Comparative study on BIS thiourea cadmium acetate crystals using HRXRD, etching, microhardness, UV-visible and dielectric characterizations

〈1 1 1〉 oriented bis thiourea cadmium acetate (BTCA) crystal of diameter 15 mm and length 45 mm was grown for the first time by the unidirectional Sankaranarayanan-Ramasamy (SR) method. The conventional and SR method grown BTCA crystals were characterized by using high-resolution X-ray diffraction (HRXRD), chemical etching, Vickers microhardness, UV-vis, dielectric studies and differential scanning calorimetry. The HRXRD analysis indicates that the crystalline perfection of SR method grown crystal is good without having any low angle internal structural grain boundaries. The transmittance of SR method grown BTCA is 14% higher than that of conventional grown crystal. The dielectric constant was higher and the dielectric loss was less in SR method grown crystal. The crystals grown by SR method possess less dislocation density and higher microhardness.     

Effect of Co2+ on the growth,optical properties and laser damage threshold of potential nonlinear optical l-alanine single crystal

Good transparent bulk single crystals of pure l-alanine (LA) and cobalt doped LA crystals have been synthesized and successfully grown by slow-cooling method from their aqueous solutions. The concentration of metal dopants in the mother solution with 0.5 mol% for cobalt was carried out individually and crystals were obtained with well defined morphology. The as grown metal doped and pure single crystals were characterized by single crystal XRD studies which confirm that the incorporation of metallic dopants has not changed the basic structure of the parent crystal. The absorption of these crystals was analyzed and the result confirms that they possess low absorption in the range 230–1100 nm. Fourier transform infrared (FTIR) spectroscopy was carried out to investigate the molecular vibrations of these crystals and to confirm the incorporation of the dopants. The thermal properties have been studied by TGA/DTA curves. The EDAX measurement and surface morphology were studied for pure and metal doped LA crystals. The second harmonic generation (SHG) signals were observed using Nd: YAG laser with fundamental wavelength of 1064 nm in pure and metal doped crystals. The laser damage threshold was measured for pure and metal doped LA crystals and also tested by using a Q-switched Nd: YAG laser showed enhanced LDT value for metal (Co²⁺) doped LA crystal compared to pure LA crystal due to the metallic substitutions thus proving their useful candidature for nonlinear optical applications.     

Scattering behavior of nonabsorbing metallic nanoparticles

The optical property of nanosized metallic particles is unique and size-dependent, which cause color variation. In this work, the relationship between diameter and refractive index of nonabsorbing metallic nanoparticles and their scattering properties is studied by using Mie theory. Obtained results indicate that the optical scattering of metallic nanoparticle depends on their refractive index and diameter. The effect of refractive index on optical scattering depends on the nanoparticle diameter. So that, for very fine nanoparticle (10 nm diameter) the effect of refractive index on scattering is not significant. But the effect of refractive index of large size nanoparticle (700–900 nm diameter) on their optical scattering is higher than fine and medium size nanoparticles. The wavelength with maximum scattering depends on refractive index and nanoparticles diameter. In addition, the colorimetric study indicates that the color of nanoparticle depends on their size and refractive index. So that, the lightness, hue, and colorfulness of nanoparticles is changed by changing size and refractive index.     

Investigation on the bulk crystal growth,crystalline perfection,refractive index and piezoelectric properties of borate single crystals for piezoelectric and electro-optic applications

Low solubility potassium pentaborate tetrahydrate (KB5), ammonium pentaborate tetrahydrate (AB5) and mixed (KAB5) single crystals have been grown by the Sankaranarayanan-Ramasamy (SR) method. The crystal structures and space groups have been confirmed by powder XRD analysis. The direction of the grown crystal was confirmed by the back reflection X-ray Laue pattern. The crystalline perfection (CP) of the crystals have been evaluated using HRXRD studies. The transmittance spectra of the grown crystals were recorded by UV–Vis-NIR transmission studies showing that all the crystals have 90% transmittance in the entire visible region and found that the crystals' cut off wavelengths were below 200 nm. The optical studies such as refractive index (RI) and birefringence interferometry (BI) were reported. The RI for five different wavelengths of KB5, AB5 and KAB5 crystals were analyzed using the prism coupling method (PCM). Electromechanical behavior of the grown crystals was observed using piezoelectric coefficient (d₃₃) measurement. Vickers Microhardness (VMH) measurement carried out at 30 °C shows increased hardness as the load increases.     

Studies on optical, mechanical and transport properties of NLO active l-alanine formate single crystal grown by modified Sankaranarayanan-Ramasamy (SR) method

Bulk single crystals of l-alanine formate of 10 mm diameter and 50 mm length have been grown with an aid of modified Sankaranarayanan-Ramasamy (SR) uniaxial crystal growth method within a period of ten days. The optical properties of the grown crystal were calculated from UV transmission spectral analysis. The second harmonic generation efficiency of the grown crystal was confirmed by Kurtz powder test. In order to determine the mechanical strength of the crystal, Vicker’s microhardness test was carried along the growth plane (0 0 1). Dielectric studies reveal that both dielectric constant and dielectric loss decreases with increase in frequency. Photoconductivity study confirms the negative photoconducting nature of the crystal.     

Enhancement of the crystalline perfection of <0 0 1> directed KDP single crystal

<0 0 1> directed good quality potassium dihydrogen phosphate (KDP) single crystal has been grown by Sankaranarayanan–Ramasamy (SR) method with the vision to improve the crystalline perfection and efficiency. A seed crystal of diameter 25 × 15 × 3 mm³ was mounted in the ampoule, where the diameter of the ampoule was much bigger than the seed. The size of the crystal grown was 30 × 20 × 60 mm³. The obtained transparency for the crystal grown by SR method is 93% and by conventional method is 85% in the entire visible region. The HRXRD analysis indicates that the crystalline perfections of the crystals are excellent without having any very internal structural grain boundaries. The obtained FWHM for conventional method grown crystal is 12 arc s and for SR method is 6 arc s. Low dielectric loss indicates that the <0 0 1> directed crystal contains minimum defects. Higher mechanical stability was observed in SR method grown KDP compared to the other. Laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm. The optical transmission study and the powder SHG measurement show the suitability of the ingot for nonlinear optical applications.     

Spectroscopy and efficient laser emission of Yb3+: LuAG single crystal grown by μ-PD

A LuAG shaped rod crystal, doped with Yb³⁺, has been grown by μ-PD technique. The crystal diameter was about 3 mm and the length around 130 mm. A complete spectroscopic investigation in the temperature range 10–300 K is reported and data has been utilized to model the laser behavior. In the laser experiment the Yb:LuAG sample was placed in an X cavity and pumped longitudinally obtaining an efficient CW laser emission. The Yb:LuAG laser yielded a maximum output power of 23 mW with a slope efficiency of 32% and a threshold around 35 mW, at lasing wavelength of 1030 nm. No significant depolarization effects were observed, indicating a crystal growth with negligible stress. The output beam profile was investigated, yielding M² ≈ 1.0 in both directions, further confirming the good optical quality of the sample.     

Growth and characterization of pure and doped bis thiourea zinc acetate: Semiorganic nonlinear optical single crystals

Metal–organic coordination complex single crystals bis thiourea zinc acetate (BTZA) and Cd²⁺ doped BTZA have been synthesized and grown successfully by slow-cooling technique from their aqueous solutions. Single crystals of pure and Cd²⁺ doped BTZA with dimensions of 35 × 4 × 2 mm³ and 10 × 5 × 6 mm³, respectively were obtained with well defined morphology. The as grown single crystals are characterized by single crystal XRD studies and melting point measurements which reveal the incorporation of metallic dopants has not changed the structure of the parent crystal. The powder X-ray diffractogram of the grown crystals has been recorded and the various planes of reflection identified shows shift in the peak positions. The metal coordination with thiourea through sulphur in pure and Cd²⁺ doped BTZA were ascertained by FTIR studies and optical absorption study to identify the UV cut-off range. The presence of metals in pure and Cd²⁺ doped BTZA crystal lattice were confirmed by atomic absorption spectroscopy (AAS). The thermal decomposition of pure and Cd²⁺ doped BTZA crystals were investigated by thermo gravimetric analyses (TGA) and differential thermal analysis (DTA) indicate that doped crystals are more stable than pure crystals. The dielectric response of the crystals were studied in the frequency range 100 Hz–5 MHz at different temperatures and the results are discussed. Second harmonic generation (SHG) measurement confirms that the pure and Cd²⁺ doped BTZA have nonlinear optical (NLO) property. Laser damage threshold value of 12.44 MW/cm² has been determined using Q-switched Nd:YAG laser operating at 1064 nm and with 8 ns pulses in single shot mode for pure BTZA single crystal is reported for the first time.     

Unidirectional growth,optical, mechanical and dielectric studies on a novel NLO crystal: l-Arginine 4-nitrophenolate 4-nitrophenol dihydrate

The bulk single crystal of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP), an efficient organic NLO material of size 74 mm in length, 18 mm in diameter, was grown successfully by Sankaranarayanan–Ramasamy (SR) method. Single crystal X-ray diffraction study reveals that LAPP crystallizes into monoclinic system with the space group P2₁. The unidirectional growth along the plane (1 1 0) was confirmed from the powder XRD pattern with the sharp peak having maximum intensity. Optical absorption spectrum shows that LAPP has highly transparent in the entire visible and IR region with a wide band gap of 3.9 eV for large photon absorption. Vickers micro hardness measurement was performed to know the mechanical strength of the crystal. Dielectric profile of LAPP at room temperature brings forth low value of dielectric loss and dielectric constant at higher frequencies. Photoluminescence study reveals that LAPP exhibit green emission in the wavelength region 538 nm. The SHG efficiency of the crystal is measured by Kurtz's powder test using Nd:YAG Laser.     

Growth of 〈1 0 0〉 directed ADP crystal with slotted ampoule

Good quality ammonium dihydrogen phosphate single crystals have been grown by: (i) Sankaranarayanan–Ramasamy (SR) method and (ii) SR method with slotted ampoule. The grown crystals were subjected to UV–Vis spectroscopy, high-resolution X-ray diffractometer, dielectric, piezoelectric and laser damage threshold studies. Compared to the (1 0 0) plane of the conventional method grown ADP crystal and 〈1 0 0〉 directed SR method grown ADP crystal, the crystal grown by SR method with slotted ampoule has higher growth rate, higher optical transparency, high crystalline perfection, low dielectric loss, high piezoelectric charge coefficient and high laser damage threshold due to diffusion of segregated impurities away from the growing crystal in the slotted ampoule growth.     

Growth,linear and nonlinear optical studies on guanidinium 4-nitrobenzoate (GuNB): An organic NLO material

Single crystals of guanidinium 4-nitrobenzoate (GuNB) were grown using solvent evaporation technique by mixing aqueous solutions of guanidine carbonate and 4-nitrobenzoic acid at ambient temperature. X-ray diffraction analysis characterized the unit cell parameters of the grown crystal and the crystal belongs to monoclinic system. The optical properties of the grown crystal have been studied by means of transmission measurements in the wavelength region between 200 and 1200 nm. The optical constants such as refractive index (n) and extinction coefficient (k) have been determined from the transmittance data. The optical band gap (E_g), the real and imaginary parts of the dielectric constant of the grown crystal was determined. Second harmonic generation (SHG) efficiency of the grown crystal has been studied using Nd:YAG laser and was measured as 3.2 times that of KDP. The low dielectric constant suggests the suitability of this compound material for NLO applications.     

Growth, optical and thermal studies on organic nonlinear optical crystal: 2-Furoic acid

2-Furoic acid (2FA), an organic third order nonlinear optical single crystal, has been synthesized and grown successfully by slow solvent evaporation technique. The space group and lattice parameters of the grown crystals were obtained by single crystal X-ray diffraction analysis. The presence of the functional groups was confirmed by Fourier Transform Infrared (FTIR) spectroscopy. Optical absorption studies reveal low absorption in the UV and visible regions and the UV cut-off wavelength is found to be at 240 nm. The thermal stability of the material examined by TGA analysis, reveals that the material is thermally stable up to 130 °C. The third order nonlinear optical parameters (nonlinear refractive index, nonlinear absorption coefficient and real and imaginary parts of the third order nonlinear optical susceptibility) were derived by Z-scan technique. This reveals that the crystal has a negative refractive index, which indicates the defocusing nature of the material.     

Optical properties of large germanium monocrystals

Optical characteristics of germanium monocrystals with a diameter of 150 and 200 mm grown by the Czochralski and directional crystallization methods were studied. We measured spectral transmittance of the monocrystals in the wavelength range of 2.3–25.0 μm, directional transmission and light scattering in the 2.4–3.0 μm range, and noninhomogeneity of the refractive index of monocrystals by the interference technique at 3.39 μm. The measurements were performed on antimony-doped germanium monocrystals with a diameter of 200 mm and thickness of 15 mm (grown by the directional crystallization method) and 18 mm thick (grown by the Czochralski method). Measurements were also performed on a germanium monocrystal with a diameter of 150 mm and thickness of 15 mm grown by the Czochralski method without adding a ligand. The measurement results revealed different optical quality of monocrystals, expressed in the nature and amount of refractive index inhomogeneity, which imposes restrictions on the use of blanks.     

宽波段高优值声光晶体-PbBr2

用坩埚下降法沿[001]方向生长了长度为60mm、直径为25mm的溴化铅晶体,测定了其折射率主轴方位及其主折射率,测得该晶体的透过率范围复盖03μm～25μm的整个区域.     

Optical and dielectric studies of gel grown α-hopeite single crystal

Single crystals of α-hopeite exhibiting high transparency were grown by single diffusion gel growth technique. Single crystal X-ray diffraction analysis reveals that the crystal belongs to orthorhombic system. The values of several structural and physical parameters have been determined for the grown crystal. The optical absorption study reveals the transparency of the crystal and is noticed in the entire visible region and the cut-off wavelength was found to be 230 nm. The optical band gap found to be at 3.25 eV. The dependence of extinction co-efficient (k) and the refractive index (n) on the wavelength was also shown. The dielectric constant and dielectric loss of the crystal was studied as a function of frequency and temperature. Transport properties of the grown crystal have been studied from the Cole-Cole plot.     

Synthesis,growth and characterization of an organometallic complex tri-allylthiourea cadmium bromide single crystals

Allylthiourea cadmium bromide (ATCB) is a promising organometallic second order nonlinear optical material. ATCB was synthesized in Millipore water and single crystals of ATCB were grown by isothermal solvent evaporation as well as by conventional temperature lowering methods. Crystal structure of the as grown ATCB was analyzed by single crystal X-ray diffraction and also by powder X-ray diffraction pattern. Structural perfection of the as grown single crystal was studied through multicrystal X-ray diffraction analysis. The nature of co-ordination and the functional groups present were investigated by the Fourier transform infrared spectrum. The melting point of the crystal was studied through differential scanning calorimetric analysis. The optical absorption spectrum of the as grown crystal exhibits the lower cut-off (295 nm) with the wide transparent UV–VIS–NIR wave band. The SHG property was identified by Kurt’z powder technique. The linear refractive index of the as grown crystal was measured for different laser wavelengths. The reverse indentation size effect for the as grown crystal was confirmed from the mechanical studies. Growth mechanism and surface features of the as grown single crystals were analyzed by chemical etching analysis.     

Investigation of dielectric properties and diffraction efficiency enhancements caused by photothermal effect in DR9 dye-doped nematic liquid crystal

In this work, we studied dielectric properties and laser-induced refractive index changes originating from photothermal effects of liquid crystal material doped with Disperse Red 9 (DR9) dye. Dye concentration is arranged to be between percentages changing from 0.2 wt.% to 1 wt.% in E63 nematic liquid crystal. Nonlinear optical properties such as diffraction efficiency (η) and refractive index modulation (Δn) were investigated by diffraction grating measurements. It was found the diffraction efficiency of pure E63 nematic liquid crystal is 1%. As the doping amount of DR9 dye in nematic LC is increased, diffraction efficiency took higher values and the maximum diffraction efficiency of 10% was gained with E63 doped with 0.8 wt.%DR9 dye. Moreover, dielectric permittivity and dielectric anisotropy values of the samples were investigated in the frequency range of 100 Hz-10 MHz by using dielectric spectroscopy technique. It was observed that dielectric constant values of the liquid crystal material are strongly affected by doping with dye.     

Effect of electron beam on structural,linear and nonlinear properties of nanostructured Fluorine doped ZnO thin films

Electron beam induced effects on Fluorine doped ZnO thin films (FZO) grown by chemical spray pyrolysis deposition technique were studied. The samples were exposed to 8 MeV electron beam at different dose rate ranging from 1 kGy to 4 kGy. All films exhibit a polycrystalline nature which shows an increase in crystallanity with irradiation dosages. The electron beam irradiation effectively controls the films surface morphology and its linear optical characteristics. Z-Scan technique was employed to evaluate the sign and magnitude of nonlinear refractive index and nonlinear absorption coefficient using a continuous wave laser at 632.8 nm as light source. Enhancement in the third order nonlinear optical properties was were noted due to electron beam irradiation. Tailoring the physical and NLO properties by electron beam, the FZO thin films becomes a promising candidate for various optoelectronic applications such as phase change memory devices, optical pulse compression, optical switching and laser pulse narrowing.     

X-ray photoelectron spectroscopy, high-resolution X-ray diffraction and refractive index analyses of Ti-doped lithium niobate (Ti:LiNbO3) nonlinear optical single crystal

Congruent LiNbO₃ single crystals with Ti ion dopants (2 and 5 mol%) were successfully grown by Czochralski technique in the automatic diameter control facility. As-grown crystal boules were oriented into (0 0 1) direction cut and optically polished for all measurements. Influence of Ti-ion incorporation into LiNbO₃ was studied by core level XPS analysis. Powder X-ray diffraction studies were carried out on doped lithium niobate for phase identification. High-resolution X-ray diffraction technique was used to study the crystalline quality through full-width at half-maximum values. The refractive index values are more for doped samples than for pure sample as determined by prism coupling technique with different laser sources.     

Structural,optical, thermal and mechanical characterization of an organic nonlinear optical material: 4-methyl-3-nitrobenzoic acid single crystal

Organic single crystals of 4-methyl-3-nitrobenzoic acid (4M3N) have been grown by slow evaporation solution growth technique at room temperature. The single crystal X-ray diffraction study reveals that 4M3N crystallizes in monoclinic system with space group P21/n. The crystalline perfection of the crystal was analyzed by high resolution X-ray diffraction (HRXRD) measurements. The functional groups present in 4M3N have been identified from FT-IR and FT-Raman spectra. The lower cut-off wavelength of 4M3N is found to be 404 nm and the optical band gap is calculated as 2.91 eV. The refractive index shows normal behavior with wavelength. The physio chemical changes, decomposition and stability of the 4M3N compound were established by TG-DTA studies. Vickers microhardness measurement concludes that 4M3N belongs to soft material (n=2.5) category. The LDT value is found to be higher than that of KDP and some of the important organic NLO materials. The third order nonlinear refractive index and nonlinear absorption coefficient of the 4M3N have been measured by Z-scan studies. The imaginary and real parts of the third-order susceptibility values were determined as Im χ³=9.129×10⁻¹¹ esu and Re χ³=1.4034×10⁻⁹ esu respectively. The dislocation density was calculated to be 3.0448×10⁶ cm⁻² which indicates the quality of the crystal.