Coherent Controlling Single Photon Asymmetric Transmission in the Atom Chirally Coupled Waveguide System

We theoretically investigate the influences of two coherent driving fields on the asymmetric transmission of single photon in the atom-waveguide system. The atom is considered as a Λ system. One transition of the atom chirally couples to the waveguide. The other transition is driven by two coherent driving fields. The transmission probabilities for the single photon incidents from the left (T_lr) and right (T_rl) are given respectively. The calculated results show that one can realize T_lr = 0 (T_rl ≠ 0) or T_rl = 0 (T_lr ≠ 0) by manipulating the phase difference between the two coherent driving fields. The influence of the decay rate of the metastable state on the asymmetric transmission is also discussed. (paper)