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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors reported the third order nonlinear optical properties of a cesium hydrogen tartrate (CT) single crystal, which was crystallized in an orthorhombic crystal system with noncentrosymmetric space group P212121.
Abstract: The compound preparation, crystallization, spectroscopic characterizations and third order nonlinear optical properties of an organometallic nonlinear optical cesium hydrogen tartrate (CT) single crystal is reported. The title compound was crystallized in orthorhombic crystal system with noncentrosymmetric space group P212121. The functional group and their vibrational states were analyzed by FTIR spectroscopy. The optical band gap was found to be 5.98 eV. The recorded photoluminescence was evident for inter-band defect energy levels in the title crystal. The calculated CIE coordinates on RGB color gamut shows the blue light emitting capacity of CT crystal. Nonlinear optical properties of the title material under continues wave and pulsed laser excitation is reported for the first time. The intensity dependent refractive index (n2), absorption coefficient (β) and third order nonlinear optical susceptibility (χ(3)) of CT under continues wave excitation were found to be 0.569 × 10−8 (cm2W−1), 0.265 × 10−4 (cmW−1) and 8.78 × 10−7 (esu) respectively. The variation of β was studied under pulsed excitation with varying peak intensities. The values were found to be 0.72 × 10−10 (mW−1), 0.68 × 10−10 (m/W−1) and 0.64 × 10−10 (mW−1) for peak intensities of 0.61 × 10−12 (Wm−2), 1.23 × 10−12 (Wm−2) and 2.46 × 10−12 (Wm−2) respectively which confirms the presence of effective two photon absorption in CT. The optical limiting threshold at three intensities mentioned above were found to be 1.36 × 10−12 (Wm−2), 1.55 × 10−12 (Wm−2) and 1.79 × 10−12 (Wm−2) respectively. The value of Meyer’s index (n) by Vickers micro hardness test was found to be 3.74 and it shows CT crystal belongs to soft material category. The thermogravimetric analysis showed that the CT crystal is thermally stable up to 215 °C. The dielectric constant (e), dielectric loss (tan δ), AC and DC conductivity as a function of frequency and temperature were studied. The superior mechanical, thermal and dielectric properties with intensity tunable optical nonlinearity of cesium hydrogen tartrate single crystal promotes it as a promising candidate for optical limiting application.

29 citations

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TL;DR: In this article, Ni1−xZnxFe2O4 (x = 0, 0.25, and 0.5) nanoparticles were successfully synthesized via microwave assisted combustion method and characterized by XRD, FTIR, and SEM-EDAX.
Abstract: In this study, Ni1−xZnxFe2O4 (x = 0, 0.25, and 0.5) nanoparticles were successfully synthesized via microwave-assisted combustion method and characterized by XRD, FTIR, and SEM–EDAX. XRD results enunciate that the nanoparticle crystallizes in cubic spinel structure with an average crystallite size (40.2, 37.2, 35.1 nm), and also, the lattice strain, specific surface area, X-ray density were evaluated. The morphology and chemical compositions of Ni, Zn, Fe, and O elements were confirmed by the SEM–EDAX studies. For all the samples, vibrational stretching modes of Mtetra–O site (597 (S1), 593 (S2), 583 (S3) cm−1) and Moctra–O site (416 (S1), 421 (S2), 422 (S3) cm−1) were related to the distribution of the cation Ni2+/Zn2+ and Fe3+ ions among the octahedral and tetrahedral sites. From the UV–Vis–DRS spectra, the optical energy band gap has been estimated to be 1.75–2.01 eV. The dielectric constant and loss were measured by varying the applied frequency (50 Hz to 200 kHz) at room temperature. The electronic polarizability (α) was calculated using Penn analysis, Clausius–Mossotti equation, and energy band gap value. Third-order nonlinear optical parameters such as the nonlinear absorption coefficients (10−5 cm/W), refractive index (10−9 cm2/W) and the third-order nonlinear susceptibilities (10−6 esu) were determined by Z-scan technique. The antibacterial studies were tested against Bacillus cereus, Staphylococcus aureus, Shigalla flexneri and Klebsiella pneumonia bacterial strains. The existing results point out that the synthesized Ni/Zn/Fe2O4 nanoparticles are possible candidates for photonic devices, optical switches, optical limiting and also for pharmaceutical applications.

29 citations

Journal ArticleDOI
TL;DR: An organic nonlinear optical l -threoninium tartrate (LTT) single crystal was successfully grown by slow evaporation method using de-ionized water as solvent as mentioned in this paper.

28 citations

Journal ArticleDOI
TL;DR: In this article, the authors explored the third order nonlinear optical behavior of phase pure Yb3+:YAG nanoparticles for the first time by Z-scan technique.
Abstract: The present report explores third order nonlinear optical behavior of phase pure Yb3+:YAG nanoparticles for the first time by Z-scan technique. The measurement was carried out using diode pumped continuous wave (CW) Nd:YAG laser at 532 nm. The Yb:YAG nanoparticles exhibit characteristic near-infrared (NIR) emission at 1030 nm under 940 nm excitation. The nanoparticles exhibit high nonlinear refractive index (n2 = 8.649 × 10−8 cm2/W) and low nonlinear absorption coefficient (β = 0.109 × 10−4 cm/W) giving an appreciable figure of merit (FOM) of ∼74.50. The excitation power (8.2–10.5 W cm−2) dependent emission spectra were recorded to study exchange energy interaction of Yb3+ ions with YAG host lattice. By utilizing the nonlinear refractive index ‘n2’ from Z-scan measurement, thermo-optic coefficient (dn/dt) was calculated to demonstrate Yb3+:YAG nanomaterial for high power compact solid state laser gain amplifier systems.

28 citations

Journal ArticleDOI
TL;DR: In this paper, the structural and third-order nonlinear optical properties of Sr2+-doped ZnO nanostructures synthesized by chemical precipitation technique are systematically investigated by UV-vis absorption, X-ray diffraction (XRD), Photoluminescence spectroscopy and Field emission scanning electronic microscopy (FESEM), respectively.
Abstract: We present the structural and third order nonlinear optical properties of Sr2+-doped ZnO nanostructures synthesized by chemical precipitation technique. The prepared nanoparticles are systematically investigated by UV–vis absorption, X-ray diffraction (XRD), Photoluminescence spectroscopy and Field emission scanning electronic microscopy (FESEM), respectively. UV–vis absorption spectra show that the particles have a higher absorption in UV region and possess a large optical transparency in visible region. XRD patterns show that all the prepared nanoparticles are well crystallized with hexagonal wurtzite structure. The incorporation of Sr in ZnO was also confirmed by fluorescence quenching. FESEM images showed the formation of nanostructures with sheet-like structure. Third-order nonlinear optical properties of the nanostructures have been studied by Z-scan technique using diode pumped continuous wave (cw) laser system at a wavelength of 532 nm. Experimental results reveal that the materials exhibit saturable absorption (SA) and self-defocusing nature.

27 citations


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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

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TL;DR: This Review gives emphasis to the nonlinear optical properties of photoactive materials for the function of optical power limiting and describes the known mechanisms of optical limiting for the different types of materials.
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...

424 citations

Journal ArticleDOI
TL;DR: In this article, a review highlights the applied protocols to ameliorate the photoactivity of graphitic carbon nitride (g-C3N4) based nanocomposites through combining with various materials.

381 citations

Journal ArticleDOI
TL;DR: In this article, the authors survey the recent advances in nonlinear optics and the applications of two-dimensional (2D) materials and highlight a few representative current applications of 2D materials to photonic and optoelectronic devices.
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.

235 citations

Journal ArticleDOI
TL;DR: In this article, the nonlinear optical properties of metal nanoparticles (including copper, silver, gold, and bismuth nanoparticles) doped in various bases have been discussed.
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.

232 citations