Ultra-sensitive high aspect-ratio flexible optical fibers for multi-parameter high-resolution sensing

A new class of optical fibers characterized by a high aspect ratio quadrilateral cross-section is introduced, termed high-aspect-ratio-flat-fiber (HARFF). HARFFs demonstrate superior performance in applications demanding an asymmetric, deterministic response, providing enhanced sensitivity, precision, and resilience. Using advanced laser-based processing combined with stack-and-draw fabrication, we engineered HARFFs with tailored mechanical properties, yielding ultra-sensitive pressure sensors with over three orders of magnitude improvement in sensitivity over conventional optical fiber designs. We demonstrated further sensitivity enhancement in HARFFs through a multi-material microstructure by achieving increased temperature sensitivity in Sn-alloy-filled HARFFs. Our findings highlight the transformative potential of HARFFs, opening new avenues for innovations in non-circular high aspect-ratio fiber optics.