| Summary: | Today’s narrowest linewidth lasers are limited by mirror motion in the reference optical resonator used to stabilize the laser’s frequency. Recent proposals suggest that superradiant lasers based on narrow dipole-forbidden transitions in cold alkaline earth atoms could offer a way around this limitation. Such lasers operating on transitions with linewidth of order mHz are predicted to achieve output spectra orders of magnitude narrower than any currently existing laser. As a step towards this goal, we demonstrate and study a laser based on the 7.5-kHz linewidth dipole-forbidden ^{3}P_{1} to ^{1}S_{0} transition in laser-cooled and tightly confined ^{88}Sr. We can operate this laser in the bad-cavity or superradiant regime, where coherence is primarily stored in the atoms, or continuously tune to the more conventional good-cavity regime, where coherence is primarily stored in the light field. We show that the cold-atom gain medium can be repumped to achieve quasi-steady-state lasing. We also demonstrate up to an order of magnitude suppression in the sensitivity of laser frequency to changes in cavity length, verifying a key feature of the proposed narrow linewidth lasers.
|
|---|