Metal layer integration in one-dimensional photonic crystal for enhanced malaria biosensor sensitivity

Photonic crystal-based biosensors are attracting growing interest due to their high sensitivity and ultrafast response in biomedical diagnostics. We present a theoretical analysis and performance comparison of two one-dimensional photonic crystal (1D-PhC) structures aimed at malaria detection. The variation in the refractive index of the defect layer corresponding to various stages of malaria causes a shift in the transmission peak of the defect mode. The Transfer Matrix Method (TMM) is used to compute the transmission spectra. A Finite Element Method (FEM) tool COMSOL Multiphysics is used for studying the electric field distribution in the PhC structure. The integration of the metal layer on either side of the defect layer improved sensing performance. To investigate the tunable characteristics, variations were made in the type of metal, metal layer width, defect layer refractive index and incident angle for TE and TM polarisations. The presence of surface plasmon waves at the metal-dielectric interface enhances the sensitivity to small changes in the refractive index, enabling more effective detection. The novelty of the work includes the development of a PhC-based biosensor for malaria detection with sufficient sensitivity and transmission intensity using a small volume of sample defect. Sensor with silver layer achieved a sensitivity of 265.2 nm/RIU, a quality factor of 1.35 × 10², a resolution of 3.771 × 10⁻⁴ RIU, a figure of merit (FOM) of 49 RIU⁻¹ and response time of 18 fs with transmission 63 %. The proposed structure has a total thickness of 3.12 μm and offers a compact, cost-effective design with ultrafast response.