Photoactive photonic liquid crystal fiber polarization switches

This study presents a light-controlled photonic liquid crystal fiber (PLCF) polarization switch. The solid-core PCF has an index-guiding effect that reduces the insertion loss produced by infiltrating liquid crystals (LCs) with a low refractive index (RI). The proposed approach achieves photoactive tuning through the trans-cis photoisomerization of doped azobenzene, which modulates the RI of infiltrated LCs. This design achieves an optically tunable extinction ratio of average 10 dB and photonic bandgap in the wavelength range of 1527-1538 nm under 30 mW laser illumination. The repeatable and switchable phase change is nearly 60°, corresponding to a response time of 100 ms, which is to date the fastest light-tunable PLCF polarization switch available.