Performance Analysis of High Contrast Sub Wavelength Grating for Biomedical Sensing Applications

Abstract

Traditional biosensing technologies have limitations such as complex sample preparation, expensive operating systems, and limited sensitivity. These constraints have driven the need for advanced sensing platforms with improved performance metrics. Recently, high-contrast subwavelength gratings (HCGs) and surface plasmon resonance have been suggested among the most powerful candidates in optical biosensing since they can manipulate light at a subwavelength scale with a high degree of freedom. Optical biosensors based on HCGs represent a rising class of optical sensors that allow label-free detection non-invasive diagnostics, and in situ place data acquisition, thus providing large advantages over conventional sensing technologies. High contrast subwavelength gratings (HCSGs) are periodic microstructures with a grating period smaller than the wavelength of incident light. These microstructures exploit resonant effects and photonic band gaps, which permit powerful light-material interactions required for sensitive detection mechanisms. Using these properties, HCGs can work as a promising platform for biosensing applications and eliminate the need for sophisticated approaches. In this research, a performance analytical study of high-contrast subwavelength gratings for biomedical sensing applications has been done and the goal is to improve our design and enlarge their utility in the detection of biomolecular interactions. A generic framework is developed to evaluate the performance of HCSG-based sensors, considering factors such as grating parameters (grating thickness, grating height, grating periods, etc.), the refractive index contrast, and functionality for biomolecular recognition. This research explores the optimization of HCSG-based biosensors, specifically focusing on their design parameters that affect performance metrics such as resolution, sensitivity, and detection limits. By using advanced simulation techniques, including FDTD (finite-difference time-domain) methods, the study analyses the various effects of design parameters of HCSGs, such as grating period, depth, and duty cycle, on the sensor's sensitivity and performance. Furthermore, parametric research is carried out to establish the most efficient grating design for maximizing sensor performance in real-world biomedical sensing applications. Highly reflective mirror technologies are majorly required in bio-sensing applications to eliminate complex multiple diffraction orders. Various grating parameters, i.e. width, thickness, and period are analyzed to get optimized values and high reflectivity for high-contrast subwavelength grating (HCSG) structure. Besides these parameters, polarization modes, angle of incidence, and refractive index have been diversely analyzed to monitor their effects on HCSG structure concerning reflectivity. The simulation results manifest that the optimized parameters help to achieve the best reflectivity that can be further utilized in bio-sensing applications. The best-optimized parameters in our research for HCSG structure are polarization mode (TM mode), angle of incidence (0°, 4°), grating width (S = 0.5855 μm), grating thickness (tg = 0.495 μm), and grating period (L = 0.77 μm). Along with these parameters, as the refractive index of the surrounding material of grating changes, a wavelength of reflectivity dip shifts towards the right side. All these parameters result in 99.998% reflectivity for HCSG structure that can be further utilized in bio-sensing applications. This research's fundamental contribution is the establishment of a structure that considers HCGs' unique properties. The framework includes a set of performance parameters, such as detection limit, sensitivity, and figure of merit, which provide a comprehensive analysis of sensor performance. This evaluation method provides essential facts about how HCGs can be adapted for various medicinal applications and establishes the basis for future research. A high contrast grating-based surface Plasmon resonance-based biosensor with high detection accuracy has been proposed. High sensitivity has been obtained by using a high value of dielectric material. The detection accuracy and sensitivity are optimized utilizing the metal layer thickness and its width in the continuation of periodic gratings. With the help of the finite difference time domain (FDTD), the enhanced values of sensitivity are obtained and compared to the photonic crystal waveguide and surface plasmon resonance sensor. The proposed sensor also overlaps the fabrication constraints of various metals as a high value of dielectric material has been employed. HCG-based plasmonic (SPP) biosensors using Titanium oxide and Indium Tin Oxide (ITO) have been investigated to meet the best configuration. that overlap the fabrication constraints by using a high value of dielectric materials. In comparison to the Photonic crystal waveguide and surface plasmon resonance sensor, the reported sensor exhibits a higher resolution in terms of detection accuracy. The presence of high contrast grating provides stability and improves the detection accuracy 560 µm−1 and sensitivity 3150 nm-RIU−1. The value of a high dielectric constant enhances the interaction of surface plasmon resonance and has the lowest influence on sensitivity DA and Sn. A high value of dielectric constant and periodic grating provides a possibility for this geometry to be acknowledged in any wavelength spectral domain. The research suggests that HCG-based sensors present a feasible path toward highly sensitive, dependable, and compact biosensing devices, especially when paired with plasmonic changes.