Frequency comb cavity-enhanced spectroscopy has proven itself extremely useful in terms of the effective bandwidth, measurement precision, and acquisition speed. At the same time integrated solutions for both comb source and cavity, based on silicon nitride microring resonators, are readily available. The combination of these two factors motivates our work, in which we demonstrate comb-cavity coupling for cavity-enhanced wideband spectroscopy on-chip. By means of a thermo-optic tuning we can characterize the integrated dispersion of the microring resonator as well as to assess the corresponding lineshape data. THz Kerr frequency comb spanning up to 800 nm makes it possible to overperform industrial table-top tunable sources in terms of the available bandwidth, power consumption, and compactness. We analyze a simple model for the evaluation of the cavity-enhanced spectroscopy performance and perform numerical simulations, which are shown to be in a good agreement with experimental results. Our platform offers intriguing applications in diverse fields, spanning from biology and medicine to photonic design and fundamentals of light-matter interaction.
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