Eur. Phys. J. D 12, 241-253 (2000)
https://doi.org/10.1007/s100530070019

Bose-Einstein condensates in optical lattices: Spontaneous emission in the presence of photonic band gaps

¹ Fachbereich Physik der Universität Konstanz, Postfach 5560 M674, 78457 Konstanz, Germany
² Centre for Lasers and Applications, and Department of Physics, Macquarie University, Sydney, New South Wales 2109, Australia

Received: 27 March 2000
Published online: 15 November 2000

Abstract

An extended Bose-Einstein condensate (BEC) in an optical lattice provides a kind of periodic dielectric and causes band gaps to occur in the spectrum of light propagating through it. We examine the question whether these band gaps can modify the spontaneous emission rate of atoms excited from the BEC, and whether they can lead to a self-stabilization of the BEC against spontaneous emission. We find that self-stabilization is not possible for BECs with a density in the order of 10¹⁴ cm^-3. However, the corresponding non-Markovian behavior produces significant effects in the decay of excited atoms even for a homogeneous BEC interacting with a weak laser beam. These effects are caused by the occurrence of an avoided crossing in the photon (or rather polariton) spectrum. We also predict a new channel for spontaneous decay which arises from an interference between periodically excited atoms and periodic photon modes. This new channel should also occur in ordinary periodic dielectrics.