Polarization‐Selective Metamaterial Absorber for Long‐ to Very Long‐Wavelength Infrared Broadband

ABSTRACT Metamaterial absorbers have received extensive research interest and sustained attention due to their excellent resonance characteristics, including ultrathinness, lightweight structure, and high light absorption. The broadband polarization‐sensitive metamaterial absorber based on surface plasmon polaritons has the advantages of high energy utilization efficiency and good stability, making it a potential substitute for traditional polarization devices. This study demonstrates the polarization‐selective absorption mechanism of Cu/Si/Ti three‐layer absorbers for long‐wavelength infrared light, achieving an extinction ratio of 14. Subsequently, a four‐structure composite‐material surface pattern design was proposed, which achieved an average extinction ratio of 9 in the range of 8–14 μm through various localized surface plasmon resonance coupling mechanisms. By further utilizing nested composite structures to extend the operating range to the very long‐wavelength range, an average extinction ratio of 17 was achieved in the range of 16–30 μm. This series of designs provides a new method for broadband polarization‐selective absorbers by adjusting the excitation conditions of localized surface plasmon resonance. The proposed absorber can be integrated into the focal plane of infrared detectors to achieve polarization‐sensitive infrared imaging, with enormous potential applications in military reconnaissance, environmental monitoring, biosensing, and other fields.