We introduce diffraction-theory-inspired analytic description of the metasurface comprising an array of graphene subwavelength hemispheres. Our theory describes light interaction with the random metasurface, in which the periodicity is broken by accidentally damaged meta-atoms in the nodes of a two-dimensional periodic lattice. Both numerical modeling and experiment show that such a nm-thin metasurface possesses giant broadband absorption in the THz spectral range that remains intact even when a substantial portion of meta-atoms, i.e. graphene hemispheres, is damaged. Moreover, defective fabrication of graphene free-standing metasurface may enhance the absorptive properties.
By spin‐coating a few hundred of nanometer thick poly(methyl methacrylate) (PMMA) film on a micron or a sub‐micron scale structure, the structure can be transferred on an arbitrary substrate. More precisely, by using a thin PMMA support layer and releasing the structure from the transient substrate into water, the PMMA with the structure can be collected on a desired substrate. Here, this technique is demonstrated to be suitable for transferring metallic binary grating and few‐layer Bragg gratings from flat substrates onto 3D‐printed convex lenses. Moreover, the thin PMMA film is sufficiently strong to support centimeter size free‐standing areas. This enables fabrication of 1.5 μm thick, free‐standing structure of a Bragg‐grating with PMMA. Thus, the presented technique provides a powerful tool for transfer printing of micron scale structures.
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