Jayeta Banerjee

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.

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...

Surface plasmon resonance mediated fringe modulation using a birefringent lens creating radial shearing environment

A cost-effective simple technique to observe and analyze the surface plasmon resonance modulated radially sheared interference images using a birefringent lens (BL) is reported. Theoretical and experimental investigations have been presented for metallic thickness optimization, angle selection depending on the numerical aperture of BL, together with real and complex plane analysis of resonance parameters for better understanding of experimental results. Simultaneous observation of p- and s-polarizations using Wollaston prism also supports the modulation because of coupling of surface plasmons with p-polarization, whereas the unperturbed s-polarization can be used as reference. Moreover, we have also utilized this technique as the refractive index sensor for the analyte in contact with the plasmon generating metallic film.

Moiré pattern generation by dual shearing and its modulation by surface plasmon resonance.

A novel surface plasmon resonance (SPR)-mediated Moiré fringe generation is theoretically and experimentally investigated using a birefringent lens (BL) and a Wollaston prism. Birefringent lens having two longitudinally shifted focal points provides radial shear, whereas Wollaston prism introduces lateral shear between the two radially sheared patterns for mutual orthogonal polarizations. Thus Moiré-like pattern is produced at the overlapping region of those patterns. Brief theory and experimental demonstration of coherent and incoherent Moiré fringe generation by such dual shearing is presented. The appearance and disappearance of Moiré pattern with the rotation of the analyzer axis has also been demonstrated. A modified experimental setup has also been developed to observe the influence of plasmonic excitation on such patterns which can be further utilized for photonic applications such as sensing and imaging.

Fresnel-zone-like moiré patterns: optical generation and plasmonic modulation with proposed surface profilometry application

A novel scheme of surface plasmon resonance-assisted Fresnel-zone-like moire pattern generation has been theoretically and experimentally investigated in a dual shearing environment. Lateral shear is followed by radial shear with the help of a Wollaston prism and a birefringent lens, respectively. The superposition of two contrast-reversed Fresnel-zone-like patterns (FZP) with parallel equi-spaced straight lines interestingly generates the displaced replication of the original FZP, particularly when the lateral shear is of a sufficient amount. Modulation due to plasmonic excitation has also been observed on such patterns for two different substrate materials. Binary representation of radially sheared images has been illustrated and further utilized for the proposed non-contact surface profilometry of metal coatings.

Theoretical Differential Phase Analysis for Characterization of Aqueous Solution Using Surface Plasmon Resonance

Surface plasmon resonance (SPR)-based differential phase analysis has been presented. Real as well as complex plane analysis of resonance parameters have been undertaken for the optimum selection of metal thicknesses in a bimetallic SPR configuration working under both angular and spectral regime. Theoretically, we can characterize the aqueous solution in terms of this differential phase variation due to the variation of sample parameters such as concentration and temperature. In this respect, two case studies, namely, concentration of hemoglobin in human blood and sensing of temperature of water have been demonstrated and proposed theoretically. By monitoring the change of differential phase, proposed approach leads to a very sensitive measurement of concentration and temperature.

Generation of Moiré pattern and its modulation by surface plasmon resonance

Theoretical and experimental investigation of surface plasmon resonance (SPR) assisted radially sheared interference imaging using a birefringent lens having two longitudinally shifted focal points has been reported. As Wolllaston prism can introduce lateral shear between the two mutual orthogonal polarizations of radially sheared pattern, Moiré-like pattern is produced at overlapping region of those patterns. Brief theory and experimental demonstration of coherent and incoherent Moiré fringe generation has been done. Surface plasmon resonance (SPR) mediated Moiré pattern has been demonstrated which can be further utilized for other nanophotonic applications.

Surface Plasmon Resonance Based Differential Phase Analysis Using Mach-Zehnder Interferometric Set-up

A novel scheme of experimental surface plasmon resonance (SPR) based differential phase analysis using Mach-Zehnder interferometric set-up has been demonstrated. Two glass prisms have been used in the two arms of the interferometric set-up. SPR modulated interferometric fringes can be observed with the use of thin Al coating on the hypotenuse surface of the glass prism, placed in one of the arms of interferometric set-up. Moreover, the change in fringe pattern can also be interpreted in terms of the direct difference of phase between Al-coated and uncoated glass prisms. SPR based direct difference of phase between test and reference beams can be measured using this technique which can be utilized for nanoplasmonic sensing.

Theoretical Investigation on Coupled Plasmon Waveguide Resonance in Real and Complex Domain for High Precision Nanoplasmonic Sensing

Numerical investigations on modified multilayer coupled plasmonic structure, termed as coupled plasmon waveguide resonance (CPWR) structure, have been presented in real as well as complex plane domain. Coupling of waveguide resonance and plasmonic resonance results in dual resonance. Reflectance, field enhancement, and phase-dependent resonant behavior have been analyzed in angular interrogation for three different metal layers in order to optimize the structure with proper choice of metal layers. The resonance parameters have also been theoretically investigated in differential angular regime for better comparison of the shape of different resonance curves. Complex amplitude reflection and transmission co-efficients are analyzed with circular graphical plots in the complex plane. Simultaneous observations of the real and imaginary parts as well as amplitude and phase of the reflection and transmission co-efficients have been demonstrated. Different conventional optical polymers have been considered as waveguide layer materials and their respective real and complex plane analyses demonstrate the comparison for the proper choice of the waveguide layer. Moreover, the resonance parameters and the differential plots in real as well as complex plane for coarse and precise measurement have also been investigated for nanoplasmonic sensing applications to provide improved resolution.