%0 Journal Article %J Optica %D 2018 %T Kerr-microresonator solitons from a chirped background %A Daniel C. Cole %A Jordan R. Stone %A Miro Erkintalo %A Yang, Ki Youl %A Yi, Xu %A Kerry J. Vahala %A Scott B. Papp %K frequency combs %K Integrated photonics %K Microcavity devices %K Optical signals %K Phase modulation %K Pulse propagation and temporal solitons %K Signal Processing %K Temporal solitons %X Optical frequency combs based on solitons in nonlinear microresonators open up new regimes for optical metrology and signal processing across a range of expanding and emerging applications. In this work, we advance these combs toward applications by demonstrating protected single-soliton formation and operation in a Kerr-nonlinear microresonator using a phase-modulated pump laser. Phase modulation gives rise to spatially/temporally varying effective loss and detuning parameters, leading to an operation regime in which multi-soliton degeneracy is lifted and a single soliton is the only observable behavior. We achieve direct, on-demand excitation of single solitons as indicated by reversal of the characteristic &\#x201C;soliton step.&\#x201D; Phase modulation also enables precise, high bandwidth control of the soliton pulse train&\#x2019;s properties, and we measure dynamics that agree closely with simulations. We show that the technique can be extended to high-repetition-frequency Kerr solitons through subharmonic phase modulation. These results will facilitate straightforward generation and control of Kerr-soliton microcombs for integrated photonics systems. %B Optica %I Optica Publishing Group %V 5 %P 1304–1310 %8 Oct %G eng %U http://opg.optica.org/optica/abstract.cfm?URI=optica-5-10-1304 %N 10 %R 10.1364/OPTICA.5.001304