Comment on “Large enhancement of four-wave mixing by suppression of photon absorption from electromagnetically induced trasparancy

In this Comment we deal with a recent study of Ying Wu et al. Phys. Rev. A 67, 013811 2003 on a four-wave mixing process. We show that the authors’ claim, that a large enhancement of the generation efficiency can be obtained by suppression of photon absorption from electromagnetically induced transparency, is not correct.