Tunable photonic crystal fiber couplers with a thermo-responsive liquid crystal resonator

We theoretically address the thermo-optical response of multicore photonic crystal fiber (PCF) couplers infiltrated with nematic liquid crystals (LCs). The proposed PCF coupler consists of two identical cores separated by a third one which acts as a liquid crystal resonator. With an appropriate choice of the design parameters associated with the liquid crystal core, phase matching at a single wavelength can be achieved, thus enabling thermo-tunable narrow-band resonant directional coupling between the input and the output cores. The verification of the proposed coupler design is ensured through an accurate PCF analysis based on finite element and beam propagation methods. The enhanced thermo-optical properties of LC-based PCF couplers are highly attractive for photo-thermal sensing applications.