Theoretical analysis of composite nanostructure with three-dimensional photonic lattice for ultra-broadband and polarization-independent absorption

In this study, we present a composite nanopillar array with an average absorption efficiency near 100% in an ultra-broad wavelength range from 300 nm to 2000 nm. In particular, the average absorption in the band range from 400 nm to 1000 nm is close to 99% due to the strong coupling between the composite nanopillars and a complementary absorption generated by the two kinds of nanopillars in one period. The real and imaginary parts of the absorber’s impedance present a fluctuation near 1 and 0 in the entire wavelength range, which indicates an ultra-weak reflection of the absorber. The device also shows insensitivity to the polarization state and angle of incidence. The research offers a novel strategy for achieving high-efficiency light absorption in an ultra-broad wavelength range and boosts the potential value of composite nanostructures for thermophotovoltaic cells, electromagnetic stealth, and stray light suppression. •Propose an ultra-broadband absorption structure based on a three-dimensional photonic lattice.•Absorption complementation of composite nanostructure.•The analysis method in this paper provides new strategies and ideas for future R&D.