An optical homodyne technique for measurement of amplitude and phase of subangstrom ultrasonic vibrations

An optical homodyne technique is utilized to measure sub-angstrom dynamic mechanical deformations. For measurement in the frequency domain, where synchronous detection is used both the amplitude and phase of the mechanical signal can be measured with a high sensitivity; displacements less than 10^-2Å were measured with normal environment acoustic noise. Measurement in the time domain is also feasible with reduced sensitivity.