Excitation of Type 1 HMM with a Grating for Biosensing Applications

Abstract

This thesis explores the excitation of bulk plasmon polariton (BPP) modes in type 1 hyperbolic metamaterials (HMMs) for biosensing applications. Utilizing a nanorod array embedded in a dielectric and enhanced by a diffraction grating, the study demonstrates the potential for achieving high sensitivity in refractive index biosensors. The methodology involves finite-difference time-domain (FDTD) simulations using Tidy3D software, focusing on the reflectance response and field intensity distributions of the nanostructures. Initial simulations of a nanorod array revealed standing wave patterns indicative of surface plasmon polariton (SPP) modes. The introduction of a grating structure, with a pitch optimized for BPP mode excitation, resulted in significant enhancement of the electromagnetic field intensity. This enhancement was particularly notable at a wavelength of 1.2625 μm, demonstrating a maximum normalized intensity approximately nine times that of the incident field. Further analysis showed that the BPP modes exhibited a strong dependence on the grating pitch and the dielectric refractive index, underscoring their potential for high-sensitivity biosensing. For the BPP mode, the calculated figure of merit (FOM) was 66.67 and the sensitivity (S) was 800 nm/RIU, substantially higher than the 16.00 FOM and S=400 nm/RIU observed for SPP modes. While the grating-based approach offers a compact and practical platform for exciting BPP modes, the sensitivity results were lower than those achieved with prism coupling methods. This suggests the need for further simulations and experimental validation to optimize the grating design and improve coupling efficiency. In conclusion, this work advances the understanding of BPP mode excitation in HMMs, highlighting the feasibility of using grating structures for biosensing applications. Future research should focus on refining the grating parameters and conducting experimental tests to validate these findings and explore their practical implementations in compact biosensing devices.