Frequency-Pushing Effect in Single-Mode Diode Laser Subject to External Dual-Beam Injection

The frequency-pushing effect in single-mode diode lasers subject to single-beam injection and dual-beam injection is studied experimentally. The physical process of the frequency-pushing effect has been analyzed in detail using a medium-gain model in a single-beam injection system. A ¿pushed to lock¿ phenomenon has been observed in dual-beam injection system and has also been analyzed using the medium-gain model. This model can also be used to explain the maximum of conversion efficiency in an injection-locked frequency convertor. First, we produce a conventional mapping of nonlinear dynamic regions, including stable locking, period doubling, chaos, undamped relaxation oscillations, and bistability, as functions of the detuning frequency and injection ratio in single-beam injection system. Then, a pushed stable locking range is observed when two masters are injected simultaneously. The direction of pushing is towards negative detuning frequencies and low injection ratios, which allows a larger detuning frequency and lower injection ratio in choosing the lasers used as pump source in injection-locked frequency convertor.