Temporal Solitons in a Coherently Driven Active Resonator

Optical frequency combs are lightwaves composed of a large number of equidistant spectral lines. They are important for metrology, spectroscopy, communications and fundamental science. Frequency combs can be generated by exciting dissipative solitons in lasers or in coherently driven passive resonators, both of which suffer from significant limitations. Here, we show that the advantages of each platform can be combined by operating an active cavity pumped below the lasing threshold. We generate a novel kind of soliton and show that 10% of its power can be extracted from a cavity with effective loss as low as 3%, highlighting the potential of low finesse resonators for soliton formation. Moreover, we find that amplified spontaneous emission has negligible impact on the soliton's stability. Our results open up new avenues for frequency comb generation by showing that two pumping schemes can be efficiently combined to generate a high power ultra stable pulse train.