Loss-reduced photonic liquid-crystal fiber by using photoalignment method.

We present a loss-reduced photonic liquid-crystal fiber (PLCF) using the noncontact photoalignment method. The photoexcited and adsorbed azo dye on the capillary surface of a PLCF induces uniform and highly ordered orientation of the liquid crystal (LC). The anchoring force of the photoalignment effect is combined with that generated by surface boundary conditions of the photonic crystal fiber (PCF). Transmission loss resulting from LC scattering can be reduced from -2.8 to -1.3 db/cm within 10 min. This photoinduced alignment yields a permanent boundary for the LC in the PCF that reduces scattering loss and can be further modulated by electrical fields. The electrical tunable effect and fast dynamic response of the photoaligned PLCF are also presented. This low-loss PLCF can be applied conveniently in various PLCF devices.