High-quality multiple-working-wavelength photonic crystal diodes based on the Fano resonance of nonlinear defects

All-optical photonic crystal diodes based on the Fano resonance of nonlinear defects are studied. The diodes can achieve nonreciprocal transmission ratios of 31.7 dB and 33.9 dB at working wavelengths of 1534.83 nm and 1536.02 nm, respectively. The function of two defects' coupling to the performance of unidirectional light transmission is also analyzed. When two Fano cavities are cascaded to form a two-branch-channel diode, unidirectional light propagation at 1536.88, 1538.76, 1612.80, and 1616.78 nm wavelengths is achieved along two opposite forward directions, and the nonreciprocal transmission ratios are 36.5, 30.3, 23.9, and 19.6 dB, respectively.