Conference Papers
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Item A new nonlinear optically active donor-acceptor-type conjugated polymer: Synthesis and electrochemical and optical characterization(2010) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.; Suchand Sandeep, C.S.S.; Philip, R.A new donor-acceptor-type poly[3-{5-[3,4-didodecyloxy-5-(1,3,4-oxadiazol- 2-yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}-9-dodecyl-9H-carbazole] (P) has been synthesized through multistep reactions. The new polymer P exhibited good thermal stability and film-forming behavior. The electrochemical band gap is estimated to be 2.15 eV. The polymer emits intense green fluorescence in the solid state. Third-order nonlinear optical (NLO) studies showed that the strong absorptive nonlinearity observed for the polymer is of the optical limiting type, which is due to an "effective" three-photon absorption (3PA) process. This 3PA process can have potential applications in photonic devices. The studies revealed that the new polymer P is a promising material for development of efficient optoelectronic devices. © 2010 TMS.Item Nonlinear optical properties of a newly synthesized thiophene based conjugated polymer(2011) Sunitha, M.S.; Vasudeva Adhikari, A.V.; Vishnumurthy, K.A.; Philip, R.We have synthesized a new donor-acceptor (D-A) conjugated polymer containing 3,4-aralkyloxy and alkoxy substituted thiophene and 1,3,4-oxadiazole as donor and acceptor moieties respectively, through precursor polyhydrazide route. The required polyhydrazide was synthesized from 3,4-dihydroxythiophene diester through multistep reaction. The new polymer was characterized by using FTIR, 1H NMR spectroscopy, followed by Elemental analysis. The average molecular weight of the polymer was determined by Gel Permeation Chromatography. The band gap of the polymer was calculated by using UV-visible and cyclic voltametry. Further, its NLO properties in THF solution were investigated both by the Z-scan and degenerate four-wave mixing (DFWM) techniques using 532 nm, 7 nanosecond laser pulses. The results indicate that they exhibit good optical limiting behavior due to effective two-photon absorption (TPA). Values of the effective TPA coefficient (β), third-order non-linear optical susceptibility (χ(3)) and figure of merit (F) were calculated. The optical and electrochemical properties reveal that the polymer is a promising candidate for opto-electronic applications. © 2011 American Institute of Physics.Item Synthesis and characterization of a new conjugated polymer bearing pyrazole and thiophene moieties as potent NLO material(2011) Vishnumurthy, K.A.; Vasudeva Adhikari, A.V.; Sunitha, M.S.; Philip, R.In this communication we describe the design and synthesis of a new conjugated polymer (P) carrying 3,4-dialkoxythiophene, 1,3,4 oxadiazole and pyrazole units, from its monomers through condensation polymerization method. The structure of newly synthesized polymer was established by FT-IR, 1H NMR, elemental analysis and gel permeation chromatographic techniques. Further, its electrochemical, linear and nonlinear optical properties of the polymer have been investigated. The optical and electrochemical band gap was found to be 2.39 eV. Z-scan results reveal that the polymer exhibits strong optical limiting behavior due to effective three-photon absorption (3PA). The value of 3PA coefficient was found to be 1.1×10-20m3/W2, which is comparable to that of good optical limiting materials. The fluorescence quantum yield of the polymer in solution was determined using quinine sulfate as standard and it was found to be 42%. © 2011 American Institute of Physics.Item Synthesis and third-order nonlinear optical studies of four-coordinated copper(I) complexes(2011) Kumar, H.C.S.; Rudresha, B.J.; Badekai Ramachandra, B.R.; Philip, R.; Guru Row, T.N.G.Three Cu(I) halide complexes [Cu(L)(PPh3)X] (L=1,10- phenanthroline, X=Cl (1), Br (2) and I (3), PPh3=triphenylphosphine) have been synthesised and characterised by spectroscopic techniques. Further structure of the complex 1 was confirmed by single crystal X-ray diffraction analysis. The nonlinear optical properties of the complexes were investigated at 532 nm using single beam Z-scan technique with nanosecond laser pulses. The complexes showed strong optical limiting behavior due to effective three-photon absorption (3PA). The values of 3PA coefficients (γ) for 1, 2 and 3 were found to be 3.2×10-24m3/W2, 6.0×10-25m3/W2 and 1.2×10 -23m3/W2 respectively, which are comparable to good optical limiting materials. These studies demonstrate that the Ligand→copper coordinative bonds facilitate the polarization of the electronic π-system which optimizes the third-order NLO response in the reported complexes. © 2011 American Institute of Physics.Item Effect of Laser Beam Spot Size on the Dynamics of Ultrashort Laser-Produced Plasma in Vacuum(Institute of Electrical and Electronics Engineers Inc., 2018) Sankar, P.; Shashikala, H.D.; HARILAL, S.S.; Philip, R.The hydrodynamic expansion features of a laser-produced plasma is governed by initial plume conditions and hence the spot size of the laser beam.1-3 In this work, we investigated the expansion dynamics of a laser produced-plasma as a function of laser spot diameter in a vacuum environment (10-5 Torr) using multiple diagnostic tools. The diagnostic tools used were space-and time-resolved optical emission spectroscopy, 2-D fast-gated self-emission imaging and ion analysis using Faraday cup. The plume dynamics measured for varying spot sizes involves intriguing physics and hence demands detailed investigations, in view of a multitude of applications of laser ablation (LA) including elemental detection (LIBS, LA-LIF etc.), micromachining, laser-welding, nano-structuring, ion beam generation and pulsed laser deposition. © 2018 IEEE.