The 2-μm to 6-μm mid-infrared supercontinuum generation in cascaded ZBLAN and As₂Se₃ step-index fibers

Fiber-based mid-infrared (MIR) supercontinuum (SC) sources benefit from their spectral brightness and spatial coherence that are needed for many applications, such as spectroscopy and metrology. In this paper, an SC spanning from 2 μm to 6 μm is demonstrated in cascaded ZrF₄-BaF₂-LaF₃-AlF₃-NaF (ZBLAN) and As₂Se₃ step-index fibers. The pump source is a ZBLAN fiber-based MIR SC laser with abundant high-peak-power soliton pulses between 3000 nm and 4200 nm. By concatenating the ZBLAN fiber and the As₂Se₃ fiber, efficient cascading red-shifts are obtained in the normal dispersion region of the As₂Se₃ fiber. The spectral behavior of cascaded SC generation shows that the long-wavelength proportion of MIR SC generated in the ZBLAN fiber plays a critical role for further spectral extension in the As₂Se₃ fiber.