
Coherent Interactions with Two-Level Systems 225
If the source is an atom, spherical waves are emitted with identical fluctuations
at all points at equal distance from the source. Macroscopically, we are used to
looking at a volume average of randomly distributed dipoles. Some new sources
have the emitted dipoles arranged in a regular fashion. For instance, multiple
quantum well lasers are made of “sheets” of emitting atoms which are thinner
than the wavelength of the light. This particular arrangement of emitters has
important implications for the macroscopic properties of the source [5, 6].
4.2. COHERENT INTERACTIONS WITH
TWO-LEVEL SYSTEMS
4.2.1. Maxwell–Bloch ...