9410795 Gayen The objective of the proposed research is to develop tunable solid- state lasers which will operate in the near-ultraviolet, and blue- green spectral regions. The strong, broad-band fluorescence that results from 5d-to-4f vibronic transitions in trivalent rare earth ion-doped crystals is particularly suitable for the four-level mode of laser operation in these wavelengths. Since the 5d electrons are strongly coupled to the host lattice, a careful choice of active ions (Ce3+, Pr3+) and host crystals would be used to optimize the 5d-to-4f fluorescence, and to simultaneously minimize the detrimental effect of excited-state absorption. The properties of the absorption, excitation, and fluorescence spectra, fluorescence lifetime and intensity would be used to extract key spectroscopic parameters which are pertinent to laser action, such as absorption and emission cross sections, oscillator strengths, radiative and nonradiative decay rates and line strengths. Laser-pumped lasing experiment would be conducted to demonstrate laser action in promising crystals. Detailed measurements of output characteristics, quantum electronic properties and loss mechanisms would be undertaken. The goal is to be able to formulate the selection and design criteria for these crystals. The results of this project would have an impact on such diverse areas as underwater laser communication, optical storage, cytometry and biotechnology, as well as the development of phosphors for radiologic imaging and scintillators for radiation detection. ***
