Enhancing the axial resolution of an optoacoustic microscopy imaging instrument by using a pico-second pulse duration laser

In conventional optoacoustic microscopy, nanosecond pulse duration lasers are employed. When a laser delivering shorter pulse durations is used, it is expected that, from a theoretical point of view, broader, higher-frequency acoustic waves to be generated, therefore a better axial resolution of the instrument. In the present report, this advantage, offered by a picosecond duration pulse laser, to experimentally demonstrate that the axial resolution of an optoacoustic microscopy instrument can be enhanced was exploited. In comparison to a 2 ns pulse duration, an improvement in the axial resolution of ~50% is demonstrated by using excitations with pulses of duration <100 ps. Details of an optoacoustic microscopy instrument, operating at 532 nm, capable to provide high-resolution axial and lateral optoacoustic images, are also presented. The capabilities of the instrument are demonstrated by in-vivo images of Xenopus laevis brain with a similar ~3.8 µm lateral resolution throughout the whole axial imaging range.