Multifunctional Metamirrors for Broadband Focused Vector-Beam Generation

Reducing a set of bulk optics-based components to a single ultrathin and compact element that enables the same complex functionality has become an emerging research area, propelling further miniaturization and integration in photonics. In this work, it is designed and experimentally demonstrated a multifunctional metamirror for focused vector-beams generation in the near-infrared range using gap-surface plasmon meta-atoms that enable efficient linear-polarization conversion along with the complete phase control over reflected fields, reproducing thereby the combined functionalities of conventional parabolic reflectors and spatial light modulators. The proof-of-concept fabricated metamirror exhibits the excellent capability of radial- and azimuthal-polarization conversion (approximate to 78% and approximate to 75% on average) and focusing (average efficiency of approximate to 35% and approximate to 34%) within the wavelength range of 800-950 nm under x- and y-excitation, respectively. It is further shown that this approach can be extended to realize multifocal metamirrors with distinctly engineered wavefronts focused at different locations in the same focal plane. The multifunctional metamirror design developed in this study opens new avenues in the advanced research and applications targeting photonics integration of diversified functionalities.