Perturbing period-one laser dynamics for frequency-modulated microwave generation with external locking

Period-one (P1) dynamics of two lasers under a common injection are perturbed for externally locked frequency-modulated continuous-wave (FMCW) generation. The first laser is injected into P1 dynamics at frequency f0, where the dynamics is perturbed by a slow modulation to induce adiabatic sweeping for FMCW generation and a fast modulation to seed the whole comb for external locking. The second laser is injected into a faster P1 dynamics at 3f0 that is perturbed for harmonic locking. The central frequency is boosted to 4f0 by coherently combining the lasers. FMCW generation with external locking is demonstrated with a sweep range of 6 GHz, comb contrast enhanced to 42 dB, and 4f0 reaching 80 GHz. Inherent competition between external locking and frequency modulation is revealed, although an optimal strength is identified for locking the whole comb. Wide tuning of the central frequency is also supported.