Relative Second Harmonic Generation Efficiency Research Articles

Isostructural Crystals of Bis(Guanidinium) Trioxofluoro-Phosphate/Phosphite in the Ratio 1/0, 0.716/0.284, 0.501/0.499, 0.268/0.732, 0/1—Crystal Structures, Vibrational Spectra and Second Harmonic Generation

The title structures of bis(guanidinium) trioxofluorophosphate, bis(guanidinium) trioxofluorophosphate-phosphite (0.716/0.284), bis(guanidinium) trioxofluorophosphate-phosphite (0.501/0.499), bis(guanidinium) trioxofluorophosphate-phosphite (0.268/0.732), and bis(guanidinium) phosphite are crystal-chemically isotypic. Their structures correspond to the structure of bis(guanidinium) trioxofluorophosphate which was determined by Prescott, Troyanov, Feist & Kemnitz (Z. Anorg. Allg. Chem. 2002, 628, 1749–1755). The P and O atoms of the substituted trioxofluorophosphate and phosphite anions share the same positions while the P-F and P-Hhydrido are almost parallel and oriented in the same direction. Two symmetry-independent anions and two of three symmetry-independent cations are situated on the crystallographic mirror planes. The ions are interconnected by N-H⋯O hydrogen bonds of moderate strength. The most frequent graph set motif is R22(8), which involves interactions between the primary amine groups and the trioxofluorophosphate or phosphite O atoms. Fluorine, as well as the hydrido hydrogen, avoids inclusion into the hydrogen-bond network. The Hirshfeld surface analysis was also performed for the comparison of intermolecular interactions in the title structures of bis(guanidinium trioxofluorophosphate and bis(guanidinium) phosphite. The title crystals were also characterized by vibrational spectroscopy methods (FTIR and Raman) and the second harmonic generation (SHG). The relative SHG efficiency considerably decreases from bis(guanidinium) trioxofluorophosphate to bis(guanidinium) phosphite for the fundamental 1064 nm laser line.

Impact of L-Leucine on the structural and optical properties of potassium dihydrogen phosphate (KDP) crystals

IntroductionPotassium Dihydrogen Phosphate (KDP) is an exceptionally good non-linear optical (NLO) material used for optoelectronics, electro-optics, etc. The inclusion of amino acids enhances the properties of KDP because amino acids have properties like molecular chirality and zwitterionic nature. ObjectiveIn this study, our primary goal was to describe the effects of L-Leucine doping on KDP and to study the changes in its optical and structural properties for different applications related to non-linear optics. MethodsPure KDP and L-Leucine doped KDP (1 mol% and 2 mol%) crystals were grown using the slow evaporation method at room temperature. The crystals have been characterized using Powder X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, Ultraviolet-Visible (UV-Vis) Spectroscopy, Photoluminescence (PL) Spectroscopy and Relative Second Harmonic Generation (SHG) measurement. ResultThe FTIR spectroscopy confirms the presence of amino acid, L-Leucine in KDP as implied by functional groups. The UV-Vis spectroscopy helps with the optical transparency of crystals and the bandgap of pure KDP was observed to be enhanced with the addition of L-Leucine. The PL spectra confirm the existence of point defects in the grown crystals. Furthermore, L-Leucine doping in KDP improves its relative SHG efficiency. ConclusionIt has been seen those optical properties of pure KDP is immensely improved with the addition of L-Leucine without altering the KDP lattice.

Optical, mechanical and thermal characterization of l-threonine single crystals grown in dimethyl urea solution

An organic material of a noncentrosymmetric l-threonine single crystal was grown in a dimethyl urea solution using the slow evaporation method. The grown crystal was transparent and colorless, with a size of about 20 × 7 × 4 mm3, obtained within a period of 10 days. The grown crystal was subjected to various studies, such as x-ray diffraction (XRD), Fourier transform infrared (FTIR), microhardness, ultraviolet–visible (UV–Vis) transmittance, thermogravimetric analysis and differential thermal analysis (TGA/DTA) and second harmonic generation (SHG). l-threonine crystals grown in a dimethyl urea solution show relative SHG efficiency of 0.92 times that of potassium dihydrogen phosphate. The functional groups of the crystals have been confirmed by FTIR analysis. The mechanical strength of the crystal was estimated by the Vickers hardness test. The lattice parameters of the grown crystal were determined by single crystal XRD and powder XRD studies, and the diffraction peaks were indexed. A UV–Vis spectrum was recorded in the wavelength range of 200–1100 nm to find the suitability of the crystal for nonlinear optical applications. The thermal stability of l-threonine crystal grown in dimethyl urea was checked using the TGA/DTA analysis.

Effect of Mn(II) doping on crystalline perfection, nonlinear, optical and mechanical properties of KDP single crystals

The effect on crystalline perfection, second harmonic generation (SHG) efficiency, optical transparency and mechanical properties due to Mn(II) doping in KDP single crystals grown by slow evaporation solution technique by adding different quantities of MnCl2 in the solution has been investigated. The actual incorporated quantity of Mn(II) in the crystals was evaluated by atomic absorption spectroscopy. Powder XRD study confirms the crystal system of KDP and found no additional phases at all doping levels (1 to 5 mol%). The influence of Mn(II) doping on the crystalline perfection has been assessed by high-resolution XRD and these studies revealed that the grown crystals could accommodate Mn(II) in the interstitial positions of the crystalline matrix of KDP only up to some critical concentration, above which the crystal developed structural grain boundaries. The relative SHG efficiency of the crystals was found to be increased sharply at low concentrations (1 mol%), and above this value it was decreased as the concentration increases though it is still higher than that of pure KDP. UV-Vis studies also revealed the same behavior with a significant enhancement at 1 mol% concentration and later gradually decreased. Good increment in the hardness values has been observed by increasing the doping concentrations.

Synthesis, growth, thermal, optical and mechanical properties of 2-Aminopyridinium 4-methylbenzoate Dihydrate

Organic NLO material of 2-Aminopyridinium 4-methylbenzoate Dihydrate (2A4M) was synthesized using 2-Aminopyridinium and 4-methylbenzoic acid as starting materials. Single crystals of 2A4M were grown by the slow evaporation solution growth technique at room temperature using water as a solvent. The grown crystal was characterized by single crystal XRD to confirm the crystal system and lattice parameters. From the optical studies the optical band gap and the refractive index of the material are found to be 2.9 eV and 1.40 at 1200 nm. Functional groups of the crystallised material were confirmed by FTIR vibrational spectrum. Thermal behaviour of the title compound was studied using thermogravimetric (TG) and differential thermal analyses (DTA). The initial weight loss is found up to 125 °C, which corresponds to 13.2% i.e. presence of 2 mole of water in the lattice. The grown crystal was subjected to Vickers hardness test and the brittleness index, fracture toughness, yield strength were estimated. The etching studies reveal the growth pattern and dislocations present in the grown crystal. The second harmonic generation (SHG) behaviour of 2A4M was tested by Kurtz–Perry powder technique. The relative SHG efficiency of 2A4M is found to be 3.03 times that of the reference material KDP.

Growth and characterization of l-leucine l-leucinium picrate single crystal: A new nonlinear optical material

Single crystals of l-leucine l-leucinium picrate (LLLLP) were grown by the slow evaporation solution technique. The crystal system and lattice parameters were confirmed by single crystal XRD. The UV–vis transmission spectra were recorded for the grown crystal and relative second harmonic generation (SHG) efficiency was measured for the first time. The relative SHG efficiency of the material was found to be ∼1.5 times higher than that of KDP. The crystalline perfection of the grown crystal was assessed by high-resolution XRD. The functional groups present in the crystal were confirmed by FT-IR analysis. The thermal studies were carried out and show that the grown crystal is stable up to 195 °C.

Unidirectional growth ofL-cysteine hydrochloride monohydrate: first time observation as nonlinear optical material and its characterization

A bulk size (∼60 mm length and 20 mm diameter) single crystal of L-cysteine hydrochloride monohydrate has been successfully grown for the first time by the unidirectional Sankaranarayanan–Ramasamy method and found to be a nonlinear optical material by observing the second harmonic generation (SHG). The crystal structure has been confirmed by single-crystal as well as powder X-ray diffraction analysis. The Fourier transform–Raman technique was used to study the vibrational modes and functional groups. The grown crystal was found to be highly transparent. The crystalline perfection has been evaluated by high-resolution X-ray diffractometry and the grown crystal was found to be free from macroscopic defects such as structural grain boundaries. The relative SHG efficiency and laser damage threshold values were found to be 1.2 and 5.5 times that of a potassium dihydrogen phosphate crystal, respectively. The dielectric constant, dielectric loss and alternating current conductivity were measured by an impedance analyser over a wide range of frequency between 100 Hz and 5 MHz. The dielectric constant was found to be stable for the entire range of frequency with very small dielectric loss, making this material suitable for device applications. The present investigation reveals that the title compound, since it can be grown with desirable size along a predetermined direction and it is a good nonlinear optical material with the prerequisite optical and dielectric properties, is a good candidate for photonic or opto-electronic applications.

Enhancement of SHG efficiency by urea doping in ZTS single crystals and its correlation with crystalline perfection as revealed by Kurtz powder and high-resolution X-ray diffraction methods

The enhancement of second-harmonic generation (SHG) efficiency by urea doping in tristhioureazinc(II) sulfate (ZTS) single crystals and its correlation with crystalline perfection have been investigated. ZTS is a potential semiorganic nonlinear optical material. Pure and urea-doped single crystals of ZTS have been successfully grown by the slow evaporation solution technique. The presence of dopant has been confirmed and analysed by Fourier transform infrared spectrometry. The influence of urea doping at different concentrations on crystalline perfection has been thoroughly assessed by high-resolution X-ray diffractometry (HRXRD). HRXRD studies revealed that the ZTS crystals could accommodate urea up to a critical concentration without any deterioration in crystalline perfection. Above this concentration, very low angle structural grain boundaries developed and it seems the excess urea above the critical concentration was segregated along the grain boundaries. At very high doping concentrations, the crystals were found to contain mosaic blocks. The SHG efficiency has been studied using the Kurtz powder technique. The relative SHG efficiency of the crystals was found to increase substantially with the increase in urea concentration. The correlation found between crystalline perfection and SHG efficiency is discussed.

Effect of ammonium malate on growth rate, crystalline perfection, structural, optical, thermal, mechanical, dielectric and NLO behaviour of ammonium dihydrogen phosphate crystals

The effect of ammonium malate on the growth rate, structural, optical, thermal, mechanical, dielectric properties, crystalline perfection and second harmonic generation (SHG) efficiency of ammonium dihydrogen phosphate single crystals grown by the slow cooling method has been investigated. The lattice parameters of the grown crystals were obtained by the single-crystal X-ray diffraction analysis. Fourier transform infrared studies confirm the functional groups of the crystals. UV–vis study shows that the transparency is increased much by the dopant. Thermal analysis was performed to study the thermal stability of the grown crystals. Vickers hardness measurements reveal the higher hardness of the doped crystals. Low dielectric losses were observed from the dielectric measurements for the doped ADP crystals. The high-resolution X-ray diffraction studies show that the crystalline perfection of the crystals is good. The relative SHG efficiency measurements revealed that the dopant has enhanced the efficiency.

POLAR ORDERING IN THERMOTROPIC MESOGENS RESOLVED BY SCANNING NLO MICROSCOPY

A nonlinear optical (NLO) microscope has been developed based on recording the second harmonic generation (SHG) signals of the B 2- and B 4-phases of bent-shaped liquid crystalline (LC) materials. We observed that the microstructures of the polar order can be accurately characterized by 2D scanned images implementing this device. Specifically, we have investigated two bent-core compounds, which have either B 4 or B 2 phases at room temperature and exhibit SHG activity. The NLO microscope was calibrated according to the Maker fringe method allowing the in situ evaluation of the relative SHG efficiency. The developed NLO-microscopy device may serve as an important tool to characterize liquid crystalline features at a microscopic scale for both, fundamental and applied research.

Studies on the Growth and Characterization of l-Asparaginium Picrate (LASP)A Novel Nonlinear Optical Crystal

Good quality single crystals of l-asparaginium picrate have been grown by a low-temperature solution growth technique. The UV−visible−NIR absorption spectra were recorded for the grown crystal and relative second harmonic generation (SHG) efficiency was investigated to explore the NLO characteristics of the material for the first time in the literature. The relative SHG efficiency of the material is 66.5 times greater than that of KDP and 10 times higher than that of urea. The dielectric and mechanical behavior of the specimen were also studied. The structural perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectroscopic studies were also performed for the identification of different modes present in the compound.

POLAR MICRO STRUCTURES OF THE B2- AND B4-PHASES OF BENT-SHAPED LC-MOLECULES RESOLVED BY NONLINEAR OPTICAL MICROSCOPY

A nonlinear optical (NLO) microscope has been developed based on recording the second harmonic generation (SHG) signals of the B 2- and B 4-phases of bent shaped liquid crystalline (LC) materials. We observed that the microstructures of the polar order can be accurately characterized by 2D scanned images implementing this device. Specifically, we have investigated two bent-core compounds, which have either B 4 or B 2 phases at room temperature and exhibit SHG activity. The NLO microscope was calibrated according to the Maker-fringes method allowing the in situ evaluation of the relative SHG efficiency. The developed NLO microscopy device may serve as an important tool to characterize liquid crystalline features at a microscopic scale for both fundamental and applied research.

Synthesis and nonlinear optical properties of some substituted ruthenium(II) η 5-cyclopentadienyl η 5- or η 6-arene salts

Treatment of a suspension of AgBF 4 in absolute methanol with a solution of η 5-C 5H 5Ru(PPh 3) 3Cl ( 1) and an arene gives [(η 5- or η 6-arene)Ru(η 5-C 5H 5]BF 4; where the η 5 or η 6-arenes are thiophene ( 2), nitrobenzene (3), N,N-dimethyl-4-nitroaniline ( 4), 2-methyl-4-nitroaniline ( 5) and N-(4-nitrophenyl)( l)-prolinol ( 6). The relative efficiency of second-harmonic generation (1064 nm→532 nm) for compounds ( 1–6) is 0.7 to 1.0 × urea.