title: The frequency-dependent directivity of a planar fabry-perot polymer film ultrasound sensor.
abstract: A model of the frequency-dependent directivity of a planar, optically-addressed, Fabry-Perot (FP), polymer film ultrasound sensor is described and validated against experimental directivity measurements made over a frequency range of 1 to 15 MHz and angles from normal incidence to 80 degrees. The model may be used, for example, as a predictive tool to improve sensor design, or to provide a noise-free response function that could be deconvolved from sound-field measurements in order to improve accuracy in high-frequency metrology and imaging applications. The specific question of whether effective element sizes as small as the optical-diffraction limit can be achieved was investigated. For a polymer film sensor with a FP cavity of thickness d, the minimum effective element radius was found to be about 0.9 d, and that an illumination spot radius of less than d/4 is required to achieve it.
authors.affiliation: Department of Medical Physics and Bioengineering, University College London, UK. bencox@mpb.ucl.ac.uk
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Cox
authors.forename: Paul C
authors.initials: PC
authors.lastname: Beard
mesh_terms: D016880:Anisotropy; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007368:Interferometry / Q000295:instrumentation* / Q000379:methods; D008567:Membranes, Artificial; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods
chemical_list: D008567:Membranes, Artificial; D011108:Polymers