T. C. Brunold, H. U. Güdel, M. F. Hazenkamp, G. Huber and S. Kück
Excited state absorption measurements and laser potential of Cr⁴⁺ doped Ca₂GeO₄
Appl. Phys. B 64, 647-650 (1997)                 

Abstract: Polarized continuous wave excited state absorption (ESA) measurements on Cr⁴⁺ doped Ca₂GeO₄ in the 450-2000 nm spectral region at room temperature are presented. Weak ESA bands due to the ³T₂ ³T₁(F) transition are observed between 1200 and 2000 nm and stronger ESA bands due to ³T₂ ³T₁(P) peak below 1200 nm. The overlap of the ³T₂ ³T₁(F) ESA band with the emission which extends from 1100 to about 1600 nm will significantly affect the laser performance of Cr⁴⁺ doped Ca₂GeO₄. The effective peak stimulated emission cross section at 1350 nm in E||b polarization is only about 3 × 10^–20 cm². However, our results indicate that tunable laser action between 1300 and 1500 nm should, in principle, be possible.