Dynamically Tunable Coherent Perfect Absorption Based on Bound States in the Continuum in Borophene Metamaterials

A symmetry‐protected bound states in the continuum (BIC) mechanism based on borophene metamaterials, achieving broadband coherent perfect absorption (CPA) with dual‐band absorption peaks in the near‐infrared waveband, is proposed. Through coupled mode theory analysis incorporating near‐field and far‐field coupling effects, structural parameter optimization enables synchronized strong critical coupling states for both absorption bands. Benefiting from weak angular dispersion induced by the flat‐band characteristics of deep subwavelength periodic structures, the system demonstrates high stability in absorption efficiency and resonant wavelengths under wide‐angle incidence (within 60°). Under coherent beam excitation, the system not only achieves CPA states but also realizes absorption switching functionality via precise control of the inter‐beam phase difference. Notably, dynamic carrier density modulation significantly broadens the CPA operational bandwidth, effectively overcoming the narrowband limitations inherent to conventional CPA systems. This study establishes a novel theoretical framework and implementation strategy for advancing multifunctional tunable absorbers and all‐optically controlled devices.