Tunable optical filter based on self-rolled-up microtube incorporating nematic liquid crystal

A widely tunable filter in TiO2 self-rolled-up microtube (SRM) with nematic liquid crystal (NLC), which fills the hollow core of the SRM, is proposed as a novel three-dimensional filter structure. Since the total free energy of the NLC is under the influence of elastic distortion energy, the applied static electric field, and optical power, the reorientation of the liquid crystal is computed by minimizing this quantity in this research. The dependency of the NLC refractive index on applied electric field shows that the dynamic wavelength tuning range of an 8 μm-radius NLC SRM can reach up to the maximum value of 90.6 nm with an operation voltage of 30 V, which is enough to achieve the wavelength tunability from S-band to L-band.