ABSTRACT
In this paper, we present electrooptic experiments on photonic crystal fibers filled with a liquid crystalline blue phase. These fibers guide light via photonic band gaps (PBGs). The blue phase is isotropic in the field-off state but becomes birefringent under an electric field. This leads to a polarization dependent shift of the PBGs. Interestingly, the effect on the PBGs is asymmetrical: while the short wavelength edges of the PBGs shift, the long wavelength edges are almost unaffected. By performing band gap and modal analyses via the finite element simulations, we find that the asymmetric shift is the result of the mixed polarization of the involved photonic bands. Finally, we use the band gap shifts to calculate effective Kerr constants of the blue phase.
ABSTRACT
Microstructured fibres which consist of a circular step index core and a liquid crystal inclusion running parallel to this core are investigated. The attenuation and electro-optic effects of light coupled into the core are measured. Coupled mode theory is used to study the interaction of core modes with the liquid crystal inclusion. The experimental and theoretical results show that these fibres can exhibit attenuation below 0.16 dB cm(-1) in off-resonant wavelength regions and still have significant electro-optic effects which can lead to a polarisation extinction of 6 dB cm(-1).
Subject(s)
Liquid Crystals/chemistry , Models, Chemical , Optical Fibers , Refractometry/instrumentation , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Light , Liquid Crystals/radiation effectsABSTRACT
Photoactive materials are highly promising candidates for novel applications as they enable all-optical control of photonic devices. Photochromic molecules exhibit a reversible change of their dielectric function upon irradiation with light of proper wavelength. The trans- and cis-isomers of azobenzene exhibit different absorption properties due to the effect of the configuration on the polarizability of the molecule. Here, we introduce a novel molecular/semiconductor hybrid device which is fully tunable by all-optical means via the integration of a semiconductor microdisk into a photo-adressable polyelectrolyte material. We demonstrate that such polyelectrolyte superlattices can be used to tune semiconductor photonic resonators with high precision and without any significant degeneration of device performance. Moreover, we demonstrate an all-optically tunable laser based on this hybrid concept.
Subject(s)
Electrolytes/chemistry , Electrolytes/radiation effects , Lasers , Semiconductors , Equipment Design , Equipment Failure Analysis , Light , MiniaturizationABSTRACT
Wave-guiding in the visible spectral range is investigated for a micro-structured crystal fiber filled with a dual-frequency addressable nematic liquid crystal mixture. The fiber exhibits a solid core surrounded by just 4 rings of cylindrical holes. Control of the liquid crystal alignment by anchoring agents permits relatively low attenuation. Samples with different anchoring conditions at the interface of the silica glass and the liquid crystal show different transmission properties and switching behavior. Polarization dependent and independent fiber optic switching is observed. Due to a dualfrequency addressing scheme, active switching to both states with enhanced and reduced transmission becomes possible for planar anchoring. Even a non-perfect fiber shows reasonable transmission and a variety of interesting effects.
Subject(s)
Data Display , Liquid Crystals/chemistry , Liquid Crystals/radiation effects , Refractometry/instrumentation , Signal Processing, Computer-Assisted/instrumentation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Photons , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Liquid crystal research is a growing and ramifying tree, as illustrated by the cartoon by John W. Goodby, President of the International Liquid Crystal Society: Thanks to a sunny, multidisciplinary environment, it grows from strong roots (experimental methods) and produces/synthesises ever new fruit (fullerene, dendrimer, banana and biaxial liquid crystals), as demonstrated by contributions to the recent European Conference on Liquid Crystals in Halle, Germany.
ABSTRACT
A diffraction grating or more complex optical phase object can be formed and preserved from a crosslinked liquid crystalline film. The gratings are formed from electrically conductive liquid crystals, which show a rich variety of dissipative structures depending on the applied AC field strength and frequency. Addition of a crosslinking agent and irradiation with UV light thereby "freezes" the structures.
