Dressed Atom Approach to Line Broadening

Abstract

When a two state atom is placed in an optical field whose frequency w is near the atom’s resonant frequency ω₀, the atom cycles rapidly between its ground and excited states (|g> and |e> respectively). It is often more convenient — both mathematically and physically — to describe this system in terms of the dressed states |w(t)> and |s(t)>, i.e.

$$|\psi >= {a_w}(t)|w(t) > + {a_s}(t)|s(t) > $$

(1)

where a_w and a_s are time independent in the absence of perturbations other than the oscillatory field. The fact that |w(t)> and |s(t)> are time dependent coherent superpositions of |g> and |e> is reflected in the notation.