Optical spectra and relaxation of Cr3+ ions in YAlO3

Optical absorption and emission spectra of Cr3+ ions in YAlO3 have been investigated at 300 and 77°K. In the cubic field approximation, the spectra can be fitted by the parameters Dq = 1800 cm−1, B = 590 cm−1, C = 2980 cm−1. An intense vibronic spectrum is associated with 2E → 4A2 fluorescence transitions. Measurements of absorption cross sections and oscillator strengths, thermal broadening and shifts of the R-line fluorescence, and lifetimes of the 2E fluorescence and Cr3+-Cr3+ pair lines are reported. At low temperatures and chromium concentrations, the radiative quantum efficiency of the 2E state is approximately unity. Other relaxation processes become important at temperatures > 400°K. The possibility of observing stimulated emission from YAlO3:Cr3+ is discussed.