A 7 × 1 chalcogenide fiber combiner with high transmission efficiency for mid-infrared high power lasers

• A robust 7 × 1 mid-infrared fiber combiner based on chalcogenide glass was fabricated by tapering method. • Watts-level (as high as to 2.48 W) output laser power was achieved at 4.7 μm wavelength in our fiber combiner. • The power superposition of multiple lasers was demonstrated in our fiber combiner. • High efficiency and power delivery were achieved via refractive index matching solution at the fiber combiner's output. Fiber combining technology enables the merging of multiple mid-infrared lasers to achieve higher power outputs. However, detailed fabrication methods tailored for mid-infrared applications are rarely reported. In this study, we designed and fabricated a 7 × 1 fiber combiner using infrared chalcogenide glass and evaluated its performance for mid-infrared laser transmission. The fiber combiner consists of three main regions: the input fibers, the taper region, and the taper waist. When the taper ratio is 2 and the taper region length is 15 mm, the combiner demonstrates a uniform optical field distribution and achieves a simulated maximum transmission efficiency of 67.7 %. Experimental results confirmed the simultaneous superposition of laser power across different wavelengths, achieving watts-level output power at a 4.7 μm wavelength for the first time. To address the issue of high Fresnel losses caused by the high refractive index (n = 2.4) of chalcogenide glass at the input and output interfaces of the fiber, we applied a refractive index matching liquid to both ends of the fiber combiner. The average transmission efficiency per port reached 72.84 %, with a maximum transmission power of 2.48 W per single fiber. This advancement surpasses the milliwatt-level power limitations of previous mid-infrared fiber combiners, highlighting the potential of high-power chalcogenide fiber combiners in mid-infrared applications.