The absorption and emission spectra and the rate parameters for the important energy-exchange processes relevant to the laser transition in -doped and -codoped GeGaS glasses are presented. The rate parameters are determined after optical excitation with a tunable pulsed optical parametric oscillator that excites the and energy levels directly. For the singly doped samples, the energy-transfer upconversion (ETU) macroscopic rate parameters for the upper and lower laser levels were measured for a range of concentrations. In correspondence with ZBLAN and the fluoride crystals, the ETU process of the lower laser level is measured to be stronger than the corresponding ETU process of the upper laser level. Such a condition enables energy recycling to occur. A higher rate of energy transfer from the level of to deactivator is measured as compared with the corresponding energy transfer from level to both the deactivator and OH impurity. With these favorable energy-transfer conditions, the prospect for the future development of highly efficient ∼3-µm fiber lasers with GeGaS glass as the host material is excellent.
© 2002 Optical Society of America