Laser fabrication of perfect absorbers

摘要

We describe design and characterization of electromagnetic metasurfaces consisting of sub-wavelength layers of artificially structured 3D metallic elements arranged into two-dimensional arrays. Such metasurfaces allow novel ways to control propagation, absorption, emission, and polarization state of electromagnetic waves, but their practical realization using traditional planar micro-ano-fabrication techniques is extremely difficult at infrared frequencies, where unit, cell size must be reduced to few micrometers. We have addressed this challenge by using femtosecond direct laser write (DLW) technique as a high-resolution patterning tool for the fabrication of dielectric templates, followed by a simple metallization process. Functional metasurfaces consisting of metallic helices and vertical split-ring resonators that can be used as perfect absorbers and polarization converters at infrared frequencies were obtained and characterized experimentally and theoretically. In the future they may find applications in narrow-band infra-red detectors and emitters, spectral filters, and combined into multi-functional, multi-layered structures.