Growth and characterization of metal ions and dyes doped KDP single crystals for laser applications

The organic dyes (Amaranth, Rhodamine B and Methyl Orange) are doped in Potassium Dihydrogen Phosphate crystals. Influences of supersaturation and dye concentration in the solution, on the color and crystal habit of Potassium Dihydrogen Phosphate, were observed. Amaranth in the solution at low super saturation and high dye concentration colored the pyramidal section (1 0 1) of the crystals. The highly super saturated solutions produce entirely colored crystals. Dyes doped Potassium Dihydrogen Phosphate crystals were also grown by solution growth technique. The concentration of dopants in the mother solution was varied from 0.1 to 10 mol%. The studies on pure and doped Potassium Dihydrogen Phosphate crystals clearly indicate the effect of dopants on the crystal structure, in the absorption of IR frequencies and the non-linear optical property. The frequencies with their relative intensities are obtained in Fourier Transform-Infrared spectra of pure and doped Potassium Dihydrogen Phosphate. The very weak bands for dopants indicate its presence in low concentration. The absence of even such a weak band in the case of Potassium Dihydrogen Phosphate doped with Amaranth indicates the strong interaction with O-H groups. The calculated IR frequency 3333 cm⁻¹ for O-H stretching was in close agreement with the experimentally obtained one for pure Potassium Dihydrogen Phosphate at 3340 cm⁻¹.The doped crystals show good second harmonic generation efficiency. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Dye doping improves the Nonlinear Optical properties of the grown crystals. Results of the growth kinetics of Potassium Dihydrogen Phosphate crystals in the presence of impurities are also discussed.     

Growth and characterization of l-proline cadmium chloride monohydrate single crystals

A novel semi-organic material of l-proline cadmium chloride monohydrate (l-PCCM) has been successfully synthesized and single crystal was grown by slow evaporation solution growth technique at room temperature. The grown single crystals have been characterized by different instrumentation techniques like XRD, FTIR, UV-Vis-NIR and TG/DTA measurements. Its nonlinear optical property has been tested by Kurtz powder method. The mechanical properties of grown crystals have been studied using Vickers microhardness tester. Its relative SHG efficiency is two times higher than that of potassium dihydrogen phosphate (KDP) single crystal.     

Growth and characterization of nonlinear optical diglycinehydrobromide single crystals

Diglycinehydrobromide (DGHB) a semi-organic nonlinear optical material with the molecular formula C₄H₁₁N₂O₄⁺Br⁻ has been synthesized at ambient temperature. Chemical composition of the synthesized material was confirmed by CHN analysis. Functional groups present in the sample were identified by FT-IR and Raman spectral analysis. Bulk single crystals of DGHB were grown by slow evaporation method at constant temperature. Powder X-ray diffraction pattern of the grown DGHB has been indexed. Unit cell parameters of the grown DGHB crystals were determined. Thermal stability of DGHB was determined from TGA/DTA and DSC response curves. Mechanical hardness of the grown crystal DGHB was determined and Vickers hardness number was calculated. The optical transparency and the lower cutoff of UV transmission were identified from the recorded UV-vis-IR spectrum of DGHB. The Kurtz powder second harmonic generation test shows that the crystal is a potential candidate for optical second harmonic generation.     

The growth of l-Glutamic acid hydrochloride crystals by Sankaranarayanan-Ramasamy (SR) method

An efficient semiorganic nonlinear optical crystal l-Glutamic acid hydrochloride has been grown by using the novel uniaxial crystal growth method of Sankaranarayanan and Ramasamy with a slight modification in the experimental setup. This method allows the crystals to grow in one specified axis with well developed facet. The grown crystal has a cylindrical morphology with good optical quality. The grown crystal has been characterized by powder X-ray diffraction and UV-Vis-NIR analyses. The NLO efficiency of the crystal has been confirmed by using the Kurtz powder technique.     

Optical, structural and microhardness properties of KDP crystals grown from urea-doped solutions

Potassium dihydrophosphate single crystals were grown from aqueous solutions onto a point seed using temperature reduction method by doping with different molar values of urea. The characterization of the grown crystals was made by visible and Fourier transform infrared spectroscopy, Vicker's hardness studies, X-ray powder diffraction, non-linear optical and laser damage threshold measurements. By comparing these crystals with the ones grown from the pure solution, it is shown that 0.2-2.0 M of the urea additive enhances the laser damage threshold and the second harmonic efficiency more than by 25 and 20%, respectively. By means of the Bond method using a multipurpose three-crystal X-ray diffractometer it is shown that the presence of urea additive increases the crystal lattice parameter c of the grown crystals, whereas the lattice parameter a is by an order less sensitive to the changing urea concentration in the solution. The Vicker's hardness studies at room temperature carried out on (1 0 0) and (0 0 1) crystallographic planes show an increased hardness of the doped crystals (grown in the presence of urea additive) on the plane (0 0 1) in comparison with that of pure potassium dihydrophosphate crystal.     

The use of smoothed particle hydrodynamics for simulating crystal growth from solution

Most numerical simulations for crystal growth processes have been performed using the finite volume and finite element techniques. Both of these methods require adaptive meshes to track the growth and dissolution interfaces. In addition, in the growth of ternary systems the solid and liquid phases must be solved simultaneously, which requires iterations at the interfacial boundaries between solid and liquid regions. Such iterations slow down simulations tremendously, and also lead to numerical instabilities. In order to address these issues, an alternative mesh-free, Lagrangian method, known as smoothed particle hydrodynamics (SPH) has been investigated. For the simulation, the liquid phase diffusion (LPD) growth of Si_xGe_1−x has been selected, since both experimental and finite volume simulation results were available for comparison. This comparison between finite volume and SPH simulations shows that although SPH has the potential to accurately model the crystal growth process, the number of SPH particles required for accurate predictions is upwards of 60,000 particles for the Reynolds number of the LPD system. This high number of particles translates to a computational time of approximately six times longer than the equivalent finite volume simulations. However, future improvements made to the relatively young SPH method may overcome such computational difficulties.     

Investigation on the nucleation kinetics of antiferroelectric ADP admixtured ferroelectric TGS crystals

Induction period and interfacial energy have been determined for the aqueous solution growth of ammonium dihydrogen orthophosphate admixtured triglycine sulphate. It is observed that the induction period decreases exponentially with supersaturation and hence the nucleation rate increases with the increase of supersaturation. The solubility of synthesized ADPTGS has been estimated at different temperatures. ADPTGS has a positive temperature coefficient of solubility. Nucleation parameters such as radius of the critical nucleus, number of molecules in the critical nucleus and critical free energy change have also been investigated.     

Investigation on growth and characterization of a new inorganic NLO material: Zinc sulphate (ZnSO4:7H2O) doped with Magnesium Sulphate (MgSO4:7H2O)

Single crystal of Zinc sulphate doped with Magnesium sulphate, a nonlinear material, was grown from aqua solution by slow evaporation method at room temperature. Good quality single crystals were grown by slow evaporation technique (four weeks) and the crystals subjected to single crystal X-ray diffraction and FT-IR analyses to confirm the formulation of new crystals. The TGA and DTA reveal that the material has good thermal stability. The UV-Vis spectrum confirms that the material has wide optical transparency and the existence of the second harmonic generation has also been ascertained by Kurtz powder method.     

Structural and morphological characterization of flux grown YTa7O19, Nd:YTa7O19, Nd:LaTa7O19 and NdTa7O19 crystals

YTa₇O₁₉ (YHT), Nd:YTa₇O₁₉ (Nd:YHT), Nd:LaTa₇O₁₉ (Nd:LHT) and NdTa₇O₁₉ (NHT) single crystals have been grown by spontaneous nucleation from high-temperature solutions using K₂Mo₃O₁₀-B₂O₃ as a flux and structurally characterized by X-ray diffraction techniques. The effect of the flux composition on the crystal morphology is discussed. The distribution of the Nd³⁺ ions in doped crystals has been investigated by electron microprobe analysis, evidencing non-uniform segregation coefficients. The Raman spectra of the investigated compounds are presented, and a reinterpretation of the fine structure present in the optical spectra is proposed in the light of the crystallographic information.     

Dielectric and structural studies on sulphamic acid (SA) single crystal

Sulphamic acid single crystal of the size 14 × 8 × 6 mm³ has been grown by slow cooling solution growth method at 35.5 °C. Fermi resonance vibrations of N-S stretching and SO₃ rocking have been observed from micro-Raman analysis. Different shapes of etch patterns have been observed for etchants like water, ethanol and HCl for different etching periods. The dielectric constant and dielectric loss have been measured for different frequencies at different temperatures.     

Deformation mechanisms in titanium dioxide single crystals

Single crystals of TiO₂ grown by a floating-zone method have been compressed in two directions, [1 0 0] and [0 0 1], at temperatures between 300 and 1300°C in an argon atmosphere. They deformed by {10¯1 1 01 slips, except [1 0 0] specimens tested below 600° C, where twinning preceded the slip deformation. Above 800° C, an oxygen reduction occurred during compression tests and the flow stress data were not reproducible. Below 700° C the data were reproducible and the resolved yield stress increased steeply with decreasing temperature. From the temperature and strain-rate dependences, activation analyses have successfully been performed. Activation volume becomes as small as 2b ³ at high stress, and the deformation below 700° C is concluded to be governed by the Peierls mechanism. The total activation enthalpy of deformation by the Peierls mechanism is 0.32eV. Applying the string model for the kink-pair formation, the results are consistent if the 101 dislocation is dissociated into two 1/2101 partial dislocations. No twinning-anti-twinning asymmetry of slip was observed.     

Growth of TGS single crystal by conventional and SR method and its analysis on the basis of mechanical, thermal, optical and etching studies

Unidirectional <001> bulk ferroelectric Tri glycine sulphate (TGS) single crystal of diameter 18 mm and length 150 mm was successfully grown by SR method. The grown TGS single crystal was characterized using etching, Vicker's microhardness, TG-DTA and UV-Vis analysis. The TGS crystals grown by SR method have higher hardness than conventional method grown crystals. Dislocation density (DD) is less in SR grown crystal compared to conventional method grown TGS crystals. The transmittance of SR grown TGS is 8% higher than that of the conventional grown crystal.     

Ultrasonic-template method synthesis of CdS hollow nanoparticle chains

A facile and efficient ultrasonic-template method has been developed for the fabrication of CdS hollow nanoparticle chains. The structures and morphologies of products were characterized by XRD and TEM. UV-Vis and photoluminescence (PL) spectra recorded the optical properties of CdS hollow nanoparticle chains, which showed obvious blue shift relative to the CdS bulk materials. Systematic studies found that the ultrasonic irradiation, concentration of template (polyacrylicamide) and injection method of reaction solution in the system were important factors on the controlled synthesis of hollow nanoparticle chains. The possible mechanism for the formation of CdS hollow nanoparticle chains was also discussed.     

Growth and characterization of pure and potassium chloride-doped Zinc Tris-thiourea Sulphate (ZTS) single crystals

Single crystals of pure and potassium chloride-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solution by slow evaporation technique. The grown crystals were subjected to various studies such as XRD, FTIR, atomic absorption, SHG and TGA-DTA studies. The melting point and density of the grown crystals were also measured. The various studies revealed the incorporation of the impurity (potassium chloride) into ZTS crystals and the investigations indicated that the impurity played an important role in the changes of the spectral and structured properties of ZTS crystals.     

Growth and characterization of l-asparagine thiourea monohydrate (LATM): A nonlinear optical single crystal

l-Asparagine thiourea monohydrate (LATM) single crystal has been successfully grown (size 15 × 10 × 3 mm³) by slow evaporation solution growth technique. To the best of our knowledge this is the first report to the literature. The grown crystal was characterized by powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopic analysis. The UV-Vis transmittance spectrum shows that the material has wide optical transparency in the entire visible region. The relative second harmonic generation was confirmed by Kurtz powder technique. The mechanical properties have been studied using Vickers microhardness tester. The birefringence of the crystal was measured in the visible region and it was found to vary with the wavelength.     

Effect of incorporation of titanium dioxide nanocrystals on bulk properties of KDP crystals

The impact of titanium dioxide (anatase) nanocrystals on growth process, optical and structural properties of KDP single crystal was studied. As-grown crystals were characterized by High Resolution Three-crystal X-ray Diffractometer, optical diagnostics of elastic scattering, cone-shaped interference method, and spatial profile analysis method. In the composite system KDP:TiO₂ the effect of giant nonlinear optical response of anatase nanoparticles was revealed, in particular in the intensity range up to 20 MW/cm² the change of sign of the nonlinear refraction index was found. These results can be explained by the resonance excitation of defective states on TiO₂ nanoparticle surface.     

Feasibility study on Czochralski (Cz) growth of 3-methoxy 4-hydroxy benzaldehyde (MHBA) single crystals for nonlinear optical applications

Reported large nonlinear optical coefficients such as d₂₂ = 23.8d₃₆^KDP, d₂₁ = 13.5d₃₆^KDP, d₂₃ = 29.1d₃₆^KDP, d₂₅ = 12.8d₃₆^KDP of 3-methoxy 4-hydroxy benzaldehyde (MHBA) attract research on its bulk crystal growth for device application. The X-ray rocking and X-ray topographic studies of Cz-grown organic monoclinic crystals invariably reveal closely aligned sub-crystals which made melt growth difficult. In this context, the single crystal growth of MHBA by Czochralski pulling technique has been successfully demonstrated for the first time in the literature. Comparison study of obtained X-ray powder diffraction data with the literature confirmed the monoclinic structure. High-resolution X-ray diffraction (HRXRD) study confirms the better crystalline perfection of the grown crystal in comparison to that of solution-grown crystals and revealed the optimization of the growth process along [211¯] direction. TG, DTA and optical transmission studies carried out on the grown crystal exhibit its thermal and optical properties for SHG application.     

On the growth of KDP and KDP:Ni single crystals by the gel technique

Kinetic aspects of KDP and KDP:Ni single crystal growth in the gel technique are examined; the growth is controlled by volume diffusion. The growth rates of KDP and KDP:Ni are in the same range as those frequently encountered in industrial crystallization.     

Dispersion of photoelastic constants in doped KDP crystals

The photoelastic behaviour ofkdp crystals with additives like borax,adp, nickel phosphate, manganese phosphate and sodium dihydrogen orthophosphate has been studied as a variable birefringent compensator. The dispersion of the stress birefringence with wavelength was studied for a single orientation.     

Dielectric parameters of KDP single crystals added with urea

Potassium dihydrogen orthophosphate (KDP) having superior nonlinear optical properties has been exploited for variety of applications. We have grown KDP single crystals added with urea by the slow evaporation method from aqueous solutions. Dielectric measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 313 to 423 K by the conventional parallel plate capacitor method. The present study indicates that the dielectric parameters increase with the increase in temperature but do not vary systematically with respect to impurity concentration. Also, it indicates that 0.6 mole% urea addition to KDP leads to low permittivity value dielectrics.