  Metasurface based super absorbers exhibit near unity absorbance. While the
absorption peak can be tuned by the geometry/size of the sub-wavelength
resonator, broadband absorption can be obtained by placing multiple resonators
of various size or shapes in a unit cell. Metal dispersion hinders high
performance broadband absorption at optical frequencies and careful designing
is essential to achieve good structures. We propose a novel analytical
framework for designing a broadband super absorber which is much faster than
the time consuming full wave simulations that are employed so far. Analytical
expressions are derived for the wavelength dependency of the design parameters,
which are then used in the optimization of broadband absorption. Numerical
simulations report an average polarization-independent absorption of ~97 in the
450 to 950 nm spectral region with a near unity absorption (99.36) in the 500
to 850 nm region. Experimentally, we demonstrate an average absorption over 98
in the 450 to 950 nm spectral region at 20 degree incident angle The designed
super absorber is polarization insensitive and has a weak launch angle
dependency. The proposed framework simplifies the design process and provides a
quicker optimal solution for high performance broadband super absorbers.
