Fast Spectroscopy Based on a Modulated Soliton Microcomb

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
$1.13\:\mathrm{MHz}$
to
$72\:\mathrm{kHz}$
, 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
$\mathrm{16\,\,\mathrm{GHz/\mu s}}$
. 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.