High-Speed Q-Modulation of Injection-Locked Semiconductor Lasers

We propose a novel approach for high-speed direct modulation of optically injection-locked semiconductor lasers by modulating the photon lifetime (or the Q-factor). Based on the injection locking rate equations, the frequency response is analytically derived and numerically simulated. Compared with conventional current modulation for injection-locked lasers, Q-modulation has the same resonance frequency, but the dc-to-resonance roll-off caused by the real-pole frequency is largely eliminated, and the response beyond the resonance frequency decays much slower; therefore, a significant enhancement in the modulation bandwidth can be achieved. We also show that the two modulation methods have similar chirp characteristics.