Wideband switchable unidirectional transmission in a photonic crystal with a periodically nonuniform pupil.

Wideband switchable diode-like transmission can be exhibited by an asymmetric dielectric photonic crystal, when the host medium is changed from air to a coherent atomic gas (CAG), a strongly dispersive medium. Significant modification of diffraction-enabled one-way transmission due to the CAG is possible in both frequency and incidence-angle domains in the short-wave infrared regime. In particular, new one-way and high-contrast passbands, which are as much as 1.0 THz in bandwidth, can appear at fixed incidence angle within a stop band of the CAG-free structure and tuned by varying the oscillator strength of the CAG. These passbands correspond to relatively small, either positive or negative, values of the dielectric susceptibility of the CAG.