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Random bits generated from physical entropy in the timing of microwave bursts are investigated using a laser diode. The bursts are generated by chaotic dynamics for yielding bits at gigabits per second for wireless distribution.

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 f 0 , 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 3 f 0 that is perturbed for harmonic locking. The central frequency is boosted to 4 f 0 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 4 f 0 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.