Showing papers by "G. Vinitha published in 2019"

Investigation on structural, optical, thermal and gamma photon shielding properties of zinc and barium doped fluorotellurite glasses

Abstract: Fluorotellurite glasses based on zinc and barium fluorides with total dopant concentration limited to 40 mol% in tellurite glass matrix were obtained by melt quenching technique. Explicit effects of both the zinc and barium fluorides on the tellurite glass network were observed from their response to various studies. The tendency of fluorine atoms to break the network was observed from the formation of more non-bridging sites instead of bridging sites from Raman measurements. Formation of these non-bridging fluorine sites instead of non-bridging oxygen led to an increase in the optical band gap of these samples from 3.36 eV to 3.52 eV. The reduction in the glass transition temperature from 316 °C to 299 °C observed with zinc fluoride doping is due to the breakage in the rigid network structure, while the increase from 316 °C to 329 °C with barium fluoride doping is correlated to the effect of size of barium atoms in the network. Radiation shielding properties calculated in terms of parameters like mean free path, mass attenuation coefficient etc., showed that the presence of more heavily doped elements like barium in the glass matrix led them to exhibit better shielding properties which can be utilized as replacement materials for concrete and lead based glasses as efficient shielding materials.

Intensity tunable optical limiting behavior of an organometallic cesium hydrogen tartrate single crystal

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.

Third order nonlinearity and optical limiting behaviors of Yb:YAG nanoparticles 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.

Effect of Sr2+ doping on the linear and nonlinear optical properties of ZnO nanostructures

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.

Growth and characterization of organic material 3,4,5-trimethoxybenzaldehyde single crystal for optical applications

Abstract: The organic material 3,4,5-trimethoxybenzaldehyde has been grown by slow evaporation technique using methanol as solvent. Single crystal X-ray diffraction studies shows that the grown 3,4,5-trimethoxybenzaldehyde single crystal belongs to the monoclinic system with the centrosymmetric space group P21/c. FTIR and FT-Raman spectra were recorded to identify the functional groups present in the crystal. The optical property of the grown crystal was analyzed by UV-Vis-NIR measurement. The thermal property of the grown crystal was analysed by thermogravimetric (TG) and differential thermal analyses (DTA). The dielectric studies were analyzed by using the parallel plate capacitor method. The third order nonlinear optical properties of 3,4,5-trimethoxybenzaldehyde was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser. The mechanical property of the grown crystal was analysed by using microhardness studies.

Crystal structure, spectroscopic, thermal, mechanical, linear optical, second order and third order nonlinear optical properties of semiorganic crystal: l-threoninium phosphate (LTP)

Abstract: An optically good quality semiorganic single crystal of l-threoninium phosphate (LTP) was grown by solvent evaporation technique at room temperature. Single and powder XRD revealed the orthorhombic crystal structure of LTP with non-centrosymmetric space group Pna21. Linear optical behaviour of the title crystal was realized using UV–visible spectroscopy. The lower cut-off value was found to be 200 nm with broad optical transparency in entire visible region. Functional group and its bonding nature in the titular compound are explored by FTIR spectroscopic analysis. The LTP is thermally stable up to 241 °C and deferent level of decompositions with respect to temperature was analyzed using TG/DTA. Mechanical properties of LTP were studied using Vickers’ microhardness tester. The fracture toughness (Kc), Knoop hardness (Hk), brittleness index (Bi) and elastic stiffness constant (C11) of LTP were calculated using micro-indentation data. Laser damage threshold value of LTP was found to be 4.92 GW/cm2 which is convincingly high to use the crystal in lasing applications. The second harmonic generation efficiency of LTP is 2.1 times greater than the conventional KDP crystal. The nonlinear refractive index (n2), the nonlinear absorption coefficient (β) and third-order nonlinear susceptibility (χ(3)) of the title crystal was found to be 1.19 × 10−15 m3/W, 4.742 × 10−9 m/W and 5.382 × 10−14 m/W (esu) respectively. The single beam Z-Scan unit equipped with 532 nm continues wave laser was used to measure the third-order nonlinear optical parameters of grown crystal.

Crystal growth, optical, physico-chemical and third-order nonlinear optical studies of morpholinium oxalate: a new organic single crystal for optical limiting application

Abstract: A single crystal of morpholinium oxalate (MO) was grown by the technique of slow evaporation at ambient temperature utilizing water as a solvent. Single crystal XRD reveals the MO crystal belongs to the monoclinic system with a centrosymmetric space group of P21/n. Powder XRD study demonstrates the crystalline quality. HRXRD study illustrates the crystalline perfection of the crystal and it is the key necessity for device fabrication. The optical transmittance (55%), cut-off wavelength (λ = 330 nm) and band gap energy (Eg = 2.61 eV) were determined by optical studies. Laser-induced surface damage threshold (LDT) analysis appraises the aptness of grown crystal for device fabrications and also the surface roughness of the sample was determined. The thermal stability and decomposition of the crystal were studied by thermogravimetric (TG) analysis and it was found that the material was thermally stable up to 179 °C. The various thermodynamical parameters were determined from TG analysis. The dielectric constant ɛ’ and dielectric loss ɛ’’ divulges the electrical properties of MO crystal and the various electronic parameters were also calculated. The nonlinear optical (NLO) behavior and optical limiting property were analyzed from Z-scan technique. Microhardness measurement was executed to recognize the mechanical strength of the MO crystal and its hardness value is 1.65 kg/mm2.

Growth, Optical, Thermal, Mechanical, Laser Damage Threshold and Electrical Polarizability of Cadmium Chloride Doped l -Alanine (LACC) Single Crystal for Optoelectronic Applications

Abstract: l-Alanine doped with cadmium chloride crystal was grown by slow evaporation technique in an optimum condition using de-ionized water as solvent. Single crystal x-ray diffraction analysis was carried out to confirm the unit cell parameters and cell volume. The presence of amine vibrations and carboxylic acid vibrations affirm the presence of l-alanine in grown material by Fourier transform infrared (FT-IR) analysis. The ultraviolet visible near-infrared region (UV–Vis-NIR) spectrum revealed that the grown crystal has a lower cut-off wavelength at 246 nm and has high transmission in the entire visible region. Further, energy gap and the refractive index of the crystal were also calculated. Thermo-gravimetric (TG) and differential thermal analysis (DTA) were carried out, and it is estimated that the material is thermally stable up to 233°C and the melting point of the crystal was found to be 298°C. The mechanical strength of the material is estimated for various loads using Vicker’s microhardness and it reveals that material belongs to a soft material category. The electrical polarizability was calculated using known values such as valence electron, molecular weight, energy gap and density of the material. Z-scan technique for nonlinear studies was carried out on a LACC crystal to determine the third order nonlinear absorption (β), nonlinear refractive index (n2) and third order nonlinear susceptibility (χ(3)) using continuous wave Nd: YAG laser of 532 nm. Grown crystal shows that the material is very much suitable for second harmonic generation for frequency conversion applications.

Growth, structural and optical limiting property of a new third order nonlinear optical material: piperazinium bis (2-carboxypyridine) monohydrate

Abstract: Piperazinium bis (2-carboxypyridine) monohydrate (PPPA) was successfully synthesized and crystal was grown from aqueous solution. PPPA compound crystallized in centric (or achiral) space group P21/C. The lattice perfection was analyzed by high-resolution X-ray diffraction rocking curve measurement. The chemical structure was confirmed by FTIR and NMR spectral studies. The range of optical transmittance of PPPA crystal was elucidated from UV–visible spectral studies. Optical resistance was estimated from LDT studies using Nd:YAG laser. Thermal stability have also investigated for PPPA compound which shows that PPPA crystal is potentially applicable for optical applications. Mechanical stability and material’s category were established from the Vicker’s hardness studies. Growth mechanism of PPPA was revealed from etching studies. The grown crystal was investigated for third order susceptibility by Z-scan technique. It was found to that they behaved as saturable absorber and self defocused in refraction which is essential for optical switching and limiting applications. Its second molecular hyperpolarizability (γ) at 532 nm was estimated to be 3.4746 × 10−9 esu.

Photocatalytic degradation of acid red-85 dye by nickel substituted bismuth ferrite nanoparticles

Abstract: Visible light driven photocatalytic property of nickel doped BiFeO3 nanoparticles were explored from the degradation of Acid red-85 dye. Fuel (citric acid) assisted auto-combustion method was adopted for the synthesis of BiFe(1−x)NixO3 (x = 0.25, 0.5, 0.75 and 0.10) nanoparticles. The synthesized particles were characterized by x-ray diffraction, from which reduction in crystallite size has been observed from 57 nm to 28 nm. Lattice parameters also have been calculated for the same which shows an increase in lattice parameters confirming the presence of nickel in the BiFeO3 lattice. Morphological studies were carried out using high resolution scanning electron microscopy on undoped and 10% nickel doped BiFeO3 samples which show a decrease in particle size in the doped sample compared to the bare BiFeO3 similar results have been observed in Transmission Electron Microscopy images. Reduction in the optical band gap from 2.2 eV to 2.02 eV of BiFeO3 compared to 10% Nickel doped bismuth ferrite is observed. Vibrating sample magnetometer studies performed at room temperature indicates that addition of nickel increases both remnant and saturation magnetization to the bismuth ferrite sample thus helping in the removal of photocatalyst after treatment. Photocatalytic study on the Acid red-85 dye by visible light irradiation showed the complete degradation of dye in 40 min. The 10% Nickel doped BiFeO3 showed the best photocatalytic activity. The enhancement in the photocatalytic activity of the doped BiFeO3 is because of efficient charge separation which has been confirmed by photoluminescence studies.

Studies on third order nonlinear optical properties of Nickel Boro Phthalate NLO crystal

Abstract: Single crystals of Nickel Boro Phthalate (NBP) are grown by the slow evaporation technique. The crystals are subjected to Single crystal X-ray diffraction to analyse the crystal lattice parameters, and the crystal structure is found to be triclinic. The presence of functional groups has been estimated qualitatively from the Fourier transform infrared spectroscopy and elemental analysis is done using the Energy dispersive X-ray spectral study. The UV-visible spectral studies indicate a broad window of transparency in the entire visible and infrared region and the fundamental frequency is determined to be 285 nm. Optical properties such as the dielectric constant, polarizability, susceptibility, optical and electrical conductivity are presented graphically. Third-order nonlinear parameters are evaluated by the Z scan technique using continuous wave 532 nm diode- pumped Nd:YAG laser. Closed aperture mode indicates the self-defocusing nature and negative nonlinearity of the crystal. Open aperture mode reveals the saturation absorption within the crystal. The nonlinear optical parameters such as nonlinear refractive index n2, nonlinear absorption coefficient β and nonlinear susceptibility χ (3) are also determined.

Growth, structure perfection and characterization of 2-methylimidazolium hydrogen oxalate dihydrate (2MIO) single crystal for NLO applications

Abstract: 2-Methylimidazolium hydrogen oxalate dihydrate (2MIO) organic single crystals of good quality have been grown by slow evaporation solution growth technique (SEST). Structure of the compound was determined by single crystal X-ray diffraction (SCXRD) analysis and it reveals that 2MIO crystallized in monoclinic space group P21/n. The high resolution X-ray diffraction (HRXRD) analysis was carried out to find the crystalline quality. The functional groups of 2MIO have been identified by FT-Raman and FT-IR analyses. The optical UV–Vis–NIR transmittance was recorded and the cut-off edge was found at 314 nm. It is worthwhile to mention that the stability and decomposition of the 2MIO material were established by the analysis of TG/DTG and DSC measurements. The crystal hardness was obtained. The dielectric property studies were carried out at different temperatures. Nonlinear optical susceptibility was determined for 2MIO by Z-scan study.

Growth of Morpholin-4-ium hydrogen tartrate single crystal for optical limiting application

Abstract: A new third order nonlinear optical single crystal of Morpholin-4-ium hydrogen tartrate has been grown by the slow evaporation method. The lattice parameters and crystalline purity of this orthorhombic crystal were measured by single crystal X-ray diffraction and powder X-diffraction technique respectively. The optimized geometry shows that the morpholinium ring exist in a chair form where tartrate anions are linked via N H⋯O hydrogen bonds, forming chains. These chains are linked via N H⋯O and O H⋯O hydrogen bonds, involving the morpholinium cation. The vibrational spectral investigation predicts that the red shifting of O H and N H stretching wavenumbers are due to O H⋯O and N H⋯O intermolecular interactions, respectively which are also evident form NBO analysis. The photoluminescence spectrum shows luminescence at the blue region with an appreciable lifetime leading to applications in blue OLEDs. Third order nonlinear optical properties like self-defocusing, saturable absorption and optical limiting at 532 nm are identified by Z-scan analysis. The laser damage threshold (LDT) energy have been measured by using Nd:YAG laser of wavelength 532 nm. The field dependent nature of first and second order hyperpolarizabilities and luminescence properties suggest that MHT crystal is a potential candidate for OLED and nonlinear optical applications.