CQN Comb: Optical frequency comb generation via cascaded quadratic nonlinear effects
We have published a paper that reports a detailed experimental study of the spectral properties of CQN comb, a relatively new class of optical frequency combs.

The CQN comb is based on CW-pumped cascaded nonlinear effects in a quadratically nonlinear optical medium. The method was discovered in 2013 (see our Research page) and has since been studied by several groups both experimentally and theoretically. One of the remaining open questions is the exact role of phase-mismatch on the CQN comb properties. Our experimental study shows that control of the phase-mismatch is important for minimizing the CQN comb phase noise, and potentially provides a path to cavity soliton formation. (Interestingly, the first experimental proof of CQN soliton operation was just reported*). In addition, our work serves as a benchmark for future theoretical work.

The article was accepted for publication in IOP JPhys Photonics. The preprint can be found at arXiv:2004.07526 (17 Apr 2020)

* The first experimental observation of soliton generation in a CW-pumped CQN resonator was reported by Bruch et al. on the same day as our paper was published in ArXiv; see their excellent ArXiv preprint at https://arxiv.org/abs/2004.07708 (17 Apr 2020)