This Small Business Innovation Research Phase I project is intended to demonstrate the practical feasibility of photorefractive polymers for use in laser ultrasonic receivers. Laser ultrasound can be used for remote measurements of parts in hostile environments where traditional transducer-based ultrasound techniques cannot be used. The primary component of most laser-based ultrasound receivers is some type of interferometer. One promising type of interferometric receiver uses real-time holography in photorefractive material. The photorefractive material functions as an adaptive beamsplitter, coherently combining a plane-wave reference beam and a probe beam which has been distorted while interrogating the test surface. Due to limitations in the photorefractive materials, none of the current interferometric receivers has performed near their theoretical capability. The goal of this program is to implement a robust and highly sensitive laser ultrasonic receiver by combining heterodyne detection scheme with a photorefractive polymer as the real-time adaptive beamsplitter. We also seek to tailor the photorefractive polymer properties in order to reach the theoretical capability of the designed laser-based ultrasound receiver.
Laser-based ultrasound has applications in wide range of industrial markets. It offers the capability to improve the inspection rate of conventional scanning systems and it will enable the inspection of many parts that cannot be tested with other techniques. It is particularly promising as an in-process diagnostic for components that are at high temperature and/or are moving at high velocities.
