Dual-band MWIR and broadband LWIR perfect absorber based on graphene and Ti rings embedded structure

This paper proposes a dual-band mid-wave infrared (MWIR: 3–$5\mu m$) and tunable broadband long-wave infrared (LWIR: 8–$14\mu m$) perfect absorber based on embedded Ti rings and graphene. The absorber consists of a graphene top layer, dielectric layers of Si₃N₄, Al₂O₃, and Si, with four Ti rings and a cross-shaped graphene pattern embedded in the Si layer, all supported by a Ti substrate. The numerical results indicate that two near-perfect absorption peaks at $\lambda$ ₁ = $3.23\mu m$ (99.80%) and $\lambda$ ₂ = $4.13\mu m$ (99.53%) within the MWIR range. Broadband absorption exceeding 90% is achieved across 6.67—$14.17\mu m$, with an average absorption of 96.3% over the LWIR window. The broadband performance originates from synergistic Fabry-Pérot(F-P) resonances in the multilayer dielectric stack and surface plasmon resonances (SPR) enabled by the Ti and graphene hybrid configuration, which endows the proposed structure with a broader bandwidth and superior absorption capability compared to previously reported designs. With advantages including broadband operation, high absorption, and high stability, the proposed absorber holds significant potential for infrared thermal imaging, infrared stealth and detection.