Highly birefringent chalcogenide optical fiber for polarization-maintaining in the 3-8.5 µm mid-IR window

A highly birefringent polarization-maintaining chalcogenide microstructured optical fiber (MOF) covering the 3-8.5 µm wavelength range has been realized for the first time. The fiber cross-section consists of 3 rings of circular air holes with 2 larger holes adjacent to the core. Birefringence properties are calculated by using the vector finite-element method and are compared to the experimental ones. The group birefringence is 1.5x10^-3 and fiber losses are equal to 0.8 dB/m at 7.55 µm.