Studies on optical and mechanical properties of new organic NLO crystal: Guanidinium 4-aminobenzoate (GuAB)

Organic nonlinear optical crystal of guanidinium 4-aminobenzoate (GuAB) has been successfully grown by slow evaporation solution growth technique. The grown crystal is up to the dimension of 36 × 8 × 6 mm³. The crystal is characterized by single crystal XRD for obtaining unit cell parameters. Optical properties of the grown crystal have been studied by means of UV–Vis–NIR transmission and absorption spectra in the range of 200 to 1000 nm. The refractive index and band gap energy of the GuAB crystal are obtained as 1.68 and 3.73 eV respectively. Mechanical hardness has been carried out on the grown crystal.     

Studies on the nonlinear optical single crystal: Ammonium d,l-tartrate (C4H9NO6)

The organic nonlinear optical material ammonium d,l-tartrate single crystal has been successfully grown by slow evaporation solution technique (SEST). The grown crystals were characterized by single crystal XRD and the lattice parameters have been confirmed. The structural perfection of the grown crystal was analyzed by high-resolution X-ray diffraction measurement. The optical transmittance spectrum shows that the material has a good optical transparency in the entire visible region with the UV cut-off wavelength at 234 nm. Thermogravimetric and differential scanning calorimetric measurements were performed to study the thermal properties of the grown crystal. Chemical etching studies were attempted to determine the dislocation density of the grown crystal. Mechanical behavior was assessed using Vickers hardness testing carried out on (0 0 1) crystallographic plane. The Kurtz–Perry powder SHG technique confirms the NLO property of the grown crystal and the efficiency of AMT crystal was found to be 1.3 times that of standard KDP crystal.     

Optical investigations on Tb3+ doped l-Histidine hydrochloride mono hydrate single crystals grown by low temperature solution techniques

The potential nonlinear optical material of Terbium (Tb³⁺) ion doped l-Histidine hydrochloride monohydrate (LHHC) single crystals were successfully grown. Tb³⁺:LHHC crystals of 7 mm × 5 mm × 3 mm and 59 mm length and 15 mm diameter have been grown by the slow solvent evaporation and Sankaranarayanan-Ramasamy (SR) techniques respectively. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystalline structure and morphology. High resolution X-ray diffraction (HRXRD) studies revealed that the SR grown sample shows relatively good crystalline nature with 9″ full-width at half-maximum (FWHM) for the diffraction curve. Functional groups were identified by Fourier transform infra-red spectroscopy (FTIR). The optical transparency and band gaps of grown crystals were measured by UV–Vis spectroscopy. Thermogravimetric and differential thermal analysis (TG/DTA) studies reveal that the crystal was thermally stable up to 155 °C in SR grown crystal. Surface morphology of the growth plane was observed using scanning electron microscopy (SEM). The incorporation of Tb ion was estimated by EDAX. The frequency-dependent dielectric properties of the crystals were carried out for different temperatures. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the SR method grown crystal. Second harmonic generation efficiency of SEST and SR grown crystals are 3.2 and 3.5 times greater than that of pure KDP. The Photoluminescence (PL) studies of Tb³⁺ ions result from the radiative intra-configurational f-f transitions that occur from the ⁵D₄ excited state to the ⁷F_j (j = 6, 5, 4, 3) ground states. The decay curve of the ⁵D₄ level of emission was observed with a long life time of 319.2041 μs for the SR grown Tb³⁺:LHHC crystal.     

Growth and characterization of new semiorganic nonlinear optical single crystal L-Phenylalanine L-Phenylalaninium perchlorate (LPPAPC)

The new semi-organic nonlinear optical crystal, L-Phenylalanine L-Phenylalaninium perchlorate (LPPAPC) has been grown through synthesis between L-Phenylalanine and perchloric acid. The bulk crystals of dimension 5.5 × 0.4 × 0.3 cm³ were obtained by submerged seed solution method. The new compound was characterized by UV–Vis-NIR spectroscopic technique. In addition to that the solid-state structure of the crystal has been determined by single crystal X-ray diffraction technique. LPPAPC was thermally stable up to 272 °C as determined by TG/DTA studies. Also, the second harmonic generation (SHG) of the LPPAPC crystal was observed using Nd: YAG laser with a fundamental wavelength of 1064 nm.     

Growth and characterization of bis thiourea cadmium iodide: A semiorganic single crystal

Single crystals of bis thiourea cadmium iodide[CdI₂(CH₄N₂S)₂], abbreviated as BTCI, a semiorganic material has been successfully grown by both slow evaporation and slow cooling methods. Crystal of dimensions up to 3.3 × 1.0 × 1.5 cm³ is reported. Single crystal X-ray diffraction analysis has been carried out to confirm monoclinic system and etching studies for their perfection. The morphology of the grown crystal was also identified by single crystal X-ray diffraction analysis. The powder X-ray diffractogram of the crystal has been recorded and the various planes of reflection are identified. The presence of functional groups and the coordination of metal ions to thiourea were confirmed by FTIR analysis. Transmission spectra reveals that the crystal has low UV cutoff of 324 nm and has a good transmittance in the entire visible region enabling its use in optical applications. The thermal behaviour of the crystal has been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), which indicates that the material does not decompose before melting. Studies of dielectric properties (dielectric constant and dielectric loss) both as function of frequencies (100 Hz to 5 MHz) for varying temperatures in the range 308–348 K suggests good candidate for electro optic modulators.     

Experimental and theoretical characterization of semiorganic nonlinear optical material l-leucine hydrobromide

Semiorganic nonlinear optical material l-leucine hydrobromide (LEHBr) has been synthesized and single crystals were grown by solvent evaporation method at a constant temperature of 35 °C. CHN test, FTIR and XRD analysis were performed for identification of the material. Thermal and mechanical stability of the grown crystal were investigated by DTA-TGA analysis and microhardness measurement respectively. Suitability of LEHBr for NLO application was studied by optical transmission study and second harmonic generation (SHG) efficiency measurement. SHG efficiency was found to be 4 times of KDP. First hyperpolarizability, dipole moment and polarizability of LEHBr were calculated at the framework of Hartree–Fock (HF) with 6-311G(d) basis set. First order hyperpolarizability was found to be 3.233 × 10⁻³³ esu which is 4.9 times of urea.     

Growth and Faraday rotation characteristics of TbVO4 crystals

TbVO₄ (TV) single crystals with dimensions of 18 × 18 × 16 mm³ were grown by Czochralski method under different atmosphere. XPS studies revealed the presence of V⁴⁺ and Tb⁴⁺ in TV crystal grown at 99.9% N₂ atmosphere, which caused a wide absorption peak centered at 950 nm in the transmission spectrum. TV crystal grown at 80% N₂ + 20% CO₂ mixed atmosphere has high transmittance at 600–1500 nm waveband. Faraday rotation spectra of TV crystal were measured. TV crystal has a larger Faraday rotation than terbium gallium garnet (TGG) crystal at 500–1500 nm waveband.     

A comparative study of ferroelectric triglycine sulfate (TGS) crystals grown by conventional slow evaporation and unidirectional method

Unidirectional 〈0 1 0〉 TGS single crystal of diameter 35 mm and length 80 mm was grown by Sankaranarayanan–Ramasamy (SR) method. Nearly two times higher d₃₃ value has been obtained for the SR grown TGS crystal compared to conventional grown TGS. The etch pit density of SEST and SR method grown TGS crystal is 2.1 × 10² cm^?2 and 1.5 × 10² cm^?2 respectively. The values of hardness were found to be 152 kg/mm² for SR grown TGS and 108 kg/mm² for SEST grown TGS crystal. The average laser damage threshold obtained on the SEST grown TGS crystal was 29 mJ/cm² whereas a high damage threshold of 39 mJ/cm² was obtained for the SR grown crystal. The SR method grown TGS has 5% higher transmittance as against conventional method grown crystal. Dielectric study showed higher dielectric permittivity and lower dielectric loss in SR grown TGS crystal.     

Structural,optical, thermal,photoconductivity, laser damage threshold and fluorescence analysis of an organic material: β-P-amino benzoic acid single crystal

β-P-amino benzoic acid, an organic single crystal was grown by slow evaporation technique. Single crystal X-ray diffraction studies show that the grown crystal has β-polymorph of P-amino benzoic acid [β-PABA] form and the lattice parameters are a = 6.30 Å, b = 8.61 Å, c = 12.43 Å α = γ = 90° and β = 100.20°. FTIR analysis confirms that bands at 1588 cm⁻¹, 1415 cm⁻¹ are assigned to ring skeletal vibrations of title compound. The molecular structure of the grown crystal has been identified by Nuclear Magnetic Resonance spectral study. The optical absorbance spectrum from 200 to 1100 nm shows that there is an edge absorbance in UV region. Optical band gap of the crystal has been assessed from the absorbance spectrum. The thermal properties of crystals were evaluated from TG-DTA analysis, it exhibits that there is no weight loss up to 187 °C. Laser damage threshold indicates that the grown crystal has no surface damage up to 35 mJ. Photoconductivity and fluorescence spectral experiments are also carried out and the results are discussed.     

Bridgman growth of large-aperture yttrium calcium oxyborate crystal

Large-aperture yttrium calcium oxyborate YCa₄O(BO₃)₃ (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm × 68 mm × 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.     

Synthesis,crystal structure and solubility of C6H14N4O2,C4H4O4,2H2O

Synthesis, crystal structure and solubility of a new non-linear optical material l-arginine maleate dihydrate have been reported here. From the solubility studies with different solvents, water was found to be the most suitable one. Title compound crystallized in the triclinic space group P1 with Z=1 and unit cell dimensions a=5.264(3) Å, b=8.039(3) Å, c=9.784(3) Å, α=106.19(3)°, β=97.24(3)°, γ=101.66(2)°. The present complex of l-arginine contains a positively charged zwitterionic arginine molecule and a negatively charged semi-maleate ion. The molecules are held together by a three-dimensional network of hydrogen bonds.     

Investigation on growth,structural, optical,thermal, dielectric and mechanical properties of organic l-prolinium trichloroacetate single crystals

A new organic nonlinear optical material l-prolinium trichloroacetate (l-PTCA) single crystal has been synthesized and grown by slow solvent evaporation technique at room temperature using water as solvent. Single-crystal X-ray diffractometer was utilized to measure unit cell parameters and to confirm lattice parameter. The powder X-ray diffraction pattern of the grown l-PTCA has been indexed. The modes of vibration of different molecular groups present in the sample were identified by the FTIR spectral analysis. The optical transmittance window and the lower cutoff wavelength of the l-PTCA have been identified by UV–vis–NIR studies. Thermal stability of the l-prolinium trichloroacetate was determined by TGA/DTA measurements. Dielectric measurements were carried out at various temperatures at frequency range 10–1 MHz. The mechanical properties of the grown crystals have been analyzed by Vickers microhardness method. The chemical etching studies were carried out on the grown crystals. Its SHG efficiency has been tested by Kurtz powder method.     

Bridgman growth of Sr3NbGa3Si2O14 single crystal

A new langasite structure piezoelectric single crystal Sr₃NbGa₃Si₂O₁₄ (SNGS) had been grown by the vertical Bridgman method for the first time. SNGS crystalline powder was synthesized as the starting material by sintering the mixture of 4N pure SrCO₃, Nb₂O₅, SiO₂ and Ga₂O₃ at 1200 °C for 16 h. 〈0 0 1〉-oriented La₃Ga₅SiO₁₄ (LGS) crystal of Ø10 mm × 35 mm was used as seed. A SNGS crystal with 25 mm in diameter and 40 mm in length has been grown from its stoichiometric melt. The transmittance spectra were measured and the transmittance of SNGS crystal was found to be greater than 80% in wavelength of 400–1000 nm.     

Influence of air annealing temperature and time on the optical properties of Yb:YAG single crystal grown by HDS method

8 at.% Yb:YAG plate single crystal with the dimension of 170 mm × 150 mm × 30 mm was grown in vacuum by Horizontal Directional Solidification method. Aimed at blue-green color centers, annealing treatments of 15 mm × 15 mm × 1 mm samples from 900 °C to 1400 °C for 5 h and at 900 °C from 5 h to 40 h in air were conducted. The absorption spectra, emission spectra, fluorescence lifetime and X-ray photoelectron spectroscopy of samples under different annealing conditions were measured at room temperature, respectively. Annealing at above 1000 °C for 5 h or at 900 °C for 40 h made the blue-green color centers disappear and the samples turned to transparent. Absorption coefficients decreased in the 300 nm–800 nm wavelength range, emission intensities increased and emission bands broadened around 486 nm and 1029 nm with increasing temperature up to 1200 °C, then varied inversely. These values decreased or increased monotonically with increasing annealing time at 900 °C. The maximal increases of fluorescence lifetime were 62.3% and 64.7%, respectively. The calculated emission cross section of 1200 °C for 5 h was up to 4.4 × 10⁻²⁰ cm². In X-ray photoelectron spectroscopy, the concentrations of oxygen vacancies reduced from 1.28% down to absence by annealing. These experiments show that color centers are detrimental to the optical properties of HDS-Yb:YAG laser crystal and optimal annealing treatments should be conducted.     

Blue fluorescent organic light emitting diodes with multilayered graphene anode

As an innovative anode for organic light emitting devices (OLEDs), we have investigated graphene films. Graphene has importance due to its huge potential in flexible OLED applications. In this work, graphene films have been catalytically grown and transferred to the glass substrate for OLED fabrications. We have successfully fabricated 2 mm × 2 mm device area blue fluorescent OLEDs with graphene anodes which showed 2.1% of external quantum efficiency at 1000 cd/m². This is the highest value reported among fluorescent OLEDs using graphene anodes. Oxygen plasma treatment on graphene has been found to improve hole injections in low voltage regime, which has been interpreted as oxygen plasma induced work function modification. However, plasma treatment also increases the sheet resistance of graphene, limiting the maximum luminance. In summary, our works demonstrate the practical possibility of graphene as an anode material for OLEDs and suggest a processing route which can be applied to various graphene related devices.     

Growth and properties of sodium tetraborate decahydrate single crystals

Sodium tetraborate decahydrate (Na₂B₄O₇·10H₂O) single crystals were grown from aqueous solution by slow solvent evaporation method and its functional groups have been confirmed by FTIR. Grown crystals were found to be hard in nature (n = 1.8). From optical studies band gap of the material was found to be 4.1 eV and PL emission peak was found at 340 nm which can be due to annihilation self trapped excitons present in borate crystals. Dielectric constant was found to increase with temperature up to 70 °C. Conductivity obeys Jonscher's power law as seen at different temperatures. Activation energy of the crystal was found to be 2.05 eV.     

Structural,optical and dielectric studies of novel non-linear Bisglycine Lithium Nitrate piezoelectric single crystal

The novel non-linear semiorganic Bisglycine Lithium Nitrate (BGLiN) single crystals were grown by slow evaporation technique. The structural analysis revealed that it belongs to non-centrosymmetric orthorhombic structure. The presence of various functional groups in the grown crystal was confirmed by FTIR and Raman analysis. Surface morphology of the grown crystal was studied by scanning electron microscopy. The optical studies show that crystal has good transmittance (more than 80%) in the entire visible region and a wide band gap (5.17 eV). The optical constants such as extinction coefficient (K), the reflectance (R) and refractive index (n) as a function of photon energy were calculated from the optical measurements. With the help of these optical constants the electric susceptibility (χ_c) and both the real (ε_r) and imaginary (ε_i) parts of the dielectric constants were also calculated which are required to develop optoelectronic devices. In photoluminescence studies, a broad emission band centered at 404 nm was found in addition to a small band at 352 nm. A broad transition (from 29 to 33 °C) was observed with low dielectric constant value. A high piezoelectric charge coefficient (d₃₃) of 14 pC/N was measured at room temperature which implies its usefulness for various sensor applications. The second harmonic generation efficiency of crystal was found to be 1.5 times to that of KDP. From thermo gravimetric analysis and differential thermal analysis, thermal stability and melting point (246 °C) were investigated. The dielectric behavior, optical characterization, piezoelectric behavior and the non-linear optical properties of the Bisglycine Lithium Nitrate single crystals were reported for the first time which established the usefulness of these crystals for various piezo- and opto-electronics applications.     

Optical and thermal properties of crystalline Tb: KLu(WO4)2

A single crystal of Tb: KLu(WO₄)₂ with dimensions of 40 mm × 40 mm × 18 mm has been grown by the top-seeded solution growth (TSSG) method. The color of the crystal is brown. Absorption and fluorescence spectra were measured at room temperature. The measured specific heat is a little lower than that of Yb: KLW (0.365 J/g K) at 90 °C. The measured mean linear coefficients of thermal expansion are α_a = 17.1643 × 10^− 6 K^− 1_, α_a^⁎ = 14.0896 × 10^− 6 K^− 1, α_b = 8.7938 × 10^− 6 K^− 1, α_c = 23.1745 × 10^− 6 K^− 1, α_c^⁎ = 20.2866 × 10^− 6 K^− 1. The results indicate that the crystal has a large anisotropy. The refractive index was measured.     

Investigation on third order nonlinear optical,electrical and surface properties of organic stilbazolium crystal of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate

The third order nonlinear optical, electric and dielectric properties of an organic stilbazolium derivative of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate (DSMOS) crystal are reported. The nonlinear refractive index (n₂), two photon absorption coefficient (β) and third order optical susceptibility χ⁽³⁾ have been measured by Z-scan technique using Gaussian beam from the Nd:YAG laser at 1064 nm. The results show a large negative nonlinear refractive index (n₂ = −1.122 × 10−9 cm²/W) with a molecular two photon absorption coefficient β value of 3.625 × 10⁻⁶ cm/W. The low dielectric constant observed in the high frequency region indicates the suitability of the sample for electro-optic applications. The surface features are also investigated by atomic force microscopy (AFM).     

Growth,microhardness, dielectric and photoconductivity studies on NPNaLi: A promising crystal for NLO applications

Single crystals of nonlinear optical sodium substituted lithium p-nitrophenolate trihydrate (NPNaLi·3H₂O) have been grown successfully by slow solvent evaporation technique. The grown crystals are subjected to powder X-ray diffraction, microhardness, dielectric and photoconductivity studies. NLO activity of the crystal is found to be increased in the presence of sodium ions. Microhardness on (1 1 0) and (1 0 1) planes reveal the anisotropic behaviour in Vicker's hardness number. Dielectric constant is found to be less and independent at higher frequencies. Electrical conductivity and photoconductivity are found to be increasing in the presence of sodium in the lattice of NPLi. The results of SEM analysis also have been revealed.