Generation of laser light via ultrasonic four-wave mixing

On the basis of the interaction between phonons in ionic crystals with anharmonic lattice vibration, we present a laser model on acoustic nondegenerate four-wave mixing. Two beams of high-frequency ultrasound, incident upon the acoustic cavity fulfilled with the medium of ionic crystal, play the role of pumping, and one of the two side-band modes of the pumping frequency as an acoustic signal mode has a strong interaction with the optical cavity mode, the coupling-out of which will be the light (far-infrared) output of a laser. The problem is treated with quantum-mechanics. The theory shows that there is the threshold phenomenon as usual lasers and a so called phase-matching condition is derived, which should be satisfied for the stability of the system.