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.

Optical limiting action of 2-amino 5-nitro pyridinium chloride crystal for laser safety devices

Abstract: Third-order optical limiting action of 2-amino-5-nitro pyridinium chloride (2A5NPCl) crystals was demonstrated for protection of photosensitive components from damages induced by widely used green CW lasers. Crystals grown by slow evaporation possess lattice parameters of a = 9.968A, b = 7.731A, c = 4.802A and β = 95.864˚. 2A5NPCl crystals are highly transparent with wide optical window of 400-1100nm. 2A5NPCl crystals exhibit strong saturable absorption and self-defocusing refraction. Third-order NLO coefficients of 2A5NPCl crystal was estimated to be n2 = -3.20x10−8cm2/W, β = -1.20x10−4cm/W and χ(3) = 5.18x10−6esu. 2A5NPCl crystal exhibits OL action with onset limiting threshold of 14 mW.

Effect of P-nitrophenol as dopant in ammonium tetroxalate dihydrate – Spectral, optical, thermal and dielectric analyses

Abstract: Single crystals of ammonium tetroxalate dihydrate doped with p-nitrophenol (PNP doped ATOXAL) were grown using the slow evaporation solution growth technique The harvested crystals possessed the P 1 ¯ space group and occupied the triclinic crystal system From UV–vis-NIR spectrum the optical parameters like optical band gap (Eg), refractive index (n), electric susceptibility (χc) and real and imaginary parts of the dielectric constant were found to be 3276 eV, 158, 0199, 2498 and 093 × 10−5 respectively at the lower cutoff wavelength The refractive index value calculated using Abbe’s refractometer was 1581 The crystal exhibited negative photoconductivity The photoluminescent emission spectrum was recorded and studied The mechanical properties have been studied using Vicker’s microhardness tester and the material belongs to the soft category The thermal property of the crystal was analysed from the TGA/DTG/DSC curves The dielectric studies carried out for varied frequencies and temperatures reveal that the material exhibits non-Debye β relaxation Z-scan studies show that the grown crystal has negative nonlinearity and saturation absorption

Growth and Characterization of Second and Third Order Acentric Studies of l-Phenylalanine l-Phenylalaninium Malonate Single Crystal

Abstract: A single crystal of l-phenylalanine l-phenylalanininum malonate (LPPMA) was synthesized by slow evaporation and was subjected to nonlinear optical examination and physio-chemical characterization. Studies on single X-ray diffraction confirm the arrangement of monoclinic space group P21 which is a vital criterion for the NLO phenomenon. The assessment of functional groups and diverse vibration modes responsible for the characteristics of the material was performed with an FTIR analysis. The UV-visible spectral examination found the wavelength of UV-cutoff at 233 nm and various optical parameters were evaluated. The mechanical strength and different criteria associated with it were assessed. The electric field response of the material was examined in terms of the dielectric constant, dielectric loss, ac conductivity and activation energy. The spectra of emission were detailed. The efficacy of second harmonic generation was studied. The parameters of nonlinearity were investigated to analyse the third-order acentric optical response in the LPPMA by Z-scan procedure.

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.