Maker Fringe Method Research Articles

SECOND-ORDER NONLINEAR OPTICAL SUSCEPTIBILITIES OF POLY[(HEXA-2,4-DIYNYLENE-1,6-DIOXY)DIBENZOATES] CONTAINING AZO CHROMOPHORE DISPERSE RED 19 BY ELECTROABSORPTION SPECTROSCOPY

The second-order nonlinear optical susceptibilities χ(2) of two isomeric polymers containing an azo dye, Disperse Red 19, were determined by the first-order electroabsorption spectroscopy (EAS), and compared with values previously obtained by SHG measurements. The para-polymer was found to have higher susceptibility than the corresponding meta-polymer. χ(2) were found to be 5–6 × 10-8 esu, which are comparable to those obtained by the Maker Fringe method.

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.

Third- and second-order optical nonlinearity of Ge–Ga–S–PbI 2 chalcohalide glasses

Two series of metal iodide doped chalcohalide glasses (100−2 x)GeS 2· xGa 2S 3· xPbI 2 (0⩽ x⩽20) and (100− x)(0.8GeS 2·0.2Ga 2S 3)· xPbI 2 (0⩽ x⩽15) were prepared and characterized. The microstructure of these glasses has been studied by Raman scattering spectra. Utilizing femtosecond time-resolved optical Kerr effect (OKE) technique at the wavelength of 820 nm, a largest third-order nonlinearity χ (3) of 2.07×10 −13 esu was obtained for the 90GeS 2·5Ga 2S 3·5PbI 2 glass, and it decreases with the addition of PbI 2 in both two series. After thermally poled, second-harmonic generation (SHG) has been observed in these glasses according to Maker fringe method and a large second-order nonlinearity χ (2) as well as 4 pm/V was obtained for the 70GeS 2·15Ga 2S 3·15PbI 2 glass. The variations of χ (2) and χ (3) on glass composition are ascribed to the evolution of micro-structural units in glass. These novel chalcohalide glasses would be expected to be the promising candidate materials for nonlinear optical devices.

Synthesis and Characterization of Nonlinear Optical Polymers Containing Carbazole and Disperse Red Dye

Dye‐containing nonlinear optical (NLO) polymers were synthesized: (1) poly(3‐(2‐(3‐(2‐isocyanatopropan‐2‐yl)phenyl)‐2‐methylpropyl)‐4‐methyl‐1‐phenylpyrrolidine‐2,5‐dione), P[(DR1,Cz)MSt‐PMI], and (2) poly(9‐vinyl‐9H‐carbazole‐co‐disperse red 1), PAV[DR1‐Cz]. The synthesized NLO polymers were characterized by 1H‐NMR, IR, and UV–VIS spectroscopy; differential scanning calorimetry (DSC); and thermogravimetric analysis (TGA). The electro‐optic (EO) coefficients (r33) and their NLO properties were evaluated by simple reflection and the Maker fringe method. The EO coefficients of P[(DR1,Cz)MSt‐PMI] and PAV[DR1‐Cz] were measured at 632.8 nm to be 106 and 46.6 pm/V, respectively. The second harmonic generation (SHG) coefficient (d33) of P[(DR1,Cz)MSt‐PMI] was measured to be 71.25 pm/V.

Synthesis and characterization of carbazole derived nonlinear optical dyes

Three kinds of carbazole derived dyes, Caz-MN, Caz-Fu, and Caz-Vm-MN of push–pull molecules were synthesized and their nonlinear optical properties measured. The second harmonic generation (SHG) coefficients, d 33, of Caz-Fu/PVK[poly(9-vinylcarbazole)] (0.1:0.9) and Caz-Vm-MN/PVK (0.1:0.9) were 2.06 × 10 −9 esu and 7.3 × 10 −9 esu, respectively. The electro-optic coefficients ( r 33) of these PVK blends with dyes were also observed to be 1.23 pm/V, 4.03 pm/V at a wavelength of 632.8 nm. The synthesized novel carbazole based dyes Caz-MN, Caz-Fu, and Caz-Vm-MN were characterized by means of 1H NMR spectroscopy, IR spectroscopy, thermogravimetric analysis, electro-optic coefficients ( r 33), and their NLO properties were evaluated by Maker fringe method.

XK2O-(33.3-x)BaO-16.7TiO2-50SiO2(mole%) 유리의 비선형 광학 및 형광 특성

Transparent glass-ceramics containing fresnoite crystals have been prepared by controlled heat treatment in K₂O-BaO-TiO₂-SiO₂, and their nonlinear optical and luminescent properties were investigated using Maker fringe method and Spectrofluorometer. The second harmonic generation was observed in all samples and the values decreased with increasing K₂O content. The luminescence of blue light at ~482 ㎚ could be observed and it was shown that the luminescent property was controlled by the K₂O content.

Structure and second-order nonlinearity of GeS 2-Ga 2S 3-X 2S 3 (X=P, As, Sb) chalcogenide glasses

To find new chalcogenide glass possessing larger second-order non-linearity, glasses with compositions Ge-Ga-X-S (X=P, As, Sb) were prepared via melt quenching technique. The amorphous nature of all the compositions of the as-quenched glasses was confirmed by X-ray diffraction(XRD). The glassy thermal properties of the as-quenched glasses were established by differential thermal analyses(DTA). The glass structure was studied by RAMAN spectra and the second order nonlinearity was studied by the Maker Fringe method after the electron beam poling(EBP) and electric/temperature field poling(ETFP) respectively. Additions of various pnicogen atoms into the Ge-Ga-S glasses lead to the difference in the second order nonlinearity of the glass. It's found that glasses with different structures result in different SHG intensities, and even more, a large second order nonlinear susceptibility χ (2) of about 9 pm/V was obtained for all the glasses and the reasons for such a large susceptibility were analyzed.

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.

ＫＣｌ（１００）基板上に作成されたバナジルフタロシアニン膜の配向評価

Vanadylphthalocyanine (VOPc) thin films with thicknesses from 100 nm to 300 nm were prepared by a molecular beam epitaxy method on KCl substrate. The molecular orientation and phase morphologies in VOPc thin film deposited on KCl substrate were investigated by Vis/UV spectra measured with each sample using a Vis/UV spectrophotometer, AFM images were measured using atomic force microscopy and the laser light incident angle dependences of second and third harmonic (SH and TH) intensities were measured by the Maker fringe method using an Nd-YAG laser. It is commonly understood that the VOPc thin film prepared on the KCl substrate has three types of phase morphology. One is epitaxy, two is the pseudomorphic layer and three is Phase I. For a thickness of 300 nm, the phase morphology which appeared in the surface neighborhood differs from the three types. The relationship between the new phase morphology and the TH intensity is analyzed using a theoretical method.

Electron-beam poling in undoped, N- or Ge-doped MDECR H:SiO2 films

Amorphous N- or Ge-doped H:SiO2 films deposited on silica by the matrix distributed electron cyclotron resonance-PECVD method were irradiated by an electron-beam with different doses in order to pole the material and induce second harmonic generation (SHG). SHG was measured using the Maker-fringe method. When irradiated at an acceleration voltage of 25 kV, an incident current of 5 nA during 480 s, the N-doped H:SiO2 films exhibited a maximum second harmonic signal in the order of 0.003 pm/V, but when irradiated with an acceleration voltage of 30 kV, at 5 nA during 240 s, the films exhibited a maximum second harmonic signal of 0.006 pm/V. With a smaller current of 0.5 nA during 25 s and 25 kV acceleration voltage, the Ge-doped H:SiO2 films (3.8 at. % Ge) showed a maximum second-order nonlinearity of 0.0005 pm/V. But an H:SiO2 films with a smaller Ge content (1.0 at. % Ge), showed a large SHG: d33=0.09 pm/V when irradiated at 25 kV, 0.5 nA during 15 s.

Molecular Organization of Nonlinear Organic Films Laminated by Langmuir-Blodgett Method

In the 21st century, the optical computation is likely to be the basic technology for processing lots of information at high speed. The aim of the present research work is to develop optical logic gates or memory chips. For this purpose, we have examined the suitability of organic nonlinear optical dye material Vanadyl-phthalocyanine (VOPc). Large single crystals of this material have been fabricated by using Molecular Beam Epitaxy (MBE) technique. The epitaxial films were formed on the substrate under optimum operating conditions. However, the epitixial growth is observed only up to a limited thickness. Above this thickness, the films become non-epitaxial, which can be improved by annealing. The reformation of the epitaxial films has been confirmed. We have also reported the effects of the environment of high temperature on the multilayered tetra-tert-butyl-Vanadyl-phthalocyanine ((t-bu)4VOPc) films, formed by Langmuir-Blodgett (LB) method. The solvent used to dissolve ((t-bu)4VOPc) was 1,2-dichloroethane. The monolayer on the surface of the water was transferred to a glass substrate by the vertical dipping method. If the multilayered stack is too thick, the molecular arrangement of the film may get disturbed. The improvement in the molecular arrangement of the LB films was examined and confirmed by measuring it’s nonlinear optical susceptibility, using Maker Fringe Method. Monolayer formation on water surface depends on the surface pressure-area isotherm. If this monolayer formation is not perfect, multiplayer stacks cannot be formed. The molecular films were aligned almost perpendicular to the substrate, as estimated from the limiting molecular area of surface pressure-area isotherm. The molecular organization of the monolayer on the substrate and the molecular structure of the multilayered ((t-bu)4VOPc) films are discussed.

Second-order nonlinear optical activity vs. chromophore content in simple organic glass/PMMA system

A simple organic glass with a connection of two nonlinear optical (NLO) moieties was synthesized by condensation reaction of alkyl-substituted dibenzaldehyde with barbituric acid. This organic glass with T g of 81 °C was formed to be optically transparent films without any phase separation even at the highest chromophore content (100 wt% loading without host matrix). The second-order NLO properties with various organic glass/PMMA composition systems were systematically studied by Maker fringe method at a wavelength of 1064 nm. We demonstrate that second-order optical nonlinearity of this organic glass/PMMA system can be progressively enlarged with increasing chromophore loading from 0 to 100 wt%.

Measurement of the second-order nonlinear optical coefficient of polymers based on surface plasmon resonance

A simple technique which uses surface plasmon resonance (SPR) enhanced second harmonic generation (SHG) to measure the second-order nonlinear optical (NLO) coefficient d33 of polymers has been presented in this paper. By comparing the SHG intensity generated from NLO polymers and that from quartz crystal based on SPR, the NLO coefficient d33 is quantitatively measured in our experiment. This technique has the advantages of simplicity and avoiding the thickness effect of polymer film on the SHG intensity. The NLO coefficient d33 obtained by this technique agrees well with that measured by the Maker-fringe method.

Second harmonic generation in AlGaN, GaN and AlxGa1?xN/GaN multiple quantum well structures

Second harmonic generation coefficients of GaN and AlxGa1–xN (x=0.08) thin films deposited by MOCVD on a sapphire 0001 substrate were deduced through the standard Maker fringes method. Measurements were performed at λ=1064 nm using a Nd:YAG Q-Switched laser. The measured ratio between the d33 and d31 coefficients allowed one to retrieve information on the degree of crystallinity of the thin film samples that was found to be higher in thicker films. The presence of tiny oscillations in the SHG detected signal as a function of the incidence angle of the fundamental beam on the samples is discussed and related to the reflectance at the sample-air interfaces. Finally, nonlinear coefficients for three AlxGa1–xN/GaN multiple quantum well (MQW) samples (x=0.08 and x=0.15) were determined and compared to the values obtained for GaN crystalline thin films.

Linear and third-order optical characterisation of polyDPCHD

We report here on linear and non-linear optical characterisation of the polydiacetylene poly[1,6-bis(3,6-dipalmitoyl- N-carbazolyl)-2,4-hexadiyne] (polyDPCHD). Thin films (14 and 32 nm) of good optical quality have been obtained by deposition of the monomer from chloroform solutions on glass by standard spin-coating technique, followed by thermal polymerisation at 115 °C. Complex index of refraction of a thin film deposited on a 1 mm thick fused silica substrate has been determined in the spectral range from 270 to 1700 nm by ellipsometry. Third-order optical susceptibility ( χ (3)) has been measured by Third Harmonic Generation (THG) technique on a thin polyDPCHD film deposited on a 160 μm thick BK7 substrate in the spectral range from 1000 to 1900 nm, using the Maker fringes method. The χ (3) dispersion shows the typical resonant behaviour due to multi-photon processes and is strictly related to the absorption spectra in the visible range. Values of χ (3) of the order of magnitude of 10 −11 esu have been obtained. A comparison between linear and non-linear optical properties of polyDPCHD and poly[1,6-bis(3,6-dihexaedcyl- N-carbazolyl)-2,4-hexadiyne] polyDCHD-HS will be presented.

LINEAR AND NONLINEAR OPTICAL PROPERTIES OF 2,7-DINITRO-9-FLUORENONE SINGLE CRYSTAL

The linear and nonlinear optical properties of 2,7-dinitro-9-fluorenone single crystals are investigated, especially those affecting the usage for optical second-harmonic generation. Sufficient optical quality plate-like crystals have been grown by sublimation in purified nitrogen flow. The crystal is transparent in the visible and near-infrared region, is negative biaxial with na>nc>nb and has birefringence with na−nb=0.52 at 532 nm. The nonlinear optical coefficients determined by Maker fringe method are d33=8 pm/V and d32=d24=0.4 pm/V. Type I and type II critical phase matching are possible in the near infrared region and type I is preferable.

Optimization and characterization of the guest-host polyetherketone polymer films for application in integrated optical devices

In order to optimize the loading of 3-(1,1-dicyanothenyl)-1-phenyl-4, 5-dihydro-1H-pryazole (DCNP) in polyetherketone (PEK-c) guest-host polymer films, ten kinds of DCNP/PEK-c thin films, in which the weight per cent of DCNP changes from 5 to 50, were prepared. Their second-order nonlinear optical coefficients χ33(2) at λ = 1064 nm were measured by using Maker fringe method after poling under the optimal poling condition. Their optical waveguide transmission losses were measured at 632.8 nm. Optimal weight per cent of the chromophore for the DCNP/PEK-c guest-host polymer system has been determined as about 20 for use in the integrated optical devices.

Synthesis of Polymers Bearing Oligo‐Aromatic Esters for Second‐Order Nonlinear Optics

We synthesized methacrylate-type polymers bearing oligo-aromatic esters as side chains to create unique second-order nonlinear optical (NLO) active polymers (PMAn-x, PMAnC-x, PMA2N-x, and PBA3N-x, x = oligo-aromatic ester contents) for the investigation of the resulting architecture. The polymers were obtained from the polymerization of methacrylated oligo-aromatic esters and the copolymerization of the esters with methyl methacrylate or tert-butyl methacrylate using a radical initiator. The cut-off wavelength (λ co ) of these polymers was shorter than the visible region aimed at, i.e. λ co = ca. 330-370 nm, which is much shorter than λ co of the typical second-order NLO polymers containing groups such as azobenzene chromophores. Second-harmonic generation (SHG) measurements of these polymer films after treatment by corona poling were carried out using the Makerfringe method. These polymer films exhibited good transparency in the visible region and a second-order nonlinear optical coefficient d 33 of 2.2-9.8 pm.V -1 . The d 33 values of some derivatives decreased with an increase of the chromophore content, which is due to a strong interaction between the side chains with increasing chromophore content.

Disperse Red 1-doped solgel planar waveguides for nonlinear optical devices operating at telecommunications wavelengths

We report on linear and nonlinear optical properties of Disperse Red 1-doped solgel waveguides. The refractive-index and optical-propagation losses of the guiding layer were measured between 0.756 µm and 1.64 µm. The spectral broadening of the chromophore charge-transfer transition in the visible is modeled with a Voigt-profile function. In the telecommunications window the attenuation is dominated by the overtones of the O—H bonds vibration bands. The nonlinear optical coefficients were measured at different poling strengths with the Maker-fringe method. The nonlinear coefficient d33 was found to be 4.5 pm V-1 at 1.58 µm for a poling field of 60 V µm-1.

Third order optical characterisation of a π-conjugated polydiacetylene by Maker fringes technique

Conjugated polymers are promising photonic materials due to the high values of non-linear optical coefficients when compared to inorganic compounds. A key point in view of applications is the figure of merit defined as the ratio between the non-linear optical and the absorption coefficients. We report on the NIR measurement of the third order optical susceptibility ( χ (3)) by third harmonic generation in polydiacetylene (poly-[1,6-bis-(3,6-dihexadecyl- N-carbazolyl)-2,4-hexadiyne], polyDCHD-HS). Samples are prepared as thin films by spin-coating technique and the χ (3) is evaluated by Maker fringes method in the spectral range from 1200 to 2000 nm. The absorption coefficient has been derived from measurements in CS 2 solution. Spectra of χ (3) show typical resonant behaviour due to the multi-photon processes and are strictly related to the absorption spectra in the visible range. Values of χ (3) are in the range of 10 −11 esu. The absorption coefficient is as low as 0.25 cm −1 at 1.5 μm showing the good figure of merit of polyDCHD-HS.