Acoustically Induced Transparency and Generation of Multifrequency Radiation

It is shown that excitation of mechanical vibration (acoustical oscillation) of a solid medium along the direction of propagation of laser radiation leads to (i) transparency of a resonant atomic transition (acoustically or vibrationally induced transparency) and (ii) generation of coherent multifrequency optical radiation (normal wave). These effects take place for any energy distribution among the spectral components of the incident (in general, multifrequency) coherent radiation and any amplitude of vibration. The amplitude of vibration determines the efficiency of the normal wave generation and its spectral structure. The mechanism of the effect is destructive interference of different spectral harmonics of the field components appearing in the reference frame of vibrating atoms.