Highdno/dTLiquid Crystals and their Applications in a Thermally Tunable Liquid Crystal Photonic Crystal Fiber

Abstract

We have analyzed the physical origins of the temperature gradient of the ordinary refractive index (d n _o /dT) of liquid crystals. To achieve a large d n _o /dT, high birefringence (Δn) and low clearing temperature play crucial roles. Based on these guidelines, we formulated two exemplary liquid crystal mixtures, designated as UCF-1 and UCF-2. The d n _o /dT of UCF-1 is ∼4× higher than that of 5CB at room temperature. By infiltrating UCF-1 into the air holes of a three-rod core photonic crystal fiber, we demonstrate a thermally tunable photonic bandgap fiber with tuning sensitivity of 27 nm/°C at room temperature. The insertion loss is less than 0.5 dB.