Enhancement of parametric efficiency by saturation suppression

The energy conservation equations due to Westervelt are used to show that saturation effects in a finite amplitude wave can in principle be suppressed, if the attenuation coefficient at the second harmonic frequency of the primary wave can be selectively increased. Introduction of microscopic air bubbles which are resonant at the second harmonic frequency is proposed as a scheme for applying this idea to a parametric array operating in water. The parameter of non-linearity also increases when the bubbles are introduced; hence parametric efficiency would be enhanced by both of these effects.