Frequency comb generation via cascaded second-order nonlinearities in microresonators

• Published in: arXiv.org 2019-12
• Main Authors: Szabados, Jan, Puzyrev, Danila N, Minet, Yannick, Reis, Luis, Buse, Karsten, Villois, Alberto, Skryabin, Dmitry V, Breunig, Ingo
• Format: Article
• Language: English
• Subjects: Lithium niobates; Miniaturization; Nonlinear dynamics; Nonlinearity; Optical frequency; Resonators
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1912.00945

Optical frequency combs are revolutionising modern time and frequency metrology. In the past years, their range of applications has increased substantially, driven by their miniaturisation through microresonator-based solutions. The combs in such devices are typically generated using the third-order \(\chi^{(3)}\)-nonlinearity of the resonator material. An alternative approach is making use of second-order \(\chi^{(2)}\)-nonlinearities. While the idea of generating combs this way has been around for almost two decades, so far only few demonstrations are known, based either on bulky bow-tie cavities or on relatively low-\(Q\) waveguide resonators. Here, we present the first such comb that is based on a millimetre-sized microresonator made of lithium niobate, that allows for cascaded second-order nonlinearities. This proof-of-concept device comes already with pump thresholds as small as 2 mW, generating repetition-rate-locked combs around 1064 nm and 532 nm. From the nonlinear dynamics point of view, the observed combs correspond to the Turing roll patterns.