Novel air-borne ultrasonic sensor using nanofoam and a laser Doppler vibrometer

We propose a novel airborne ultrasonic sensor, using nanofoam and a laser Doppler vibrometer that can operate over a wide frequency range and provide high sensitivity. Nanofoam is a porous material made by sol-gel process and has low density, low elasticity, and extremely low acoustic impedance. These properties enable nanofoam to take in acoustic energy from ultrasonic waves. In addition, nanofoam has a good optical transmittance. Because optical detection can be much faster than detection period in the sound frequency range, it has been considered that a wideband ultrasonic sensor can be realized by the combination of nanofoam and laser measurement. In this report, we describe fabrication of the proposed sensor and determine its basic properties.