All-dielectric, polarization-insensitive, high-performance optical diode operating at telecommunication dual wavelengths

Abstract An all-dielectric optical diode incorporating a two-dimensional (2D) supercell grating and a 2D subwavelength grating was numerically demonstrated for asymmetric optical transmission (AOT) at telecommunication dual wavelengths 1310 nm and 1550 nm. The C4 rotational symmetry of optical diode guaranteed independence of transmittance on the polarization states of incident light, and spatial symmetry breaking via an asymmetric dual-grating configuration enabled unidirectional light control. Employing Fourier modal method (FMM) and genetic algorithm (GA), the contrast ratios of designed optical diode at normal incidence from opposite directions reached 41.18 dB and 40.90 dB with corresponding transmittance differences of 92.64% and 93.57%, respectively. Such high performance is attributed to Fabry-Pérot (F-P) resonance and guided mode resonance (GMR). The bandwidths over 20 dB contrast ratio were also examined. A hollow dual-grating configuration with ease of fabrication on a complementary metal-oxide semiconductor (CMOS)-compatible platform was further discussed. The proposed optical diode created potential applications in optical communication, information processing, and sensing systems.