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

A mid-infrared supercontinuum source spanning from 3 to 8 μm is demonstrated using a low-loss AsSe 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 ZrF-based in-amplifier supercontinuum source spanning from 3 to 4.2 μm. The effects of both the pump power and AsSe 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.