Experimental setup for photoacoustic imaging (PAI). (a) Schematic diagram of PAI experimental setup using PMUTs. (b) Picture of the setup showing the agarose gel phantom, PMUTs array, light-guide, and embedded pencil lead targets, (c) Photoacoustic A-line signal detected by the PMUT element after 39 dB gain, from a pencil lead placed ~2.3 cm away, on excitation by the laser source. The inset shows the frequency response of the photoacoustic pulse with center frequency of ~7 MHz and approximately 68% fractional bandwidth.