Superradiance
Surpassing Normal Quantum and Thermal Limits
Standard Laser: Photons act as flywheel
Phase of light is scrambled by
thermal mirror motion
Superradiant Laser: Atoms act as flywheel
Phase of atomic dipole is weakly affected by thermal mirror motion
“A steady-state superradiant laser with less than one intracavity photon” Nature 484, 78-81 (05 April 2012) pdf / abstract
Nature News & Views pdf / abstract
We recently demonstrated a superradiant or bad-cavity laser that operates with on average as few as 0.2 photons of light inside the cavity. In this laser, the atoms replace the photons as the flywheel for phase information. To observe continuous superradiance, one must follow the Goldilocks principle and repump the atoms “just right” so as to not destroy the quantum coherence stored in the atoms.
The measured linewidth is more than 10000x below the quantum Schawlow-Townes laser linewidth that normally applies to optical lasers. We also showed that our light source is much less sensitive (by >10000) to the cavity mirror positions. Thermal mirror fluctuations limit the most narrow lasers to ~0.1 to 1Hz linewidths, and this approach may sidestep this thermal jiggling and allow lasers with linewidths of 0.001 Hz or less. Such a laser would instantly improve the best atomic clocks, and would extend coherence lengths from earth-moon distances to earth-sun distances.
For more information for a general audience please watch the video above and read:
Some press coverage: