Stable references for a superradiant Ytterbium laser

This thesis establishes a solid foundation for the superradiant ultra-stable laser built at FEMTO-ST. The work focuses on the stable references required for the operation of such laser emphasizing two key contribution: a 556 nm laser frequency stabilization to perform a magneto-optical-trap on the intercombination line of ¹⁷¹Yb and a compact tunable Fabry-Perot cavity, crucial for superradiant lasing.

We demonstrate an offset sideband frequency lock of the 556 nm laser using a single electrooptical modulator, covering the frequency gap between the reference iodine vapor cell and ¹⁷¹Yb, and to perform lock-in detection. Sub-Doppler saturated spectroscopy is performed through the vapor, generating an error signal to frequency lock the laser. A characterization setup is implemented with an optical frequency comb, where the 556 nm laser fractional frequency stability is measured to be 1.2×10^–11 at one second. Through meticulous estimation of systematic shifts, a few kilohertz accuracy is obtained.

Finally, we propose a low noise tunable compact Fabry-Perot cavity design, suitable for the superradiant lasing in a metrologically relevant regime. A controlled assembly of the cavity is proposed alongside with its ultra-high vacuum system. Subsequently, finesse and frequency stability characterization is performed using a 578 nm laser frequency locked to the resonator with a Pound-Drever-Hall scheme. A finesse ℱ of 6920 is measured through various techniques while the stability is measured to be 2.2×10^–12 at one second. Such preliminary results constitute a solid foundation for the superradiant laser.

time and frequency metrology, active optical clock, superradiance, Fabry-Perot cavity, sub-Doppler spectroscopy.

Full document (EN) : TEL-05483152