English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

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

Frequency comb generation threshold in $\chi^{(2)}$ optical microresonators