Side-viewing axicon-integrated miniature fiber probe for extended depth of focus and ultrahigh lateral resolution endoscopic imaging

The early and precise diagnosis of suspected pathological tissues or organs has increasingly embraced the utilization of 3D real-time visualization and discrimination of intricate structures facilitated by miniature optical coherence tomography (OCT) endoscopic probes. Those miniature side-viewing endoscopic fiber probes are indispensable for 3D imaging with small, narrow lumens, eliminating the potential for tissue trauma associated with direct-viewing techniques. Nevertheless, current manufacturing techniques pose limitations on the overall imaging prowess of these miniaturized side-viewing probes, hindering their widespread adoption. To surmount this challenge, an ultra-compact side-viewing OCT fiber-optic endoscopic probe with extended depth of focus (DOF) and high lateral resolution is designed based on the all-fiber composite structure. The quantitative relationship between the imaging performance and the fiber structural parameters has been theoretically analyzed. The imaging performance of the fiber probe can be flexibly tailored by adjusting the geometric parameters of the fiber-optic cascade structure. The applicability and feasibility of fiber probe prototype have been convincingly demonstrated through linear scanning and rotational scanning methodologies. This ultra-compact side-viewing OCT fiber probe's capacity to deliver microscopic structural insights paves the way for minimally invasive applications, expected to advance the frontier of early and precise diagnosis and treatment of suspected lesion tissues.