Liu and his colleagues present a scheme for realizing a narrow-dual-band perfect absorber based on the plasmonic analogy of the electromagnetically induced reflection (EIR)-like effect. In their scheme, two short gold bars are excited strongly by incident plane wave serving as the bright mode. The middle gold bar is excited by two short gold bars. Due to the strong hybridization between the two short gold bars and the middle gold bar, two absorption peaks occur. The corresponding absorption rates are both over 99%. The quality factors of the two absorption peaks are 41.76 (198.47 THz) and 71.42 (207.79 THz), respectively, and the narrow-distance of the two absorption peaks is 9.32 THz. Therefore, they are narrow enough for the absorber to be a filter and a dual-band plasmonic sensor.
The phenomenon of plasmon-induced transparency (PIT) is realized a in surface plasmon polariton waveguide at near-infrared frequencies. The right-angled slot and rectangle cavity placed inside one of the metallic claddings are respectively utilized to obtain bright and dark modes in a typical bright-dark mode waveguide. A PIT transmission spectrum of the waveguide is generated due to the destructive interference between the bright and dark modes, and the induced transparency peak can be manipulated by adjusting the size of the bright and dark resonators and the coupling distance between them. Subsequently, spectral splitting based on the PIT structure is studied numerically and analytically. Simulation
results indicate that double electromagnetically induced transparency (EIT)-like peaks emerge in the broadband transmission spectrum by adding another rectangle cavity, and the corresponding physical mechanism is presented. Yu and his colleagues’ novel plasmonic structure and the findings pave the way for new design and engineering of highly integrated optical circuit such as nanoscale optical switching, nanosensor, and wavelength-selecting nanostructure.