A Hollow-Core Fiber Based Stand-Alone Multimodal (2-Photon, 3-Photon, SHG, THG) Nonlinear Flexible Imaging Endoscope System

Abstract

Multimodal nonlinear endoscopes have been a topic of intense research over the past two decades, enabling sub-cellular and label-free imaging in areas not reachable with table-top microscopes. They are sophisticated systems that can be implemented on an optical table in a lab environment, but they cannot be easily moved within or out of the lab. We present here a multimodal and flexible nonlinear endoscope system able to perform two-photon excited fluorescence and second harmonic generation imaging with a stand-alone and movable kart integrating a compact ultrashort laser source. In addition, the system can perform three-photon excited fluorescence and third harmonic generation imaging thanks to a delivery optical fiber that connects a large frame laser system to the stand-alone kart. The endoscopic fiber probes and delivery optical fibers are based on functionalized negative curvature hollow core fibers. The endoscope distal head has a diameter $< $ 2.2 mm and can perform nonlinear imaging at max 10 frames/s over a field of view up to 600 μm with a $\sim$ 1 μm spatial resolution.