Two-photon linewidth of light “stopping” via electromagnetically induced transparency

We analyze the two-photon linewidth of a recently proposed adiabatic transfer technique for ``stopping'' of light using electromagnetically induced transparency (EIT). We show that a successful and reliable transfer of excitation from light to atoms and back can be achieved if the spectrum of the input probe pulse lies within the initial transparency window of EIT, and the two-photon detuning δ is less than the collective coupling strength (collective vacuum Rabi frequency) g√N divided by √γT, with {γ} being the radiative decay rate, N being the effective number of atoms in the sample, and T being the pulse duration. Hence in an optically thick medium light ``storage'' and retrieval is possible with high fidelity even for systems with rather large two-photon detuning or inhomogeneous broadening.