Polarization- and angle-insensitive ultrabroadband perfect metamaterial absorber for thermophotovoltaics
Ashish Kumar Chowdhary, Tanmay Bhowmik, Debabrata Sikdar
Abstract
We report an ultrabroadband perfect metamaterial absorber, comprising a two-dimensional array of a hemi-ellipsoid shaped metallo-dielectric multilayered structure. What we believe, to the best of our knowledge, is an unprecedented average absorbance of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mn>99</mml:mn> <mml:mi mathvariant="normal">%</mml:mi> </mml:math> is theoretically demonstrated in the 300 to 4500 nm spectral range at normal incidence. We use 20 pairs of molybdenum–germanium metallo-dielectric layers with tungsten as the ground metal placed on a silicon substrate. Our design is polarization-independent as well as angle-insensitive (up to 60°), making it a perfect “superabsorber.” Theoretical modeling based on effective medium theory validates our full-wave simulation results. The figure-of-merit calculations suggest that our superabsorber can outperform recently reported broadband absorbers. The proposed design has potential application in thermophotovoltaics for solar energy harvesting.