Optimization of Broadband Perfect Absorber by Weierstrass Factorization

We present a new method based on Weierstrass factorization to optimize broadband perfect absorber (BPA) made of metal-dielectric-metal elements, which is an efficient and general approximation to calculate the absorption of these subwavelength structures. With the resonant wavelengths estimated by semi-analytical equations, we design a planar BPA tiling three subunits in one unit cell and a vertical tapered BPA stacking 20 pairs of metal-dielectric layers in one unit cell. Both BPAs shows almost over 90% and wide angle absorption in the concerned range. This method can be an alternative to the traditional full vector methods in initial design.