title: Gain narrowing in few-atom systems.
abstract: Using a density matrix approach, we study the simplest systems that display both gain and feedback: clusters of 2 to 5 atoms, one of which is pumped. The other atoms supply feedback through multiple scattering of light. We show that, if the atoms are in each other's near field, the system exhibits large gain narrowing and spectral mode redistribution. The observed phenomena are more pronounced if the feedback is enhanced. Our system is to our knowledge the simplest exactly solvable microscopic system which shows the approach to laser oscillation.
authors.affiliation: FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ, Amsterdam, The Netherlands. t.savels@amolf.nl
authors.forename: Tom
authors.initials: T
authors.lastname: Savels
authors.forename: Allard P
authors.initials: AP
authors.lastname: Mosk
authors.forename: Ad
authors.initials: A
authors.lastname: Lagendijk