Enhancement of ultrasound generated by evanescent light in confined geometry

This paper demonstrates a new approach for generating ultrasound, utilizing evanescent light. Evanescent light generated during total internal reflection at the prism surface, is utilized for generating ultrasound in aluminum specimen. It has been found that ultrasound can be generated in the aluminum specimen only by evanescent light. The amplitudes of ultrasound generated by evanescent light were unexpectedly nine times larger than the ones generated by direct laser irradiation. These results indicate that the possibility of a novel ultrasound pulse-echo transducer with near-field optics for measuring objects smaller than the wavelength of light.