This work demonstrates photo alignment and electrical tuning effects in photonic liquid crystal fiber (PLCF). Applying voltages of 0 approximately 130V and 250 approximately 400V shifts the short and long wavelength edges of the transmission bands by about 45 nm and 74 nm toward longer wavelengths, respectively. An electro-tunable notch filter is formed in the PLCF without the use of gratings. The range of tunability of the notch filter is around 180 nm with an applied voltage of 140 approximately 240 V. This photo-induced alignment yields a permanently tilted LC structure in PCF, which reduces the threshold voltage, and can be further modulated by electric fields. The polarization dependent loss and fast response time of photo-aligned PLCF is also demonstrated. The finite-difference frequency-domain method is adopted to analyze the shift of the transmission bandgap, and the simulation results are found to correlate well with experimental data.

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.