Temporal Dynamics and Spatial Imaging of THermally-induced Optical Reflection of Sound (THORS) Barriers

Abstract

Thermally Induced Optical Reflection of Sound (THORS) is a novel technique that allows a user to optically manipulate sound waves in a medium by photothermally exciting that medium with infrared light, thereby creating a transient barrier due to the changes in compressibility of the medium. This phenomenon offers numerous potential applications in fields as varied as acoustic suppression and reflection, photoacoustic spectroscopy and imaging, and ultrasonic waveguiding. Previous results have revealed maximum suppression efficiencies as great as 72 ± 5% using a continuous THORS barrier system with a multi-pulsed carbon monoxide laser operating at 5.5 ± 0.25 μm and 1 ms pulses. To greater understand the spatial variations in medium compressibility between the excited medium and the surrounding environment, we have employed Raman imaging to visualize these barriers.