Fig. 5
From: Planar metasurface-based concentrators for solar energy harvest: from theory to engineering
(a) Conceptual depiction of the spectrum of solar irradiance, i.e., the power density of solar radiation as a function of wavelength. (b) Schematic of the aperiodic HCTA lens (left panel of b(I)), optical microscopy image of a fabricated HCTA lens (middle panel of b(I)), and SEM images (right panel of b(I)) of the Si posts that form the HCTA lens. b(II) Logarithmic scale electric energy density at the plane of focus. b(III) Measured plane of focus FWHM spot size, transmission, and focusing efficiency of the HCTA micro-lens as a function of focusing distance. (a) Reproduced with permission [18]. Copyright 2021, published by Springer Nature. (b) Reproduced with permission [175]. Copyright 2015, NPG