Internal laser modulation by acoustic lens-like effects

A cylindrical acoustic wave in a laser medium will function as a time-varying, converging-diverging optical waveguide. An analytical examination of the trajectories of light rays propagating through a medium subjected to acoustic waves is presented. The use of acoustically-generated, periodic refraction index perturbations for modulating the output of a Nd³⁺-doped glass laser without having to insert lossy optical elements into the Fabry-Perot feedback interferometer is reported. The properties of this type of laser control are 1) increased output laser energy, 2) periodic time variation of the resonance mode structure, 3) uniform pulse heights, and 4) repetitive pulse train at a controlled frequency.