Resonant wavelength and wavelength separation tunable dual-channel fiber Bragg grating based on filling functional material into highly birefringent photonic crystal fiber

Abstract: Resonant wavelength and wavelength spacing tunable dual-channel fiber Bragg gratings based on filling functional material into highly birefringent photonic crystal fibers is proposed and investigated. The tuning properties of the resonance wavelength of Bragg gratings depended on altering the liquid indices filled in the holes of PCF are theoretically investigated. It is demonstrated that the resonant wavelengths are tuned as wide as 40 nm with a slope of 80 nm per refractive index unit (RIU), and wavelength spacing as large as 5 nm with a slope of approximate 12 nm/RIU corresponding to the two orthogonal polarization states. Key words: Highly birefringent PCF; Functional material; Fiber Bragg grating 1. Introduction Photonic crystal fibers (PCFs) have attracted much attention of scientific researchers in past years due to their unique characteristics, such as endlessly single-mode operation, designable dispersion properties, large mode area, and highly nonlinear performance [1-5] . Quite a few works have been done involving gratings inscribed on various photonic crystal fibers [6-8] . Since photonic crystal fibers allows for the sophisticated tailoring of their properties, via changing the number, the position, the size and the shape of the air holes around the fiber core, thus gratings on various PCFs can have unique properties. Furthermore, filling the air holes with polymer, isotropic liquid or liquid crystal of interesting properties, thermally or electrically tunable operation can also be achieved in gratings on PCFs.