Phonon physics in ruby studied by optical pumping and luminescence

Two examples are treated of nonequilibrium phonons in ruby as studied with optical pumping for generation and luminescence for detection. The first example concerns nonequilibrium 29cm-1 and near-zone-boundary phonons generated in the nonradiative decay from higher multiplets to 2A¯(2E) and E¯(2E). The second example shows that coherent phonons are produced by stimulated emission over the Zeeman transition within the E¯(2E) metastable doublet.