SHG Measurements Research Articles

Chiral and Porous Coordination Polymers Based on an N-Centered Triangular Rigid Ligand

Four cadmium and cobalt coordination polymers with unique structures and topologies have been successfully synthesized under solvothermal conditions by employing an elongated triangular rigid N-containing ligand tris(4-(1H-imidazol-1-yl)phenyl)amine (TIPA) and 5-hydroxyisophthalic acid (5-OH-H2bdc) as anion coligand. Compounds 1−4 were characterized by single crystal X-ray structure analyses, thermogravimetric analyses, SHG, and photoluminescent measurements. Compound 1 crystallizes in the chiral space group C2 (No. 5) and features a 2D → 3D parallel/parallel inclined polycatenated framework. Compound 2 crystallizes in trigonal symmetry with a high-symmetry space group R3 and features a 2D porous noninterpenetrating coordination network. Compound 3 crystallizes in the monoclinic space group P21/n and shows a 2D → 3D parallel/parallel polycatenation framework, and compound 4 crystallizes in the orthorhombic chiral space group P212121 (No. 19) and shows a very rarely 3D + 3D heterogeneous 2-fold interpenet...

Synthesis, crystal structure and nonlinear optical property of Rb 3V 5O 14

The new nonlinear optical crystal Rb 3V 5O 14 has been synthesized by solid state reaction and characterized by single-crystal X-ray diffraction, IR and thermogravimetric analysis. The crystal Rb 3V 5O 14 crystallizes in the trigonal system with space P31 m (No. 157), a= b=8.7134(12) Å, c=5.2807(11) Å and α=90°, β=90°, γ=120°, Z=1, ρ=3.516 g/cm 3. It is a layered structure that is very flat and strongly parallel to c. The V 5O 14 layer structure consists of corner-linked square and triangular pyramids. The layers are separated by Rb + ions, which fit equally well on the V 5O 14 layer. The Kurtz powder SHG measurement, using 1064 nm radiation, showed that the second-harmonic generation efficiency of Rb 3V 5O 14 is about two times that of KDP.

Electron irradiation effects on 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

In this paper, we report the electron irradiation effects on the properties of an organic NLO single crystal of 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole. The crystal was irradiated with electron beam of different doses and was characterized by powder XRD, UV-Vis, FTIR, DSC, microhardness and SHG measurements. In XRD, the peaks are shifted due to irradiation. The SHG efficiency has been found to enhance rapidly with irradiation. The investigation of the influence of electron irradiation on the surface morphology of the grown crystal reveals the formation of craters on the surface. The laser damage threshold remains constant as the dose rate increases whereas refractive index increases after irradiation.

Growth and properties of novel organic nonlinear optical crystal: l-alaninium tartrate (LAT)

A new organic nonlinear optical crystal l-alaninium tartrate (LAT) has been grown by slow evaporation method at room temperature. Single crystal X-ray diffraction studies reveal that the crystal has monoclinic structure with space group P2 1. From FT-IR spectrum, the CH vibrations of tartaric acid generate peaks at 2977 and 2960 cm −1. The thermal studies indicate that the grown LAT is stable up to 118 °C, SHG measurements and UV–Vis–NIR spectroscopy. Photoconductivity studies of LAT reveal its negative photoconducting nature. The second harmonic generation efficiency of LAT crystal is found to be 174 mV. The laser damage threshold is found to be 8.16 GW/cm 2. The dielectric constant and dielectric loss of the crystal were studied as a function of frequency and the results are discussed. The AC/DC conductivity studies are carried out and reported for the first time.

Thermal, mechanical, electrical, linear and nonlinear optical properties of l-arginine dihydrofluoride single crystal

Abstract l -arginine dihydrofluoride of dimensions upto 15×10×9 mm 3 was successfully grown by slow evaporation technique from aqueous solution. The crystal was characterized by X-ray diffractometry, Elemental analysis, FT-IR, UV–Vis–NIR spectroscopy, thermal and microhardness studies. The dielectric constant and dielectric loss of the crystal were studied as function of frequency. Photoconductivity studies were also carried out on the sample. Kurtz powder SHG measurement confirms the NLO property of the grown crystals.

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.

At the boundary to banana-shaped liquid crystals: polar properties of phases formed by new asymmetric achiral four-ring bent-core mesogens

New asymmetric four-ring bent-core compounds derived from N-benzoylpiperazine are presented. The mesophases were characterized by polarizing microscopy, DSC, X-ray diffraction, dielectric, electro-optical and SHG measurements. In some homologues the SmA as well as SmC phase can be transformed into a polar structure by applying an electric field. It was found for the first time that the polar SmI phase shows a ferroelectric switching which is obviously based on the collective rotation of the bent molecules around their long axes. It is remarkable that the ferroelectric structure is preserved on cooling into the solid state.

Non-centrosymmetric behavior of a clay film ion-exchanged with chiral metal complexes

SHG measurements on a highly transparent clay film ion-exchanged with chiral metal complexes revealed that the mono-molecular layer of the chiral complexes in an interlayer space acquired a non-centrosymmetric character.

Ferroelectric Phase Transitions in the BIMEVOX Solid Solutions

Ceramic solid solutions Bi 4 (V 1 − x Me x ) 2 O 11 − y with x = 0 ÷ 0.3, Me = Zr, Ga, Fe were prepared by the solid state reactions and were studied by the DTA/DSC, X-ray diffraction, dielectric spectroscopy and the second harmonic generation (SGH) method. The temperature dependences of the SHG signal confirmed the noncentosymmetric structure of the samples with x ≤ 0.05 at room temperature. Similar features were observed in the SHG and dielectric property measurements, which give an indication of the strong domain walls “pinning” by oxygen vacancies inherent to the Bi 4 (V 1 − x Me x ) 2 O 11 − y structures.

Second order nonlinear optical networks with excellent poling stability from a new trifunctional thiophene based chromophore

Two new trifunctional thiophene based dyes suited for crosslinking were synthesised from the same structural core, i.e. 4-[[5-[(4-nitrophenyl)azo]-2-thienyl]azo]benzenamine. Crystal structure and second order nonlinear optical properties were determined on a related difunctional dye that can be considered as a representative and simplified model of the trifunctional compounds, determining on it the μβ value of 4950 × 10 −48 esu (6111 × 10 −80 C 2 m 4 V −2). The presence of three acrylic or hydroxyl functional groups in the dyes allowed to incorporate the chromophoric fragment into two different kinds of crosslinked materials possessing “frozen” long-lasting dipole order. The traditional guest-host approach used for one of them was exceeded by covalently anchoring the chromophore to a functionalised polymer in a three-dimensional unique network. In this way a promising NLO active material was obtained. The value of the d 33 coefficient (determined by SHG measurement using the Maker fringe technique) was 11 pm/V for the poled/crosslinked film. Very good thermal and temporal stability of the chromophore poling-induced dipole alignment was attained.

Orientational ordering of 4-pentyl-4′-cyanobiphenyl molecules evaporated on multi-layered polyimide film

Using optical second-harmonic (SH) generation and polarized absorption (PA) measurements, the orientational ordering process of 4-pentyl-4′-cyanobiphenyl (5CB) was studied during evaporation onto the alignment layer of polyimide (PI) Langmuir–Blodgett films. The intensity of SH signal increased in the beginning of the deposition, but it saturated after the first 5CB monolayer was formed. The PA measurement suggested that a layer-by-layer growth was induced after the formation of 5CB monolayer with accompanying the orientational ordering. The orientational order of the first 5CB monolayer was studied in terms of the orientational order parameters, S 1 = 〈cos θ〉 and S 2 = 〈(3cos 2 θ − 1)/2〉, using the SHG and PA measurements. It was found that S 1 decreased as the thickness of PI alignment layer increased from 0.4 to 4.4 nm, while S 2 was nearly constant. These results indicate that the Coulomb interaction between the permanent dipole of 5CB and its image dipole makes a significant contribution to the orientational ordering of deposited 5CBs.

Environment-Induced Surface Dynamics of a Biomimetic Ionomer Studied Using in Situ Second Harmonic Generation

The environmental-induced surface dynamics of the biomimetic phosphoryl choline (PC)-functionalized poly(trimethylene carbonate) ionomer has been studied and compared to its unfunctionalized counterpart using in situ second harmonic generation measurements. Whereas the nonpolar liquid n-hexane did not induce any surface dynamic processes in the ionomer under study, the presence of water initiated a Debye-type dynamic reaction at the surface of the PC ionomer, which had no equivalent in the unfunctionalized material. This first-order reaction was attributed to a surface enrichment process of the functionalized ionomer in the hydrophilic environment involving movement of the PC endgroups from aggregates in the bulk to the surface. The time constant of the process was found to be about 6 min, and the corresponding activation energy was 0.4 eV. The dehydration process of the PC-functionalized ionomer in nitrogen gas atmosphere could be described by two time constants, one slightly below 1 min and the other one just above 13 min. The results presented in this work show that SHG measurements are well suited for the study of polymer surface restructuring dynamics in response to environmental changes. Such information is very important for the successful design and implementation of biomimetic polymers intended for biomedical applications.

Growth, optical and thermal studies of nonlinear optical L‐arginine perchlorate single crystals

AbstractA potentially useful semiorganic nonlinear optical (NLO) material, L‐arginine perchlorate, has been synthesized and bulk crystals have been grown by slow cooling technique. The grown crystals were characterized by single crystal X‐ray diffraction, UV‐Vis‐NIR spectroscopy, FT‐IR, thermal analysis and SHG measurements. The grown crystals were thermally stable upto 153°C and exhibit SHG efficiency of about 0.17 with respect of Urea. The etching studies have been carried out on the grown crystal. LAPC has good optical transmission not only in the visible range, however, also in the near UV part of the spectra and hence it is a potential material for nonlinear frequency conversion. The refractive index was measured by the Brewster's angle method. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Effect of Corona Poling and Thermo Cycling Sequence on NLO Properties of The Guest-Host System

In the case of doped polymer system SHG efficiency is proportional to the concentration and orientation degree of NLO-active molecules. Unfortunately, corona poling realised at elevated temperatures causes concentration decrease of NLO-active molecules due to crystallization. On the basis of our studies of the film optical images, refractive index and SHG measurements of the dimethylaminobenzylidene 1,3-indandione and PMMA guest-host system, we have demonstrated that optical quality is improved and second order NLO efficiency is higher, when the external poling electric field is switched on from the very beginning of the sample heating process.

Polar Nematic Phase in Lyotropic Solutions of Poly(γ-benzyl glutamate) and Its Temperature Instability As Detected by SHG Measurement

Polar Nematic Phase in Lyotropic Solutions of Poly(γ-benzyl glutamate) and Its Temperature Instability As Detected by SHG Measurement

Synthesis and characterization of a new nonlinear optical single crystal: L‐Lysinium trifluoroacetate

AbstractSingle crystals of a new L‐Lysine salt: L‐Lysinium trifluoroacetate {abbreviated as LLyTFA; [(NH2)‐(CH2)4‐CH‐(NH3)‐(COOH)]+ CF3COO‐} were grown by slow evaporation of an aqueous solution at room temperature. The grown crystals were subjected to single crystal X‐ray diffraction, FTIR and UV‐Vis‐NIR spectrum analyses. The UV‐Vis‐NIR spectrum shows that the absorption is very less in the whole of the region from ultraviolet to near IR. The Kurtz‐Perry powder SHG measurement using a Nd:YAG laser of wavelength 1064nm confirms the frequency doubling of the crystal and its powder SHG efficiency was measured as deff = 0.96 deff (KDP). (© 2007 WILEY ‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Growth, optical and thermal characterization of bis(thiourea)zinc chloride single crystals

Single crystals of nonlinear optical material bis(thiourea)zinc chloride (BTZC) were successfully grown by the temperature lowering method and also by the slow evaporation method at constant temperature 28.5°C from its aqueous solutions having various pH values. The best quality crystal was obtained at pH value of 3.13. Studies on structural, thermal properties of the crystals have been carried out on the basis of X-ray diffraction (XRD), infrared spectroscopy (IR), differential thermal analysis (DTA) and thermogravemetric analysis (TGA). DTA study indicates the possibility of structural changes without weight loss. The values of specific heat calculated from DSC data indirectly demonstrate the high damage threshold of BTZC crystal. The crystals possess wide optical transmission window between 290nm and 2000nm. Kurtz powder SHG measurement confirms the nonlinear optical property of the grown crystals.

NLO Behavior of Polymers Containing Y‐Shaped Chromophores

AbstractNew polyurethanes containing Y‐shaped chromophores, symmetrical derivatives of 4‐(dicyanomethylene)‐2‐methyl‐6‐[p‐(dimethylamino)styryl]‐4H‐pyran, have been prepared. The polymers show high glass transition temperatures (Tg) and a good thermal stability. SHG measurements on poled polymer films of the synthesized polymers have been carried out and a maximum d33 of 15 pm · V−1 has been found at 1 368 nm fundamental wavelength. Time stability measurements on the most active polymer have shown that after the initial fast relaxation, the d33 value remains constant at 80 °C for 60 d.magnified image

Hole trapping in polydiacetylene field effect transistor studied by optical second harmonic generation

Hole trapping in polydiacetylene field effect transistor (PDA-FET) was studied by the electric field induced second harmonic generation (EFISHG). Response of SHG signal from PDA-FET with an application of external voltage was monitored. Applying positive voltage to source and drain electrodes with respect to gate electrode, SHG signal was not observed during bias application, whereas the signal was enhanced after turning off the bias. Since positive bias promotes hole injection from source and drain electrodes, electric field formed by trapped holes in PDA layer activated the SHG signal. Microscopic SHG measurement implies that the trapped holes are concentrated around source and drain electrodes.

Growth and characterization of doped hippuric acid crystals for NLO devices

AbstractModified hippuric acid (HA) single crystals have been grown from aqueous solution of acetone by doping with NaCl and KCl using slow evaporation technique at constant temperature, with the vision to improve the physicochemical properties of the sample. The characterisation of grown crystals was made by X‐ray powder diffraction, density and melting point measurements. TGA/DTA studies indicate that doped crystals are more stable than pure crystals. The optical transmission study and Kurtz powder SHG measurement shows the suitability of doped crystals for NLO applications. Dopant concentration is identified with ICP atomic emission spectrometer system. The Vicker's hardness studies at room temperature, carried out on (111) crystallographic plane shows increased hardness of the doped crystals. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)