Self-Injection Locking of a Gain-Switched Laser Diode
Artem E. Shitikov, Valery E. Lobanov, Nikita M. Kondratiev, Andrey S. Voloshin, Evgeny A. Lonshakov, Igor A. Bilenko
Abstract
We experimentally observe a self-injection locking regime of the gain-switched laser to a high-$Q$ optical microresonator. We reveal that the comb generated by the gain-switched laser experiences a dramatic reduction of comb-teeth linewidths in this regime. We demonstrate the Lorentzian linewidth of the comb teeth of sub-kHz scale as narrow as for a nonswitched self-injection locked laser. Such a setup allows generation of high-contrast electrically tunable optical frequency combs with tunable comb-line spacing in a wide range from 10 kHz up to 10 GHz. The characteristics of the generated combs are studied for various modulation parameters---modulation frequency and amplitude, and for parameters, defining the efficiency of the self-injection locking---locking phase, coupling efficiency, and pump frequency detuning.