Apparatus that generates acoustic signals at discrete multiple

Abstract

Spherical annulus piezoelectric transducers 62, 64 and spherical disc piezoelectric transducer 66 form a spherical shell having a radius of curvature R with a focal point 70 near the end of cladded-core acoustic waveguide 72. Each transducer 62, 64, 66 generates a bulk acoustic wave of a unique frequency and transmits it to focal point 70 where it enters core 74 of cladded-core acoustic waveguide 72. Alternatively, a conical annulus piezoelectric transducers 92, 116 on a prism 90 generate bulk acoustic waves of multiple discrete frequencies and focus them through cladding 75 and into core 74 of cladded-core acoustic waveguide 72. Surface acoustic waves of multiple discrete frequencies can be generated by multiple sets of curvilinear interdigital conductors 132, 134 on a piezoelectric substrate 122. The shape of curvilinear interdigital conductors 132, 134 focuses the surface acoustic waves at focal point 70 located near the end of acoustic waveguide 72. The surface acoustic waves are converted into bulk/longitudinal waves by either curvilinear corrugations 142, 146 or by a coupling medium that causes the surface acoustic waves to become leaky longitudinal waves. Alternatively, the surface acoustic waves can be coupled to the core of the acoustic waveguide by converting them into either bulk/longitudinal waves or leaky longitudinal waves and guiding them through the cladding to the core. When the acoustic signals travel through the cladding to couple to the core, the acoustic waveguide can transmit optical signals.