A focused lens for measuring object response to modulated radiation pressure

Abstract

An ultrasonic lens was designed and tested for use in modulated radiation pressure experiments for the purpose of exciting and identifying the low frequency modes of objects in water. The lens was designed to produce a focused beam, and care was taken to minimize the spherical aberration introduced by the lens. This was done by carefully specifying the shape of the lens surface that was then machined using a computer-controlled lathe. The lens was placed in contact with an electrically excited piezoceramic plate. The quality of the focused sound field was tested and found to display properties predicted by simple models of the focal plane wave-field. The lens was then used to drive low-frequency modes of elastic objects in water using modulated ultrasonic radiation pressure in a way previously summarized involving a commercially made focused transducer [T. D. Daniel et al., J. Acoust. Soc. Am. 140, 3123 (2016)]. [Work supported by ONR.]