Soliton frequency comb at microwave rates in a high-Q silica microresonator

Abstract

Frequency combs are having a broad impact on science and technology because they provide a way to coherently link radio/microwave-rate electrical signals with optical-rate signals derived from lasers and atomic transitions. Integrating these systems on a photonic chip would revolutionize instrumentation, time keeping, spectroscopy, navigation, and potentially create new mass-market applications. A key element of such a system-on-a-chip will be a mode-locked comb that can be self-referenced. The recent demonstration of soliton mode locking in crystalline and silicon nitride microresonators has provided a way to both mode lock and generate femtosecond time-scale pulses. Here, soliton mode locking is demonstrated in high-Q silica resonators. The resonators produce low-phase-noise soliton pulse trains at readily detectable pulse rates-two essential properties for the operation of frequency combs. A method for the long-term stabilization of the solitons is also demonstrated, and is used to test the theoretical dependence of the comb power, efficiency, and soliton existence power on the pulse width. The influence of the Raman process on the soliton existence power and efficiency is also observed. The resonators are microfabricated on silicon chips and feature reproducible modal properties required for soliton formation. A low-noise and detectable pulse rate soliton frequency comb on a chip is a significant step towards a fully integrated frequency comb system.

Stokes solitons in optical microcavities

“…The Raman terms containing derivatives cause soliton self frequency shift and subsequently a phase change 7 . However, they minimally affect pulse width and peak power 8,9 . As the primary soliton and Stokes soliton have no abolute phase coherence, these terms have been omitted.…”

Microresonator-based solitons for massively parallel coherent optical communications

“…DKS have already been used in applications such as self-referencing of optical frequency combs [24,25], low noise microwave generation [26] and dual soliton comb spectroscopy [22,27].…”

Detuning-dependent properties and dispersion-induced instabilities of temporal dissipative Kerr solitons in optical microresonators

“…Moreover, we reveal how these crossings induce deviations in the relation between comb power and detuning, which can be a limitation for stabilization techniques based on the comb power alone [9,48]. The presented method also enables the longterm operation of soliton-based combs with stabilized bandwidth and power.…”

“…With proper tuning of the pump laser, these processes result in the formation of DKS in the cavity sustained via the double balance between cavity loss and parametric gain, as well as dispersion and Kerr nonlinearity [1,2,[5][6][7]. These DKS-based frequency combs have been demonstrated in several microresonator platforms, enabling on-chip photonic integration [2,[8][9][10]. Compared to other optical frequency comb platforms, DKS combs extend the repetition rate to the microwave and milli-meter wave domain, while simultaneously providing wide bandwidth and compact form factor.…”