Chalcogenide-Glass Nested Anti-Resonant Nodeless Fibers in Mid-Infrared Region

We propose two types of chalcogenide-glass nested anti-resonant nodeless fibers (CNANFs) with four anti-resonant elements, in which a smaller tube is nested. One type of CNANF theoretically achieves ultra-low loss of 2.6 dB/km at the wavelength of 10.6 μm and can be used for the delivery of a high-power CO
₂
laser. The other CNANF is a polarization-maintaining CNANF in the broadband mid-infrared (mid-IR) region. We investigate the tradeoff between loss and birefringence in the mid-IR region and achieve a low loss of <;1 dB/m and high birefringence of >1 × 10
^-4
simultaneously over a large wavelength band by adjusting the air-core size and the thickness of the vertical/horizontal outer tubes. Both CNANFs show strong capability for higher order mode suppression.