where Ω Ω p and Ω Ω c are the Rabi frequencies of the probe field (of frequency ω ω p ) and the coupling field (of frequency ω ω c ) in resonance with the transition frequencies ω ω 1 − − ω ω 3 and ω ω 2 − − ω ω 3 , respectively, and H.c. stands for the Hermitian conjugate of the entire expression. We will write the atomic wave function as