Absolute calibration of interferometric systems for detection and measurement of surface acoustic waves

A calibration method for interferometric systems is shown to produce a minimum wave amplitude to which these systems may be calibrated in the measurement of harmonic surface acoustic waves. The calibration limit is ~3 orders of magnitude larger than the theoretical detection limit. The method proposed allows experimental determination of the detection limit of these systems. The calibration of a fiber-optic heterodyne interferometer is demonstrated, and the experimentally derived detection limit for the interferometer is shown to be 5.5 x 10(-15) m for unity detection bandwidth. This limit is obtained for a mirrored specimen with 0.14 mW of laser power incident on the optical detector.