Photonic crystal fibers with high index infiltrations for refractive index sensing

We report on the experimental demonstration of a refractive index sensing technique based on the photonic bandgap (PBG) shift in two types of solid-core photonic crystal fiber (PCF) structures with a series of high refractive index infiltrations. Bandgap edge and central wavelength with a significant red-shift are observed with the increase of infiltration material index. The measurement results from both structures agree well with the frequency scaling law, which helps to simplify the process of sample preparation in PCF-based sensors using the infiltration method. Refractive index resolution up to 10⁻⁶ refractive index unit (RIU) can be achieved experimentally, which is two orders of magnitude higher than that in PCF-based long-period gratings.