Optically shifting the focal plane to allow depth scanning of delicate biological structures and processes in their natural environment offers an appealing alternative to conventional mechanical scanning. Our technique uses a deformable mirror-based photoacoustic remote sensing microscopy (PARS) with a focus shifting of Δz ∼ 240 µm. We achieve this by integrating a deformable mirror that functions as a varifocal mirror for axial scanning. First, the system's focal shift capability was demonstrated with USAF resolution targets and carbon fiber phantoms, followed by in-vivo visualizations of blood vessels in chicken embryo chorioallantoic membrane (CAM). This work represents an initial step toward developing a non-contact, label-free, and aberration-free PARS imaging system with axial scanning capability.

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