Thermorefractive noise reduction of photonic molecule frequency combs using an all-optical servo loop

J. Connor Skehan, Anamika Nair Karunakaran, Poul Varming, Óskar B. Helgason, Patrick B. Montague, Jochen Schröder, Minhao Pu, Kresten Yvind, Victor Torres-Company, Peter A. Andrekson*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Phase and frequency noise originating from thermal fluctuations is commonly a limiting factor in integrated photonic cavities. To reduce this noise, one may drive a secondary “servo/cooling” laser into the blue side of a cavity resonance. Temperature fluctuations which shift the resonance will then change the amount of servo/cooling laser power absorbed by the device as the laser moves relatively out of or into the resonance, and thereby effectively compensate for the fluctuation. In this paper, we use a low noise laser to demonstrate this principle for the first time in a frequency comb generated from a normal dispersion photonic molecule micro-resonator. Significantly, this configuration can be used with the servo/cooling laser power above the usual nonlinearity threshold since resonances with normal dispersion are available. We report a 50 % reduction in frequency noise of the comb lines in the frequency range of 10 kHz to 1 MHz and investigate the effect of the secondary servo/cooling noise on the comb.

Original languageEnglish
JournalOptics Express
Issue number21
Pages (from-to)35208-35217
Publication statusPublished - 9 Oct 2023

Bibliographical note

Funding Information:
Funding. Knut och Alice Wallenbergs Stiftelse Vetenskapsrådet (VR-2015-00535, VR-2020-00453); European Research Council (GA-771410); Marie Sklodowska-Curie Grant Agreement (861152).

Publisher Copyright:
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.


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