MEASUREMENT OF THERMAL LENSING IN CR3-DOPED COLQUIRIITES()

The first direct measurements of thermally induced tensing in end-pump ed Cr3+-doped LiSAF, LiSGAF, LiSCAF, and LiCAF are reported. Using a s ensitive measurement technique, focal lengths as long as 40 m were mea sured. A thermal model has been created to determine the temperature r ise as a function of position inside the laser crystal. This new model calculates the temperature distribution by considering quantum defect , upconversion, and upper state lifetime quenching as heating sources. Thermal lensing in the colquiriites is significantly reduced because of compensation of the temperature-dependent refractive index by the i nduced photoelastic stress inside the colquiriite crystal.