Infrared spectroscopy of chromium-doped cadmium selenide

The maximum optical-absorption cross section of Cr^sup 2+^ ions was evaluated from near-infrared (NIR) absorption spectroscopy and direct measurements of the chromium concentration in Cr^sup 2+^:CdSe crystals. The emission lifetime of the excited state, ^sup 5^E, of Cr^sup 2+^ was measured as a function of Cr^sup 2+^ concentration in the 2×10^sup 17^ -2×10^sup 18^ ions/cm^sup 3^ range and as a function of temperature from 77-300 K. Lifetime values were as high as 6 µs in the 77-250 K range and decreased to 4 µs at 300 K because of nonradiative decays. Assuming that most of the Cr dopant is in the Cr^sup 2+^ state, an optical-absorption cross section σ^sub a^ of (1.94±0.56) × 10^sup -18^ cm^sup 2^ was calculated. Implications for laser performance are discussed.[PUBLICATION ABSTRACT]