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

Abstract

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.

arXiv comment7 pages, 5 figures

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Cited by in corpus (5)

• Bright-soliton frequency combs and dressed states in chi(2) microresonators
• Dual backgrounds and their stability during ${\chi }^{(2)}$ comb generation in microresonators
• Fine structure of second-harmonic resonances in χ^{(2)} optical microresonators
• Parametric conversion via second harmonic generation and two-hump solitons in phase-matched microresonators
• Tunable frequency conversion and comb generation with a superconducting artificial atom