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T. A. Prasada Rao

Bio: T. A. Prasada Rao is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Kerr effect & Liquid crystal. The author has an hindex of 8, co-authored 21 publications receiving 168 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the real part of the third order nonlinear susceptibilities χ(3) (−ω, ω, 0, 0) in the isotropic phase of two nematic liquid crystals was determined from electrooptic Kerr effect experiments.
Abstract: We report for the first time the determination of the real part of the third order nonlinear susceptibilitiesχ(3) (−ω, ω, 0, 0) in the isotropic phase of two nematic liquid crystalsp-(ethoxybenzylidine)-p-butylaniline (EBBA) andp-(methoxybenzylidene)-p-butylaniline (MBBA) from electrooptic Kerr effect experiments The highest value ofχ(3) observed near nematic-to-isotropic transition temperature, at 6328 nm is found to be 1067×10−20 m2V−2 for EBBA and 6602×10−20 m2V−2 for MBBA

3 citations

Journal ArticleDOI
TL;DR: In this article, the velocity of acoustic waves generated by photoacoustic effect using a pulsed ruby laser in benzene, chlorobenzene, carbontetrachloride and acetone in the pure form using delay time technique is reported.

2 citations

Journal ArticleDOI
TL;DR: Optical phase conjugation via degenerate four-wave mixing is studied in iodine solutions under pulsed laser radiation at two wavelengths (532 nm and 694 nm).
Abstract: Optical phase conjugation via degenerate four-wave mixing is studied in iodine solutions under pulsed laser radiation at two wavelengths (532 nm and 694 nm). The effect of using four different solvents (1,2-dibromoethane, xylene, methanol and ethanol) is studied at 532 nm. Phase conjugate reflectivities in the range of 0·1% to 0·3% are observed. The solutions exhibit a maximum reflectivity at an optimum concentration. The experimental data is analysed using the Caro-Gower model.

2 citations

Journal ArticleDOI
TL;DR: In this paper, the real part of the third-order nonlinear susceptibility, x (3), was determined from electro-optic Kerr effect experiments in the isotropic phase of a nematic liquid crystal 4′-n-pentyl-4-cyanobiphenyl (K15).
Abstract: In this paper, we report for the first time the determination of the real part of the third-order nonlinear susceptibility, x (3)(−ω, ω, 0, 0), measurements in the isotropic phase of a nematic liquid crystal 4′-n-pentyl-4-cyanobiphenyl (K15) from electro-optic Kerr effect experiments. The value of x (3) obtained at 632·8 nm is found to be 1·08 × 10−18 m2 V−2 corresponding to a temperature 35·5°C and is the highest so far reported to the best of our knowledge.

2 citations

Journal ArticleDOI
TL;DR: In this article, the electro optical Kerr coefficient of organic liquids belonging to the homologous series of Ketone, Aldehyde and Nitriles is measured over the temperature range of 285K to 313K.

1 citations


Cited by
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Journal ArticleDOI
Hari Singh Nalwa1
TL;DR: The current status of organic low-molecular weight and polymeric materials for third-order nonlinear optics is reviewed in this paper, where the importance of organic materials lies in their promise of large nonlinear optical figure of merit, high optical damage thresholds, ultrafast optical responses, architectural flexibility, and ease of fabrication.
Abstract: The current status of organic low-molecular weight and polymeric materials for third-order nonlinear optics is reviewed. The importance of organic materials lies in their promise of large nonlinear optical figure of merit, high optical damage thresholds, ultrafast optical responses, architectural flexibility, and ease of fabrication. Organic materials exhibiting interesting third-order nonlinear optical properties are discussed to illustrate the importance of structure–property correlations. Results on emerging organic materials that include liquids, dyes, fullerenes, charge-transfer complexes, π-conjugated polymers, dye-grafted polymers, organometallic compounds, composites, and liquid crystals are presented. Organic nonlinear optical materials seem promising for a wide range of applications and their potential for integrated optics should be further explored.

413 citations

Journal ArticleDOI
TL;DR: In this article, the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components are discussed.
Abstract: Liquid crystals are nowadays widely used in all types of display applications. However their unique electro-optic properties also make them a suitable material for nondisplay applications. We will focus on the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components. Both the basic operating principles as well as the recent state-of-the art are discussed.

215 citations

Journal ArticleDOI
TL;DR: In this paper, a new organic stilbazolium derivative crystal 2-[2-(3-hydroxy-4-methoxy-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate dehydrate (C25H23NO5S·2H2O) (VSNS) was synthesized successfully.
Abstract: A new organic stilbazolium derivative crystal 2-[2-(3-hydroxy-4-methoxy-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate dehydrate (C25H23NO5S·2H2O) (VSNS) was synthesized successfully. Single crystals were grown in a mixed solvent of methanol–acetonitrile (1 : 1) using a slow evaporation method at room temperature. Solubility of the synthesized VSNS material was experimentally determined for various temperatures using a methanol–acetonitrile mixed solvent. A single crystal X-ray diffraction study confirmed the crystal structure and morphology of VSNS. The crystalline nature of the title material was analyzed by powder X-ray diffraction analysis, and the presence of expected functional groups and the molecular structure of VSNS was identified by FT-IR and 1H NMR spectroscopic studies. Optical absorption was recorded using UV-Vis-NIR spectral analysis, and linear optical constants such as the absorption coefficient, band gap, extinction coefficient, refractive index and reflectance were calculated. The luminescence property of the crystal grown showed green emission radiation. The thermal stability of the crystal was analyzed by TG–DTA studies, and the hardness, Meyer index, yield strength, and elastic stiffness constant were estimated using a Vickers microhardness tester. Layer growth pattern was observed in chemical etching studies using a Carl Zeiss optical microscope at 50× magnification. Laser damage threshold energy was measured using an Nd:YAG laser (1064 nm). Variation of the dielectric response of the grown crystal was studied at room temperature. The third-order nonlinear optical property of VSNS was investigated in detail using a Z-scan technique with He–Ne laser at 632.8 nm. The second-order molecular hyperpolarizability γ of the crystal grown was 7.986 × 10−34 esu. This encouraging result of the Z-scan studies suggests that the VSNS crystal is a candidate material for photonics devices, optical switches, and optical power limiting applications.

145 citations

PatentDOI
TL;DR: The use of DFWM as an ultrafast time gate for the detection of ballistic light in optical mammography appears to hold great promise for improving the current state of the art.
Abstract: Optical imaging through turbid media is demonstrated using a degenerate four-wave mixing correlation time gate. An apparatus and method for detecting ballistic and/or snake light while rejecting unwanted diffusive light for imaging structures within highly scattering media are described. Degenerate four-wave mixing (DFWM) of a doubled YAG laser in rhodamine 590 is used to provide an ultrafast correlation time gate to discriminate against light that has undergone multiple scattering and therefore has lost memory of the structures within the scattering medium. Images have been obtained of a test cross-hair pattern through highly turbid suspensions of whole milk in water that are opaque to the naked eye, which demonstrates the utility of DFWM for imaging through turbid media. Use of DFWM as an ultrafast time gate for the detection of ballistic and/or snake light in optical mammography is discussed.

65 citations

16 Aug 2011
TL;DR: In this article, a general overview of solvent effects on the electronic absorption and fluorescence spectra is presented, including the possible correlations (with advantages and disadvantages) between adsorption/fluorescence maxima and various solvent parameters.
Abstract: This article contains recent progress and including the author's work in the field of solvent effects on the absorbance and fluorescence spectra. UV-Vis absorption or/and emission (fluorescence) band positions, intensity and shape of solvent-sensitive molecules show changes in organic solvents of varying polarities. A general overview of solvent effects on the electronic absorption and fluorescence spectra is presented. In order to describe the behavior in different solvents were selected the examples of compounds with varying architectures. The solvent effects on the intramolecular charge transfer bands are discussed using the possible correlations (with advantages and disadvantages) between adsorption/fluorescence maxima and various solvent parameters.

57 citations