Generation of Optical Frequency Combs in an Optical Microresonator Pumped by a 780-nm Laser Diode in Self-Injection Locking Regime

Experimental data for the generation of optical frequency combs in magnesium fluoride microcavities with whispering gallery modes at 780 nm are presented. This wavelength corresponds to the normal group velocity dispersion for pumping by a laser diode operating in self-injection locking regime. It is shown that the excitation of frequency combs is caused both by the processes in the microresonator and by the processes in the laser diode. It is found that, in the self-injection locking regime, initially suppressed, longitudinal modes of the laser diode can be amplified, which leads to the generation of hybrid, laser-enhanced side components. As a result, combs with a highly effective conversion of pumping energy and a low level of phase noise are excited.