Author
S. Venugopal Rao
Other affiliations: University of St Andrews, National University of Singapore, Indian Institute of Technology, Jodhpur ...read more
Bio: S. Venugopal Rao is an academic researcher from University of Hyderabad. The author has contributed to research in topics: Femtosecond & Laser. The author has an hindex of 41, co-authored 206 publications receiving 4635 citations. Previous affiliations of S. Venugopal Rao include University of St Andrews & National University of Singapore.
Papers published on a yearly basis
Papers
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TL;DR: In this article, the authors investigated nonlinear absorption of Rhodamine B dye in methanol and water near resonance (532 nm) on the higher energy (435 nm) and lower energy (600 nm) sides of the absorption band using an open-aperture Z-scan technique with nanosecond pulses.
Abstract: We have investigated nonlinear absorption of Rhodamine B dye in methanol and water near resonance (532 nm) on the higher-energy (435 nm) and lower-energy (600 nm) sides of the absorption band, using an open-aperture Z-scan technique with nanosecond pulses. We observed reverse saturable absorption (RSA) at 435 nm in both of the solvents, and a transition from saturable absorption (SA) to RSA with an increase in either intensity or concentration at 600 nm in methanol. A transition from RSA to SA with an increase in concentration at 600 nm was observed with water as the solvent. We used theoretical analysis based on rate equations to determine the two-photon and excited-state absorption coefficients from the experimental results.
167 citations
TL;DR: In this paper, nonlinear optical properties of 2(3), 9(10), 16(17), 23(24) tetra tert-butyl phthalocyanine were studied using Z-scan technique with 800 nm femtosecond and 532 nm nanosecond pulses.
166 citations
TL;DR: In this paper, the sign and magnitude of the third-order nonlinearity from the closed aperture Z-scan data were evaluated while the nonlinear absorption properties were assessed using the open aperture data.
164 citations
TL;DR: The third-order nonlinear optical and optical limiting properties of 2,3,9,10,16,17,23,24,24-octakis-(heptyloxy)-phthalocyanine, 2.3, 9, 10, 16, 17, 23, 24, 24 octakis-hexagonal phthalocyanin zinc(II) (symmetric) and 2(3)-(butane-1,4-dioic acid)-9(10),16(17),23(24)-tri tert-butyl ph
133 citations
TL;DR: In this paper, the authors present experimental results on the measurement of third-order optical nonlinearity in the ns and ps domain, in several Tetra Tolyl Porphyrin molecules (TTP) using degenerate four wave mixing (DFWM) and Z-Scan techniques.
122 citations
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TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
Journal Article•
28,685 citations
TL;DR: Nonlinear Optical Characterizations of Multiphoton Active Materials 1282 5.2.1.
Abstract: 4. Survey of Novel Multiphoton Active Materials 1257 4.1. Multiphoton Absorbing Systems 1257 4.2. Organic Molecules 1257 4.3. Organic Liquids and Liquid Crystals 1259 4.4. Conjugated Polymers 1259 4.4.1. Polydiacetylenes 1261 4.4.2. Polyphenylenevinylenes (PPVs) 1261 4.4.3. Polythiophenes 1263 4.4.4. Other Conjugated Polymers 1265 4.4.5. Dendrimers 1265 4.4.6. Hyperbranched Polymers 1267 4.5. Fullerenes 1267 4.6. Coordination and Organometallic Compounds 1271 4.6.1. Metal Dithiolenes 1271 4.6.2. Pyridine-Based Multidentate Ligands 1272 4.6.3. Other Transition-Metal Complexes 1273 4.6.4. Lanthanide Complexes 1275 4.6.5. Ferrocene Derivatives 1275 4.6.6. Alkynylruthenium Complexes 1279 4.6.7. Platinum Acetylides 1279 4.7. Porphyrins and Metallophophyrins 1279 4.8. Nanoparticles 1281 4.9. Biomolecules and Derivatives 1282 5. Nonlinear Optical Characterizations of Multiphoton Active Materials 1282
1,864 citations
Journal Article•
TL;DR: In this article, a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators were developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of 3D micro-optical and micromechanical structures, including photonic-bandgap-type structures.
Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.
1,833 citations