Crystals Of Good Optical Quality Research Articles

On the low-temperature isotropic point in Rb2SO4 crystals

In this work, Rb2SO4 single crystals of good optical quality were synthesized and the spectral (300–700 nm) and temperature (300–77 K) dependencies of birefringence were experimentally investigated. It was found that with a temperature decreasing, at a temperature of T = 85 K and a light wavelength of λ = 500 nm, the birefringence value in the Y direction is zero (Δny = nz – nх = 0), which testifies to the existence of a new isotropic point. The influence of uniaxial compression on changes in Δny (Т, λ) was studied, and their significant sensitivity was revealed. The temperature-baric and spectral-baric changes of the isotropic point position were analyzed, based on which the temperature-spectral-baric diagram of the isotropic state of the crystal was constructed, which will be of practical importance for the use of crystal as an active element in a crystal-optical temperature sensor for a low-temperature region. Based on the Δny (Т, λ, σ) dependencies, the combined piezo-optic coefficients of the crystal were estimated, and it was assumed that not only thermal but also mechanical deformation of the optical indicatrix takes place in the vicinity of the isotropic point.

Studies on 4 - dimethylaminopyridinium salicylate monohydrate's optical, mechanical, and laser damage threshold

Slow evaporation solution growth was used to grow single crystals of 4-dimethylaminopyridinium salicylate monohydrate. Single crystals of good optical quality with dimensions up to 14 × 6 x5 mm3 are obtained. Single crystal X-ray diffraction analysis verified the unit cell parameters of the grown crystals. In the wavelength range of 200–1100 nm, the UV–Vis–NIR Transmittance spectrum was observed. Vicker's microhardness test was used to examine the mechanical behaviour of the grown crystal. Using 5 ns laser pulses at a 10 Hz repetition rate from a Q-switched Nd: YAG laser with a wavelength of 1064 nm, the laser damage threshold value was calculated.

Ab initio calculations of the electronic structure and specific optical features of β-LiNH4SO4 single crystals

In the present work complex experimental and theoretical studies of electronic and optical properties for β-lithium-ammonium sulfate crystals of good optical quality are performed using the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). Standard immersion and spectroscopic techniques accompanied by the theoretical quantum-chemical calculations in the density functional theory (DFT) framework were applied. Calculations of band structure and related properties were carried out within a framework of local density and generalized gradient approximations as well as hybrid B3LYP functionals. The energy levels features and their origin are established from the DFT calculations and they were ferified by XPS and XES measurements. Theoretical and experimental refractive indices dispersions along the principal crystallographic directions (nx, ny and nz) as well as birefringence dispersion (Δnx, Δny and Δnz) in the visible spectral range are obtained. It was found a closeness of nx and ny curves for the titled crystals. More precise birefringence examining predicts their intersection at λ ≈ 190 nm.

Investigations on growth and characterization of glycine admixture sodium molybdate crystals for nonlinear optical applications

Single crystals of semi-organic nonlinear optical material tris-glycine sodium molybdate were grown by slow evaporation technique from aqueous solution at room temperature. Good optical quality crystals with dimensions of 2.3×1×0.5cm3 were obtained. Single crystal X-ray diffraction was used to measure the unit cell parameters and affirmed the crystal structure. Powder X-ray diffraction revealed that the crystallinity of the crystals grown. Fourier transform infrared spectra confirmed the complex formation of glycine and sodium molybdate. Ultra violet absorption studies indicate that the crystals were transparent in the entire visible range. Direct optical band gap and indirect optical band gap values of the grown crystals were calculated from the Tauc plot. Vickers microhardness test was performed to understand the mechanical strength of the crystals. Thermal stability and melting point of the grown crystal was identified from thermo gravimetric analysis and differential thermal analysis. The surface morphology of the grown crystals was studied using scanning electron microscope analysis. Chemical composition and purity of the crystal was corroborated by energy dispersive X-ray analysis. The nonlinear optical property of the crystal was measured by Kurtz and Perry powder technique using Nd:YAG laser operating at 1064nm.

EDTA effect on Copper Sulphate Penta Hydrate-A NLO Material

Ethylene Diamine Tetra Acetic acid (EDTA) doped copper sulphate penta hydrate were grown for five different parent -dopant combinations using slow solvent evaporation method at 300 K and good optical quality crystals were harvested for minimum dopant ratio. The single crystal X -ray diffraction studies reveal the crystal system of the doped crystal to be triclinic with cell

Optical, structural and electrical properties of pure and urea doped KDP crystals

Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed.

Structural Investigations and Thermal Behavior of (EMIm)[Cr(C2O4)2]·2H2O [1‐Ethyl‐3‐methylimidazolium Chromium(III) Dioxalate Dihydrate

AbstractThe crystal structure of EMIm diaquobis(μ‐oxalato)chromate(III) (1‐ethyl‐3‐methylimidazolium chromium(III) dioxalate dihydrate) was determined from X‐ray single crystal diffraction studies. A pale violet crystal of good optical quality was used for the structure determination at –100(2) and 25(2) °C. The basic crystallographic data for the low temperature structure are as follows: triclinic symmetry, space group P$\bar{1}$ , a = 7.6202(8) Å, b = 9.7668(9) Å, c = 10.7171(11) Å, α = 109.257(9)°, β = 90.494(8)°, γ = 105.685(8)°, V = 720.75(1) Å3. The crystal structure was solved by direct methods and refined (using anisotropic displacement parameters for all non‐hydrogen atoms) to a final residual of R1 = 0.039 for 2062 independent observed reflections [I > 2σ(I)]. The compound is built up from alternating layers parallel to (010) containing (EMIm)+ cations or Cr(C2O4)2(H2O)2– anions, respectively. The two crystallographically independent Cr(C2O4)2(H2O)2 octahedra reside on centers of symmetry (Wyckoff sites 1a and 1f). The corners of the octahedra consist of four oxygen atoms from two oxalate groups and two additional water molecules. EMIm+ cations provide linkage between different octahedral layers by hydrogen bridging. The water molecules in turn form hydrogen bonds with adjacent octahedra within the same layer. According to DTA/TG experiments the present compound shows several thermal processes in the range between room temperature and 1000 °C. However, pyrolysis is reproducibly yielding pure inorganic composites, qualifying this novel organic‐inorganic hybrid salt also as a stable precursor for nanoscalar ceramic materials. The final product consists of a distinct mixture of Cr2O3 and Cr3C2 in the molar ratio of 1:1. Concomittant oxide and carbide formation is an unprecedented disintegration pathway of the thermal treatment of oxalatochromates without reducing atmosphere.

Template-growth of periodically domain-structured KTiOPO_4 [Invited

We performed the first growth, from a high temperature solution, of a 38.86 μm-periodicity PPKTP crystal of good optical quality over a thickness of more than 800 μm onto each of the two faces perpendicular to the c direction of a PPKTP substrate previously obtained by electric field poling. The quasi-phase matched second harmonic generation properties in the grown layer and substrate are similar and in accordance with calculation.

Acentric nonlinear optical N-benzyl stilbazolium crystals with high environmental stability and enhanced molecular nonlinearity in solid state

We have developed a new cation core structure, N-benzyl stilbazolium nonlinear optical chromophore with a non-polar benzyl group to achieve acentric molecular ordering in the crystalline state. New N-benzyl stilbazolium crystal, BP3 (N,N-dimethylamino-N′-2,5-dimethylbenzyl-stilbazolium p-toluenesulfonate), exhibits an acentric crystal structure with the monoclinic P21 phase with a large macroscopic optical nonlinearity of 540 times the powder second harmonic generation efficiency of urea at the non-resonant wavelength of 1.9 µm. Compared to conventional rod-shaped N-alkyl stilbazolium crystals, an enhanced hyperpolarizability of the chromophoresβ0 in the solid state can be utilized in bent-shaped N-benzyl stilbazolium crystals. This is attributed to the decreased inter-chromophore interactions due to the larger chromophore–chromophore separation induced by the bulky and bent-shaped N-benzyl group, so-called site-isolation effect. Moreover, by introducing the non-polar dimethylbenzyl group, BP3 crystals show a high environmental stability: they exhibit almost one order of magnitude smaller solubility in water than conventional stilbazolium crystals and also do not form a hydrated centrosymmetric phase even if crystallized in water-containing solvents. We have grown good optical quality crystals large enough for optical characterization. With as-grown BP3 crystals without additional polishing and cutting procedures we have demonstrated THz generation by optical rectification using 180 fs pulses at the pump wavelength of 836 nm.

Hydrothermal crystal growth of the potassium niobate and potassium tantalate family of crystals

Single crystals of KNbO 3 (KN), KTaO 3 (KT), and KTa 1− x Nb x O 3 ( x=0.44, KTN) have been prepared by hydrothermal synthesis in highly concentrated KOH mineralizer solutions. The traditional problems of inhomogeneity, non-stoichiometry, crystal striations and crystal cracking resulting from phase transitions associated with this family compounds are minimized by the hydrothermal crystal growth technique. Crystals of good optical quality with only minor amounts of metal ion reduction can be grown this way. Reactions were also designed to provide homogeneous distribution of tantalum and niobium metal centers throughout the KTN crystal lattice to maximize its electro-optic properties. Synthesis was performed at relatively low (500–660 °C) temperatures in comparison to the flux and Czochralski techniques. This work represents the largest crystals of this family of compounds grown by hydrothermal methods to date.

Structural Investigations and Thermal Behavior of (NH4)[Cr(C2O4)2]·2H2O

AbstractSingle crystals of ammonium chromium(III) dioxalate dihydrate (or ammonium diaquo bis(μ‐oxalato)chromate(III)) have been obtained from aqueous solution of oxalic acid and ammonium dichromate. A pale violet crystal of good optical quality was used for the structure determination at −100(2) and 25(2) °C, respectively. The basic crystallographic data for the low temperature data set are as follows: monoclinic, space group C2/m, a = 6.597(2) Å, b = 7.301(2) Å, c = 9.983(3) Å, β = 92.32(2)°, V = 480.5(2) Å3. The structure was solved by direct methods and refined (using anisotropic displacement parameters for all non‐hydrogen atoms) to a final residual of R1 = 0.032 for 503 independent observed reflections (I>2σ(I)). The compound is isotypic with the corresponding rubidium salt. The structure is built up from alternating layers parallel to (001) containing (NH4)+ ions or Cr(C2O4)2(H2O)2 octahedra, respectively. The corners of the octahedra consist of four O atoms from two oxalate groups and two additional water molecules. The ammonium cations (occupying Wyckoff‐site 2a) are disordered among two possible orientations. They provide linkage between different octahedral layers by hydrogen bridging. The water molecules in turn form hydrogen bridges with adjacent octahedra within the same layer. Further structural characterization included infrared spectroscopy. According to DTA/TG experiments the present compound shows several thermal processes in the range between room temperature and 900 °C.

Application of accelerators for the research and development of scintillators

We introduce experimental systems which use accelerators to evaluate scintillation properties such as scintillation intensity, wavelength, and lifetime. A single crystal of good optical quality is often unavailable during early stages in the research and development (R&D) of new scintillator materials. Because of their beams' high excitation power and/or low penetration depth, accelerators facilitate estimation of the properties of early samples which may only be available as powders, thin films, and very small crystals. We constructed a scintillation spectrum measurement system that uses a Van de Graaff accelerator and an optical multichannel analyzer to estimate the relative scintillation intensity. In addition, we constructed a scintillation time profile measurement system that uses an electron linear accelerator and a femtosecond streak camera or a microchannel plate photomultiplier tube followed by a digital oscilloscope to determine the scintillation lifetimes. The time resolution is approximately 10 ps. The scintillation spectra or time profiles can be obtained in a significantly shorter acquisition time in comparison with that required by conventional measuring systems. The advantages of the systems described in this study can significantly promote the R&D of novel scintillator materials.

Growth and Characteristic of YbAl 3 (BO 3) 4 Crystal

YbAl 3(BO 3) 4 crystal of good optical quality was grown by the flux method. The structure of YbAl 3(BO 3) 4 crystal was determined by single-crystal X-ray diffraction. The experiment shows that YbAl 3(BO 3) 4 belongs to the double borates with a trigonal structure. The space group is R 32 and its unit cell constants were measured to be a = 0.92965 nm, c = 0.72129 nm, V = 0.53673 nm 3, Z = 3. The transmittance spectra were measured. The cut-off of YbAl 3(BO 3) 4 crystal is 216 nm, and there are two absorption peaks located at 940 and 975 nm from 190 nm to 2600 nm. The thermal properties of YbAl 3(BO 3) 4 crystal were studied for the first time. The average thermal expansion coefficients were determined to be 2 × 10 −6/°C, 9.5 × 10 −6/°C along a- and c- direction. The specific heat of YbAl 3(BO 3) 4 crystal was measured to be 0.6695 J·(g·°C) −1 at room temperature. All results indicate that the YbAl 3(BO 3) 4 crystal is an excellent stoichioimetric laser material.

Growth and characterization of semiorganic NLO crystals of LAHClBr

AbstractSingle crystals of non‐linear optical (NLO) LAHClBr were grown by slow evaporation technique from its aqueous solution. Good optical quality crystals having dimensions up to 12 × 9 × 7 mm3 were obtained. The lattice parameters and morphology for the grown crystals were determined using single crystal XRD. The crystals were characterized by FT‐Raman, optical absorption, thermal (DTA and TGA) and dielectric studies. LAHClBr was found to be thermally stable up to 124.3°C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigation of the Growth Rate Formula and Bulk Laser Damage Threshold KDP Crystal Growth from Aqueous Solution by the Sankaranarayanan-Ramasamy (SR) Method

A system is reported for evaporation-controlled crystal growth of potassium dihydrogen phosphate (KDP) from aqueous solution by the Sankaranarayanan−Ramasamy (SR) method. KDP (KH2PO4) single crystals of 10-, 20-, and 40-mm diameter and 60-mm height have been grown at an average growth rate of 5 mm/day from the point seed in a glass crystallizer. The growth rate formula is derived for the SR method. The grown crystals were characterized by UV−vis, laser Raman, second harmonic generation efficiency, and laser damage threshold studies. The SR method is an efficient method to grow crystals of good optical quality.

Spectroscopic properties of Er3+ transitions in SrWO4 crystal

Er 3 + : Sr W O 4 crystal of good optical quality was grown by Czochralski technique method. Polarized absorption and emission spectra of Er3+ ions in SrWO4 crystal have been investigated. The Judd-Ofelt (JO) theory was applied to the polarized absorption spectra of Er3+:SrWO4 to obtain the three JO parameters: Ω2=7.41×10−20cm2, Ω4=0.25×10−20cm2, and Ω6=1.71×10−20cm2. The radiative probabilities, radiative lifetimes, and branch ratios of Er3+:SrWO4 were calculated. The stimulated emission cross sections of the potential laser transitions at 1535nm were determined using the reciprocity method and the Fuchtbauer-Ladenberg formula, and the potential laser gain versus wavelength for the I13∕24→I15∕24 transition has been estimated and discussed.

Thermal properties and polarized spectral analysis of Tm 3+:SrWO 4 crystal

Tm 3+:SrWO 4 crystal of good optical quality with sizes of 15 mm×60 mm was grown successfully by Czochralski technique method. The orientation procedure of this crystal was discussed. The principal coefficients of thermal expansion along (001), (010), (100) directions were precisely measured to be 2.73×10 −5, 1.00×10 −5, 1.05×10 −5 °C −1, respectively. Based on the Judd–Ofelt theory, we obtained the three intensity parameters: Ω 2=7.41×10 −20, Ω 4=0.25×10 −20, and Ω 6=1.71×10 −20 cm 2. The radiative probabilities, radiative life times, and branch ratios of Tm 3+:SrWO 4 were calculated. The room temperature polarized fluorescent spectra and fluorescent decay curve were measured. The luminescent quantum efficiency of the 3H 4 level was investigated and the quantum efficiency is determined to be approximately 69.84% for this material.

Growth and thermal properties of Sm:YAl 3(BO 3) 4 crystal

Sm:YAl 3(BO 3) 4 crystal of good optical quality has been grown by the fluxed method. X-ray diffraction experiment show that the crystal has the same structure as that of YAl 3(BO 3) 4 crystal and its unit cell constants have been measured to be a=9.28954 Å, c=7.24132 Å, vol=541.17 Å 3. The thermal properties of Sm:YAl 3(BO 3) 4 crystal have been studied for the first time. The average thermal expansion coefficients are determined to be 2×10 −6/°C, 9.5×10 −6/°C along a- and c-direction. The specific heat of the crystal has been measured to be 0.71 J/g °C at room temperature.

Synthesis, crystal growth and characterisation of novel NLO material: 4-Hydroxy benzaldehyde-N-methyl-4-stilbazolium tosylate

A novel material 4-hydroxy-benzaldehyde-N-methyl-4-stilbazolium tosylate has been successfully synthesized. Good optical quality crystals were grown using solution growth technique. Powder and single-crystal X-ray studies have been carried out for grown crystals and lattice parameters have been identified. FTIR spectra were recorded to identify the various functional groups present in the crystal. NMR spectrum studies have also been done. The second harmonic generation test of the grown crystal has been carried out.

Synthesis, crystal growth and FTIR, NMR, SHG studies of 4-methoxy benzaldehyde- N-methyl-4-stilbazolium tosylate (MBST)

A novel organic nonlinear optical material 4-methoxy benzaldehyde-N-methyl-4-stilbazolium tosylate has been synthesized and good optical quality crystals were grown by slow cooling solution growth technique. Powder X-ray diffraction studies have been carried out and the lattice parameters were calculated. FTIR spectra were recorded to identify the various functional groups present in the crystal. NMR spectrum studies have also been done. The powder second harmonic generation studies were done with Kurtz powder technique and the results were compared with urea.