Generation of coherent phonons in ruby

Abstract

In conditions of inversion of spin-level populations at T = 1.7° K the resonant stationary coherent phonon emission has been revealed in ruby at frequency ν = 9.12 GHz. The intensity of emission is I S ≈ 10 −6 W·cm −2. The frequency spectrum consists of very narrow lines generated simultaneously on several modes of hypersonic ruby cavity. Monochromatism of emission in each line is Δν/ ν ⩽ 2 × 10 −6. The spectrum nature permits to suppose the levelwidth of elementary spin excitation to be Δν s < 3 × 10 5 Hz, i.e. at least 2–3 orders it is narrower than the inhomogeneously broadened resonant line in ruby. The lifetime of resonant phonons in ruby was defined: τ = 7 × 10 −6 sec.