Broadband long-wavelength infrared (LWIR) optical absorbers have important applications in thermal emission and imaging, infrared camouflaging, and waste heat and biothermal energy utilization. However, the practical application of broadband LWIR optical absorbers requires low-cost and facile fabrication of large-area structures with limited thickness. This paper reports the design and fabrication of an ultrathin, broadband, omnidirectional, and polarization-independent LWIR optical absorber composed of anodized aluminum oxide and highly doped Si using the gradient refractive index strategy. The average absorption of the broadband optical absorber is higher than 95% in the 8–15 μm wavelength range, and it has wide incident angle and polarization tolerances. More than 95% of the optical energy in the wavelength range from 8 to 13 μm was absorbed within a depth of 8 μm, making this absorber the thinnest broadband LWIR dielectric absorber so far. The absorption remained above 90% after annealing at 800 °C in air. The infrared camouflage of the proposed absorber was successfully demonstrated with a human body background. With the advantages of facile fabrication, low-cost materials, restricted absorption thickness, and excellent thermal stability, the developed broadband LWIR optical absorber is very promising for the practical applications mentioned above.

中文翻译：

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使用全介电耐火材料的超薄，宽带，全向和偏振无关的红外吸收剂

宽带长波红外（LWIR）光学吸收器在热发射和成像，红外伪装以及废热和生物热能利用中具有重要的应用。然而，宽带LWIR光吸收器的实际应用需要低成本且容易地制造厚度受限的大面积结构。本文报道了使用梯度折射率策略设计和制造的超薄，宽带，全向和偏振无关的LWIR光吸收器，该光吸收器由阳极氧化铝和高掺杂Si组成。宽带光吸收器在8-15μm波长范围内的平均吸收率高于95％，并且具有宽入射角和偏振容差。在8到13微米的波长范围内，超过95％的光能在8到13微米的波长范围内被吸收，这使该吸收器成为迄今为止最薄的宽带LWIR电介质吸收器。在空气中800°C退火后，吸收率保持在90％以上。所提出的吸收体的红外伪装已成功地以人体为背景进行了演示。凭借制造容易，成本低廉的材料，吸收厚度受限制以及出色的热稳定性等优势，开发的宽带LWIR光吸收器对于上述实际应用非常有前途。所提出的吸收体的红外伪装已成功地以人体为背景进行了演示。凭借制造容易，成本低廉的材料，吸收厚度受限制以及出色的热稳定性等优势，开发的宽带LWIR光吸收器对于上述实际应用非常有前途。所提出的吸收体的红外伪装已成功地以人体为背景进行了演示。凭借制造容易，成本低廉的材料，吸收厚度受限制以及出色的热稳定性等优势，开发的宽带LWIR光吸收器对于上述实际应用非常有前途。