Laser-based ultrasound detection using photorefractive quantum wells

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 ${\text{6.7×10}}^{\text{−7}}\mathrm{\hspace{0.17em}\AA (}\mathrm{W/Hz}{)}^{\text{1/2}}.$