AlCu Alloyed Thin Films for Perfect Absorbers in a Planar Bilayer Configuration

Metamaterials and metasurfaces present new opportunities for manipulating the optical response at the nanoscale. For instance, single-, double-, and broad-band perfect absorbers have been implemented with a careful design of its subwavelength building blocks. However, the methods of fabrication required are not readily accessible. As an alternative to achieve such optical behavior, we have tuned the optical response of metallic thin films by alloying Al and Cu. In this work, we show that a single-band, omnidirectional, near-unity absorption (> 99%) is obtained for a system composed of Si and AlCu. Moreover, depending on the thickness of the semiconductor layer the absorption can be adjusted at a selected wavelength ranging from the NIR to visible. Additionally, we obtained a dual-band perfect absorber with both peaks presenting absorption > 98%. The results reported here can herald for the design of next-generation electro-optical devices, such as photodetectors, bolometers, and optical filters.