Tailored Photoacoustic Apertures with Superimposed Optical Holograms

Abstract

AbstractA new method of generating potentially arbitrary photoacoustic wavefronts with optical holograms is presented. This method uses nanosecond laser pulses at 1064 nm that are split into four time-delayed components by means of a configurable multipass optical delay apparatus which serves to map the pulses onto phase-delayed regions of a given acoustic wavefront. A single spatial light modulator generates separate holograms for each component which are imaged onto a photoacoustic transducer comprised of a thermoelastic polymer. The spatially- and temporally-modulated holograms facilitate a phased array effect which enables beam steering of the resulting acoustic pulse. For a first experimental demonstration of the method, as verified by simulation, an acoustic beam is steered in four directions by around 5 degrees.