Abstract

The ability to render a medium transparent to a resonant laser field opens a wide range of applications, from slow light and dark state polariton physics to light-matter interfaces. In atomic vapours at room temperature, Doppler broadening plays, in general, a negative role tending to reduce transparency. In a two-level (2L) system Doppler-free transparency can be achieved by means of self-induced transparency (SIT) (Fig. 1(a,d)), which consists in preparing an optical pulse propagating in the medium such that an integer number of Rabi oscillations are performed [1]. Therefore, SIT requires a very precise temporal control of the Rabi frequency, i.e. the pulse area being an integer multiple of 2π. In three- (3L) and/or multi- level atomic systems, resonant transparency could be achieved by using induced atomic coherences, e.g., by means of the coherent population trapping (CPT) [2] and the electromagnetically induced transparency (EIT) phenomena [3] or via a double-STIRAP process [4]. In all these cases, the required two-photon (or Raman) resonance condition severely restricts the applications of the previous approaches to laser fields with nearly identical frequencies.

© 2009 IEEE