Ultra-Sensitive Glucose Detection in Biological Fluids Using Optimized Photonic Crystal Nanocavity Sensor

This article presents a biosensor design based on a two-dimensional rods-in-air photonic crystal (PhC) slab with a hexagonal lattice structure for detecting glucose concentrations in both urine and blood. The band structure is analyzed using the plane-wave expansion method (PWE), while sensing parameters are analyzed using the finite -difference time-domain (FDTD) method. To enhance sensor performance, the nanocavity width and the radii of silicon rods above the w1 waveguide are optimized. The sensor provides a large band gap and strong light confinement within the cavity region, enabling highly sensitive detection of refractive index variations. Both 2D and 3D designs of the structure are investigated. The sensor exhibits a noticeable frequency shift and variation in transmitted output power in response to small refractive index variations. Numerical simulations confirm the high performance of the sensor, achieving a sensitivity of 1000 nm/ RIU, a high quality factor of 1.8956×10\((^{\rm 4})\), a low detection limit of 1.256×10\((^{-5})\) RIU and a high figure of merit of 8968.385 RIU\((^{-1})\). Moreover, since PhC fabrication is inherently prone to imperfections during manufacturing, the impact of these fabrication-induced disorders on sensor performance is thoroughly assessed. Finally, the small footprint area of the proposed design, 100.55 \((\mu\text{m}^2)\) and its excellent performance make it well-suited for on-chip photonic integrated circuit applications.