Faculty Publications

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Publications by NITK Faculty

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Author: search.filters.author.Das, P.P.Has files: No

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    Design, fabrication and characterization of 5 μm ring resonator
    (Optica Publishing Group (formerly OSA), 2016) Kollia, V.R.; Yadunath, T.R.; Resmi, R.K.; Hegde, G.; Badrinarayana, T.; Das, P.P.; Srinivas, T.
    We present the design, simulation, fabrication and characterization of microring resonator on SOI platform. Proposed feature size device resonates at a wavelength of 1565.92 nm. The fabricated device has potential applications in communication and sensing. © OSA 2016.
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    Integrated optics-based quantum communication devices
    (SPIE spie@spie.org, 2017) Ramakrishnan, R.K.; Samad, S.A.; Archana, K.; Yadunath, T.R.; Das, P.P.; Srinivas, T.
    Quantum communication or more specifically quantum information processing is considered as the future of information science and technology. In this paper we propose a scheme to implement quantum communication at the device level using integrated optics. We implement the quantum communication protocol BB84, in a waveguide based circuit using integrated optics. We also propose a high dimensional quantum key distribution method implementation using integrated optics. In the earlier one polarized photons are used as the carriers of quantum information, while in second one electromagnetic modes in the waveguide are used to carry quantum information. The high dimensional quantum communication method is used to increase the information content of protocol thus increasing on the data rates. This is done by encoding into a larger state space. We have used electromagnetic modes for encoding since the polarization method is not efficient to carry information in a larger state space. © 2017 SPIE.
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    Photonic crystal ring resonator: A promising device for a multitude applications
    (SPIE spie@spie.org, 2017) Yadunath, T.R.; Kumar, R.R.; Tupakula, T.; Kandoth, A.; John, K.; Ramakrishnan, R.K.; Das, P.P.; Badrinarayana, T.; Mohan, S.; Hegde, G.M.; Srinivas, T.
    In this paper a 2D Photonic Crystal array in SOI platform having hexagonal periodicity with a ring defect incorporated along with two bus waveguides is conceptualized and realized for various applications of optical communication, sensing etc. The ring structure filters out a resonant wavelength from the spectrum carried to it through the line defect where the resonated peak is determined by the effective ring radius. The hexagonal architecture enables more coupling length than an ideal ring structure which helps in better intensity accumulation. The resonant peak exhibited at 1554nm in simulation, which is observed in the optical characterization at 1543nm. This is attributed to the fabrication tolerance. © 2017 SPIE.
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    Multiple Order and Broadband Optical Orbital Angular Momentum Source using a Single Photonic Crystal Device
    (Institute of Electrical and Electronics Engineers Inc., 2020) Yadunath, T.R.; Ravindran, R.; Hegde, G.; Das, P.P.; Srinivas, S.
    A promising optical integrated circuit device design for the generation of broadband, low order OAM modes with topological charges of +1 and +2 is successfully conceptualized using a combination of ring and point defect in thin photonic crystal slab structure with circular array of holes. © 2020 IEEE.
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    Highly efficient catalytic reductive degradation of various organic dyes by Au/CeO2-TiO2 nano-hybrid
    (Springer India sanjiv.goswami@springer.co.in, 2017) Saikia, P.; Miah, A.T.; Das, P.P.
    Highly improved catalytic reductive degradation of different organic dyes, in the presence of excess NaBH4 over Au/CeO2-TiO2 nano-hybrid as the catalyst is reported in this study. CeO2-TiO2 nanocomposite was prepared by a facile co-precipitation method using ultra-high dilute aqueous solutions. Small amount of Au (only 1 wt%) was loaded onto the nanocomposite material by deposition-precipitation with urea (DPU) method to fabricate the ternary Au/CeO2-TiO2 nano-hybrid. The catalysts were characterized by the representative techniques like XRD, BET surface area, ICP-AES, UV-Vis diffuse reflectance spectroscopy, TEM and XPS. The Au/CeO2-TiO2 nano-hybrid along with NaBH4 exhibited remarkable catalytic activities towards all the probed dyes, namely Methylene Blue, Methyl Orange, Congo Red, Rhodamine B and Malachite Green, with a degradation efficiency of ?100% in a short reaction time. The degradation reaction followed pseudo-first-order kinetics with respect to the concentration of the dye. Different parameters that affect the rate of the reaction are discussed. A plausible mechanism for methylene blue degradation has also been proposed. [Figure not available: see fulltext.] © 2017, Indian Academy of Sciences.
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    Dependence of the 0.5 × (2e2/h) conductance plateau on the aspect ratio of InAs quantum point contacts with in-plane side gates
    (American Institute of Physics Inc. subs@aip.org, 2017) Das, P.P.; Jones, A.; Cahay, M.; Kalita, S.; Mal, S.S.; Sterin, N.S.; Yadunath, T.R.; Advaitha, M.; Herbert, S.T.
    The observation of a 0.5 × (2e2/h) conductance plateau in asymmetrically biased quantum point contacts (QPCs) with in-plane side gates (SGs) has been attributed to the onset of spin-polarized current through these structures. For InAs QPCs with the same width but a longer channel length, there is roughly a fourfold increase in the range of common sweep voltage applied to the SGs over which the 0.5 × (2e2/h) plateau is observed when the QPC aspect ratio (ratio of length over the width of the narrow portion of the structure) is increased by a factor 3. Non-equilibrium Green's function simulations indicate that the increase in the size of the 0.5 × (2e2/h) plateau is due to an increased importance, over a larger range of common sweep voltage, of the effects of electron-electron interactions in QPC devices with a larger aspect ratio. The use of asymmetrically biased QPCs with in-plane SGs and large aspect ratio could therefore pave the way to build robust spin injectors and detectors for the successful implementation of spin field effect transistors. © 2017 Author(s).
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    Graphene-mediated band gap engineering of WO3 nanoparticle and a relook at Tauc equation for band gap evaluation
    (Springer Verlag service@springer.de, 2018) Baishya, K.; Ray, J.S.; Dutta, P.; Das, P.P.; Das, S.K.
    Engineering the band gap of semiconductors is often crucial in the quest for developing new and advanced technologies. In this report, the implication of graphene on the band gap optimization of tungsten trioxide (WO3) is discussed. Simple one-step sol–gel process was followed to anchor WO3 nanoparticles in graphene. Graphene induces a redshift in the band gap of WO3. Band gap narrowing of 6.60% is observed for 7 wt% graphene-tethered WO3. Interestingly, a profound difference is observed in estimating the band gap energy values following the usual Tauc equation. Our observation suggests that the differential form of Tauc equation is better suited to determine the band gap energy of inorganic semiconductors than the typical extrapolation method. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Capacitance and impedance spectroscopy studies of polymer light emitting diodes based on MEH-PPV:BT blends
    (Elsevier Ltd, 2019) K M, N.K.; Sterin, N.S.; Das, P.P.; Umesh, G.; Satyanarayan, M.N.
    Light emitting polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is blended with a wide bandgap electron transport material benzothiadiazole (BT) and its effect on the electronic properties has been studied by capacitance and impedance spectroscopy (IS) in PLEDs. The impedance data is fitted using equivalent circuit models and the minimum parallel resistance (Rp) at zero bias have been obtained for 1:3 ratio of MEH-PPV:BT blended devices. The negative capacitance (NC) shows the occurrence of the trap-assisted non-radiative recombination mechanism at low frequencies in the unblended MEH-PPV PLEDs. Further, this behavior is seen to be reduced in PLEDs with MEH-PPV:BT blends. This clearly suggests that the blending of MEH-PPV and BT at different weight ratios results in the suppression of trap-assisted recombination. This can be attributed to the elimination of trap states due to the dilution of semiconductor material on account of the addition of wide bandgap host material. Moreover, the blended devices have shown a significant improvement in the conductivity at small bias voltages. © 2019 Elsevier B.V.
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    Width dependence of the 0.5 × (2e2/h) conductance plateau in InAs quantum point contacts in presence of lateral spin-orbit coupling
    (Nature Publishing Group Houndmills Basingstoke, Hampshire RG21 6XS, 2019) Das, P.P.; Cahay, M.; Kalita, S.; Mal, S.S.; Jha, A.K.
    The evolution of the 0.5Go (Go = 2e2/h) conductance plateau and the accompanying hysteresis loop in a series of asymmetrically biased InAs based quantum point contacts (QPCs) in the presence of lateral spin-orbit coupling (LSOC) is studied using a number of QPCs with varying lithographic channel width but fixed channel length. It is found that the size of the hysteresis loops is larger for QPCs of smaller aspect ratio (QPC channel width/length) and gradually disappears as their aspect ratio increases. The physical mechanisms responsible for a decrease in size of the hysteresis loops for QPCs with increasing aspect ratio are: (1) multimode transport in QPCs with larger channel width leading to spin-flip scattering events due to both remote impurities in the doping layer of the heterostructure and surface roughness and impurity (dangling bond) scattering on the sidewalls of the narrow portion of the QPC, and (2) an increase in carrier density resulting in a screening of the electron-electron interactions in the QPC channel. Both effects lead to a progressive disappearance of the net spin polarization in the QPC channel and an accompanying reduction in the size of the hysteresis loops as the lithographic width of the QPC channel increases. © 2019, The Author(s).
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    Improved electrochemical performance of graphene oxide supported vanadomanganate (IV) nanohybrid electrode material for supercapacitors
    (Elsevier Ltd, 2020) Kumari, S.; Maity, S.; Anandan Vannathan, A.A.; Shee, D.; Das, P.P.; Mal, S.S.
    Graphene oxide (GO)-supported polyoxometalates (POMs) have been considered as promising electrode materials for energy storage applications due to their ability to undergo fast and reversible redox reactions. Herein, vanadomanganate-GO composites (K7MnIVV13O38.18H2O-GO with 2:1 and 4:1 ratio) were investigated for use as potential electrode materials in supercapacitors (SCs). The K7MnIVV13O38.18H2O (MnV13) was synthesized and anchored on GO through electron transfer interaction and electrostatic interaction to make the composite electrodes for the present study. All synthesized electrode materials were fully characterized by various techniques, e.g., Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDS) and High Resolution-Transmission Electron Microscopy (HR-TEM). The electrochemical properties of MnV13/GO composites with different MnV13/GO ratios were investigated by two-electrode cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) in different electrolytes. The MnV13/GO composite of ratio 2:1 in 1 M LiCl electrolyte and that of ratio 4:1 in 1 M Na2SO4 electrolyte showed significant specific capacitance values of 269.15 F/g and 387.02 F/g, respectively and energy density of 37.38 Wh/kg and 53.75 Wh/kg, respectively for a scan rate of 5 mV/s. Interestingly, the 1:1 (MnV13/GO) composite in 1 M Na2SO4 and 1 M LiCl electrolytes showed very low specific capacitance values as the deposition of MnV13 on GO was not sufficient, as indicated by FTIR and SEM. Thus, it is evident that the specific capacitance value of these composite materials depends on the amount of MnV13 deposited on GO and these composite materials exhibit the potential to improve the performance of GO-based SCs. © 2019