Zeeman-coherence-induced transparency and gain without inversion in laser-cooled rubidium

We report experiments demonstrating the effects of optical pumping, coherent population trapping and light polarisation on electromagnetically induced transparency in simple h-type configurations of rubidium 87 where the relevant coherences are within the three Zeeman substates of the F = 1 component of the 5S(1/2) ground level. Inversionless gain is also demonstrated. The sample is cooled to below 1 mK in a magneto-optic trap operating without repumping light to give a working population of F = 1 ground state atoms. The experimental results are compared with master equation computations of a closed seven-substate-model representing the ground level (F = 1) and the excited levels F' = 0 and F' = 1. (C) 1998 Elsevier Science B.V. All rights reserved.