Hours-long lasing and progress toward ultra-narrow linewidth lasers in a laser-cooled strontium cavity-QED system

Laser-cooled neutral atoms are an excellent platform for quantum computation, sensing, and probing new physics. Most cold atom experiments operate in a time-sequenced fashion where successive cooling and trapping stages initialize the atoms, often leading to cycle times of several seconds or longer. Continuous experiments will benefit from increased bandwidth and decreased dead time. We have demonstrated the continuous cooling and coupling of ⁸⁸Sr atoms to a high-finesse optical cavity at a rate of 2.1(3)*10⁷ atoms/s. Using this continuous atomic source, we studied self-organization physics in the context of continuous recoil-driven lasing. The lasing was induced by laser cooling beams that drove a two-photon Raman process between momentum states of the internal atomic ground state. The continuous laser cooling maintained a population inversion between low and high-momentum states leading to Raman gain and continuous lasing. More recently, we switched our system to ⁸⁷Sr to open the clock transition with the goal of developing a continuous superradiant laser. Superradiant lasers hide the phase memory in highly coherent atoms using ultra-narrow optical transitions. This makes them intrinsically robust against vibrations and well-suited for ultra-narrow mHz linewidth lasers.