Compact 3-8  μm supercontinuum generation in a low-loss As₂Se₃ step-index fiber

A mid-infrared supercontinuum source spanning from 3 to 8 μm is demonstrated using a low-loss As₂Se₃ commercial step-index fiber. A maximum average output power of 1.5 mW is obtained at a low repetition rate of 2 kHz. Thanks to the low NA step-index fiber, the output is single mode for wavelengths above ∼5  μm. The pump source consists of an erbium-doped ZrF₄-based in-amplifier supercontinuum source spanning from 3 to 4.2 μm. The effects of both the pump power and As₂Se₃ fiber length on the output characteristics are studied. To the best of our knowledge, this is the first compact supercontinuum source ever reported to reach 8 μm in a standard step-index fiber.