Interplay Between Modulation Instability (MI) and Optical Comb Generation in a Brillouin Fiber Resonator: Cascaded Brillouin Lasing Comb and Brillouin-Kerr Comb

We have demonstrated the formation of two different types of optical frequency comb in a Brillouin fiber resonator with modulated pump technology. One is the Brillouin lasing comb (BLC) due to the cascaded Brillouin scattering. The latter is the Brillouin-Kerr frequency comb (BKC) that is formed because of the four-wave-mixing. The effect of modulation instability (MI) on the comb formation in these two different regimes is studied. In the first regime, the frequency spacing of the comb is determined by the Brillouin frequency shift. We have observed the competition and switching of MI and SBS in the resonator by changing the pump power. In the second regime, the modulated pump and its associated side frequencies serve as multiple frequency pumps, leading to the generation of BKC. The frequency spacing of BKC can be precisely tuned, depending on the modulation frequency of the pump. MI contributes to the BKC formation. Under a pump power of 1.4 W with a modulation frequency of 12 GHz, MI-assisted BKC with a spectrum covering over 30 nm is obtained. Our results deepen the understanding of the interaction between MI and Brillouin comb in Kerr resonators.