Superradiant laser

A superradiant laser is a laser that does not rely on a large population of photons within the laser cavity to maintain coherence.[1][2]

Rather than relying on photons to store phase coherence, it relies on collective effects in an atomic medium to store coherence. Such a laser uses repumped Dicke superradiance (or superfluorescence) to sustain emission of light that can have a substantially narrower linewidth than a conventional laser.[3]