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We demonstrate a laser-based adaptive ultrasonic homodyne receiver using dynamic holography in AlGaAs/GaAs photorefractive multiple quantum wells. The dynamic hologram acts as an adaptive beamsplitter that compensates wavefront distortions in the presence of speckle and requires no path-length stabilization. The photorefractive quantum wells have the unique ability to achieve maximum linear homodyne detection regardless of the value of the photorefractive phase shift by tuning the excitonic spectral phase. We achieve a root mean square noise-equivalent surface displacement of 6.7ϫ10 Ϫ7 Å(W/Hz) 1/2 .

We present a method to separate the effects of trap gratings and electro-optic gratings in BaTiO(3) crystals, and we determine the true spatial shift between the electro-optic grating and the optical intensity pattern. At small beam-crossing angles this spatial shift is strongly affected by a photogalvanic current in the crystal.

A continuous-wave dye laser having a self-pumped phase conjugator in place of its usual output mirror will slowly change its own output wavelength with time. The laser has a bandwidth of 1.5 GHz and can self-scan to either longer or shorter wavelengths over a 37-nm range. The phase conjugator uses self-pumped four-wave mixing in a BaTiO(3) crystal. A ring laser that uses two-wave mixing in the same crystal is also observed to have a frequency offset of a few hertz compared with the frequency of the pumping beam. These two effects are related; both are caused by a spontaneously moving photorefractive-index grating in the BaTiO(3) crystal.

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