Wafer-scale self-assembled 2.5D metasurface for efficient near-field and far-field electromagnetic manipulation

Although current 2D metasurfaces have emerged as a paradigm platform for electromagnetic (EM) manipulation with enhanced and flexible functions over conventional optical components, their performance is intrinsically limited by constrained interaction with the EM waves due to reduced dimensions. Besides, fabrication of 2D metasurfaces over large areas remains complex and high cost especially in the visible spectrum, further limiting their practical applications. Here, a kind of metal-insulator-metal (MIM) 2.5D metasurfaces is proposed with enriched EM manipulation capabilities in both near-field and far-field compared with their planar counterparts. Moreover, wafer-scale fabrication with high uniformity is also realized by a lithography-free method. As a proof of concept, we experimentally demonstrate three kinds of centimeter-scale metadevices achieving broadband EM absorption (average absorption over 91% within 400-1200 nm), structural color display (coverage of the primary colors red, green and blue (RGB)) and surface-enhanced Raman scattering (largest enhancement factor of 3.29 x 10(7) and relative standard deviation less than 9%), respectively. It is envisioned that the proposed 2.5D metasurfaces may empower many potential applications in EM absorption, sensing and optical displays.