Effects of polarized excitation on the PJ manifolds emission in KYF4:Pr single crystal

A room temperature spectroscopic investigation on KYF₄:1.25 at%Pr³⁺ is presented. The effects on the optical properties of the multisite-disordered nature of the sample are studied and discussed. In particular we report on the broadening of the ³P_J absorption lines, at 10 and 300 K, and the 450–770 nm emissions as a function of observation and pump polarization. The evidence of a peculiar difference between emission under polarized excitation, parallel or orthogonal to the c axis, is shown. The ³P₀ lifetime was 45 μs in agreement with that measured in other fluoride hosts.     

Generation of annularly symmetric periodic ferroelectric domains in Nd doped near stoichiometric LiTaO3 crystals by the vapor transport equilibration processing

Annually symmetric periodic ferroelectric domain and near stoichiometry have been generated simultaneously from Nd-doped congruent LiTaO₃ crystals by using the vapor transport equilibration (VTE) processing for the first time. The periodic width in the domain structure of 0.5 mol% Nd doped stoichiometric LiTaO₃ crystal was found to be about 70 μm, and the wavelength decreased with the increasing Nd concentration. It can be noticed by transmission spectra that VTE treated LT crystals shows blue shift as compared to congruent LT crystals. Also, various absorption bands were observed in Nd-doped LiTaO₃ crystals corresponding to the transitions from ⁴I_9/2 ground state of Nd³⁺ ions, indicating its potential in the self-lasing quasi-phase matching (QPM) applications.     

Growth and spectroscopic analysis of semi-organic bisthiourea sodium fluoride crystal

A semi-organic bisthiourea sodium fluoride (BTSF) is synthesized at ambient temperature and the single crystal of bisthiourea sodium fluoride is grown in slow evaporation technique using water as solvent. The cell parameters of the grown crystal are estimated from single crystal XRD analysis and also unambiguous assignments of fundamental modes of various molecular groups are made from the recorded FTIR and FT-Raman spectra. The thermal stability of the grown crystal is investigated using thermo-gravimetric analysis studies. Optical transmittance percentage of the grown crystal is measured from UV-VIS studies.     

Improved nonvolatile holographic storage properties in Zr:Ru:Fe:LiNbO3 crystal by blue light recording

Lithium niobate crystal triply doped with zirconium, ruthenium and iron was grown by conventional Czochralski method and its nonvolatile storage characteristics were investigated by means of two-wavelength technology, where blue and red beam were used as recording and readout light, respectively. In oxidized Zr:Ru:Fe:liNbO₃ crystal, short response time of 9.1 s and high recording sensitivity of 0.92 cm/J were demonstrated, together with high fixed diffraction efficiency of 44.9% maintained. These excellent properties were attributed to the elimination of intrinsic defects by ZrO₂ doping and effective excitation of electrons by blue light. Our experimental results indicated this doped LiNbO₃ crystal was an outstanding medium for holographic storage applications.     

Organic nonlinear optical crystal 4-hydroxy-N-methyl 4-stilbazolium besylate synthesis and characterization

Novel organic nonlinear optical material 4-hydroxy-N-methyl 4-stilbazolium besylate has been synthesized and 7 mm × 5 mm × 3 mm size crystals were grown by slow evaporation technique. Single crystal X-ray diffraction analysis reveals that the crystal lattice is monoclinic. From powder X-ray diffraction analysis the diffraction planes have been indexed. Fourier transform infrared spectrum for our sample confirms the presence of functional groups in the grown crystal. Second harmonic efficiency was determined using Kurtz powder method in comparison with urea to confirm the nonlinearity of the material. The results are discussed in detail.     

Studies on lithium l-ascorbate dihydrate: An interesting chiral nonlinear optical crystal

Lithium l-Ascorbate dihydrate (LLA) is a new metal organic nonlinear optical crystal belonging to the saccharide family. Single crystals of LLA were grown from aqueous solution. Solubility of the crystal has a positive temperature coefficient facilitating growth by slow cooling. Rietveld refinement was used to confirm the phase formation. The crystal has prismatic habit with (010), (001) and (10−1) prominent faces. Thermal analysis shows that the crystal is stable up to 102 °C. Transmission spectrum of the crystal extends from 302 nm to 1600 nm. Dielectric spectroscopic analysis revealed Cole–Cole behaviour and prominent piezoelectric resonance peaks were observed in the range of 100–200 kHz. Second harmonic generation (SHG) conversion efficiency of up to 2.56 times that of a phase matched KDP crystal was achieved when the (010) plate of LLA single crystal was rotated about the +ve c axis, by 9.4° in the clockwise direction. We also observed SHG conical sections which were attributed to noncollinear phase matching. The observation of the third conical section suggests very high birefringence and large nonlinear coefficients. A detailed study of surface laser damage showed that the crystal has high multiple damage thresholds of 9.7 GW cm⁻² and 4.2 GW cm⁻² at 1064 nm and 532 nm radiation respectively.     

Physicochemical properties of organic nonlinear optical crystal for frequency doubling: Glycine acetamide

Non-linear optical (NLO) crystal of glycine acetamide (GA) is synthesized and grown in aqueous solution by slow evaporation technique. The cell parameters of the grown crystal are identified from single crystal XRD and the functional groups are confirmed in vibrational analysis. Temperature dependence of the material is probed using TGA/DTA. Mechanical strength of the grown material is tested by Hardness studies. UV-VIS-NIR spectral study explains the transmission ability of the crystal in visible range also the photoluminescence spectrum explains the transition mechanism of ions. The NLO activity of the crystal is confirmed by Kurtz power technique.     

Defect states in Pr doped lutetium pyrosilicate

We study defect states in Pr³⁺-doped Lu₂Si₂O₇ crystal by wavelength resolved thermally stimulated luminescence both below and above room temperature. We identify the TSL peaks, analyze them by the initial rise technique and calculate the characteristic parameters of the corresponding traps. The role of tunnelling of charge carriers between traps and recombination centers up to RT is observed and discussed. The TSL spectra show that the charge carrier recombination predominantly occurs at Pr³⁺ centers. We also provide some comparison with the LPS:Ce³⁺ crystal prepared by the same method.     

Influence of NH4Cl on the < 1 0 0> directed growth and properties of ADP crystal

Good quality, pure and ammonium chloride added < 1 0 0> directed ADP single crystals with different sizes were grown by Sankaranarayanan-Ramasamy method with the vision to improve the properties of the crystal. The grown crystals have cylindrical morphology and the crystals were subjected to UV-Vis., DTA, microhardness, laser damage threshold, dielectric, piezoelectric and SHG studies. The addition of ammonium chloride improves the quality and yields crystals with transparency more than 80% in minimum duration of growth. Higher laser damage threshold and mechanical stability were observed in ammonium chloride added ADP crystals. Low dielectric loss shows that the grown crystal contains minimum defects. Good piezoelectric behaviour was observed for the grown crystals. The SHG efficiency of the crystals was obtained using Nd-YAG laser, which is approximately 3 times that of pure ADP and shows the suitability of the ingot for nonlinear optical applications.     

A study on optical, thermal, mechanical, dielectric, piezoelectric and NLO properties of unidirectional ammonium chloride added ammonium dihydrogen phosphate crystal

<0 0 1> directed ammonium dihydrogen phosphate single crystal with the addition of 1 mol% of ammonium chloride in the mother solution has been grown by Sankaranarayanan-Ramasamy method. The grown crystal has cylindrical morphology with good optical quality. It has good thermal stability up to 200 °C. Higher mechanical stability was observed in ammonium chloride added crystal compared to pure crystal. Moreover, the addition of ammonium chloride improves the quality and yields highly transparent crystal in minimum duration of growth. Good piezoelectric behaviour was observed for the grown crystal. Low dielectric loss shows that the grown crystal contains minimum defects. The optical transmission study and the powder SHG measurement show the suitability of the ingot for nonlinear optical applications.     

Synthesis, growth and characterization analysis of nickel mercury thiocyanate crystal (NMTC)

The nonlinear optical single crystal of NiHg(SCN)₄ has been successfully synthesized and good quality single crystal has been grown by slow cooling solution growth technique. The grown single crystals have been analyzed by different characterization analyses in order to know its suitability for various applications. The functional groups have been identified from the FTIR analysis. The TG/DTA analysis reveals the thermal behavior of NMTC. The optical behaviour was assessed by UV–Vis analysis and was found with no absorption in the entire visible region and it may be useful for second harmonic and other relevant applications. The relative second harmonic generation efficiency was evaluated by Kurtz powder technique and was found to be good in comparison with the standard inorganic potassium dihydrogen phosphate.     

Solvothermal synthesis and photoluminescence properties of ZnO nanorods and nanorod assemblies from ZnO2 nanoparticles

Without the use of any extra surfactant or template, hexagonal phase ZnO crystallites consisting of individual nanorods or nanorod assemblies were synthesized simply by solvothermal treatment of several nanometer ZnO₂ nanoparticles in three different solvents (including ethanol, 80 wt.% hydrazine hydrate aqueous solution and ethylenediamine) at 150 °C for 24 h. The structures and optical properties of the resultant products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM), and room temperature photoluminescence (RTPL) spectra. The RTPL spectra of the resultant products all showed a much stronger ultraviolet bandgap emission peaking at around 387 nm and a weaker emission associated with the defect level. The as-synthesized ZnO crystallites are promising materials for the optoelectronic devices due to their excellent UV emission properties.     

Crystal structure and third-order nonlinear optical property study of a copper complex constructed by DMIT ligand

A copper complex constructed by the ligand: 1,3-dithiole-2-thione-4,5-dithiolato (DMIT) has been synthesized and its crystal structure has been determined by means of X-ray single crystal diffraction. The central copper(II) ion coordinates with two DMIT which constructed a square environment. Intermolecular C–H?S hydrogen bonds between cation groups and ligands lead to the formation of a two-dimensional supramolecular network. Its third-order nonlinear optical property has been studied using Z-scan technique at different peak laser irradiance with 20 picosecond (ps) pulses at wavelength 1064 nm. Its molecular second hyperpolarizability γ was determined to be 4.03 × 10⁻⁵⁷ m⁴ C V⁻³.     

Growth and characterization of a new semi-organic nonlinear optical sodium paranitrophenolate paranitrophenol dihydrate single crystal

A new semi-organic nonlinear optical sodium paranitrophenolate paranitrophenol dihydrate single crystal is grown successfully using methanol as solvent by slow evaporation technique to dimensions of 14 × 5 × 4 mm³ in a period of 7 days. The grown crystal is characterized by X-ray diffractometry and UV-Visible spectral analysis. X-ray diffraction data reveals that the crystal belongs to monoclinic system with space group C2. Optical absorption studies illustrate low absorption in the entire UV and Visible region. The second harmonic generation (SHG) efficiency of the crystal measured by Kurtz's powder technique infers that the crystal has NLO coefficient 5 times greater than that of KDP crystal. Remarkable mechanical strength with the work hardening coefficient less than 2 and thermal stability up to 120 °C of the grown crystal is reported.     

Single crystal growth,structure and properties of TlHgBr3

High-quality inclusion-free single crystals of ternary thallium mercury bromide, TlHgBr₃, were successfully grown by Bridgman–Stockbarger method. For the pristine surface of the TlHgBr₃ single crystal, X-ray photoelectron core-level and valence-band spectra were measured. The comparison on a common energy scale of the X-ray photoelectron valence-band spectrum of TlHgBr₃ and the X-ray emission Br Kβ₂ band, representing peculiarities of the energy distribution of the Br 4p states revealed that the main contribution of the valence Br p states, occurred in the upper portion of the valence band, with also their significant contributions in other valence band regions. It has been determined that TlHgBr₃ is a semiconductor with the bandgap energy value of E_g = 2.51 eV at 100 K. The E_g value decreased up to 2.44 eV when temperature increased to 300 K.     

Optical,mechanical and transport properties of unidirectional grown l-tartaric acid bulk single crystal for non-linear optical application

Good optical quality bulk single crystal of l-tartaric acid has been grown by directional solidification crystal growth method from aqueous solution. Crystal of dimension 77 mm length and 12 mm diameter has been grown at a growth rate of 2.5 mm day⁻¹ which is the maximum size and growth rate achieved so far. The grown crystal was confirmed by powder XRD analysis and the presence of the functional groups in the crystal lattice was confirmed by Fourier transform infrared spectral analysis. Transmission spectral analysis shows that the crystal has more than 90% of transmittance in visible and near infrared region which exhibits the good optical quality of the crystal. The optical band gap was estimated to be 4.8 eV and it shows indirect optical transition. Thermal analysis shows the crystal to be thermally stable up to 172 °C and the load variation of the hardness has been explained on the basis of normal indentation size effect from microhardness study.     

Electronic and optical properties of the group IV doped copper gallium chalcopyrites

Ternary chalcopyrite semiconductors are well known as promising materials for photovoltaic applications. The substitution of group IV atoms in sulfur and selenium copper gallium chalcopyrites GaCuX₂, with X = S and Se, could have important implications either for photovoltaic or spintronic applications. To better understand these effects, we have made first-principles calculations on the doped chalcopyrites with group IV atoms, with different concentrations and geometries. Many of these materials have an intermediate band that modifies the optical properties of the host semiconductor. The sub-gap absorptions have also been determined using the absorption coefficients.     

One-pot Microwave Assisted Synthesis of Homogeneously Alloyed CdSexTe1-x Nanocrystals with Tunable Photoluminescence

Aqueous soluble homogeneously alloyed CdSe_xTe_1-x (0 ≤ x ≤ 1) semiconductor nanocrystals (NCs) were synthesized by co-reduction of sodium selenite (Na₂SeO₃) and sodium tellurite (Na₂TeO₃) at 120 °C under microwave irradiation. The optical modulation of the photoluminescence (PL) between 600 and 710 nm could be facilely demonstrated through changing molar ratios of Se to Te. The PL quantum yields (QYs) of CdSe_xTe_1-x NCs were lower than that of CdTe NCs. On the other hand, it could be higher than that of CdSe NCs.     

Crystal growth and frequency conversion of BaMgF4 single crystal by temperature gradient technique

The BaMgF₄ single crystal was grown by the temperature gradient technique. Highly pure MgF₂ and BaF₂ powders were used as raw materials and CaF₂ single crystal was chosen as a seed to induce BaMgF₄ single crystal grow along 〈0 0 1〉 orientation. The short cut-off wavelength of BaMgF₄ single crystal was determined to be 130 nm which is consistent with the previously reported result. We realized second harmonic generation from 1064 nm to 532 nm laser, and 800 nm to 400 nm femtosecond laser in single domain BaMgF₄ by using birefringent phase matching. 355-nm-wavelength laser was produced by Sum-Frequency Generation from 1064-nm- and 532-nm-wavelength laser, which is the shortest coherent radiation obtained in the UV in the BaMgF₄ crystal.     

Influence of rare-earth ion doping on magnetotransport behavior of potassium doped manganites

The effect of A-site cationic radius <r_A> on structural, electronic and magnetic properties of the perovskite manganites Ln_0.67K_0.33MnO₃ (Ln = La, Pr & Nd) have been investigated. The X-ray diffraction studies show a structural transformation from rhombohedral to orthorhombic with decreasing <r_A>. The ferro to paramagnetic transition decreases from 280 to 110 K and the temperature dependent resistivity shows a metal to insulating transition at room temperature for La_0.67K_0.33MnO₃ while insulating behavior was observed in the case of Pr and Nd substituted samples. Further, La_0.67K_0.33MnO₃ sample exhibits room temperature magnetoresistance, and may be exploited for device applications. The sign of the thermopower is negative at 300 K and its magnitude increases with decreasing <r_A>. The lanthanum based sample shows an upturn in the resistivity data at 30 K and the observed behavior may be attributed to the combined effect of weak localization, electron–electron and electron–phonon scattering. The paramagnetic insulating part of resistivity and thermopower data was analyzed using small polaron hopping mechanism.