A structurally right-handed chiral sculptured thin film (STF) with a central 90 deg-twist defect was made by thermal evaporation of chalcogenide glass and the use of a serial bi-deposition process to exhibit a narrowband hole in the spectrum of the right-circularly polarized light reflected when right-circularly polarized light is normally incident on the chiral STF. In an attempt to build a tunable filter, the chiral STF was then infiltrated with a highly birefringent nematic liquid crystal (LC), which caused a linear reflectance peak to redshift by ∼350 nm . But the circular Bragg phenomenon exhibited by the uninfiltrated chiral STF was greatly diminished owing to the similarity in the constitutive properties of the LC and the chalcogenide glass. No temperature dependence of the shifted peak was observed, which provided clear evidence that the LC molecules are not ordered inside the chiral STF but are randomly aligned instead.
Deformable Helix Ferroelectric Liquid Crystal (DHFLC) devices with nanodimensionally short pitch are examined for
the purpose of applications in biomedical optical imaging. While nematic Liquid Crystal (NLC) devices have been used
in our previous research as retarders, optical filters and polarization rotators and integrated into biomedical optical
imaging systems, the current research is devoted to DHFLCs and to highlight the advantages that these devices can offer.
Ferroelectric Liquid Crystal (FLC) devices are considerably faster than Nematic LC devices, the DHFLC sub group
possesses other, more desired effects. The desired electro-optical response of the device is continuous, hysteretic-free
and insensitive to the sign of the applied voltage. This can be achieved by using the DHFLC V-shaped switching effect
which is observed when the helix pitch magnitude is shifted to nanoscale below 400nm (sub-wavelength) down to 150
nm. DHFLC cells with a sub-wavelength helix pitch have small light scattering in the visible spectral range when the
applied voltage is below the critical level of the helix unwinding. Designs, experimental results and simulations are
presented particularly for the reflectivity at oblique incidence showing some unique properties including polarization
independent modulation, faster response and surface waves excitation.
A structurally right-handed chiral sculptured thin film (STF) with a central 90º-twist defect was made by thermal evaporation of chalcogenide glass and the use of a serial bi-deposition process to exhibit a narrowband hole in the spectrum of the right-circularly polarized light reflected when right-circularly polarized light is normally incident on the chiral STF. The chiral STF was then infiltrated with a highly birefringent nematic liquid crystal (LC), which caused a linear reflectance peak to redshift by ~350 nm, but the circular Bragg phenomenon exhibited by the uninfiltrated chiral STF was greatly diminished owing to the similarity in the constitutive properties of the LC and the chalcogenide glass. No temperature dependence of the shifted peak was observed, which provided clear evidence that the LC molecules are not ordered inside the chiral STF but are randomly aligned instead.
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