Synthesis,growth and characterization of a novel semiorganic nonlinear optical single crystal: l-Asparagine cadmium chloride monohydrate

The semiorganic single crystal of l-asparagine cadmium chloride monohydrate was grown by slow evaporation solution growth technique at room temperature. The presence of various functional groups has been identified by using FT IR spectral analysis ranging between 4000 and 400 cm^?1. Chemical composition of the synthesized material was confirmed by elemental analysis. The crystalline nature of new crystal was confirmed by powder XRD pattern. The UV–vis–NIR spectroscopic study revealed that the grown crystal has good optical transmittance. The dielectric constant has been carried out over a frequency range from 100 Hz to 1 MHz. The mechanical strength was studied using Vicker's microhardness tester.     

Multi-spectral antireflection coating on zinc sulphide simultaneously effective in visible,eye safe laser wave length and MWIR region

In recent years multi-spectral device is steadily growing popularity. Multi-spectral antireflection coating effective in visible region for sighting system, laser wavelength for ranging and MWIR region for thermal system can use common objective/receiver optics highly useful for state of art thermal instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (450–650 nm), Eye safe laser wave length (1540 nm) and MWIR region (3.6–4.9 μm) has been reported. Comprehensive search method of design was used and the number of layers in the design was optimised with lowest evaluated merit function studied with respect to various layers. Finally eight-layer design stack was established using hafnium oxide as high index layer and silicon-di-oxide as low index coating material combination. The multilayer stack had been fabricated by using electron beam gun evaporation system in Symphony 9 vacuum coating unit. During layer deposition the substrate was irradiated with End-Hall ion gun. The evaporation was carried out in presence of oxygen and layer thicknesses were measured with crystal monitor. The result achieved for the antireflection coating was 85% average transmission from 450 to 650 nm in visible region, 95% transmission at 1540 nm and 96% average transmission from 3.6 to 4.9 μm in MWIR region.     

Synthesis,growth and characterization of a semiorganic nonlinear optical single crystal: L-Valine cadmium bromide

A semiorganic nonlinear optical material L-valine cadmium bromide was synthesized and single crystal grown from an aqueous solution by the method of slow evaporation technique at room temperature. The grown crystal was characterized by Powder X-ray diffraction and FT IR studies. The LVCB crystallizes in monoclinic system with cell parameters a = 10.144(2) Å, b = 5.54(1) Å, c = 12.07(2) Å, β = 109.115(2)° with space group P₂₁. Thermal behavior and stability of crystal were studied using thermogravimetric analyses (TGA) and differential thermal analysis (DTA) techniques. The suitability of this material for NLO application was studied by optical absorption studies and second harmonic generation (SHG) efficiency measurement by Kurtz–Perry powder method.     

Structural,optical and mechanical property analysis of magnesium sulphate admixtured l-Threonine: A novel optoelectronic material

l-Threonine is an important amino acid and famous due to their property of frequency conversion and electro optic modulation. Single crystals of magnesium sulphate admixtured l-Threonine was grown by slow evaporation technique. Good quality single crystal with dimension 58 × 5 × 10 mm³ was harvested after 60 days. The powder X-ray diffraction pattern of the grown crystal has been indexed. The optical transmission spectrum shows that the magnesium sulphate admixtured l-Threonine possess good optical transparency in the entire visible region with Ultra Violet cut-off wavelength at 250 nm. The presence of fundamental functional groups was identified by Fourier Transform Infra Red spectral analysis. The structure of the grown crystal was established using Fourier Transform-Nuclear Magnetic Resonance spectral analysis. The thermal behaviour of the crystal has been discussed by Thermal Gravimetric Analysis and Differential Thermal Analysis. Magnesium sulphate admixtured l-Threonine was characterized by Energy dispersive analysis of X-ray. The second harmonic generation efficiency of magnesium sulphate admixtured l-Threonine crystal is found to be same as that of potassium dihydrogen phosphate crystal.     

Structural,optical and electrical characteristics of a new NLO crystal

A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P2₁. The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 °C. The grown crystal was optically transparent in the wavelength range of 400–1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm². The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal.     

Experimental and theoretical studies on bis(glycine) lithium nitrate (BGLiN): A physico-chemical approach

Good quality and bulk size single crystal (size: 20×13×8 mm³) of bis(glycine) lithium nitrate (BGLiN) was grown by a slow evaporation solution technique from the aqueous solutions at constant temperature i.e. 27 °C using synthesized materials. Crystal system and lattice parameters were determined by single crystals as well as powder X-ray diffraction analysis. The lattice parameters of the titled compound are a=10.0223 Å, b=5.0343 Å, c=17.0510 Å, and V=860.312 Å³ and it crystallized in an orthorhombic system with space group Pca2₁ obtained by single crystal XRD. Elemental composition was confirmed by energy dispersive X-ray spectroscopic analysis. Optical absorption spectrum was recorded and various optical parameters such as optical transmission (~60%), and optical band gap (4.998 eV) were calculated. Photoluminescence study shows that the grown crystal is free from major defects. Crystalline perfection of the grown crystal was assessed and found good. Ground state optimized geometry has been obtained by using DFT with 6-31G(d,p) basis set. HOMO and LUMO energy gap was found to be 6.01 eV and dipole moment was 1.65 D.     

A new method of synthesis on high-quality AgGaS2 polycrystalline

High-pure, single-phase, free of voids and high mass density AgGaS₂ polycrystalline was synthesized by a new method, i.e. two-temperature zone vapor-transporting together with the mechanical and melt temperature oscillation method (TVMMTOM), directly from high-purity (6 N) elements silver, gallium and sulfur with excess sulfur. The mechanism and advantages of the new method for synthesizing high-quality AgGaS₂ were discussed. It is found that the polycrystalline material synthesized by the new method is superior to that synthesized by the conventional method, what is more the new method can avoid the explosion of the synthetic quartz ampoule. Adopting the modified Bridgman method an integral and crack-free AgGaS₂ single crystal with diameter of 14 mm and length of 63 mm has been obtained. It was found that there was a (1 0 1) cleavage face and the four order X-ray spectrum of the {1 0 1} faces was observed. By the method of DSC analysis the melting and freezing points of the AgGaS₂ single crystal were about 995 and 955 °C. The transmission spectra of the AgGaS₂ sample of 10 × 8 × 2 mm³ were obtained by means of UV and IR spectrophotometer. The limiting wavelength was 470 nm and the band gap was 2.64 eV. It can be found in the infrared spectrum that the infrared transmission was above 55% from 4000 to 800 cm⁻¹, and the infrared transmittance of the crystal is up to 63% at 10.6 μm, which is higher than that of the crystal grown using polycrystalline materials synthesized by the conventional method. The value of α in 10.6 μm was 0.267 cm⁻¹. Above mentioned results showed that the crystal was of good quality and TVMMTOM is preferable for synthesizing high-quality AgGaS₂ polycrystalline materials.     

Synthesis and growth of sodium bitartrate monohydrate a new organometallic nonlinear optical single crystal

Sodium bitartrate monohydrate (SBTMH) a new organometallic nonlinear optical material, with molecular formula, [C₄H₅NaO₆ · H₂O] has been synthesized at ambient temperature. Spectral, thermal and optical techniques have been employed to characterize the new material. Bulk single crystals of size 13 × 4 × 4 mm³ of SBTMH have been grown by slow cooling method. The unit cell parameters of the grown crystal were determined by single crystal XRD. Functional groups present in the sample were identified by FTIR spectral analysis. Thermal stability of SBTMH was determined using TGA/DTA. The grown crystals exhibit nonlinear properties. The dielectric response of the crystal with varying frequencies was studied. The optical transparency range and the lower cut-off wavelength of the material were identified from the UV–vis–NIR absorption spectrum.     

Enhancement of second harmonic generation efficiency: Cs(I)-doped tris(thiourea)zinc(II) sulphate crystals

The effect of dopant cesium (Cs(I)) over a concentration range from 1 to 10 mol% on the growth process, morphology, thermal and optical properties of tri(thiourea)zinc(II) sulfate (ZTS) single crystals grown by slow evaporation solution growth technique has been investigated. Incorporation of Cs(I) into the crystal lattice was well confirmed by energy dispersive X-ray spectroscopy (EDS). The lattice parameters of the as-grown crystals were obtained by single crystal X-ray diffraction analysis. The reduction in the intensities observed in powder X-ray diffraction patterns of doped specimen and slight shifts in vibrational frequencies in fourier transform infrared spectra (FT-IR) indicate the lattice stress as a result of doping. Thermal studies reveal the purity of the material and no decomposition is observed up to the melting point. High transmittance is observed in the visible region and the cut-off λ is ～280 nm. The surface morphology of the as-grown specimens was studied by scanning electron microscopy (SEM). The second harmonic generation (SHG) efficiency of the host crystal is enhanced greatly in the presence of high concentrations of the dopant.     

Grain size effect on the universality of AC conductivity in SnO2

Nanocrystalline tin oxide (SnO₂) material with different grain sizes was synthesized by using a chemical precipitation method. This material was characterized by using the X-ray diffraction and transmission electron microscopy. The electrical properties of compressed nanocrystalline SnO₂ were studied by using impedance spectroscopy. AC conductivity data for SnO₂ material having grain sizes between 9 and 34 nm were analyzed using a power law. The exponent n is found to be 0.5 for bulk (34 nm) and unity for material with grain size below 18 nm. The results show a universal behavior for very low average grain sizes and the non-universal behavior for larger grain sizes even at room temperature.     

Optical and dielectric studies of solution grown glycinium maleate single crystal

Bulk single crystals of glycinium maleate have been grown from aqueous solution by slow evaporation method by optimizing the growth parameters within a period of 15 days. From X-ray diffraction analysis, the crystal was found to crystallize in monoclinic structure (space group C_2/c) with a = 17.866 Å, b = 5.684 Å, c = 17.408 Å and β = 112.65°. Presence of characteristic functional groups was confirmed in FTIR analysis. UV–Vis spectral analysis has revealed the absence of any high absorbance region between the wavelengths ranging from 300 to 900 nm. The optical band gap was calculated and found to be 3.91 eV. The activation energy for conduction at different frequencies was calculated and found to decrease from 0.54 eV to 0.41 eV as frequency increased from 100 Hz to 2 MHz. The dielectric behavior, conduction mechanism and the optical characterization of the glycinium maleate single crystals are being reported for the first time.     

Nanocrystalline SnO2–TiO2 thin film deposited on base of equilateral prism as an opto-electronic humidity sensor

Present paper reports the synthesis of SnO₂–TiO₂ nanocomposite, its characterization and performance as opto-electronic humidity sensor. Nanocrystalline SnO₂–TiO₂ film was deposited on the base of an equilateral prism using a photo resist spinner and the as prepared film was annealed at 200 °C for 2 h. The crystal structure of the prepared film was investigated using X-ray diffraction (XRD). Minimum crystallite size of the material was found 7 nm. Surface morphology of the film was investigated by Scanning electron microscope (SEM LEO-0430, Cambridge). SEM image shows that the film is porous. Differential scanning calorimetry (DSC) of as synthesized material shows two exothermic peaks at about 40 and 110 °C, respectively which are due to the evaporation of chemical impurities and water. Further the prepared film was investigated through the exposure of humidity and relative humidity (%RH) was measured directly in terms of modulation in the intensity of light recorded on a digital power meter. The maximum sensitivity of sensor was found 4.14 μW/%RH, which is quite significant for sensor fabrication purposes.     

Linear and nonlinear optical properties of N-(3-nitrophenyl) acetamide single crystals

Optically transparent nonlinear optical bulk single crystal of N-(3-nitrophenyl) acetamide (3NAA) of dimension 7 mm × 6 mm × 5 mm has been grown from its aqueous solution by slow solvent evaporation technique. The grown crystal was characterized by powder X-ray diffraction to confirm the crystal structure. Investigation has been carried out to assign the vibrational frequencies of the grown crystals by Fourier Transform Infrared Spectroscopy and FT-NMR technique. Thermal behaviour of the grown crystals was studied by thermogravimetric analysis. The second harmonic generation efficiency of 3NAA was determined by Kurtz and Perry powder technique. The optical absorption study confirms the suitability of the crystal for device applications. The mechanical properties of the grown crystals have been studied using Vickers microhardness tester. Dielectric, microhardness and photoconductivity studies also carried out for the grown sample.     

Low loss propagation in slow light photonic crystal waveguides at group indices up to 60

We have designed slow light photonic crystal waveguides operating in a low loss and constant dispersion window of Δλ = 2 nm around λ = 1565 nm with a group index of n_g = 60. We experimentally demonstrate a relatively low propagation loss, of 130 dB/cm, for waveguides up to 800 μm in length. This result is particularly remarkable given that the waveguides were written on an electron-beam lithography tool with a writefield of 100 μm that exhibits stitching errors of typically 10–50 nm. We reduced the impact of these stitching errors by introducing “slow–fast–slow” mode conversion interfaces and show that these interfaces reduce the loss from 320 dB/cm to 130 dB/cm at n_g = 60. This significant improvement highlights the importance of the slow–fast–slow method and shows that high performance slow light waveguides can be realised with lengths much longer than the writing field of a given e-beam lithography tool.     

Morphology and optical properties of Mg and Sr doped CaF2 nanocrystals

Magnesium (Mg) and Strontium (Sr) doped Calcium fluoride nanocrystals were synthesized by co-precipitation method. The cubic structure of the samples was confirmed by Powder X-ray diffraction. The average crystallite size of Mg doped samples was found to be ~ 25 nm whereas in Sr doped one it was ~ 35 nm. The morphological features revealed that the nanocrystals were agglomerated, crispy and porous. The as-prepared samples showed the presence of hydroxyl groups. The optical absorption spectrum of as-prepared Mg doped samples showed a strong absorption band peaked at ~ 233 nm whereas the Sr doped one showed a prominent absorption peak at 248 nm. A strong PL emission was observed at ~ 300 nm in Mg doped samples. However, the Sr doped samples showed two prominent emissions at ~ 345 and 615 nm.     

Rapid synthesis of LiCr0.15Mn1.85O4 by glycine–nitrate method

LiCr_0.15Mn_1.85O₄ spinel has been successfully synthesized by glycine–nitrate method (GNM). The presence of pure spinel phase was confirmed by long term XRPD measurements and the Rietveld structural refinement. Lattice parameter was estimated to be 8.2338 Å. Average particle size of prepared powder material is below 500 nm. The BET surface area is 9.6 m² g^− 1. As a cathode material for lithium batteries LiCr_0.15Mn_1.85O₄ shows initial discharge capacity of 110 mA h g^− 1 and capacity retention of 83% after 50 cycles.     

Growth of SnO2 nanoparticles via thermal evaporation method

Tin oxide (SnO₂) nanoparticles were fabricated by evaporation of Sn powers at 1000 °C in air pressure. The as-deposited SnO₂ particles were single crystal structure, which were mostly spherical shape, the diameter of particles was ranging from 200 to 600 nm. The photoluminescence (PL) spectrum showed that a sharp emission peak at around 393 nm with the excitation wavelength at 325 nm, which suggested possible applications in nanoscaled optoelectronic devices. It was also found that the holding time affects the morphology of the products. The formation mechanism of SnO₂ particles was discussed.     

Microwave-assisted synthesis of iron(III) oxyhydroxides/oxides characterized using transmission electron microscopy,X-ray diffraction,and X-ray absorption spectroscopy

Microwave-assisted synthesis of iron oxide/oxyhydroxide nanophases was conducted using iron(III) chloride titrated with sodium hydroxide at seven different temperatures from 100 to 250 °C with pulsed microwaves. From the X-ray diffraction (XRD) results, it was determined that there were two different phases synthesized during the reactions which were temperature dependent. At the lower temperatures, 100 and 125 °C, it was determined that an iron oxyhydroxide chloride was synthesized. Whereas, at higher temperatures, at 150 °C and above, iron(III) oxide was synthesized. From the XRD, we also determined the FWHM and the average size of the nanoparticles using the Scherrer equation. The average size of the nanoparticles synthesized using the experimental conditions were 17, 21, 12, 22, 26, 33, 28 nm, respectively, for the reactions from 100 to 250 °C. The particles also had low anisotropy indicating spherical nanoparticles, which was later confirmed using transmission electron microscopy (TEM). Finally, X-ray absorption spectroscopy (XAS) studies show that the iron present in the nanophase was present as iron(III) coordinated to six oxygen atoms in the first coordination shell. The higher coordination shells also conform very closely to the ideal or bulk crystal structures.     

CVD synthesis and radial deformations of large diameter single-walled CNTs

Single-walled carbon nanotubes (CNTs) were synthesized by a chemical vapor deposition (CVD) method on transmission electron microscopy (TEM) silica coated nickel grids using carbon monoxide as carbon source and iron nanoparticles as catalyst. The produced CNTs were as large as 11 nm in diameter. Investigations on the CNT deformations based on high-resolution TEM images showed that the deformation of CNTs due to their interaction with the substrate occurs at diameters larger than 2.7 nm. Small deformation of free standing tubes was found to occur at diameters above approximately 4.5 nm.     

Thorium free antireflection coating in MWIR region on Silicon optics

Most infrared transmitting optics have high refractive indices which in turn have high per surface reflection loss. So antireflection coating has very important role in increasing the transmission in the desired wavelength region. In this paper a study has been carried out on the design and fabrication of Thorium free antireflection coating effective for Silicon substrate in MWIR (3.6–4.9 μm) region. The wave band 3.6–4.9 μm is chosen for the reported work because the detected system used in MWIR region has a band selection filter effective in the same wavelength region. Comprehensive search method was used to design the multilayer stack on Silicon substrate. The coating materials used in the design were Germanium (Ge) and Silicon dioxide (SiO₂). The fabrication of coating was made in a coating plant fitted with Cryo pump system and Residual Gas Analyzer. The evaporation was carried out at high vacuum (2–6 × 10–6 mbar) using Electron Beam Gun and layer thicknesses were measured with crystal monitor. The result achieved for the antireflection coating was 96% average transmission in 3.6–4.9 μm band which withstood MIL-F-48616 environmental testing. This work provides an alternate antireflection coating on Silicon by replacing radioactive Thorium Fluoride, used as a coating material in most IR antireflection coating designs.