2-μm2-μm lasers with fluoride crystals: Research and development

In the present work we present a review of the 2μm laser based on fluoride crystals. We will provide a brief description of the theoretical aspects of rare earth ions embedded in insulating crystals, with particular attention to the advantages in using fluoride single crystals and the growth technique. The core article is represented by an overall survey of the laser and spectroscopic properties: Sections 4 and 6 will present the spectroscopic properties of the Tm,Ho and Tm, respectively, explained in the frame of the rate equation formalism and we will report a summary of the literature results. Finally 5 and 7 will describe the state-of-the-art for the two systems.