Violet laser emission in copper halides

Abstract

With two-photon excitation into the longitudinal exciton or into the excitonic continuum copper halides show laser emission at wavelengths of 413.3 nm (CuI), 422.5 nm (CuBr), and 391.9 nm (CuCl). The linewidth of the emission is very narrow in CuI and CuBr (below 0.004 nm) and much broader in CuCl (0.4 nm). The laser transition occurs between the bottleneck of the exciton polariton and the longitudinal optical phonon.