Study on detecting ultrasound by means of near-field light

Abstract

This report presents a fundamental study on detecting ultrasonic waves utilizing near-field light. Scanning near-filed optical microscope (SNOM) is developed by modifying atomic force microscope (AFM). Obtaining AFM and SNOM images by changing probe-sample distance, the dependency of the distance for the intensity of scattered near-field light within 20 nm area is verified, which is related to the penetration depth of the near-field. AFM and SNOM images under the ultrasonic vibration show that the scattered light changes with the amplitude of the ultrasonic vibration. These results reveal the feasibility of detecting ultrasound using near-field light.