title: Superradiance on the millihertz linewidth strontium clock transition.
abstract: Laser frequency noise contributes a significant limitation to today's best atomic clocks. A proposed solution to this problem is to create a superradiant laser using an optical clock transition as its gain medium. This laser would act as an active atomic clock and would be highly immune to the fluctuations in reference cavity length that limit today's best lasers. We demonstrate and characterize superradiant emission from the millihertz linewidth clock transition in an ensemble of laser-cooled87Sr atoms trapped within a high-finesse optical cavity. We measure a collective enhancement of the emission rate into the cavity mode by a factor of more than 10,000 compared to independently radiating atoms. We also demonstrate a method for seeding superradiant emission and observe interference between two independent transitions lasing simultaneously. We use this interference to characterize the relative spectral properties of the two lasing subensembles.
authors.affiliation: JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO 80302, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Norcia
authors.affiliation: JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO 80302, USA.
authors.forename: Matthew N
authors.identifier: 0000-0002-6227-5603
authors.initials: MN
authors.lastname: Winchester
authors.affiliation: JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO 80302, USA.
authors.forename: Julia R K
authors.initials: JR
authors.lastname: Cline
authors.affiliation: JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO 80302, USA.
authors.forename: James K
authors.initials: JK
authors.lastname: Thompson
keywords: Superradiance; cavity QED; lattice clock; strontium