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.

Improved third-order optical nonlinearity and optical limiting behaviour of (nanospindle and nanosphere) zinc ferrite decorated reduced graphene oxide under continuous and ultrafast laser excitation

Abstract: Nanohybrids consisting of uniform nanospheres and nanospindles of zinc ferrite attached to reduced graphene oxide were prepared by hydrothermal reaction. Zinc ferrite decorated reduced graphene oxide exhibited enhanced nonlinear absorption, refraction and optical limiting (OL) action under continuous wave (532 nm, 50 mW) and ultrafast (800 nm, 150 fs) excitation. The enhancement can possibly be attributed to the synergistic effect stemming from the observed reverse saturable absorption and self-defocusing in the material. The role of defects in improving the nonlinear optical (NLO) performance of ZnFe2O4–rGO was explained with the aid of Raman spectroscopy and ground state absorption studies. Using fs and cw excitation, the estimated nonlinear absorption coefficient [γ3PA(fs) = 4.0 × 10−12 m W−1, β(cw) = 6.5 × 10−5 m W−1], nonlinear refractive index [n2(fs) = 4.2 × 10−18 m2 W−1, n2(cw) = 4.7 × 10−12 m2 W−1] and third order nonlinear optical (NLO) susceptibility [χ (3) (fs) = 1.9 × 10−15 esu, χ (3) (cw) = 4.2 × 10−6 esu] of nanospindle ZnFe2O4–rGO were found to be higher than those of its other counter parts. The estimated NLO parameters were found to be higher than those of other known OL materials such as functionalized hydrogen exfoliated graphene, CdO. Thus zinc ferrite decorated rGO nanostructures with proficient NLO coefficients have potential scope for utilizing them as smart materials for OL applications.

Facile preparation of high fluorescent carbon quantum dots from orange waste peels for nonlinear optical applications.

Abstract: A facile and eco-friendly hydrothermal method was used to prepare carbon quantum dots (CQDs) using orange waste peels. The synthesized CQDs were well dispersed and the average diameter was 2.9 ± 0.5 nm. Functional group identification of the CQDs was confirmed by Fourier transform infrared spectrum analysis. Fluorescence properties of the synthesized CQDs exhibited blue emission. The fluorescence quantum yield of the CQDs was around 11.37% at an excitation wavelength of 330 nm. The higher order nonlinear optical properties were examined using a Z-scan technique and a continuous wave laser that was operated at a wavelength of 532 nm. Results demonstrated that the synthesis of CQDs can be considered as promising for optical switching devices, bio-scanning, and bio-imaging for optoelectronic applications.

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.