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  • 1
    ISSN: 1292-895X
    Keywords: PACS. 61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order - 42.65.Ky Harmonic generation, frequency conversion - 42.82.Et Waveguides, couplers and arrays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability which did not show any sign of degradation within the monitored period of several months. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. The alignment led to an inherent channel waveguide for p-polarized light without additional preparation steps. The photopolymerization did not induce scattering sites in the waveguide and the normalized losses were less than 2 dB/cm. The material offers a great potential for the design of nonlinear optical devices such as frequency doublers of low-power laser diodes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1057-9257
    Keywords: amphiphilic indandione-1,3 pyridinium betaine ; Langmuir-Blodgett films ; monolayers ; linear dichroism ; non-linear optical properties ; second-harmonic generation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Linear dichroism and second-harmonic generation (SHG) have been measured in Langmuir-Blodgett (LB) multilayers of Z-type structure of amphiphilic indandione-1,3 pyridinium betaine (IPB) with an aliphatic tail containing 17 carbon atoms (C17IPB). The dichroic ratio As/Ap of electronic absorption of s- and p-polarised light and the SHG intensity show that the ‘heads’ of C17IPB molecules are predominantly oriented along the deposition direction of monolayers on a quartz substrate. Orientation parameters and mean statistical azimuthal and tilt angles are evaluated as a function of the number of monolayers. The SHG efficiency has been measured in C17IPB monolayers on a water surface as a function of surface pressure. The effective hyperpolarisability β of the IPB molecule has been determined experimentally in a chloroform solution by the hyper-Rayleigh-scattering method. The obtained value of β = (138 ± 16) × 10-30 esu is in good agreement with theoretical estimates.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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