+:CsCdCl3 were estimated. Obtained experimental results, inclusive of temperature dependent absorption and fluorescence studies, transition cross-sections, and fluorescence dynamics, were interpreted from the standpoint of optimization for diode-pumped ~3-5 um laser development.