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Hyderabad, India

Rao S.V.,University of Hyderabad | Prasad A.K.,Cochin University of Science and Technology | Giribabu L.,Nanomaterials Laboratory | Tewari S.P.,University of Hyderabad
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Herein we present our results from the picosecond and nanosecond nonlinear optical studies of two novel phthalocyanines {[(SO3Na) 4CuPc] and [(SO3Na)4NiPc]} using the Z-scan technique. Open aperture Z-scan data revealed that the picosecond nonlinear absorption was dominated by three-photon absorption while in the nanosecond domain reverse saturable absorption prevailed. Closed aperture data with nanosecond pulses indicated strong thermal, negative nonlinearity while picosecond excitation demonstrated positive nonlinearity. The nonlinearity in CuPc was higher than in NiPc in both the time domains. The nonlinear coefficients extracted from the fits to experimental data were large compared to some of the recently reported works on similar molecules. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source


Hamad S.,University of Hyderabad | Podagatlapalli G.K.,University of Hyderabad | Giribabu L.,Nanomaterials Laboratory | Tewari S.P.,University of Hyderabad | Rao S.V.,University of Hyderabad
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We present our results of nonlinear optical properties of Tritolyl Corrole (TTC) and Triphenyl Corrole (TPC) studied in the form of solution using Z-scan technique with 660 nm, ∼2 picosecond (ps) pulses and 800 nm, ∼40 femtosecond (fs) pulses excitation. Picosecond open-aperture Z-scan data revealed these molecules exhibited strong saturable absorption. These molecules possessed negative nonlinear refractive index (n2). The estimated value of n2 was 6×10 -15 cm 2/W and 8×10 -15 cm 2/W for TPC and TTC, respectively. We have recently reported NLO properties of Corroles with 800 nm excitation where they exhibited strong two-photon absorption (2PA) at higher intensities and effective two-photon absorption at lower intensities in the ps regime. Femtosecond open aperture Z-scan studies indicated the presence of strong saturable absorption with effective nonlinear absorption coefficients (β) of ∼0.8×10 -13 cm/W and ∼2.7×10 -13 cm/W for TPC and TTC, respectively. We have also estimated the sign and magnitude of real part of third order nonlinearity through the closed aperture scans. We discuss the nonlinear optical performance of these organic molecules. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE). Source


Bala Murali Krishna M.,University of Hyderabad | Giribabu L.,Nanomaterials Laboratory | Narayana Rao D.,University of Hyderabad
Journal of Porphyrins and Phthalocyanines | Year: 2012

Synthesis and measurements of third order nonlinear optical (NLO) coefficients of water soluble zinc octacarboxy phthalocyanine (ZnOCPc) are reported here using different laser pulse durations. Nonlinear absorption and refraction behaviour in the nanosecond (ns), picosecond (ps) and femtosecond (fs) time domains were studied in detail. Three-photon absorption was the prevalent mechanism with femtosecond laser excitation whereas strong reverse saturable absorption due to dominant two-photon absorption (TPA) was observed with picosecond and nanosecond excitations. We have evaluated the sign and magnitude of the third order nonlinearity in fs, ps, and ns regimes. We observed large off-resonant second order hyperpolarizability (γ) with ultrafast nonlinear optical response in the femtosecond domain using degenerate four wave mixing (DFWM) technique. We also report the optical limiting characteristics and figure of merit (FOM) of ZnOCPc for optical switching. © 2012 World Scientific Publishing Company. Source


El-Sheshtawy H.S.,South Valley University | Abd El Sadek M.S.,Nanomaterials Laboratory | Yahia I.S.,Nano Science Laboratory | Yahia I.S.,King Khalid University
Nanoscience and Nanotechnology Letters | Year: 2014

The highly fluorescent thiol capped CdTe nanocrystals were synthesized by the aqueous synthesis route. In this method we used sodium tellurite (Na 2TeO3) as the Te source in contrast to the previous reported methods, which used NaHTe and H2Te that need a pretreatment for the unstable precursor. The structure of CdTe nanocrystals was investigated by means of X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), UV-visible, Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The results showed the crystallinity of the CdTe nanocrystals and the average size of CdTe QDs was 3.2 nm. An aqueous solution of CdTe capped with mercaptopropionic acid (MPA) shows a characteristic fluorescent peak at 590 nm, which decrease under the influence of both the pH and temperature. The labeling affinity of the water-soluble MPA- CdTe and some selected antibiotics such as Ceftazidime and Rifampicin were investigated in 50 mM sodium acetate buffer pH 7.4. Both antibiotics show the ability to interact with QDs nanocrystal that probed by fluorescence spectroscopy. The interaction between MPA-CdTe and Rifampicin shows a dynamic quenching process while the reaction between QDs and Ceftazidime was initiated by ground-state complex formation (static quenching) .© 2014 American Scientific Publishers All rights reserved . Source


Hamad S.,University of Hyderabad | Podagatlapalli G.K.,University of Hyderabad | Giribabu L.,Nanomaterials Laboratory | Tewari S.P.,University of Hyderabad | Rao S.V.,University of Hyderabad
AIP Conference Proceedings | Year: 2011

We report our results on femtosecond (fs) and picosecond (ps) nonlinearities in two novel Corroles (a) Tritolyl Corrole (TTC) (b) Triphenyl Corrole (TPC) studied using the Z-scan technique. Both open and closure aperture Z-scan curves were recorded with ∼40 fs and open Z-scan curves were recorded with ∼2 ps laser pulses at same wavelength of 800 nm and nonlinear coefficients were extracted for both studies. Picosecond open aperture data clearly suggested the presence of three photon absorption (3PA) for both the molecules. One of the molecule, TPC, possessed positive refractive index with a value 2×10-17cm2/W and TTC possessed negative refractive index with a value of 3×10-18cm2/W in the fs domain. Solvent contribution to the nonlinearity was also identified. We discuss the nonlinear optical performance of these organic molecules. © 2011 American Institute of Physics. Source

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