SPECTRA AND KINETICS OF YAG:0.5%Er3+ RADIATION UNDER PULSED LASER THERMAL EXCITATION

Abstract

The dependences of single-crystal YAG:0.5 %Er³⁺ spectra in the range 200-1700 nm and the kinetics of the integrated emission on the excitation energy density W of a single CO₂ laser pulse of ~100 ns FWHM duration at l_ex = 10.6 µm were experimentally investigated. The spectra qualitatively changed when W exceeded the threshold of emergence of the laser plasma W_t near the surface of monocrystals. At W < W_t, the spectra of YAG:0.5% Er³⁺ were represented by peaks of the selective emission (SE) of Er³⁺ multiplets on the pedestal of the continuous spectrum. New emission peaks and an additional pedestal corresponding to the emission spectra in a laser-induced air plasma with intensities much higher than the SE peaks appeared due to the air ionization near the crystal surface at W > W_t. The shape of the oscillograms of the integral emission in the range 600-1700 nm was characterized by a front duration of pulses τ_f = 1.0-1.6 µs and a decay time of 2.5 µs when W changes by one order. The kinetics of the integrated emission intensity was explained by calculations of the single-crystal temperature and the population of Er³⁺ energy levels in the conversion of thermal energy into the SE during unsteady energy transfer by internal radiation and thermal conductivity.