Superior Imaging Performance of All-Fiber, Two-Focusing-Element Microendoscopes

All-fiber-optic imaging microendoscopes are emerging as an important tool in bioimaging studies, including those conducted with optical coherence tomography, but physical limitations constrain the achievable beam characteristics of designs using a single focusing element. These constraints especially relevant for applications that require long working distance, high resolution, and/or minimal probe diameter. Through detailed analysis based on ABCD matrix modelling, we show side-viewing probes combining graded-index (GRIN) fiber ball lens – GRIN-ball-lens (GBLPs) offer superior performance over range numerical apertures and pave way broader applications. The GBLPs designed 1300-nm tomography is compared against commonly used single-focusing-element all-fiber designs, namely, ball-lens (BLPs) GRIN-fiber (GFPs). All possible realizations this novel design their impact requisite tradeoffs investigated, fabrication error refractive index surrounding medium. Applications GBLPs, ultra-high-resolution (sub-2 micrometer) miniature micro-endomicroscopy, discussed.