Adaptive gain interferometry: a new mechanism for optical metrology with speckle beams

We describe, for the first time to our knowledge, the use of a saturable laser gain medium to implement an adaptive gain interferometer for performing optical metrology with speckle-distorted beams. We show that interferometric formation and replay of a saturable gain hologram permit coherent extraction of fast vibrational information about an object in real time and removal of slowly varying spatial distortion. An experimental characterization of the frequency response of the adaptive gain interferometer is made by use of a diode-pumped solid-state laser amplifier, and a new theoretical formulation of the gain interferometer is also developed for the first reported time.