IDR @ IIT Bhubaneswar
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Item Metal wire waveguide based all plasmonic refractive index sensor for terahertz frequencies(2016) Padhy P.; Sahu P.K.; Jha R.A terahertz refractive index sensor for liquid analytes consisting of a copper wire waveguide and co-axial layers of PMMA and PVDF is established numerically. The dispersion behavior of the fundamental core and surface mode and their phase matching has been demonstrated that clearly explains the working mechanism of the sensor. A core mode amplitude sensitivity of 59.9 for unit change in refractive index at 269.8 ?m is obtained for the proposed sensor. It has a large evanescent field penetration depth of 48 ?m at the phase matching point that can facilitate sensing of analyte refractive index further away from the interface. A definition for group velocity sensitivity is proposed which is then evaluated for the proposed sensor. The near dispersion free behavior of the sensor core mode except around the phase matching point gives it an excellent group velocity sensitivity of 128.9 for unit change in refractive index. � 2015 Published by Elsevier B.V.Item Ultrasensitive THz - Plasmonics gaseous sensor using doped graphene(2016) Purkayastha A.; Srivastava T.; Jha R.We propose a surface plasmon resonance (SPR) based gas sensor in terahertz frequency with Otto configuration based on attenuated total reflection (ATR) technique using free standing doped graphene monolayer. Angular interrogation method has been used to study the performance of the sensor in terms of sensitivity and detection accuracy. Different chemical potential of graphene monolayer has been investigated to study its effect on these performance parameters. The results show that the optimization of the gap distance between the prism base and the graphene monolayer has significant effect on the reflectivity of SPR sensing. This SPR based gas sensor shows ultrahigh sensitivity of 34.11 deg/RIU along with an ultrahigh Figure of Merit (FOM) of more than 1150 RIU-1. � 2015 Elsevier B.V. All rights reserved.Item Graphene based surface plasmon resonance gas sensor for terahertz(2016) Srivastava T.; Purkayastha A.; Jha R.We report a SPR based gas sensor using doped graphene monolayer employing the ATR technique via modified Otto coupling configuration. The proposed gas sensor is an approach different from the already reported Otto geometry for SP excitation in terahertz frequencies where the air gap has been replaced by a dielectric spacer layer (organic material) of refractive index (nd) 1.44, 1.50 and 1.54 at operating terahertz frequency of 5�THz. The performance of the sensor with respect to key system parameters such as the thickness of the dielectric layer, sensitivity, detection accuracy and FOM are investigated in the paper using angular interrogation via Transfer matrix method. It is observed that with increasing refractive index of spacer dielectric, the proposed gaseous sensor exhibits trade off between sensitivity and detection accuracy. However, the FOM is approximately equal for refractive indices 1.44 and 1.50 of spacer material, which is ~20�% higher than that at nd�=�1.54. The FOM for nd�=�1.44, increases from 527 (analyte refractive index�=�1.00) to 741 RIU?1 (analyte refractive index�=�1.10). � 2016, Springer Science+Business Media New York.Item Highly Sensitive Side-Polished Birefringent PCF-Based SPR Sensor in near IR(2016) Dash J.N.; Jha R.We propose a highly sensitive side-polished birefringent photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR). The polished surface of the proposed structure is coated with indium tin oxide (ITO) to excite plasmon and the analytes can be placed on the flat surface easily instead of filling the voids. The birefringent nature of the structure helps in coupling more fields to the ITO-dielectric interface. With the optimum thickness of 110�nm of ITO, the structure shows a maximum wavelength sensitivity of 17000�nm/RIU with a resolution of 5.8 � 10?6�RIU. Further this also showed an amplitude sensitivity of 74�RIU?1 along with a resolution of 1.35 � 10?5�RIU. Moreover, the effect of bending on this low loss structure is also analyzed. � 2016, Springer Science+Business Media New York.Item Graphene oxide encapsulated gold nanoparticle based stable fibre optic sucrose sensor(2015) Nayak J.K.; Parhi P.; Jha R.Abstract Optical fibre based localized surface plasmon resonance (LSPR) sensor using graphene oxide (GO) encapsulated Au nanoparticles has been reported for sucrose sensing. Au-nanoparticles (AuNPs) are encapsulated with GO in fixed ratio to prevent the AuNPs from aggregation as agglomeration of AuNPs broadens the absorbance spectra by more than 25%. The TEM results support the formation of 2 nm thickness of GO around Au nanoparticle of approximate size of 30 nm thereby making the sensor stable. The GO encapsulated AuNPs was immobilized on the core of processed and functionalized optical fibre for sucrose sensing. We found that the peak absorbance changes with sucrose refractive index and the sensitivity of 2.288 ?A/RIU has been obtained i.e. the peak absorbance changes by 75.78% with 0.0395 change in refractive index of sucrose. Our experimental results are in good agreement with theory. � 2015 Elsevier B.V.Item On the Performance of Graphene-Based D-Shaped Photonic Crystal Fibre Biosensor Using Surface Plasmon Resonance(2015) Dash J.N.; Jha R.We propose a D-shaped photonic crystal fibre-based surface plasmon resonance sensor considering graphene on silver for sensing of refractive index of analyte and thickness of biolayer. The different structural and material parameters associated with sensor have been optimised. Graphene not only helps in adsorption of biomolecules due to ?-? stacking interaction but at the same time prevents oxidation of metal-like silver. Numerical simulation shows that amplitude sensitivity of the proposed structure for chemical analytes is 216�RIU?1 (refractive index unit) with a resolution of 4.6 � 10?5�RIU while the wavelength sensitivity of the proposed sensor is found to be as high as 3700�nm�RIU?1 with resolution of 2.7 � 10?5�RIU. Further, the proposed sensor can also be used for the detection of biolayer thickness in both amplitude and wavelength interrogations. An amplitude sensitivity of 0.26�nm?1 with resolution of 39�pm and wavelength sensitivity of 2�nm�nm?1 with resolution of 50�pm is achievable for the determination of biolayer thickness. The proposed structure is easy to use as there is no need of filling of voids, and the analytes can be placed easily on the flat surface of photonic crystal fibre (PCF). � 2015, Springer Science+Business Media New York.Item Graphene-Based Conducting Metal Oxide Coated D-Shaped Optical Fiber SPR Sensor(2015) Patnaik A.; Senthilnathan K.; Jha R.We report a graphene-based indium tin oxide coated surface plasmon resonance sensor built on a D-shaped optical fiber for near infrared. Different parameters of the proposed sensor have been optimized to obtain a maximal phase matching between the core guided mode and the plasmon mode using finite element method. Wavelength sensitivity of the proposed structure is as high as 5700 nm/RIU with a maximum resolution of 1.754 � 10-5 RIU. The proposed sensor can also be used for bio layer thickness monitoring with a maximum resolution of 62.5 pm in wavelength interrogation. � 2015 IEEE.Item Ultrasensitive plasmonic imaging sensor based on graphene and silicon(2013) Maharana P.K.; Srivastava T.; Jha R.We propose an ultrasensitive, accurate, and cost effective surface plasmon resonance sensor based on graphene-on-aluminum and silicon. An angular interrogation method has been theoretically used to study the performance of the sensor in terms of imaging sensitivity, which quantifies the rate of change of slopes of the reflectance curve close to resonance angle. Different optimized design parameters have been reported. It is found that the imaging sensitivity of an aluminum-based sensor is 750% greater than gold, the most widely used SPR active metal. However, graphene-on-aluminum not only prevents the aluminum oxidation but, a monolayer of graphene-on-aluminum exhibits ?400% larger imaging sensitivity compared to that of a conventional gold-film based SPR sensor. � 1989-2012 IEEE.Item On the field enhancement and performance of an ultra-stable SPR biosensor based on graphene(2013) Maharana P.K.; Padhy P.; Jha R.The effect of graphene on the electric field enhancement and performance of SPR-based sensor has been proposed and compared with Ag-Au bimetallic configuration. We found that a monolayer of graphene on Ag not only addresses the oxidation problem of Ag, but it also shows >30% field enhancement as compared with the widely reported Ag-Au bimetallic combination. Detailed calculations and simulations show that the proposed graphene-based sensor has >22% higher sensitivity and >38% narrower full-width at half-maximum than bimetallic. In addition, the better biomolecules adhesion due to graphene because of ?-stacking interaction may open a new window for ultra-stable high performance biosensors for real time bimolecular interactions. � 1989-2012 IEEE.Item Design considerations for plasmonic-excitation based optical detection of liquid and gas media in infrared(2011) Jha R.; Sharma A.K.Surface plasmon resonance (SPR) sensor schemes based on silicon (Si) and chalcogenide glass are evaluated and compared for chemical as well as gas detection in a wide range of infrared (IR) wavelengths. The plasmonic characteristics in IR are critically dependent on the dispersive behavior of the coupling substrate material. The performance of sensor has been evaluated in terms of its intrinsic sensitivity (IS) that includes the FWHM and angular shift of SPR curve for a given change in refractive index of sensing medium. Both these materials are potential candidates for opening up new routes for detection in near- and mid-IR due to their strong dispersion capabilities as compared to normal silica-based glass. The IS of chalcogenide glass-based SPR sensor is found to be larger than Si-based one for a broad wavelength range of 700-2500 nm indicating that chalcogenide glass-based probe provides more sensitive as well as accurate sensing procedure than Si-based probe. Further, for both glasses, the single probe can be used for both aqueous as well as gaseous sensing. Furthermore, for both glasses, it is found that the values of IS are much larger for gaseous sensing in comparison to liquid sensing. � 2010 Elsevier B.V.