Elongated focus optoacoustic microscopy with matched Bessel beam illumination and ultra-broadband axicon detection

Current optoacoustic microscopy configurations often have narrow focal ranges that limit their use for fast volumetric imaging applications. Here, the focal range of optoacoustic microscopes is extended by matching the elongated optical illumination profile of a Bessel beam with the pencil beam acoustic sensitivity profile of a broadband axicon detector. An inverted optoacoustic microscope was developed with interchangeable optical illumination and acoustic detection units to assess the imaging depths and resolutions retained with several combinations of illumination and detection profiles. Matching Bessel illumination with axicon detection extends the depth-of-focus 17-fold over traditional configurations. Imaging a tilted mouse ear with the matched Bessel-axicon configuration revealed vasculature over an imaging depth exceeding 4.2 mm with optical resolution, while affording a 6-fold increase in imaging volume over the same scanning duration compared to configurations employing standard Gaussian illumination, demonstrating this approach's promise for increasing applications for optoacoustic microscopy in preclinical research.