Impact of Waist Diameter on Glucose Sensing with MZI-Based Nonadiabatic Tapered MicrolNanofibers

Glucose sensors are critical in label-free optical biosensing. This study explored the use of nonadiabatic tapered micro/nano optical fibers (NATOFs) with varying diameters (
$\mathbf{10}\ \boldsymbol{\mu}\mathbf{m}, \mathbf{9}\ \boldsymbol{\mu} \mathbf{m}, \mathbf{7}\ \boldsymbol{\mu}\mathbf{m}$
, and
$\mathbf{6}\ \boldsymbol{\mu} \mathbf{m}$
) for glucose detection. These fibers were constructed using the Mach-Zehnder interferometry (MZI) principle and the fiber fusion-drawing taper technique. The optical fibers were used to measure refractive indices in glucose solutions with mass fractions ranging from 2 wt% to 20 wt%, where the refractive indices varied between 1.3346 and 1.3608. The findings revealed that decreases in waist diameter substantially enhanced sensor sensitivity, with recorded values of 1851.9 nm/RIU, 2025.8 nm/RIU, 2563.3 nm/RIU, and 2646.4 nm/RIU. Additionally, reducing the diameter of the waist region decreased the free spectral range, enhancing the sensor's accuracy in measuring glucose concentration. This study highlights the potential of micro/nanofiber optic technology in biosensor design, offering new insights for biomedical detection, food quality monitoring, environmental surveillance, and chemical analysis.