Cavity electromagnetically induced transparency of driven-three-level atoms: A transparent window narrowing below a natural width - art. no. 023811

Steady-state dynamics of a Lambda atom in a ring cavity driven by two coher ent fields are studied for arbitrary detunings, arbitrary incoherent pumpin g, and coherent driving intensities. Effects of both cavity and effective a tom number on electromagnetically induced transparency (EIT) are pointed ou t. New physical pictures for cavity EIT are given in terms of collective co operative coefficients and dispersion experienced by the probe. In the regi me of smaller collective cooperative coefficients, an absorption-gain profi le is reduced to that of a general EIT estimated by the imaginary part of a corresponding dipole moment, and its transparency window is directly propo rtional to power broadening, if the total Rabi frequency is large enough. B ut in the region of larger collective cooperative coefficients which means a dense atomic medium, longer optical path, or high-Q cavity, EIT is determ ined not only by the imaginary part but also by the real part of the corres ponding dipole moment, which results in the possibility of observing an EIT central peak with a subnatural width, while there may be nearly no power b roadening.