• DOI:10.1063/5.0021424
• Corpus ID: 220486804

Frequency comb generation threshold via second-harmonic excitation in χ(2) optical microresonators

@article{Szabados2020FrequencyCG,
  title={Frequency comb generation threshold via second-harmonic excitation in $\chi$(2) optical microresonators},
  author={Jan Szabados and Boris Sturman and Ingo Breunig},
  journal={arXiv: Optics},
  year={2020}
}

• Jan Szabados, B. Sturman, I. Breunig
• Published 10 July 2020
• Physics
• arXiv: Optics

We investigate the threshold of $\chi^{(2)}$ frequency comb generation in lithium niobate whispering gallery microresonators theoretically and experimentally. When generating a frequency comb via second-harmonic generation, the threshold for the onset of cascaded second-order processes leading to a comb is found to be approximately 85 $\mu$W. The second-harmonic generation efficiency up to this value is in excellent agreement with a previously known theoretical framework. This framework is extended here, showing that the onset of cascaded $\chi^{(2)}$ processes and the maximum of the second-harmonic generation efficiency coincide. Furthermore, we observe that the frequency distance between the comb lines is a function of the pump power. It changes from 4 free spectral ranges at the oscillation threshold to 1 free spectral range at 590 ${\mu}$W.