Martina MATUSKO : "Toward a superradiant laser: ytterbium atomic ensemble and metrological developments for ultra-stable frequency references"

PhD Defense : "Toward a superradiant laser: ytterbium atomic ensemble and metrological developments for ultra-stable frequency references”

Abstract :  This thesis presents the initial steps toward the realization of an ultra-stable superradiant oscillator. It explores the use of the quantum phenomenon of superradiance, which leverages the coherence and indistinguishability of an atomic ensemble to enhance coherent optical radiation. A superradiant laser consists of atoms collectively coupled to a Fabry-Perot cavity, operating in the bad-cavity regime to minimize sensitivity to cavity fluctuations.

In this work, the first realization and characterization of a cold ytterbium atomic ensemble are demonstrated, laying the foundation for future superradiant operation. The experimental setup for atomic transport into the cavity has been planned, enabling sequential loading of atoms for quasi-continuous superradiant emission.

To support the future characterization of the superradiant laser, a compensated optical fiber link for local ultra-stable frequency transfer has been implemented. This system features fully digital signal processing and a novel characterization method that does not require access to the remote fiber end. The achieved fractional frequency instability reaches the $10^{-18}$ range, demonstrating its suitability for high-precision frequency dissemination within an institute.