8F-1 Integrated All-Optical Ultrasound Transducers

A broadband all-optical ultrasound transducer has been designed, constructed and tested for high-frequency ultrasound imaging. It consists of a 3 mum PDMS layer sandwiched between a two-dimensional gold nanostructure and a 30 nm gold layer. A laser pulse at the resonance wavelength of the gold nanostructure is focused onto the surface for ultrasound generation, and a CW laser at a wavelength far from resonance is used as the probing beam. The signal to noise ratio of a pulse-echo signal from a 70 mum diameter transmit element combined with a 20 mum diameter receive element probing a near perfect reflector positioned 1.5 mm from the transducer surface is over 10 dB, and has the potential to be improved by at least another 40 dB, while the center frequency is 40 MHz with -6 dB bandwidth of 57 MHz. A high-frequency ultrasound array has been emulated using multiple measurements from the transducer while mechanically scanning an imaging target. Characterizations of the device´s optical and acoustical properties, as well as preliminary imaging results, strongly suggest that all-optical ultrasound transducers can be used to build high-frequency arrays for real-time high-resolution ultrasound imaging.