Intensity correlation distribution in gain-switched semiconductor laser for quantum key distribution
Yuanfei Gao, Tao Wang, Yixin Wang, Zhiliang L. Yuan · Journal of Semiconductors · 2025
Abstract In the implementation of quantum key distribution, Security certification is a prerequisite for social deployment. Transmitters in decoy-BB84 systems typically employ gain-switched semiconductor lasers (GSSLs) to generate optical pulses for encoding quantum information. However, the working state of the laser may violate the assumption of pulse independence. Here, we explored the dependence of intensity fluctuation and high-order correlation distribution of optical pulses on driving currents at 2.5 GHz. We found the intensity correlation distribution had a significant dependence on the driving currents, which would affect the final key rate. By utilizing rate equations in our simulation, we confirmed the fluctuation and correlation originated from the instability of gain-switched laser driven at a GHz-repetitive frequency. Finally, we evaluated the impact of intensity fluctuation on the secure key rate. This work will provide valuable insights for assessing whether the transmitter is operating at optimal state in practice.