An integrated optoacoustic transducer combining etalon and black PDMS structures

An integrated optoacoustic transducer combining etalon and black polydimethylsiloxane (PDMS) structures has been designed and developed. The device consists of an 11-mum-thick black PDMS film confined to a 2-mm-diameter circular region acting as an optoacoustic transmitter, surrounded by a 5.9-mum Fabry-Perot polymer etalon structure serving as an optoacoustic detector array. A pulsed laser is focused onto a 30-mum spot on the black PDMS film, defining the transmit element, while a CW laser probes a 20-mum spot on the etalon for ultrasound detection. Pulse-echo signals display center frequencies of above 30 MHz with bandwidths of at least 40 MHz. A theta-array is formed for 3-D ultrasound imaging by mechanically scanning the generation laser along a 1-D array and the detection laser around an annular array. Preliminary images with 3 metal wires as imaging targets are presented. Characterization of the device's acoustical properties, as well as preliminary imaging results, suggest that all-optical ultrasound transducers are potential alternatives to piezoelectric techniques for high-frequency 2-D arrays enabling 3-D high-resolution ultrasound imaging.