Low-loss chalcogenide anti-resonant hollow-core fiber for mid-infrared power delivery at wavelengths beyond 8 μm

Abstract

High-power single-mode quantum cascade lasers (QCLs) operating in the 8–12 μm atmospheric window have been developed rapidly for advanced long-distance applications. Chalcogenide (Chg) instead of silica-based anti-resonant hollow-core fibers (AR-HCFs) show promise for delivering such high-power single-mode mid-infrared (MIR) laser beams due to their relatively low material absorption beyond 8 μm. However, current Chg AR-HCFs still exhibit significant losses at these wavelengths, mostly attributed to the structural defect. In this paper, an As₂S₃-based AR-HCF with a cladding composed of six non-touching capillaries was fabricated by the stack-and-draw method. The fabrication process was optimized to minimize the structure defect. The measured fiber attenuation at 8.34 μm was 1.3 dB/m, which is the lowest loss for Chg AR-HCFs operating at wavelengths beyond 8 μm to the best of our knowledge. Additionally, the measured bending loss was below 0.8 dB/m at bending radii above 20 cm. The numerical aperture (NA), and beam quality factor (M²) of laser beam delivered by the Chg AR-HCF were measured to be 0.031 and ∼1.2, respectively. It therefore shows great potential to use such a fiber to extend the application of high-power MIR laser delivery beyond 8 μm.