SASER action in optically excited ruby: Angular and spectral distribution

Abstract

Selective pulsed optical excitation is used in 500-at.ppm ruby (Al2O3:Cr 3+) at 1.4 K to prepare complete population inversion of the Zeeman-split E(2 E) doublet in a zone of limited size. The inversion results in prolific stimulated emission of phonons resonant with the one-phonon transition connecting the doublet states. The phonons are detected via the R1 luminescence. The angular and spectral distributions of the associated acoustic wave are measured using a geometry with inverted zones at either end of the crystal, one serving as generator and the other as detector. The divergence appears to be governed by the geometry of the zone, while the spectral distribution is, within errors, in keeping with the inhomogeneously broadened phonon transition.