Grassani, DavideTagkoudi, EiriniGuo, HairunHerkommer, ClemensYang, FanKippenberg, TobiasBrès, Camille Sophie2019-04-172019-04-172019-04-172019-04-0410.1038/s41467-019-09590-3https://infoscience.epfl.ch/handle/20.500.14299/156093Directly accessing the middle infrared, the molecular functional group spectral region, via supercontinuum generation processes based on turn-key fiber lasers offers the undeniable advantage of simplicity and robustness. Recently, the assessment of the coherence of the mid-IR dispersive wave in silicon nitride (Si3N4) waveguides, pumped at telecom wavelength, established an important first step towards mid-IR frequency comb generation based on such compact systems. Yet, the spectral reach and efficiency still fall short for practical implementation. Here, we experimentally demonstrate that large cross-section Si3N4 waveguides pumped with 2 μm fs-fiber laser can reach the important spectroscopic spectral region in the 3–4 μm range, with up to 35% power conversion and milliwatt-level output powers. As a proof of principle, we use this source for detection of C2H2 by absorption spectroscopy. Such result makes these sources suitable candidate for compact, chip-integrated spectroscopic and sensing applications.Frequency combsIntegrated opticsMid-infrared photonicsSupercontinuum generationMid-IR spectroscopytext::journal::journal article::research article