Research Publications
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Item AZO coated microchannel incorporated PCF-based SPR sensor: A numerical analysis(2018) Dash J.N.; Das R.; Jha R.An aluminum-doped zinc oxide (AZO) coated photonic crystal fiber (PCF) is proposed and numerically analyzed for surface plasmon resonance-based refractive index (RI) sensing. A microchannel is incorporated in this PCF, which is proposed to be fabricated using a pulsed laser. Such a structure is expected to have less roughness compared to that fabricated by mechanical polishing. Furthermore, properties such as no island formation and absence of intraband transition are added advantages of AZO. Numerical simulation shows that the maximum wavelength sensitivity and the corresponding resolution of this sensor are 5000 nm/RIU and 2 � 10-5 RIU, respectively. Furthermore, the amplitude sensitivity is found to be as high as 167 RIU-1. The proposed structure can be easily fabricated and utilized for sensing applications as it does not require either coating of metals on the inner surface of holes of PCF nor filling of the voids of PCF and it requires a small amount of analyte for RI monitoring. � 1989-2012 IEEE.Item On the performance of Tamm-plasmon and surface-plasmon hybrid-mode refractive-index sensor in metallo-dielectric heterostructure configuration(2015) Das R.; Srivastava T.; Jha R.Hybrid modes formed as a consequence of coupling between Tamm-plasmon polariton (TPP) mode and surface plasmon polariton (SPP) mode in a metallo-dielectric heterostructure geometry exhibit interesting dispersive features which can be employed for realizing highly sensitive and accurate surface-plasmon-resonance (SPR) sensor. The transverse magnetically (TM) polarized TPP modes (TM-TPP), formed at the interface of distributed-Bragg reflector (DBR) and metal, are strongly dispersive as compared to SPP modes at optical frequencies that forms the basis of narrow interaction bandwidth which, in turn, results in improved accuracy of sensing. By deploying a nano/micro-fabrication compatible TiO2/SiO2-based DBR architecture in combination with different plasmon-active metals such as gold (Au), silver (Ag) and aluminum (Al), we propose a TM-TPP and SPP hybrid-mode sensor which exhibit high sensitivity ? 900 nm/RIU for analyte refractive indices varying between 1.330 and 1.345. The investigation also revealed that the hybrid-mode sensor is most accurate in case of Al-based configuration amongst Au, Ag and Al which is primarily due to weaker dispersion characteristics exhibited by Al at visible frequencies. Since, the dispersive behavior of TM-TPP modes could be tailored appropriately in any spectral band, the sensing configuration could be immensely useful for designing sensors at those wavelength where optical sources are readily available. � 2014 Elsevier B.V. All rights reserved.Item THz mode-coupling in photonic-crystal�surface-plasmon-coupled waveguides(2014) Srivastava T.; Das R.; Padhy P.; Jha R.We present a detailed design principle and propagation characteristics of a channel plasmon-photonic�crystal-coupled-waveguide (PPCCW) for realizing terahertz (THz) waveguides and waveguide-based devices. The avoided-crossing behavior exhibited by dispersion curves of the supermodes due to modal interference leads to a sharp change in group velocity close to the phase-matching wavelength. As a consequence, the group-velocity dispersion (GVD) peaks to a maxima (~1.40�נ105�ps/km�?m) and dips to a minima (~?1.60�נ105�ps/km�?m), thus exhibiting extremely large GVD. The propagation length is obtained in the order of a few centimeters. The analysis is substantiated by the frequency dependence of mode field distribution and propagation loss suffered by the supermodes of PPCCW geometry. Also, the obtained result is in good agreement with FEM-based study. The proposed waveguide is aimed at facilitating enhanced performance THz-waveguide sensors and GVD compensation modules. � 2014, Springer-Verlag Berlin Heidelberg.Item Accurate refractive-index sensing with Tamm-plasmon and surface-plasmon based hybrid configurations(2014) Das R.; Srivastava T.; Jha R.We propose hybrid photonic modes formed due to coupling between Tamm-modes and surface-plasmon polariton modes for accurate measurement of refractive indices. We found sensitivity ?900 nm/RIU and detection accuracy ?30 ?m-1 for such sensing configuration. � OSA 2014.Item Accurate refractive-index sensing with tamm-plasmon and surface-plasmon based hybrid configurations(2014) Das R.; Srivastava T.; Jha R.We propose hybrid photonic modes formed due to coupling between Tamm-modes and surface-plasmon polariton modes for accurate measurement of refractive indices. We found sensitivity ?900 nm/RIU and detection accuracy ?30 ?m-1 for such sensing configuration. � OSA 2014.Item Tamm-plasmon and surface-plasmon hybrid-mode based refractometry in photonic bandgap structures(2014) Das R.; Srivastava T.; Jha R.The transverse magnetic (TM) polarized hybrid modes formed as a consequence of coupling between Tamm plasmon polariton (TM-TPP) mode and surface plasmon polariton (SPP) mode exhibit interesting dispersive features for realizing a highly sensitive and accurate surface plasmon resonance (SPR) sensor. We found that the TM-TPP modes, formed at the interface of distributed Bragg reflector and metal, are strongly dispersive as compared to SPP modes at optical frequencies. This causes an appreciably narrow interaction bandwidth between TM-TPP and SPP modes, which leads to highly accurate sensing. In addition, appropriate tailoring of dispersion characteristics of TM-TPP as well as SPP modes could ensure high sensitivity of a novel SPR platform. By suitably designing the Au/TiO2/SiO2-based geometry, we propose a TM-TPP/SPP hybrid-mode sensor and achieve a sensitivity ?900 nm/RIU with high detection accuracy (?30 ?m-1) for analyte refractive indices varying between 1.330 and 1.345 in 600-700 nm wavelength range. The possibility to achieve desired dispersive behavior in any spectral band makes the sensing configuration an extremely attractive candidate to design sensors depending on the availability of optical sources. � 2014 Optical Society of America.Item Guided-mode analysis of tamm-plasmon polariton at metal-heterostructure dielectric interface(2014) Das R.; Pandey A.; Srivastava T.; Jha R.We present a comprehensive analysis for transverse electric (TE) and transverse magnetic (TM) polarized guided Tamm-plasmon polariton (TPP) mode at metal-heterostructure media interface. We explicitly show that the quarter-wavelength stack condition will not be satisfied for TE or TM polarized TPP mode due to the existence of null-point at metal-heterostructure media boundary. Therefore, we propose an alternate route to design TPP waveguide by solving the mode-dispersion relation for different geometrical parameters in a TiO2/SiO2 bilayer system. The guided TPP-modes (TE and TM) exhibit interesting dispersion characteristics which can be tailored as per the desired application. The group index of TM polarized TPP mode remains constant over a significant wavelength range which results into zero group-velocity dispersion (GVD) at ? ? 630 nm wavelength. Also, the propagation length for TM-polarized TPP modes vary between 25 to 50in a 630-650 nm wavelength range. However, the variation of GVD for TE-modes exhibit a monotonic variation with an exceptionally large GVD-3104 around =632.8. � 2014 IEEE.Item Highly Sensitive Plasmonic Temperature Sensor Based on Photonic Crystal Surface Plasmon Waveguide(2013) Srivastava T.; Das R.; Jha R.We propose a highly sensitive temperature sensor based on photonic crystal surface plasmon waveguides comprising different plasmonic active metals such as gold, silver, and aluminum, utilizing surface plasmon resonance phenomenon. We found that the resonance wavelength can be easily and substantially tuned over a broad spectral range by changing the temperature and also by judiciously choosing the different plasmonic metals. Employing coupled mode theory, we found that the proposed sensor can be used in harsh environment with sensitivity as high as ?70 pm/K around telecommunication window. � 2012 Springer Science+Business Media, LLC.Item Mode-coupling between surface plasmon modes and bandgap-guided modes: A comprehensive study and applications(2013) Srivastava T.; Das R.; Jha R.We present a detailed study on waveguide design principle and propagation features of a channel Bragg-surface plasmon-coupled-waveguide (BSPCW). After proposing a convenient design route, we analyze the mechanism of coupling between bandgap-guided modes and surface plasmon polariton modes with respect to change in waveguide parameters such as type of metal, metal thickness and number of unit cells. In order to understand the physical mechanism behind the mode-coupling, we observe the redistribution of modal power of the BSPCW as wavelength changes. The interesting dispersion characteristics exhibited by the BSPCW supermodes opens a novel route to realize accurate sensors and efficient dispersion compensating modules in signal processing. Therefore, this comprehensive study could serve as a tool to optimize the performance of devices dictated by the application requirements in sensor technology and optical communications. The performance of the device in terms of sensing application is also being discussed. � 1983-2012 IEEE.Item Photonic crystal surface plasmon waveguides sensor for high and accurate temperature measurement(2012) Jha R.; Srivastava T.; Das R.Highly sensitive, accurate and stable high temperature (800 K) sensor based on Photonic Crystal Surface Plasmon Waveguides is proposed. The PCW is based on widely used lithographic and nano-fabrication compatible materials like TiO 2 and SiO 2. Gold has been used as a SPR active metal. Employing coupled mode theory, the sensitivity is found to be as high as ? 66 pm/K. � 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).