Label-Free Optical Fiber Glucose Biosensor Based on Two-Mode Interference

A label-free glucose biosensor has been proposed and demonstrated in this article based on a tapered two-mode fiber (TTMF) sandwiched between two single-mode fibers (SMFs). The tapering technique helps excite the ${\textit {LP}}_{{11}}$ mode in TTMF, forming uniform interference fringe containing the ${\textit {LP}}_{{01}}$ and ${\textit {LP}}_{{11}}$ modes. The experimental results show that the sensor’s sensitivity increases, as the TTMF waist diameter decreases, and at the TTMF diameter of $13.12 \mu \text{m}$ , the maximum glucose sensitivity can reach 0.112 nm/mg/mL, while the temperature sensitivity is as low as 16.43 pm/°C. With compact structure, label-free sensing capacity, and ease fabrication, this proposed biosensor has bright application prospect in the fields of food safety, disease diagnosis, and clinical analysis.