G. Vinitha

Bio: G. Vinitha is an academic researcher from VIT University. The author has contributed to research in topics: Single crystal & Crystal. The author has an hindex of 23, co-authored 251 publications receiving 2106 citations. Previous affiliations of G. Vinitha include B. S. Abdur Rahman University & Anna University.

Growth and characterization of organic material 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline single crystal

Abstract: The organic material 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline was synthesised and the single crystal has been grown by slow evaporation technique. Single-crystal X-ray diffraction studies show that the grown 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline single crystal belongs to the monoclinic system with the centrosymmetric space group P21/n. The FTIR and FT-Raman spectra were recorded to identify the functional groups present in the grown crystal. The optical property of the grown crystal was analyzed by UV–Vis–NIR studies and determines the optical band gap, the refractive index, the optical conductivity and the Urbach energy. The photoluminescence (PL) studies show that the grown crystal has green colour emission. The thermal property of the grown crystal was analysed by thermogravimetric (TG) and differential thermal analyses (DTA). The kinetic parameters such as the activation energy, frequency factor, entropy, enthalpy and Gibbs-free energy are computed from TGA data using Coats–Redfern method. The dielectric studies were analyzed by using the parallel plate capacitor method. The activation energy is calculated from Arrhenius plot. The electronic properties such as the plasma energy, the Penn gap, the Fermi energy and the electronic polarizability are calculated. The third order nonlinear optical properties of 3,4-dimethoxybenzaldehyde-2,4-dinitroaniline was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

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.

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation.

Abstract: The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the functi...

Nonlinear optical properties and applications of 2D materials: theoretical and experimental aspects

Abstract: In this review, we survey the recent advances in nonlinear optics and the applications of two-dimensional (2D) materials. We briefly cover the key developments pertaining to research in the nonlinear optics of graphene, the quintessential 2D material. Subsequently, we discuss the linear and nonlinear optical properties of several other 2D layered materials, including transition metal chalcogenides, black phosphorus, hexagonal boron nitride, perovskites, and topological insulators, as well as the recent progress in hybrid nanostructures containing 2D materials, such as composites with dyes, plasmonic particles, 2D crystals, and silicon integrated structures. Finally, we highlight a few representative current applications of 2D materials to photonic and optoelectronic devices.

Nonlinear optical properties of metal nanoparticles: a review

Abstract: Metal nanoparticles (MNPs) hold great technological promise because of the possibility of engineering their electronic and optical properties through material design. One of the effective methods to fabricate MNPs is ion implantation. In this review, recent results on the nonlinear optical properties of nanoparticles (including copper, silver, gold, and bismuth nanoparticles) doped in various bases have been discussed. Some specific optical nonlinear properties, such as nonlinear refraction, two-photon absorption, and optical limiting, for femtosecond, picosecond, and nanosecond laser pulses have also been covered. In addition to ion implantation, we have summarized several other methods for the preparation of composite materials, and Z-scan has been used to study the nonlinear optical properties of these materials.