Studies on the optical and dielectric properties of a zinc thiourea chloride NLO single crystal

Single crystals of a nonlinear optical material, zinc thiourea chloride were grown by the slow evaporation technique. The crystal structure and lattice parameters of the grown crystal were determined by the single crystal X-ray diffraction studies. The single crystal XRD revealed that the material crystallized in a orthorhombic crystal system. Optical studies were carried out and it was found that the tendency of transmission observed from the specimen, with respect to the wavelength of light, is practically more suitable for opto-electronic applications. The optical band gap is found to be 4.30 eV. Optical constants such as the band gap, refractive index, reflectance, extinction coefficient and real (?_r) and imaginary (?_i) components of the dielectric constant and electric susceptibility were determined from the UV–vis–NIR spectrum. The dielectric constant and dielectric loss of zinc thiourea chloride were measured in the different frequency range from 50 Hz to 5 MHz at different temperatures. Further, electronic properties, such as valence electron plasma energy, Penn gap, Fermi energy and electronic polarizability of the grown crystal have been estimated.     

Crystal growth,structural and optical properties of an organic ion-complex crystal: 4-N,N-dimethylamino-4′-N′-methylstilbazolium iodide

4-N,N-dimethylamino-4′-N′-methylstilbazolium iodide (DMSI) compound was synthesized by Knoevenagel reaction method and the crystals were grown by solution growth method. From the single crystal X-ray diffraction study, it is confirmed that DMSI crystal belongs to monoclinic system. The bond-length alternation (BLA) of the DMSI molecule was found to be 0.11 Å, which is responsible for quadratic NLO response. The electronic transition properties and optical constants such as energy gap (E_g), linear refractive index (n₁) were determined using UV–visible and photoluminescence spectral studies. The second order nonlinear optical property of the crystal was examined using Kurtz–Perry powder test. Laser induced damage threshold on (0 0 1) plane of the optically polished crystal was found to be 1.24 GW/cm².     

Studies on second harmonic generation efficiency of organic material l-arginine maleate dihydrate

A crystalline organic nonlinear optical l-arginine maleate dihydrate has been grown by solution growth technique. Single crystal X-ray diffraction study confirms that the grown crystal belongs to triclinic system having non-centrosymmetric space group P₁. The optical studies were carried out to estimate the transmission range, band gap, extinction coefficient, refractive index and reflectance of the grown crystal. The fundamental solid state parameters were determined from dielectric studies to analyze the polarizability and second harmonic generation efficiency of the grown crystal. Activation energy of the grown crystal was found to be 0.218 eV from ac conductivity measurements.     

Crystal growth,structural, linear and nonlinear optical studies of 4-methyl-4′-N’-methylstilbazolium tosylate single crystals

Organic 4-methyl-4′-N’-methylstilbazolium tosylate, a new derivative of the stilbazolium tosylate family compound was synthesized by condensation method. The optical quality single crystals with dimension 5 mm × 4 mm × 2 mm were grown by slow evaporation technique at 40 °C. The crystal system and lattice parameters were found from single crystal X-ray diffraction studies. The optical transmittance, cut-off wavelength (402 nm) and band gap energy (3.09 eV) were estimated by UV–visible studies. The surface laser damage threshold study was carried out for MMST crystal using Nd:YAG laser. The third-order nonlinear optical susceptibility (χ³) for MMST crystal was estimated by employing Z-scan technique using 1064 nm laser.     

Studies on the optical and mechanical properties of organic nonlinear optical 1-(4-fluorostyryl)-4-nitrostilbene (FNS) single crystal

A new organic nonlinear optical material 1-(4-fluorostyryl)-4-nitrostilbene (FNS) has been synthesized and single crystals of FNS were grown using solvent evaporation solution growth technique (SESGT) by 2-butanon solvent. Single crystal x-ray diffraction analysis reveals the unit cell parameters of the grown crystal are a = 9.494(4) Å, b = 9.864(2) Å, c = 19.501(7) Å and it belongs to monoclinic system with noncentrosymmetric space group. Optical transmittance of the grown crystal has been studied by UV-Vis-NIR spectrum. The optical properties of FNS have been studied by means of optical transmittance measurements in the wavelength range of 190–1100 nm The optical constants were calculated from the optical transmittance (T) data such as refractive index (n), extinction coefficient (k) and reflectance (R). The optical band gap (E_g) of FNS is 3.27 eV with direct transition. The complex dielectric (?) constant of the grown FNS crystal was determined. The second harmonic generation (SHG) efficiency of the grown FNS crystal has been studied by using Kurtz-Perry powder technique and it shows 12 times relatively greater than KDP.     

Investigation of the optoelectronic properties of columbite ZnNb2O6 crystal

A high-quality ZnNb₂O₆ single-crystal grown by optical floating zone method has been used as a research prototype to analyze the optoelectronic parameters by measuring the absorption coefficient and transmittance spectra along the b-axis from 200 nm to 1000 nm at room temperature. The optical interband transitions of ZnNb₂O₆ have been determined as a direct transition with a band gap of 3.84 eV. The refractive index, extinction coefficient, and real and imaginary parts of the complex dielectric constants as functions of the wavelength for ZnNb₂O₆ crystal are obtained from the measured absorption coefficients and transmittance spectra. In the Urbach tail of 3.16–3.60 eV, the validity of the Cauchy–Sellmeier equation has also been evaluated. Using the single effective oscillator model, the oscillator energy E_o is found to be 4.77 eV. The dispersion energy E_d is 26.88 eV and ZnNb₂O₆ crystal takes an ionic value.     

Synthesis,optical, dielectric,thermal and mechanical properties of a nonlinear optical amino acid crystal: Bis-glycine hydrobromide

A semi organic material Bis-glycine hydrobromide (C₄H₁₁N₂O₄⁺Br⁻) has been synthesized by slow solvent evaporation technique. The grown crystal was subjected to single crystal X-ray diffraction studies and its crystal parameters were confirmed. The FTIR analysis confirms the presence of various functional groups present in the title compound. The Kurtz powder second harmonic generation test shows that the crystal is a potential candidate for optical second harmonic generation. The UV–vis spectrum reveals the transparency of the crystal and enumerates the direct band gap energy of the material. The dielectric constant and the dielectric loss were studied as a function of frequency. The thermal studies indicate that the material is thermally stable up to 290 °C. The hardness number was calculated to be 110 kg/mm² from the Vicker's microhardness test.     

Optical,spectral and thermal properties of organic nonlinear optical single crystal: 2,3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate

The potential organic nonlinear optical single crystal of 2,3-dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate has been grown by slow evaporation solution growth technique (SEST) using ethanol–water solution at room temperature. The powder X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non-centrosymmetric space group P2₁2₁2₁ and the cell parameters are a = 7.61 Å, b = 10.73 Å, c = 29.49 Å, V = 2410.75 Å³. The functional groups of the synthesized compound have been identified by FT-Raman and FTIR analyses. Photoluminescence spectroscopy study is determined to explore its efficacy towards device fabrications. Birefringence measurement has been carried out in order to analyze the optical homogeneity of the grown crystal. The optical constants such as reflectance (R) and extinction coefficient (K) have been determined from the transmittance data. The relative second harmonic efficiency of the compound is found to be 4 times greater than that of KDP. DTA-DSC measurements indicate that the crystal is thermally stable up to 174 °C.     

2-Phenylethylammonium p-hydroxybenzoate: Growth,structural, spectral,thermal, optical and mechanical characterization

An efficient nonlinear optical single crystal of 2-phenylethylammonium p-hydroxybenzoate (2PPHB) was grown from aqueous solution by slow evaporation solution growth method. Single crystal X-ray diffraction studies confirmed that 2PPHB crystallizes in orthorhombic crystal system with non-centrosymmetric space group of Pna2₁. The presence of functional groups in the synthesized compound was identified by FTIR spectral analysis. The grown crystals were thermally stable up to 155 °C. UV–vis absorption, photoluminescence and birefringence optical properties of grown crystal were explored. The laser induced surface damage threshold and relative second harmonic generation properties of the grown crystal were studied using Q-switched Nd:YAG laser. The variation of dielectric properties of the grown crystal with frequency was investigated for different temperatures. The mechanical response of the crystal was studied by Vicker's microhardness technique.     

Studies on optical,mechanical, dielectric properties of bisthiourea nickel bromide NLO single crystal

Bisthiourea nickel bromide (BTNB) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV–vis-NIR spectrum. Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal. The mechanical strength of the grown crystal was analyzed using Vickers microhardness tester. The dielectric constant and dielectric loss of bisthiourea nickel bromide are measured in the frequency range of 50 Hz to 5 MHz at different temperatures. The ac conductivity studies were carried out on bisthiourea nickel bromide crystals. In order to investigate the growth mechanism and surface features, etching studies are carried out for the crystal. Photoconductivity studies were carried out on bisthiourea nickel bromide crystals.     

Growth and characterization of a new organic nonlinear optical crystal: Vanillylideneaniline

Vanillylideneaniline with chemical formula C₁₄H₁₃NO₂ (VAN), a second order nonlinear optical (SONLO) organic single crystal was synthesized and grown for the first time from dimethyl formamide (DMF) employing slow solvent evaporation technique. Single crystal X-ray diffraction data reveals that the crystal belongs to noncentrosymmetric orthorhombic space group C222₁. The high-resolution diffraction curve containing single peak with full width at half maximum (FWHM) of 62 arc s ascertains VAN was perfectly crystallized and free from structural grain boundaries. The formation of the material was confirmed quantitatively by FTIR, ₁H¹ and ¹³C NMR spectral analyses. The UV–vis–NIR spectrum reveals the percentage of the transmission of VAN crystal in the entire region. The variations of dielectric constant (?_r) and dielectric loss (D) with frequency at different temperatures were investigated. The SHG of VAN crystal is confirmed by Kurtz Powder technique. The mechanical strength of the crystal was estimated by Vickers hardness test. VAN has yield strength of 8.70 MPa. Thus the grown organic VAN single crystal can be recommended as a promising candidate for SONLO application and device fabrication technology.     

Measurements of magnetic susceptibilities,their anisotropies and crystal field investigations of monoclinic single crystals of Ho2GeO5

Monoclinic single crystals of Ho₂GeO₅ were grown by a flux technique. The molar principal susceptibilities (χ₁ and χ₃) have been measured in the temperature range 300–13.5 K. The principal magnetic anisotropies (χ₁–χ_2,χ₂–χ₃ and χ₁–χ₃) are obtained from the measured anisotropies in different modes of suspensions (b-axis vertical, c-axis vertical and (1 0 0) plane horizontal) of the crystal. The molar principal susceptibility (χ₂) is obtained from the observed values of the principal anisotropies. The observed principal susceptibilities together with their anisotropies are explained by invoking the crystal field interaction of the Ho³⁺ ion with its diamagnetic neighbors in non-axial symmetry. The molar susceptibilities are correlated to the ionic values by finding out the proper orientation of the principal molar susceptibilities, i.e., crystal susceptibilities with respect to that of the ionic susceptibilities (K_x, K_y and K_z). The electronic heat capacities are calculated from the crystal field analysis showing Schottky type anomalies.     

Growth,structure and optical properties of an efficient NLO crystal-aqua maleatocopper(II)

A promising non-linear optical (NLO) crystal, aqua maleatocopper(II) (CuC₄H₂O₄·H₂O), was grown at room temperature by the controlled ionic diffusion technique. Fourier transform infrared spectrum could identify the various functional groups in the crystal. Structural analysis using single crystal XRD revealed that the compound crystallizes in the monoclinic system with space group P2₁ and unit cell parameters a = 7.7277(5) Å, b = 5.2967(3) Å, c = 7.7179(4) Å, α = γ = 109.170(5)°, β = 111.995(2)°. The thermal stability and decomposition pattern of the material were explored using thermogravimetry (TG) and differential thermal analysis (DTA). The optical band gap energy of the material was estimated as 2.2 eV from the diffuse reflectance spectroscopy. The Kurtz and Perry powder technique established the crystal to be an efficient non-linear optical (NLO) material.     

Investigation on the optical and electrical properties of MMTG crystal: A Lewis base adduct

The growth of nonlinear optical single crystal of manganese mercury thiocyanate glycol monomethyl ether (MMTG), a Lewis base adduct of manganese mercury thiocyanate (MMTC), is reported. MMTG crystallizes in orthorhombic structure with Pca2₁ space group. The optical band gap energy of the sample is found to be 3.5 eV. The sample is thermally stable up to 145 °C. The grown crystal is characterized by photoluminescence, dielectric, dc conductivity, photoconductivity and SEM studies. From the photoluminescence study, the suitability of the material for blue and green light generation is confirmed. The electric and dielectric response of the grown crystal is studied as a function of temperature and the results are discussed. The dc activation energy of the sample is found to be 0.048 eV.     

De Haas–van Alphen effect and magnetization in dodecaborides HoB12, ErB12 and TmB12

High-quality HoB₁₂, ErB₁₂ and TmB₁₂ single crystals with the fcc UB₁₂ structure are grown; field dependencies of their magnetization are measured up to 14 T; angular dependences of the magnetization in the (1 0 0) and (1 1 0) planes are calculated, and properties of their Fermi surfaces (FS) are studied using the de Haas–van Alphen (dHvA) effect. The angular dependences of the dHvA frequencies in the (1 0 0) and (1 1 0) planes are obtained and values of their effective cyclotron masses are determined. The oscillation frequencies lie in the range (11.7–127.3)×10² T, and cyclotron masses within the range (0.4–1.45)m₀. For ErB₁₂ and TmB₁₂, we found branches in the oscillation spectrum that originated from FS fragments with spins along and opposed to the field, and the energy of the exchange interaction is estimated. Its value for the γ-branch in ErB₁₂ is equal to 8.2 meV, and for the γ-, β- and θ-branches in TmB₁₂; these values are 14.5, 28.5, and 18.3 meV, respectively.     

Synthesis,growth and characterization of non-linear optical material: l-Tryptophan p-nitrophenol (LTPNP) single crystal

A new nonlinear optical organic crystal l-tryptophan p-nitrophenol (LTPNP) of dimension 19 mm × 2 mm × 1.5 mm has been grown from an aqueous solution for the first time by slow evaporation technique at ambient temperature. The crystal structure of LTPNP was confirmed by single crystal X-ray diffraction. LTPNP crystallizes in non-centrosymmetric monoclinic system with space group P₂₁. The recorded FTIR spectrum confirms the presence of various functional groups in the grown crystal and confirms the formation of LTPNP. Thermal stability and melting temperature of the LTPNP crystal were identified from TG/DTA analysis. The optical absorption study confirms the suitability of the crystal for device applications. LTPNP exhibits SHG efficiency over 1.7 orders of magnitude higher than that of urea and 4 orders of magnitude higher than that of KDP.     

Generation of 532 nm laser radiation and phase matching properties of organic nonlinear optical material

Organic nonlinear optical single crystal of l-asparagine-l-tartaric acid (LAsT) was grown by slow evaporation technique at room temperature. The grown crystal was confirmed by single crystal X-ray diffraction and FT-IR studies. The direct band gap energy was found to be 5.4 eV. The SHG efficiency of the sample is 3 times higher than that of KDP crystal. The laser damage threshold of the grown crystal was 5.7 GW/cm². The grown crystal was thermally stable up to 141 °C. Low dielectric constant at higher frequency was found by dielectric measurements. The activation energy was calculated from Arrhenius relation and it was found to be 0.088 eV. Negative photoconducting nature was obtained by photoconductivity measurements.     

Indofluorides in the AMF3-InF3 systems (A=K, Rb, Cs and M=Mg, Zn) and optical properties of Cr:K0.38Mg0.38In0.62F3

Among the fluorides disclosed in the AMF₃-InF₃ systems (A=K, Rb, Cs/M=Mg, Zn), the most favorable material for optical applications in relation with the optical quality of its crystals is K_0.38Mg_0.38In_0.62F₃ (KMI), a distorted monoclinic Magnéli-bronze, which crystals are grown from the melt. Cr³⁺ introduced in this host is optically characterized by optical spectroscopy. The chromium ions in the single crystals occupy simultaneously centrosymmetric and non-centrosymmetric sites. The broad emission band (⁴T_2 g→⁴A_2 g transition) obtained in the near infrared range is characteristic of a small crystal field effect (Dq=1476 cm⁻¹). Crystal field analysis leads to a very good agreement between calculated and experimentally observed energy levels. Furthermore, dips observed in the absorption at about 15370 cm⁻¹ are related to the calculated mixing between the wave functions, connected with the ⁴T_2 g (⁴F) and ²E_g (²G) and ²T_1 g (²G) electronic levels.     

Optical, thermal, dielectric and ferroelectric behaviour of sodium acid phthalate (SAP) single crystals

Sodium acid phthalate (SAP), an efficient semi-organic crystal having dimensions 17×8×2 mm³ has been grown from aqueous solution by slow evaporation technique at room temperature within the period of 2 weeks. The lattice parameters of the grown crystals were determined using single-crystal X-ray diffraction analysis. The presence of functional groups was estimated qualitatively by Fourier transform infrared (FTIR) analysis. The band gap energy was determined using optical absorption studies. The TG/DTA analysis reveals that the SAP crystal is thermally stable up to 141.6 °C. The dielectric constant and dielectric loss was studied as a function of frequency and the corresponding activation energy (E_a) has been calculated for the grown crystal. Scanning electron microscope studies enunciate the ferroelectric domain patterns of the SAP crystal. Ferroelectric property of the grown crystal was confirmed by hysteresis loop studies.