The growth,thermal and nonlinear optical properties of single-crystal GdAl3(BO3)4

The nonlinear optical single-crystals GdAl₃(BO₃)₄ (GAB), space group R32, were grown by the top-seed solution growth (TSSG) method. The thermal properties and the nonlinear optical characteristics have been investigated. The two principal coefficients of thermal expansion along (100) and (001) were measured to be 5.30 × 10⁻⁶, 1.88 × 10⁻⁵ K⁻¹. The transmission spectrum was measured and the second-harmonic generation (SHG) was presented. By way of our designed cross superimposed laser crystal multiplier, the frequency doubling laser at wavelength 457.5 nm was measured to be 18.2 mW and the facular properties indicated the multiplier contributed to the improvement of the frequency doubling conversion efficiency.     

Synthesis, growth and characterization of novel second harmonic nonlinear chalcone crystal

Nonlinear optical (NLO) materials are useful in many of the industrial applications. New NLO chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(4-nitrophenyl)prop-2-en-1-one (4N4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The grown crystals were subjected to single crystal X-ray diffraction study. The crystal has noncentrosymmetric structure in the orthorhombic system with space group Aba2 and unit cell parameters a=14.0647(15) Å, b=33.738(4) Å and c=6.0039(6) Å. To confirm the presence of various functional groups in the compound, FT-IR spectrum was recorded. The crystal was subjected to TGA/DTA analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique using Nd:YAG laser and its value is 28.57 times that of urea. The laser damage threshold for 4N4MSP crystal was determined using Q-switched Nd:YAG laser. The refractive index values for green and red wavelengths were measured by Brewster angle technique. The dielectric and electrical measurements were carried out to study the different polarization mechanism and conductivity of the crystal. Good thermal, mechanical, transmission and SHG response make it desirable for the NLO applications.     

Second harmonic chalcone crystal: Synthesis, growth and characterization

The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.     

A new NLO Material: L-Asparagine thiocyanate (LATC) for opto-electronic applications

L-asparagine monohydrade thiocyanate (LATC), which is potentially a non-linear optical crystal, was grown by the conventional slow evaporation solution technique (SEST) using doubly de-ionized water at room temperature. The lattice parameters were found by using single crystal X-ray diffraction analysis. Perfection of the grown crystal was confirmed by powder X-ray diffraction. The various functional groups were identified from FT-IR analysis. The optical parameters, such as the optical absorption, the band gap, photoluminescence and second harmonic generation (SHG), were analyzed on the grown crystal. The induced surface laser damage threshold was measured using a Q-switched Nd:YAG laser. The thermal behavior and stability of the grown crystal was analyzed by TG/DTA analysis. The dielectric constant (ε_r) and dielectric loss (tanδ) as a function of frequency has been investigated at different temperatures. The mechanical property of the grown crystal was studied using the Vickers micro hardness method.     

Influence of impurities and thermal treatment on spectroscopic properties and laser performance of thulium-doped yttrium vanadate crystals

Influence of impurities and thermal treatment on spectroscopic properties and laser performance of thulium-doped yttrium vanadate crystals was examined. YVO₄ crystals nominally pure, single doped with Tm³⁺ and co-doped with Tm³⁺ and Ca²⁺ were grown by the Czochralski method and then thermally treated at 1150 °C for several hours in a reducing atmosphere (vacuum) or oxidizing atmosphere (air). Samples of crystals were investigated by nuclear magnetic resonance spectroscopy (NMR) and by optical spectroscopy methods. Laser performance of samples was examined upon laser diode pumping. For pure YVO₄ and for YVO₄ containing 0.5 at. % of Tm a single-site NMR spectrum of ⁵¹V nuclei was observed with central line widths of 2.5 and 3.2 kHz (FWHM), respectively. For samples containing 5 at. % of Tm the NMR spectrum was a superposition of multi-site spectra indicating at least three kinds of vanadium sites with axial symmetry. Optical absorption spectra did not contain bands that could be ascribed to V⁴⁺ ions in tetragonal sites. Level of matrix absorption in the visible region and its increase with decreasing wavelength from about 600 to 370 nm was found to be substantially dependent on conditions of thermal treatment. Thermal treatment of crystals and additional doping with Ca did not influence the ³ F ₄ lifetime of thulium and laser performance of crystals, however. Infrared absorption spectra revealed OH^- contamination in all samples. It has been concluded that the quenching of the ³ F ₄ emission in samples containing 5 at. % of thulium is related to migration-accelerated energy transfer to hydroxyl ions acting as energy sinks. PACS 42.55.Xi; 42.62.Fi     

不同温度生长DKDP晶体的性质

用点籽晶快速生长法在不同温度区间生长了四块氘含量60%DKDP晶体,观察了不同温度下晶体生长过程,同时测量了晶体的透过光谱、摇摆曲线和1053nm激光损伤阈值。结果表明,在高温区间晶体生长外形优于低温生长的晶体。不同温区晶体的透过光谱并无明显变化,但是随着生长温度的降低,晶体的结构完整性变差,1053nm激光损伤阈值降低。     

-1不同温度生长DKDP晶体的性质

用点籽晶快速生长法在不同温度区间生长了四块氘含量60% DKDP晶体,观察了不同温度下晶体生长过程,同时测量了晶体的透过光谱、摇摆曲线和1053 nm激光损伤阈值。结果表明,在高温区间晶体生长外形优于低温生长的晶体。不同温区晶体的透过光谱并无明显变化,但是随着生长温度的降低,晶体的结构完整性变差,1053 nm激光损伤阈值降低。     

Growth, thermal, optical and birefringence studies of semiorganic nonlinear optical thiosemicarbazide cadmium chloride monohydrate (TCCM) single crystals

A semiorganic nonlinear optical material (thiosemicarbazide cadmium chloride monohydrate) (TCCM) was synthesized and single crystals was grown from aqueous solution by slow evaporation method at ambient temperature. Crystal of average size up to 5×4×3 mm³ were harvested and characterized by powder X-ray diffractometry (XRD) and Fourier transfer infrared (FTIR) technique to confirm the identity of the compound formed. The thermal stability was analyzed by TG/DTA. The birefringence values (Δ_n) were determined in the wavelength region 540-6500 Å. The second harmonic generation (SHG) from the materials was confirmed using Nd:YAG laser.     

Spectral kinetic properties of Yb3+:Na4Y6F22 and Yb3+:LiLuF4 crystals

Yb³⁺ (2.7 at.%):Na₄Y₆F₂₂ and Yb³⁺(1 at.%):LiLuF₄ crystals were grown by the Bridgman-Stockbarger method. We measured the temperature dependences of the thermal conductivity of the crystals and the absorption spectra. We determined the radiative lifetime of the Yb³⁺ ion in these crystals (1.94 msec and 2.13 msec) and calculated the stimulated emission cross section spectra. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 761–766, November–December, 2007.     

Spectroscopic analysis and laser parameters of Nd3+ in Ca3Sc2Ge3O12 garnet crystals

3 Sc₂Ge₃O₁₂ (CaSGG) single crystals with the garnet structure have been grown by means of the flux growth technique. The doping with Nd³⁺ and Mg²⁺ (as charge compensator) yields samples suitable for optical spectroscopy experiments. The absorption and emission properties have been measured at temperatures ranging from 10 to 298 K. The emission spectra give evidence of the presence of non-equivalent Nd³⁺ sites. The decay time of the 1.06-μm emission band has been measured as a function of temperature and incident power. The intensities of the 298 K absorption transitions have been analyzed by means of the Judd–Ofelt theory. The radiative lifetimes, the branching ratios (β), and the spontaneous emission probabilities have been evaluated for the ⁴F_3/2 excited state using the calculated intensity parameters. The stimulated-emission cross sections and the branching ratios have been estimated from the experimental data for the most important laser transitions indicating that this crystal can be considered an interesting material for solid-state laser applications. Received: 2 June 1998 / Revised version: 28 October 1998 / Published online: 24 February 1999     

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.     

Surface studies on bimetallic thiocyanate ligand based single crystals of MnHg(SCN)4, CdHg(SCN)4 and ZnCd(SCN)4

Bimetallic SCN ligand based single crystals of manganese mercury thiocyanate (MMTC), cadmium mercury thiocyanate (CMTC) and zinc cadmium thiocyanate (ZCTC) are grown by slow solvent evaporation technique. The growth mechanism and surface features are investigated by optical microscopic techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM). The laser induced surface damage measurements were carried out using a Q-switched Nd:YAG laser at 1064 nm with laser beam of 1.0 Hz and pulse duration 25 ps. The laser damage threshold values of MMTC, CMTC and ZCTC are found to be 15.9, 22.9 and 19.7 GW/cm², respectively. The SEM analysis of MMTC reveals the formation of elongated dendrite growth pattern caused by the fluctuations of Mn and Hg metal ligands when thiocyanate (SCN) bridges them. The etching study indicates the occurrence of different types of etch pit patterns like terraced triangles, pillars, pyramids and rods. The AFM images confirm the formation of three major hillocks with cavities in MMTC. The measured roughness values for CMTC crystal are very much lower than that of MMTC.     

Growth and characterization of Nd-doped disordered Ca3Gd2(BO3)4 crystal

A high-quality disordered Nd³⁺:Ca₃Gd₂(BO₃)₄ (Nd³⁺:CGB) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd³⁺ were determined to be Pnma and 1.06, respectively. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were systematically measured for the first time. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. The polarized spectral properties of the crystal were investigated, including the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay. The spectroscopic parameters of Nd³⁺ ions in Nd³⁺:CGB crystal have been obtained based on Judd–Ofelt theory. The anisotropy of the spectral properties for different polarized directions was discussed. Additionally, the continuous-wave (CW) laser performance at 1.06 μm was demonstrated for the first time. The maximum output power of 603 mW was achieved with corresponding optical conversion efficiency of 8.33% and slope efficiency of 9.95%.     

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.     

Structural,electrical and optical properties of gamma irradiated methyl para-hydroxy benzoate single crystals

ABSTRACT

Nonlinear optical materials (NLO) have been garnering attention due to their role in optical data storage, optical communication and laser technology. Organic crystals have emerged as an extremely important class of NLO materials, since their NLO properties compare very well with traditional inorganic NLO materials like KCl, LiNbO₃, KDP (potassium dihydrogen phosphate), etc. They offer the additional advantage that they can be grown relatively inexpensively from solution close to room temperature, unlike the inorganic NLO materials which are grown from high temperature melts. In the present work, organic transparent single crystals of methyl para-hydroxy benzoate (MHB) were grown by slow evaporation solution growth technique (SEST) from aqueous solution at room temperature. The changes in structural, electrical and optical properties of gamma irradiated MHB single crystals were studied using X-ray diffraction (XRD), UV–Visible absorption spectroscopy, Photo-luminescence (PL), Fourier transform infrared (FTIR) spectroscopy and AC conductivity measurements at room temperature. The polished MHB single crystals were irradiated with gamma rays of doses 10 and 15 kilogray (kGy). From the XRD analysis, it was observed that gamma irradiation for these doses drastically decreases the crystallinity. The optical absorption constants were examined by UV-Visible absorption spectroscopy, measured over the wavelength range of 200–800?nm, at normal incidence. The optical band gap as estimated from the Tauc plot ((αhν)² vs hν) was found to be reduced with increasing gamma irradiation doses. PL spectra showed emission at wavelengths of 361?nm (3.43?eV) and 452?nm (2.74?eV), with enhanced intensities for the irradiated crystals. FTIR spectroscopy was utilised to identify the functional groups of MHB and indicated the rupture of specific types of bonds with gamma irradiation. Apart from that, the enhancement of AC conductivity with gamma irradiation was also observed for the gamma irradiated crystals.     

Structure and NLO property relationship in a novel chalcone co-crystal

Single crystals of a chalcone co-crystal (C₁₈H₁₉NO₄/C₁₇H₁₆NO₃Br; 0.972/0.028) have been grown by slow evaporation from solution. The powder second harmonic generation (SHG) efficiency of this chalcone co-crystal is 7 times that of urea. The dependence of second harmonic (SH) intensity on particle size revealed the existence of phase matching direction in this crystal. The large SHG efficiency observed is mainly due to the unidirectional alignment of molecular dipoles, in which the dipole moment of each molecule adds to establish a net polarization. The weak N–H⋅⋅⋅O hydrogen-bond interactions help to stabilize the noncentrosymmetric crystal packing and also contribute partly to the SHG. The better thermal stability, transparency and high laser damage resistance (>1.5 GW cm⁻² at 532 nm, 8 ns) of this chalcone co-crystal indicate that it is a promising material for frequency doubling of diode lasers down to 470 nm. This molecule also shows a third-order NLO response and good optical limiting property of 8 ns laser pulses at 532 nm. The mechanism for optical limiting in this chalcone was attributed to two-photon induced excited state absorption that leads to reverse saturable absorption. The structure–property relationship in this chalcone and related compounds is discussed based on the experimental results and semiempherical hyperpolarizability calculations.     

Identification of optical nonlinearities of dye-doped nematic and polymer-dispersed liquid crystals using Z-scan technique

This study investigates the nonlinear optical properties of azo-dye-doped nematic and polymer-dispersed liquid crystal (ADDPDLC) films with nano-sized LC droplets using the Z-scan technique, which is a simple but powerful technique for measuring the optical Kerr constants of materials. The results indicate that the optical Kerr constant (n₂) of the azo-dye-doped nematic LC (ADDLC) film is large because of the photoisomerization effect and the thermal effect. Therefore, the optical Kerr constant of this material can be modulated by varying the temperature of the sample and the direction of polarization of incident laser. The range of n₂ modulated is from −5.26 × 10⁻³ to 1.62 × 10⁻³ cm²/W. The optical Kerr constants of ADDPDLC films at various temperatures are also measured. The experimental results reveal that liquid crystals in the ADDPDLC film strengthen the nonlinearity. The n₂ of the ADDPDLC film is maximal at ∼35 °C, because of the decrease in the clearing temperature of the ADDPDLC films. The clearing temperatures of the liquid crystals (E7), and the ADDPDLC film used in this work were found to be 61 °C and 43 °C, respectively.     

Thermal properties and continuous-wave laser performance of Yb:LuVO<Subscript>4</Subscript> crystal

A laser crystal of Yb:LuVO₄ with high optical quality was grown by the Czochralski technique. Its thermal properties including specific heat, thermal expansion coefficients, and thermal conductivities along the a- and c-axis have been measured for the first time. Continuous-wave laser output up to 3.5 W at 1031 nm was obtained at room temperature through end-pumping by a high-power diode laser. The corresponding optical conversion efficiency was 43% and the slope efficiency was 72%. PACS 42.55.Xi; 66.60.+a     

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.     

Two-photon absorption of high-power picosecond pulses in PbWO<Subscript>4</Subscript>, ZnWO<Subscript>4</Subscript>, PbMoO<Subscript>4</Subscript>, and CaMoO<Subscript>4</Subscript> crystals

The nonlinear process of two-photon interband absorption is studied in tungstate and molybdate oxide crystals excited by a sequence of high-power picosecond pulses with a wavelength of 523.5 nm. The transmission of the crystals is measured for the excitation pulse intensity up to 100 GW/cm². The pulse intensity in the crystals initially transparent at a wavelength of 523.5 nm is strongly limited due to two-photon absorption (TPA), and the reciprocal transmission in PbWO₄ and ZnWO₄ crystals reaches 50–60. In all crystals, TPA induces long-lived one-photon absorption, which affects the nonlinear process dynamics and leads to a hysteresis in the dependence of the transmission on the laser excitation intensity. Absorption dichroism manifests itself in a significant difference in the transmission intensities when the principal orthogonal optical axes of the crystals are excited. The TPA coefficients are determined during the excitation of two optical axes of the crystals. TPA coefficients β for the crystals vary over a wide range, namely, from β = 2.4 cm/GW for PbMoO₄ to β = 0.14 cm/GW for CaMoO₄, and the values of β can differ almost threefold when different optical axes of a crystal are excited. Good agreement is achieved between the measured intensities limited by TPA and the estimates calculated from the measured nonlinear coefficients. Stimulated Raman scattering (SRS) upon excitation at a wavelength of 523.5 nm is only detected in two of the four crystals under study. The experimental results make it possible to explain the suppression of SRS by its competition with TPA, and the measured nonlinear coefficients are used to estimate this suppression.