Design and Fabrication of 1-D, 2-D Photonic Crystals and Metasurface Based Perfect Light Absorbers

Perfect light absorbers are devices which absorb all the light that is incident up on it at a particular frequency. Perfect light absorbers find applications in designing efficient solar absobers, thermophotovoltaic energy conversion systems and stealth technologies. Two methods to realize prefect light absorbers are investigated in this thesis; one using 2-D metallic photonic crystals and using metasurface based absorbers. Photonic crystals have periodic variation of dielectric constant at a subwavelength scale of the light. These periodic variation of dielectric constant lead to the formation of photonic band gaps in these materials. The two dimensional metallic photonic crystal consist of square array of cylindrical cavities on a tantalum metal surface. These cavities on the metal surface couple to the incident electromagnetic radiation and lead to enhanced absorption. The effect of design parameters namely choice of metal, radius, depth and period of the cylinders on the absorption of light is studied and then an optimum design providing peak emissivity at 3.5 µm is arrived at and fabricated. Metasurface based aborbers on the other hand are composite materials with artifical permeability and permitivity. A qualitative picture for creating the artificial permitivity and permeability formation in this material is given in this thesis, with a contrast to the atomic scale resonance to explain the optical properties of these materials. We show how by controlling the design of the electric ring resonator and split ring resonators we can create perfect light absorption in these metasurface absorbers. We then discuss the equivalence of the complimentary electric ring resonators