Absorption Properties of Simply Fabricated All-Metal Mushroom Plasmonic Metamaterials Incorporating Tube-Shaped Posts for Multi-Color Uncooled Infrared Image Sensor Applications

Wavelength-selective infrared (IR) absorbers have attracted considerable interest due to their potential for a wide range of applications. In particular, they can be employed as advanced uncooled IR sensors that identify objects through their radiation spectra. Herein, we propose a mushroom plasmonic metamaterial absorber incorporating tube-shaped metal posts (MPMAT) for use in the long-wavelength IR (LWIR) region. The MPMAT design consists of a periodic array of thin metal micropatches connected to a thin metal plate via tube-shaped metal posts. Both the micropatches and posts can be constructed simultaneously as a result of the tube-shaped structure of the metal post structure; thus, the fabrication procedure is both simple and low cost. The absorption properties of these MPMATs were assessed both theoretically and experimentally, and the results of both investigations demonstrated that these devices exhibit suitable levels of LWIR absorption regardless of the specific tube-shaped structures employed. It was also found to be possible to tune the absorption wavelength by varying the micropatch width and the inner diameter of the tube-shaped metal posts, and to obtain absorbance values of over 90%. Focal plane array structures based on such MPMATs could potentially serve as high-performance, low-cost, multi-spectral uncooled IR image sensors.