Optical spectra and relaxation of Cr3+ ions in YAlO3

Abstract

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.