Plasmonic-enhanced multiparameter direct microcomb spectroscopy

Sensitive spectroscopic analyses of molecular systems are being revolutionized utilizing the broad, equidistant spectra of frequency combs. Recently, photonically integrated frequency combs have emerged through low-power continuous laser pumping of microring resonators, resulting in stable, low-power, and compact frequency combs. Additional important photonic building blocks are plasmonic resonators, which allow exceptional sensitivity to their environment, forming the backbone of many spectroscopic biosensing experiments. However, coupling microcombs with plasmonic systems remains unexplored. Here, we demonstrate the integration of a photonic-circuit-based frequency comb with a watercladded prism-based plasmonic resonator, enabling compact, broadband direct microcomb plasmonic spectroscopy. Our plasmonic-microcomb cavity-enhanced platform demonstrates high sensitivity and multidimensionality, opening avenues for a range of coherent, broadband, linear, and nonlinear chemical and biosensing applications.