Dual Frequency Raman Cavity Soliton Comb in a Mini Fiber Ring Cavity

Dual-frequency combs have enabled significant advances in applications such as temporal sensing and spectroscopy [1]. The recent development of the Kerr cavity soliton frequency comb has opened a new approach for generating dual-frequency combs with advantageous characteristics [2], [3]. That approach relies on the generation of two individual Kerr cavity soliton frequency combs with different repetition rates either using two different resonators or different modes within a single resonator [2]–[4]. However, due to the large free-spectral range (FSR) of conventional microresonator platforms, dual combs corresponding to cavity solitons are unpractical for some application, such as high-resolution spectroscopy. Here we demonstrate a new approach for broadband dual comb generation in Kerr nonlinear resonators that permits combs with finer line spacing than conventional microresonators. Our concept is based upon the counter-rotating pulsed-driving of a mini fibre ring resonator, and we leverage a recently discovered dissipative Raman soliton state [5], [6] to obtain comb bandwidths on par with many microresonator platforms.