Characterization of optoacoustic transducers through the analysis of angular-dependent frequency response

Comprehensive characterization of optoacoustic transducers is achieved through the analysis of their frequency response using a procedure of measuring angular dependence of the transducer sensitivity to the ultrawide-band delta pulse. The testing was performed under standard repeatable operating conditions. Back-illumination of a blackened, acoustically matched, planar surface with a short laser pulse creates an acoustic impulse which was used as an ultrawide-band ultrasonic source. The bandwidth of such a source extends well over 10 MHz (6dB point at 16 MHz for illumination with a 16 ns pulse) and the low frequency roll-off is around 300 kHz. Analysis of the angular dependence of the frequency response yields invaluable directivity information about the detector under study, which in turn permits accurate forward and inverse problem models.