Modelling of a photoacoustic probe designed for medical applications

A model is presented describing the thermoelastic photoacoustic interaction in a layered medium within a transparent fluid, where a polymer transducer is used for the detection of ultrasonic pulses. By taking the optical absorption coefficient and finite layer thickness into account, the amplitude and shape of photoacoustic transients are calculated for both forward and backward travelling directions. Additionally, photoacoustic transient interaction with the PVDF transducer has been characterised using a discrete-time algorithm for the transducer response. Good agreement with experimental waveforms are demonstrated, so that this may form the basis of system characterisation when miniature laser-ultrasound probes are used in various applications.