Spectroscopic and energy-transfer parameters for Er3+-doped and Er3+, Pr3+-codoped GeGaS glasses

The absorption and emission spectra and the rate parameters for the important energy-exchange processes relevant to the I-4(11/2) --> I-4(13/2) laser transition in Er3+-doped and Er3+, Pr3+-codoped GeGaS glasses are presented. The rate parameters are determined after optical excitation with a tunable pulsed optical parametric oscillator that excites the I-4(11/2) and I-4(13/2) energy levels directly. For the Er3+ singly doped samples, the energy-transfer upconversion (ETU) macroscopic rate parameters for the upper and lower laser levels were measured for a range of Er3+ concentrations. In correspondence with ZBLAN and the fluoride crystals, the (I-4(13/2), I-4(13/2)) --> (I-4(9/2), I-4(15/2)) 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 I-4(13/2) level of Er3+ to Pr3+ deactivator is measured as compared with the corresponding energy transfer from I-4(11/2) level to both the Pr3+ deactivator and OH impurity. With these favorable energy-transfer conditions, the prospect for the future development of highly efficient similar to3-mum fiber lasers with GeGaS glass as the host material is excellent. (C) 2002 Optical Society of America.