Photorefractive Interferometry Research Articles

Imaging of transient surface acoustic waves by full-field photorefractive interferometry.

A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

Spectrally resolved detection of mixed acoustic vibrations by photorefractive interferometry

A two-wave mixing photorefractive interferometry method in an anisotropic diffraction scheme, intended to selectively detect an acoustic vibration component at a specific frequency of interest in the presence of strong vibrations at other frequencies, is presented and validated by simulations and experiments. The achieved narrow-band detection is of particular interest for applications where weak vibration signals generated by nonlinear acoustic effects are to be detected with high sensitivity and without cross-talk from the large vibration components from which the acoustic nonlinearity is originating.