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Adaptive Compensation for Laser-based Ultrasound Detection Using Holographic Quantum Wells

D.D. Nolte, I. Lahiri, and L.J. Pyrak-Nolte, Dept. of Physics, Purdue Univ., West Lafayette, IN; M.B. Klein and G.D. Bacher, Lasson Technologies, Pacific Palisades, CA; M.R. Melloch, School of Electrical and Computer Engin., Purdue Univ., West Lafayette, IN.

Holograms that can change in time and adapt to environmental disturbances have interesting and important applications in diverse areas. The key to adaptive performance is the ability of the holographic recording process to track slow changes, such as thermal fluctuations in the optical path or mechanical vibrations. Low-frequency noise is adaptively compensated by the adapting hologram, while high-frequency signals are passed through to the detector. A classic example of an incessant problem in optics is the stability of an interferometer. With an adaptive hologram acting as a beam combiner in the interferometer, no active stabilization is necessary. Any changing path lengths are simply compensated by a corresponding shift in the interference fringes of the hologram.