Mina Ray

Resonance parameters based analysis for metallic thickness optimization of a bimetallic plasmonic structure

Metallic film thickness optimization in mono- and bimetallic plasmonic structures has been carried out in order to determine the correct device parameters. Different resonance parameters, such as reflectivity, phase, field enhancement, and the complex amplitude reflectance Argand diagram (CARAD), have been investigated for the proposed optimization procedure. Comparison of mono- and bimetallic plasmonic structures has been carried out in the context of these resonance parameters with simultaneous angular and spectral interrogation. Differential phase analysis has also been performed and its application to sensing has been discussed along with a proposed interferometric set-up.

Experimental surface plasmon resonance modulated radially sheared interference imaging using a birefringent lens

Experimental investigation on surface plasmon resonance (SPR) modulated interference has been proposed and demonstrated under radially sheared environment with the help of a birefringent lens. SPR modulated interference images captured by a charged couple device have been demonstrated in two different analyzing regime, namely, using an analyzer and using a Wollaston prism, the later being advantageous for the simultaneous observation of p- and s-polarized contribution towards SPR. We also report the analysis of the interference imaging for the two substrate materials and also for the two analytes in order to show the substrate-sample dependency of SPR. Moreover, phase dependent resonant behavior, together with the analysis of amplitude reflection co-efficient in complex plane, has been theoretically simulated and discussed in support of the present experimental investigation, which can be well utilized for biological and chemical sensing.

Performance of admittance loci based design of plasmonic sensor at infrared wavelength

Abstract. A Kretschmann-Raether prism-based three-layer structure consisting of a prism, gold (Au) metal film, and dielectric sample has been investigated with the use of admittance loci method in attenuated total internal reflection mode. High index prism materials like silicon, chalcogenide (2S2G), and SF14 have been used to study their effect on surface plasmon resonance (SPR) sensing (at 1200-nm wavelength) in infrared region by corresponding admittance loci plots and also by SPR sensing curves. The performance of the sensor based on the choice of the prism material has been discussed with the help of sensitivity plots giving due importance to the dynamic range of the designed sensor.

Role of waveguide resonance in coupled plasmonic structures using bimetallic nanofilms

Abstract. We theoretically analyze waveguide coupled surface plasmon resonance structure to investigate the coupling phenomenon between waveguide resonance and plasmonic resonance. Variations of types of metals as well as changes of thickness of the waveguide layer produce some interesting phenomena in the context of coupled plasmonics. Different modes that are generated are found to have dual contributions of waveguide and plasmonic effects. Field enhancement and reflectance contour plots with simultaneous angular and wavelength interrogation give some insight into the effect of waveguide resonance on the performance of nanoplasmonic structure. Figure of merit calculations and comparison of angular and wavelength differential curves of different nanoplasmonic structures can be used to determine the right candidature as regarding the better sensing performance compared to conventional SPR based sensor. Moreover, the important role played by the thickness of the waveguide layer is also established with supporting simulations.

Coupled plasmonic assisted progressive multiple resonance for dielectric material characterization

In this paper, we report the theoretical analysis of different types of plasmonic structures with the main emphasis on the coupled plasmon waveguide resonance due to several advantages offered by the same compared to other structures. Multiple resonance dips are found to increase with the increase in the dielectric layer thickness and this progressive nature of the dips can be efficiently utilized to characterize the dielectric material within a composite multilayer plasmonic structure. Supporting simulation results carried out in the MATLAB environment are also provided to validate the proposed application.

Equi-Reflectance Dual Mode Resonance Using Bimetallic Loaded Dielectric Plasmonic Structure

Theoretical study of the reflectance response of an asymmetrically-clad bimetallic film that supports coupled surface plasmon polariton modes has been presented. Through adjusting the relative thickness of the two metal film components, the relative coupling strength to the long range (LR) and short range plasmon modes can be altered. It is possible to obtain optimal and equi coupling (zero reflectivity) to both modes for given incident wavelength by further adjusting the overall thickness of bimetallic film. Simultaneous angular and spectral sensitivity calculations of resonance of the LR mode have been demonstrated for sensing application. Tailoring of the structure of individual metal films realizing equi- and non-equi-reflectance modes has been proposed which may further be used for plasmonic trinary logic using binary di-bit images.

Simultaneous excitation of multi-spectral surface plasmon resonance using multi-stepped-thickness metallic film

A new scheme of variable thickness ladder-like stepped metal film for simultaneous excitation of surface plasmon resonance (SPR) with different wavelength based on modified three layer Kretschmann configuration has been proposed. Metal thickness has been optimized for four different wavelengths ranging from visible to near infrared. The thickness has also been optimized for different substrates as well as different metal films in order to show the dependency of the substrate and metal layers on the ultimate performance of the plasmonic structure. A new concept of Reflectance Constrained Dynamic Range has been employed and its value has been calculated numerically and graphically for each SPR structure under consideration and for each wavelength considering water as reference sample and using the optimized metal thickness. Electric field enhancement has been evaluated for different structures and the full width half maximum has also been calculated for four working wavelengths in order to study the field c...

Circular Phase Response-Based Analysis for Swapped Multilayer Metallo-Dielectric Plasmonic Structures

In this paper, two types of nanoplasmonic structures, namely multilayer metallo-dielectric and multilayer-swapped metallo-dielectric structures have been analyzed in context of phase jumps and related phenomena due to the positional swap in the metallo-dielectric block. Phase, reflectivity, and field enhancement plots are also discussed in the angular and wavelength regime. Detailed analysis using circular phase response along with the angled histogram of the phase for both structures provides significant understanding of this swapping phenomenon. Parametric analysis of the metallo-dielectric block has also been demonstrated. Figure of merit defined in complex plane also gives some insight into the performance of the structures.

Parametric Analysis of Spectral Fano Lineshape for Plasmonic Waveguide-Coupled Dual Nanoresonator

Numerical investigations of metal-dielectric-metal waveguide-coupled dual nanoresonator is demonstrated. Phase dependent resonant behavior along with its complex plane analysis is investigated in wavelength regime. Detailed analysis of the influence of the structural parameters on the resonance curve helps to determine the correct device parameters for different plasmonic applications. This waveguide-coupled plasmonic resonator can be utilized for chemical and biological sensing. In this context, figure of merit related to the asymmetric Fano line shape is redefined, incorporating both differential phase and quality (Q)-factor. Theoretical analysis of differential phase sensitivity in wavelength regime predicts the possibility of detection of refractive index change of the order of 10-8 RIU.

Angular Piecewise Modal Analysis for Waveguide-Coupled Surface Plasmon Resonance Structure

Resonance response of waveguide-coupled surface plasmon resonance (WCSPR) structure is investigated numerically in a piecewise manner. The 2-D reflectance and phase along with the phase response circle (PRC) and complex amplitude reflection Argand diagram in angular interrogation is demonstrated for homo- and hetero bimetallic nanofilm. The gradual appearance of waveguide resonance with increasing thickness of the waveguide layer provides significant information about the coupling of waveguide and plasmonic resonance which is much needed for the choice of correct device parameters. Moreover, magnetic field enhancement is also studied for each different mode in angular piecewise manner with variations in metal layers as well as variations in WG layer using different conventional optical polymers. Angular piecewise differential phase gives some insight into the application of chemical and biological sensing and can provide an improved sensitivity by direct imaging of the fringe pattern due to the change in refractive index of the sensing medium.