Narrow bandwidth perfect absorber based on composite hybrid plasmonics

Abstract

Surface plasmon polaritons (SPPs) have shown unprecedented potential for miniaturizing photonic devices beyond the optical diffraction limit. However, their high intrinsic loss from metal material has been a major barrier to practical applications. One effective approach to reducing their effective loss is to engineer SPPs coupling by designing hybrid plasmonic waveguides (HPWs). In this work, we first theoretically calculate and analyze the coupling modes in a composite HPW (CHPW), demonstrating that the long-range and short-range supermodes in CHPW correspond to two different SPPs at two metal layer interfaces. Next, we propose and demonstrate a narrow bandwidth perfect absorber based on CHPW structure. The absorber’s bandwidth is only 12.9 nm in the visible range and 6.67 nm in the near-infrared range. Our simulation results demonstrate that the CHPW’s SPPs coupling mechanism can be extended to localized surface plasmons (LSPs) in the proposed perfect absorber, enabling a low-loss mode that contributes to the narrow bandwidth. This suggests that the CHPW configuration could facilitate the development of more advanced low-loss, high-performance plasmonic devices.