Upconversion luminescence in Cr3+:YAG single crystal under infrared excitation

The present work concerns the upconversion luminescence in Cr3+:YAG single crystal under infrared laser irradiation. During the experiment, 404 nm, 808 nm, 980 nm, and 1064 nm laser excitation sources in range of -150 degrees C-600 degrees C were employed. A strong red light emission was detected in the bulk of the samples under the infrared excitation. The red emission originated from T-4(2)g ->(4)A(2)(g) transition of Cr3+ ions and are only observed at temperatures higher than 150 degrees C; the profile of the emission curve is Gaussian-type with maxima at 500 degrees C, 600 degrees C, and 620 degrees C for A 808 nm, 980 nm, and 1064 nm respectively. This is attributable to the high-temperature nature of the upconversion luminescence, where the energy gap between the energy of a laser photon and the T-4(2)g state is compensated by simultaneous absorption of two photons.