Research Publications
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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 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 Channel Bragg-plasmon coupled waveguide(2011) Das R.; Jha R.; Srivastava T.We present a detailed analysis and recipe for designing a channel Bragg-plasmon coupled waveguide where the intermodal coupling between a band gap-guided mode and surface plasmon mode substantially modifies the phase velocity dispersion slope of supermodel. This leads to appreciably large group-velocity-dispersion with peak value of ? 4.33�104 ps/km-nm close to the optical communication band as well as interaction bandwidth of about 765 pm for 1 cm long waveguide. We also found that bandgap guided Bragg modes exhibit stronger dispersive features than the plasmon modes around ? 1.50 ?m which is exactly opposite to what is usually observed in visible region. The impact of waveguide parameters such as channel width etc. on mode-coupling mechanism is also studied with significant emphasis on the propagation loss suffered by the supermodes of the structure. � 2011 SPIE.