Cavity Induced Transparency

Perry Rice and Robert Brecha (U. Dayton) - Optics Communications 126, 230 (1996)

We consider a two-level atom inside a cavity. We find that the
absorption spectrum of the atom may exhibit a hole at line center for a weak
probe. This hole appears when the cavity linewidth is small compared to the atom-field
coupling strength, which is itself smaller than the atom's free space linewidth.
In the weak-field limit, this system is analogous to a three-level atom, where
similar absorption holes at line center occur due to electromagnetically induced
transparency (EIT). In EIT, a strong field is required to strongly mix the upper
two levels, whereas in the system we consider, it is the atom-field coupling
strength that plays this role. An alternate explanation in terms of interference
between the cavity field and atomic polarization is given. We also examine the
driven cavity case.