Abstract

In previous works [1,2] we have analysed with a three-beam heterodyne interferometer the response of a caesium atomic beam under the action two laser beams of orthogonal polarisations driving and probing two different degenerate two-level transitions, thus inducing on the system either electromagnetically induced transparency (EIT) or electromagnetically induced absorption (EIA). The joint effect of using copropagating laser beams and an orthogonally propagating atomic beam was crucial to dramatically reduce the Doppler broadening of the measured signals. In this way it was possible to measure absorption and dispersion signals for either the probe or the coupling laser with linewidths of the order of 20 kHz. These measurements confirmed the theoretical interpretation for the emergence of EIA in a degenerate two-level systems: spontaneous transfer of coherence.

© 2007 IEEE