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Q: Fachverband Quantenoptik und Photonik
Q 73: Quantum Technologies (Detectors and Photon Sources) (joint session Q/QI)
Q 73.7: Talk
Friday, March 14, 2025, 16:00–16:15, AP-HS
Investigation of AM-PM conversion noise in nonlinear extensions of a frequency comb — •Angelina Jaros1, Mattias Misera1, Thomas Puppe2, Uwe Sterr1, and Erik Benkler1 — 1Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig — 2TOPTICA Photonics AG, Lochhamer Schlag 19, 82166 Gräfelfing
An application of optical frequency combs is the transfer of frequency stability from an ultra-stable laser to the interrogation laser of an optical atomic clock. The stability transfer is limited by noise added onto the frequency comb. Its source could be the conversion of amplitude modulation (AM) of the seed comb light to phase modulation (PM) noise during the nonlinear processes employed for spectral broadening of the comb spectrum to cover the desired target wavelengths.
We investigate this AM-PM conversion in an Er:fiber fs-laser with two identical nonlinear extension branches. Single-frequency cw lasers at the fundamental and target wavelengths are employed for the generation of RF beats containing the PM. A modulator is employed to introduce AM in one branch before its nonlinear conversion stage, and the differential PM between the two wavelengths is measured after the nonlinear conversion to suppress phase noise due to path-length variations. By comparing to the second, unmodulated branch seeded by the same fundamental comb, phase noise in the seed comb and frequency noise of the cw lasers are suppressed.
The results may lead to further reduction of phase noise added by the nonlinear conversion steps in optical frequency combs.
Keywords: optical frequency combs; stability transfer; phase noise; AM-PM conversion