Dynamically adjustable and high-contrast asymmetric optical transmission based on bilateral compound metallic gratings

Abstract A dual-band asymmetric transmission (AT) device with high contrast ratio based on bilateral compound metallic gratings is proposed. The AT structure can be manufactured through connecting silver gratings on the outer surface and inner inverted T-shaped grating with an Ag film. Dual-band forward transmission arises from unidirectional surface plasmon polaritons (SPPs) excitation by the upper metallic grating when the modulated forward wave vector matches the wave vector of SPPs. The device can achieve a high transmittance of 0.67 and 0.82 with a contrast ratio of 0.997 and 0.99 at operation wavelengths 627 nm and 1238 nm, respectively. Since the SPPs coupling between two metallic structures can be used to suppress the forward transmission in specific frequency band, single-band AT function also can be realized. By adjusting those underlying parameters, the designed structure having AT capability at 624 nm and band-pass filter function at 1234 nm. The proposed structure is simple and feasible, and has great potential applications in the field of integrated optoelectronics.