ABSTRACT
In this chapter, we present a powerful method of solving the Bloch
equations or the master equation of a driven system called the
dressed-atom model. The method is valid in situations where the
Rabi frequency of the applied driving field is much larger than
the spontaneous emission rate of the atom, . Under such conditions, one can make the secular approximation that consists of
dropping terms oscillating in time with frequencies 2 and higher.
These terms, if kept in the master equation, would make corrections
to the dynamics of the system of the order of /, and thus are
negligible. Although limited in the range of parameters for which it
can be used, the dressed-atommodel provides a physical insight into
the properties and dynamics of the system. Within this model, one
can explicitly calculate energy states and transition rates between
them in a relatively simple way. The knowledge of the energy states
and transition rates is for most of the problems enough to fully
understand the underlying physics. There are two mathematically
different approaches to the dressed-atommodel, but giving the same
results, depending on whether we treat the driving field classically
or quantum mechanically. These are the semiclassical and quantum
dress-atom models. In the following we explain in details these two
dressed-atommodels.
