All-Optical Diode Suppressing Broadband Backward Transmission Using Single- and Four-Port Photonic Crystal Cavities

We present an all-optical diode suppressing broadband backward transmission using single-port and four-port photonic crystal (PC) cavities and its operation principle. We find that, by combining a four-port PC cavity and two power-dependent phase shifters that are composed by a 3-dB power divider and two single-port PC cavities, the backward transmission in the nonlinear-resonator-based all-optical diode becomes theoretically 0% for any input power and any input wavelength. To confirm the validity of our approach, the numerical analysis based on the nonlinear beam propagation method as well as the coupled mode theory is performed. The results prove that the forward transmission of -4 dB and large nonreciprocal transmission ratio of 35 dB are achievable.