Perfect sub-wavelength metamaterial fishnet-like film absorbers for THz applications

We present two designs of robust, easy to manufacture metamaterial-based films of sub-wavelength thickness capable of full absorption of the incident terahertz (THz) radiation at certain frequencies. Both designs can be either made polarization sensitive, or have 90deg rotation symmetry, which works equally well for waves of any polarization provided the incident angle is zero. All our designs work for a wide range of angles of incidence, and even if the films are optimized for normal incidence the absorption remains greater than 99% for angles up to ~35deg in the TE and ~65deg in the TM case. In the first design the maximum absorption frequency shifts considerably with angle, and in the second design the maximum absorption frequency remains almost the same at any angle. Theory, simulation data, and recent experimental results are all in a good agreement, and will be reported in the presentation. Having a low heat capacity these absorbers combined with thermo detectors can be utilized for precise frequency-selective detection of THz radiation.