Integrated mid-infrared broadband frequency conversion and evanescent sensing on a multimode chalcogenide rod platform.

Post-processing and functionalization of optical fibers with engineered properties, as well as multifiber assembly, have been the subject of intensive studies over the past few decades, to provide, for instance, unprecedented signal processing and sensing tools for a variety of applications. However, combining distinct optical functions such as nonlinear pulse processing and linear sensing on a single fiber segment has still remained an elusive challenge in the mid-infrared spectral region. Here, we report the development of very short multi-tapered chalcogenide rods to enable the dual function of supercontinuum generation and evanescent wave sensing in the mid-infrared spectral region. On the one hand, we demonstrate the generation of an ultrabroadband light spectrum ranging from 1.9 to 16 µm with significant average power in 5 cm long tapered multimode Te-As-Se rods pumped by a femtosecond mid-infrared pump laser. On the other hand, we show that a second coiled taper can also be shaped after the broadband frequency conversion and serve as an efficient compact sensing head to collect mid-infrared signatures of alcoholic solutions. Our work represents what we believe to be a new step toward the development of compact fiber devices for mid-infrared sensing technologies.