Frequency-modulated continuous-wave generation based on an optically injected semiconductor laser with optical feedback stabilization.

Based on the period-one (P1) dynamics of an optically injected semiconductor laser (SL), a photonic scheme enabling the generation of a tunable high-quality frequency-modulated continuous-wave (FMCW) signal is investigated experimentally. Under a modulated optical injection, the laser is driven into P1 oscillation with a modulated microwave frequency. In this work, optical feedback is also introduced to further reduce the microwave phase noise. The experimental results show that the central frequency of the generated FMCW signal can be widely tuned from 11.41 to 50.05 GHz by simply adjusting injection parameters while the frequency sweep range of the FMCW signal can be controlled by varying the modulation index. Under proper operating parameters, the sweep range and rate of the FMCW signal are 18.42 GHz (13.73 GHz- 32.15 GHz) and 1.14 GHz/ns, respectively. Further, by introducing an optical feedback loop, the frequency comb contrast of the FMCW signal is drastically increased by 27.15 dB when the reciprocal of the feedback delay time matches with the modulation frequency exactly due to the locking effect of the external cavity optical modes.