Photorefractive crystal-based holographic interferometry system for full-field wave propagation metrology

Although, photorefractive materials have been discovered for many years, research using pulsed laser as the light source and photorefractive material as the recording media to record a pulsed laser hologram have been scarce despite its vast application potential. A newly proposed optical configuration which adopts a Nd:YAG pulsed laser of 532nm wavelength as the light source and uses an iron-doped lithium niobate crystal as the recording media for holographic recording of an un-deformed specimen is presented. Real-time holographic interferometry was achieved by inducing repetitive impacts on the specimen through a precise piezoelectric impact hammer. With timing control better than microseconds, several interferograms created at each instance were obtained with each corresponding 9ns laser pulse. A five-step phase-shifting technology, median filter algorithm, and weighted iterative DFT phase unwrap algorithm were integrated to reconstruct the deformation information at each instance. Using a series of measured deformation data, surface wave propagation phenomenon on the specimen could be observed. Some of the potential applications for this newly developed pulsed laser holographic interferometry system are detailed.