Design of a reconfigurable two-dimensional photonic crystal filter and sensor for biomedical and industrial applications

Abstract

This study presents the design of a novel two-dimensional (2D) photonic crystal (PhC)-based reconfigurable filter and sensor. A systematic approach was employed to design periodic structures with tailored optical properties by manipulating refractive indices and introducing strategic defects. The proposed silicon PhC structure, featuring air holes with a radius of 0.26 µm, exhibits a photonic band gap (PBG) spanning 1.85 µm to 2.55 µm. The compact and multifunctional structure can perform both optical filtering and refractive index (RI) sensing within the same photonic crystal configuration through a defect-engineered approach. Optimized structural parameters enabled the filter to achieve a transmissivity of 59.33% with a quality factor (Q-factor) of approximately 71.88 at a resonant cavity air hole radius of 0.245 µm. Furthermore, the device demonstrates high sensitivity to RI variations in the range of 1.0 to 1.35 within the resonant cavity air holes (R1 and R2), with a maximum observed sensitivity of 106 nm/RIU. With compact dimensions of 3.92 µm × 2.92 µm, the design provides a versatile framework for PhC-based sensing and filtering applications. These capabilities make it highly suitable for biomedical diagnostics, industrial chemical analysis, and optical communication systems, offering a scalable and efficient solution for diverse advanced applications.