3 November 1999 Polarization nonsensitive optical phase modulator based on two DHF (deformed helix ferroelectric) liquid crystal layers
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Abstract
Calculation analysis and experimental measurements are described of the operation of optical phase modulator composed from two DHF (deformed helix ferroelectric) liquid crystal cells, mounted in series. The limit dependence of effective refractive index on molecular tilt angle in helical smectic C* phase is calculated as well as the influence of electric field on effective refractive index for different values of molecular refractive index components and tilt angle. The presence of gray scale in DHF regime is shown for crossed DHF cells and jump in change of effective refractive index was found, though the smooth deviation of average refraction index ellipsoid of single DHF layer was found at change of applied voltage from zero to untwisting value. Ferroelectric liquid crystal mixtures are developed with response times less than 0.5 ms. Developed FLC materials have very large tilt angle about 40 degrees and very short pitch of helix less than 0.2 micrometers . The model phase modulator was composed from two DHF cells mounted in series. The behavior of optical phase shift was investigated in Fizeau interferometer. The gray scale phase modulation only is obtained in accordance with calculations. The limit change of phase retardation was found 0.75 (lambda) in transmission mode between undisturbed and totally untwisted helix for cell thickness 16.5 micrometers . The strong nonlinear behavior of the phase shift versus d.c. electric field was found. The quantitative results agree with the theoretical calculations.
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Leonid A. Beresnev, Leonid A. Beresnev, Wolfgang Dultz, Wolfgang Dultz, Berndt Hils, Berndt Hils, Thomas Weyrauch, Thomas Weyrauch, Wolfgang Haase, Wolfgang Haase, } "Polarization nonsensitive optical phase modulator based on two DHF (deformed helix ferroelectric) liquid crystal layers", Proc. SPIE 3760, High-Resolution Wavefront Control: Methods, Devices, and Applications, (3 November 1999); doi: 10.1117/12.367594; https://doi.org/10.1117/12.367594
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