A robust and inexpensive all optical switch with chiral nematic liquid crystal

Abstract A switchable photonic band gap with optical addressing is demonstrated. The switch can tune over a broad wavelength range (about 80 nm) without deformation and degradation with high reproducibility. The material is a mixture of reactive and nonreactive mesogens, azo dye molecules and chiral dopant. The mixture of reactive monomers and nonreactive mesogens leads to a robust polymer template filled with nano-droplets. Due to a photo-induced phase transition, the edges of the bandgap shift to shorter wavelengths after illumination. Three concentrations of reactive monomers are investigated. The features of the device are interesting for several emerging applications: all optical photonic switches, lab-on-a-chip devices, and switchable optical devices such as sensors, reflectors, diffraction gratings, polarizers, shutters, notch- and band-pass filters, reflective displays, mirror-less tunable lasers and modulators.