Faculty Publications
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Item Z-scan and degenerate four wave mixing studies on newly synthesized copolymers containing alternating substituted thiophene and 1,3,4-oxadiazole units(2006) Kiran, A.J.; Udayakumar, D.; Chandrasekharan, K.; Vasudeva Adhikari, A.V.; Shashikala, H.D.The third-order nonlinear optical properties of newly synthesized copolymers containing alternating substituted thiophene and 1,3,4-oxadiazole units have been studied in DMF solution at 532 nm by using single beam Z-scan and degenerate four wave mixing techniques with nanosecond laser pulses. The variation of nonlinear response among the copolymers clearly indicates the dependence of ?(3) on donor and acceptor type of units present in the copolymers. The nonlinear refractive index, n2, of the investigated copolymers is found to be negative and the magnitude is as high as 10-10 esu. All samples exhibit strong reverse saturation absorption at the wavelength used and show good optical limiting of nanosecond pulses. The concentration dependence of n2 and the two-photon absorption coefficient (?) has been studied. © 2006 IOP Publishing Ltd.Item Nonlinear optical studies of 1-3-diaryl-propenones containing 4-methylthiophenyl moieties(2007) John Kiran, A.; Mithun, A.; Shivarama Holla, B.; Shashikala, H.D.; Umesh, G.; Chandrasekharan, K.The third-order nonlinear optical properties of chalcone derivatives have been studied using the single beam Z-scan technique. The dependence of ?(3) on different donor and acceptor type substituents demonstrates the electronic nonlinearity of compounds. The largest value of nonlinear refractive index, n2, measured for a high electron donor substituted molecule is -2.033 × 10-11 esu. These molecules exhibit a strong two-photon absorption and interesting optical limiting of nanosecond laser pulses at 532 nm. © 2006 Elsevier B.V. All rights reserved.Item Third order nonlinear optical properties and optical limiting in donor/acceptor substituted 4'-methoxy chalcone derivatives(2007) Ravindra, H.J.; John Kiran, A.; Chandrasekharan, K.; Shashikala, H.D.; Dharmaprakash, S.M.The third order nonlinear optical properties of 4'-methoxy chalcone and its derivatives have been investigated using a single-beam Z-scan technique with nanosecond laser pulses at 532 nm. The 4'-methoxy chalcone and its derivatives are donor-acceptor-acceptor (D-A-A) and donor-acceptor-donor (D-A-D) type intramolecular charge transfer molecules. The nonlinear response in these molecules was found to increase with increase in (a) the electron acceptor strength in D-A-A type and (b) the donor strength of the substituted group in D-A-D type molecules. The ?(3) value in these molecules is found to be of the order of 10-13 esu. The observed increase in the third order nonlinearity in these molecules clearly indicates the electronic origin. The compounds exhibit good optical limiting at 532 nm. The best optical limiting behavior was observed with the molecule substituted by a strong electron donor. © Springer-Verlag 2007.Item Nonlinear optical properties of p-(N,N-dimethylamino)dibenzylideneacetone doped polymer(2008) Kiran, A.J.; Satheesh Rai, N.; Udayakumar, D.; Chandrasekharan, K.; Kalluraya, B.; Philip, R.; Shashikala, H.D.; Vasudeva Adhikari, A.V.A bis-chalcone derivative, p-(N,N-dimethylamino) dibenzylideneacetone was synthesized. Its third-order nonlinear susceptibility was determined to be as high as 10-12 esu by employing single beam Z-scan and degenerate four wave mixing techniques using Nd:YAG 7 ns laser pulses at 532 nm. The compound was doped in to poly(methylmethacrylate) matrix and the third-order nonlinearity was investigated by using Z-scan technique. The nonlinear refractive index of the doped polymer is found to be negative, and its magnitude is of the order of 10-10 esu. The results show that the compound exhibits strong reverse saturable absorption and a good optical limiting property and hence may be used as a promising dopant material. The study on concentration dependence of nonlinear optical parameters has been presented. © 2007 Elsevier Ltd. All rights reserved.