Design and Analysis of a Photonic Crystal Nanocavity Biosensor for Glucose Measurement

Abstract

This article presents a biosensor based on a two-dimensional rod-in-air photonic crystal slab with a hexagonal lattice, specifically designed for glucose detection in both urine and blood samples. The photonic band structure is studied using the plane-wave expansion (PWE) method, while sensing parameters are analyzed using the finite-difference time-domain (FDTD) method. To enhance device performance, the nanocavity width and radii of silicon rods above the w1 waveguide are optimized. The design provides a wide bandgap and strong optical confinement within the cavity, ensuring high sensitivity to refractive-index variations. The 2D and 3D configurations of the structure are investigated. The sensor demonstrates a noticeable frequency shift and significant variation in transmitted output power in response to minute refractive-index variations. Simulation results confirm high performance, achieving a maximum sensitivity of 850 nm/ RIU, a high quality factor of 1.8956\(\times \)10\(^\textrm{4}\), a low detection limit of 1.115\(\times \)10\(^{-5}\) RIU, and a high figure of merit of \(\approx 8968\) \(\textrm{RIU}^{-1}\). Moreover, the device operates reliably over a wide temperature range (0–80 °C), and the effect of fabrication tolerances on performance is thoroughly analyzed. With its compact footprint of \(\approx 100\) \(\mu m^2\) and excellent sensing characteristics, the proposed sensor is a strong candidate for integration into on-chip photonic circuits.