Multi-channel all-optical switching based on coherent perfect absorption in atom-cavity system

We propose a high-efficiency, broadband, multi-channel all-optical switching scheme based on broadband coherent perfect absorption (CPA) in linear and nonlinear regimes in cavity quantum electrodynamics (CQED) system. Two signal fields coupled from two ends of an optical cavity excite two separate atomic transitions simultaneously under the collective strong coupling condition and produce three polariton eigenstates which can be tuned freely by varying system parameters. The output field intensities of multiple channels are zero when the CPA criterion is satisfied. However, destructive quantum interference can be induced by a free-space weak control laser tuned to the multi-polariton excitations. As a consequence, the CQED system acts as a perfect light absorber/reflector as the control field is turned on/off the polariton resonances. In particular, the proposed scheme may be used to realize broadband multi-throw all-optical switching in the nonlinear excitation regime. The proposed scheme is useful for constructing all-optical routing, all-optical communication networks and various quantum logic elements.