We present the all-fiber approach towards building a miniatured, optical-resolution photoacoustic endoscope. The catheter encapsulates two optical fibers for optical excitation and ultrasound detection, respectively. The ultrasound waves are detected with the laser-based fiber optic sensor, with a diameter of 125 μm, instead of a focused piezoelectric transducer. Photoacoustic endoscopic images from a rat rectum have been acquired in vivo with a range of 6.3 mm, a lateral resolution of 10 μm, and a 285° angular field-of-view. The catheter has a diameter of 2.3 mm and can be further reduced by replacing the bulk prism reflector.
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