Thermally tunable dual-core photonic bandgap fiber based on the infusion of a temperature-responsive liquid

A dual-core photonic bandgap fiber (PBGF) is demonstrated by infusing a high-index liquid into a dual-core air-silica photonic crystal fiber (PCF). Extremal couplings have been experimentally observed. The temperature tunable characteristics of the dual-core PBGF's bandgap guiding and dual-core coupling are experimentally and numerically investigated. When we rise temperature, the dual-core PBGFs' bandgaps have been changed: compression of bandwidth, blue-shift and depression of the guiding band. Especially, the dual-core coupling is temperature tunable because of the tunability of the infusion liquid's index. We find that the rise of temperature increases the coupling length which results in the blue-shift of the resonant peak wavelengths with a speed of 1.9nm/degreesC, for a 20mm dual-core PBGF.