Towards the realization of a single-mode photonic crystal fiber in the middle infrared

摘要

Photonic crystal fibers confine light within a periodic array of elements. We used multiple extrusions of silverhalide (AgClxBr1-x) crystalline materials to fabricate photonic crystal fibers, which are transparent in the middle infrared(mid- IR) in the spectral range 2-20μm. The cores of these fibers consisted of pure silver bromide (AgBr) of refractiveindex n=2.16, and the cladding area included concentric rings of tens of fiberoptic elements made of pure silver chloride(AgCl), of a lower refractive index n=1.98. Simulations on photonic crystal structures showed that all the fabricatedfibers guide a small number of modes. Furthermore, adding rings to such a structure should lower the number of boundmodes in the core. We measured the attenuation and the output power distribution of these fibers and carried outspectroscopic measurements in the mid- IR. Good correlation was found between the experimental and the theoreticalresults. These findings will pave the way for the fabrication of single-mode fibers in the mid- IR range.