Optical coherence modulation by ultrasonic waves 1: Dependence of partial coherence on ultrasonic parameters

Quantitative control of partial coherence by ultrasonic waves is considered theoretically and experimentally. The double coherence modulation factor obtained is space-invariant or not according to whether a light beam passes twice the same path or a different path in a progressive ultrasonic field by reflection at a plane mirror or at a right-angle prism. A double-modulation scheme using a plane mirror reflection system is found to be more effective than a single-modulation scheme for coherence control of low levels of ultrasonic power. The coherence of light is quantitatively varied with the input voltage applied to the ultrasonic transducer.