Stimulated emission and lasing in Cu(In,Ga)Se₂ thin films

Stimulated emission and lasing in Cu(In,Ga)Se₂ thin films have been demonstrated at a temperature of 20 K using excitation by a nanosecond pulsed N₂ laser with power densities in the range from 2 to 100 kW cm⁻². Sharp narrowing of the photoluminescence band, superlinear dependence of its intensity on excitation laser power, as well as stabilization of the spectral position and of the full-width at half-maximum of the band were observed in the films at increasing excitation intensity. The stimulated emission threshold was determined to be 20 kW cm⁻². A gain value of 94 cm⁻¹ has been estimated using the variable stripe length method. Several sharp laser modes near 1.13 eV were observed above the laser threshold of I _thr ∼ 50 kW cm⁻². (paper)