Fast Spectroscopy Based on a Modulated Soliton Microcomb

Abstract

Dissipative Kerr solitons (DKS)s offer an integrated platform for broad spectrum coverage, which is suitable for the high sensitivity spectroscopy. However, the large linespacing of the soliton comb limits the spectroscopy detection resolution. We overcome this limitation by modulating the soliton comb lines through an external EOM with a tunable RF source. By locking the pump laser to a reference cavity, the linewidth of the pump laser was compressed from 1.13 MHz to 72 kHz, leading to the silimar linewidth of comb lines and showing a frequency resolution of hundreds of kHz. Based on the scanned microcomb, we measured the absorption spectra of a gas cell and the high-Q optical modes in the microcavity, with a fast scanning speed of 16GHz/µs. The scanning comb allows the spectroscopy measurement to cover the whole comb mode spectrum over THz bandwidth. Our setup holds great potential for simple, robust spectroscopy measurement.

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“…This ambiguity could be resolved by simultaneously beating the signal with two independent comb sources with different repetition rates, and the optical signal frequency could be determined by comparing the two beating frequencies (dual-comb spectroscopy). Alternatively, the two comb sources could be provided by a single microresonator by either employing different mode families [255] or switching the repetition rate in real time [256].…”