Light absorption and nanofocusing on a tapered magnetic metasurface

A type of metasurface was constructed on a silicon wafer using a nanopatterned magnetic film to achieve ideal light absorption within a wide wavelength range of 3 μm–15 μm. Using the metasurface, the surface electrons could be localized efficiently into an arrayed planar magnetic nanotip and then modulated by configuring the surface architecture to produce remarkable infrared reflectivity variation. A theoretical analysis showed that the excited surface plasmon exhibit stronger electric field components at the common metal-to-air interface. The Tb14Fe68Co18 nanotip array provided more powerful nanofocusing and a lower infrared reflectivity than an array shaped on a traditional aluminum film. By adjusting the structural parameters of the nanorhombus array formed on the TbCo film system, the convergent light spot could be modulated to improve light absorption markedly.