Recent progress in the development, characterization, and theory of tunable solid-state laser media based on transition metal ions

Abstract

Tunable lasers employing transition metal (TM) activator ions currently cover a large portion of the near-IR wavelength region from ~700 to 2300 nm. The number of crystalline laser media suitable for these ions, particularly Cr3+, has been steadily growing. Significant improvements in the lasing properties have been difficult to obtain, however, because of problems with crystal growth and quality, nonradiative processes, parasitic absorption, and excited state absorption of laser and pump light. Recent experimental and theoretical work has provided some insight regarding these and other properties and their effects on laser operation. The experimental work includes measurements of laser slope efficiency as a function of output coupling, excited state absorption, photoconductivity, and laser-induced transient and cw gratings. Ab initio theoretical approaches have had some success in providing quantitative information regarding the positions of the energy levels of these ions and their dependence on the displacements of the neighboring ions in oxide and fluoride hosts. Utilization of the information obtained from these research efforts is resulting in improved properties of tunable TM lasers.