Kerr-microresonator solitons from a chirped background

Daniel C Cole,Miro Erkintalo,Scott B Papp,Ki Youl Yang,Jordan R Stone,Xu Yi,Kerry J Vahala

doi:10.1364/optica.5.001304

Abstract

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 “soliton step.” Phase modulation also enables precise, high bandwidth control of the soliton pulse train’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.

Highlights

Dissipative temporal cavity solitons in Kerr microresonators [1,2,3,4] have the potential to provide the revolutionary capabilities of frequency combs in a chip-integrable platform
In addition to exploring soliton generation, we demonstrate that phase modulation (PM) at the free-spectral range (FSR) can be used for microsecond-level control of the pulse train’s repetition rate, and we conclude by discussing how the technique can be applied to resonators with FSR too high to be directly electronically accessible
We find that PM transforms the resonator excitation spectrum from a series of N 0, 1, 2, ..., N max solitons to a smaller number of available energy levels

Summary

INTRODUCTION

Dissipative temporal cavity solitons in Kerr microresonators [1,2,3,4] have the potential to provide the revolutionary capabilities of frequency combs in a chip-integrable platform This would extend the reach of frequency combs to applications in communications, computation, and sensing with low size, weight, and power. A variety of schemes have been demonstrated to address these challenges and obtain single solitons [5,6,7,8,9], and many achieve excellent performance In general these schemes increase procedural complexity by exploiting nonadiabatic variations in pump-laser power and frequency, and/or involve at least some amount of stochastic fluctuation in the output. In addition to exploring soliton generation, we demonstrate that PM at the FSR can be used for microsecond-level control of the pulse train’s repetition rate, and we conclude by discussing how the technique can be applied to resonators with FSR too high to be directly electronically accessible

PHYSICAL MECHANISM AND THEORETICAL EXPLORATION OF THE CONCEPT

EXPERIMENTAL RESULTS

FINAL REMARKS