Abstract
We propose a highly refractive index sensor based on plasmonic Bow Tie configuration. The sensitivity of the resonator design is enhanced by incorporating a nanowall (NW) in a modified Bow Tie design where sharp tips of V-junction are flattened. This approach provides high confinement of electric field distribution of surface plasmon polariton (SPP) mode in the narrow region of the cavity. Consequently, the effective refractive index (neff) of the mode increases and is highly responsive to the ambient medium. The sensitivity analysis of the SPP mode is calculated for six resonator schemes. The results suggest that the NW embedded cavity offers the highest mode sensitivity due to the large shift of effective index when exposed to a slight change in the medium refractive index. Moreover, the device sensitivity of the proposed design is approximated at 2300 nm/RIU which is much higher than the sensitivity of the standard Bow Tie configuration.
Highlights
Surface plasmon polaritons (SPPs) are electromagnetic waves propagating along with the metal-dielectric interface with an exponentially decaying field and have an evolving apprehension of highly integrated optical circuits due to their capability to overcome the diffraction limit of light [1, 2]
This is often quantified as the bulk refractive index sensitivity (S), defined as S = Δλres/Δn, where λres is the wavelength at which the excitation of Surface plasmons (SPs) occurs and Δn is the change in the RI
FWHM is connected to the SP lifetime which typically controls the sharpness of the peak
Summary
Surface plasmon polaritons (SPPs) are electromagnetic waves propagating along with the metal-dielectric interface with an exponentially decaying field and have an evolving apprehension of highly integrated optical circuits due to their capability to overcome the diffraction limit of light [1, 2]. In COMSOL simulations, the subdomains of the sensor design are divided into triangular mesh element with a fine mesh grid size for the air medium and waveguide geometries. This allows us to obtain precise simulation results within the available computational resources. Note: In some works such as [25, 33], FOM is exceedingly high and is represented as FOM* which is calculated differently using the expression ΔR/(RΔn) at a fixed wavelength, where ΔR denotes the reflection intensity variation due to the change in the refractive index (Δn) of the surrounding medium and R is the reflection rate in the sensor structure. It can be calculated by using the expression ΔT/(TΔn), where T denotes the transmittance in the proposed structures and ΔT/Δn is the transmission change at a fixed wavelength induced by a refractive index change
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