Large-field-of-view optical-resolution optoacoustic microscopy using a stationary silicon-photonics acoustic detector

Significance: Optical-resolution optoacoustic microscopy (OR-OAM) enables labelfree imaging of the microvasculature by using optical pulse excitation and acoustic detection, commonly performed by a focused optical beam and an ultrasound transducer. One of the main challenges of OR-OAM is the need to combine the excitation and detection in a coaxial configuration, often leading to a bulky setup that requires physically scanning the ultrasound transducer to achieve a large field of view. Aim: The aim of this work is to develop an OR-OAM configuration that does not require physically scanning the ultrasound transducer or the acoustic beam path. Approach: Our OR-OAM system is based on a non-coaxial configuration in which the detection is performed by a silicon-photonics acoustic detector (SPADE) with a semi-isotropic sensitivity. The system is demonstrated in both epi- and transillumination configurations, where in both configurations SPADE remains stationary during the imaging procedure and only the optical excitation beam is scanned. Results: The system is showcased for imaging resolution targets and for the in vivo visualization of the microvasculature in a mouse ear. Optoacoustic imaging with focal spots down to 1.3 μm, lateral resolution of 4 μm, and a field of view higher than 4 mm in both lateral dimensions were demonstrated. Conclusions: We showcase a new OR-OAMdesign, compatible with epi-illumination configuration. This setup enables relatively large fields of view without scanning the acoustic detector or acoustic beam path. Furthermore, it offers the potential for high-speed imaging within compact, miniature probe and could potentially facilitate the clinical translation of OR-OAM technology.