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

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.