Photorefractive and photochromic polymers as adaptive beam combiners for laser-based ultrasound detection

Summary form only given. Photorefractive materials have attracted interest in the detection of phase modulated signals as the transient hologram in the material can convert the phase modulation into an amplitude modulation. Due to the very nature of the hologram, the principle also works for speckled beams, which enables operation with beams reflected from non-mirror-like surfaces. As the transient hologram can adapt to changes slower than the material response time, noise with frequencies below the response time is rejected, leading to better signal-to-noise ratios. These features make photorefractive materials attractive for the remote detection of ultrasonic waves in workpieces for quality testing in industrial production.