Stuttgart 2012 – wissenschaftliches Programm
Q 28.4: Vortrag
Dienstag, 13. März 2012, 14:45–15:00, V47.02
Correlated Impact of the Feedback Loops on the Noise Properties of an Optical Frequency Comb — •Vladimir Dolgovskiy, Nikola Bucalovic, Christian Schori, Pierre Thomann, Gianni Di Domenico, and Stéphane Schilt — Laboratoire Temps-Fréquence, Université de Neuchâtel, Switzerland
An optical frequency comb is characterized by two parameters, the repetition rate of the pulses frep and the carrier-envelop offset frequency fCEO. A fully stabilized comb is generally obtained by phase-locking these two parameters to a stable frequency reference, using two feedback loops acting on the laser cavity length (for frep) and on the pump power (for fCEO). However, these two actuators have a simultaneous influence on the two comb parameters, leading to some cross-coupling between the two servo loops. Here, we present the first study of the impact of this coupling onto an optical comb mode in an Er:fiber frequency comb, based on experimental measurements and on a theoretical model. An extensive experimental characterization of the comb was performed in terms of fCEO and frep dynamic response, frequency noise and total loop transfer functions. We observed a more than 10-fold improved frequency noise power spectral density of an optical comb line at 1.56 µm in a wide Fourier frequency range, resulting from this coupling, compared to a hypothetical modeled case with no coupling. The model is validated by experimental data showing a very good agreement. We also predict a significant comb linewidth reduction at a wavelength around 2 µm.