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spatial profi le. Gradient metasurfaces provide a much richer control of the wave-front in both local amplitude and phase of the emerging transmitted and refl ected beams. [ 4–7 ] Such structures enable fl at optical components for beam focusing, polarization control and phase correction, to name a few examples. [ 4–9 ] The next challenge and exciting(More)
We present here a broadband, wide-angle, and polarization-independent nearly perfect absorber consisting of mirror-backed nanoporous alumina. By electrochemically anodizing the disordered multicomponent aluminum and properly tailoring the thickness and air-filling fraction of nanoporous alumina, according to the Maxwell-Garnet mixture theory, a large-area(More)
We put forward the quantum screening effect in field emission [FE] nanodiodes, explaining relatively low field enhancement factors due to the increased potential barrier that impedes the electron Fowler-Nordheim tunneling, which is usually observed in nanoscale FE experiments. We illustratively show this effect from the energy band diagram and(More)
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