Design, theory, and measurement of a polarization insensitive absorber   for terahertz imaging
  We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. We derive geometrical-independent conditions for effective medium absorbers in general, and for resonant metamaterials specically. Our fabricated design reaches and absorptivity of 78% at 1.145 Thz 
N. I. Landy, C. M. Bingham, T. Tyler, N. Jokerst, D. R. Smith, and W.   J. Padilla