Cavity solitons in an ultrahigh-effective-Q fiber resonator enabled by Raman gain

We demonstrate temporal pattern formation in a coherently driven fiber ring cavity whose effective finesse is continuously reconfigured using distributed Raman amplification. We achieve an effective finesse of up to Feff≈800, corresponding to a linewidth of ∼725 Hz (Qeff ≈ 2.7 × 1011) at 1555 nm. By exploiting the resulting increase in effective photon lifetime, we excite stable temporal cavity solitons and generate a low-repetition-rate frequency comb with a spacing of 580 kHz. Finally, we analyze the impact of the Raman loss-compensation mechanism, particularly its associated noise, and show that a trade-off exists between soliton excitation threshold and stability.