Stefan Schäffer leads the Quantum Metrology group at NBI together with Jörg Müller. Research focuses on superradiant strontium lasers: (1) quasi-continuous superradiant lasing with sub-natural linewidth; (2) Ramsey spectroscopy enhanced by cavity sub-to-superradiant phase transitions for improved atomic clock sensing; (3) continuous atom beam for Dicke-effect-free superradiant interrogation. Key work published in PRL (2023) and Nature Communications (2024). Part of EU iqClock and ESA collaborations.