Metamaterial Superabsorbers

Plasmonic metamaterials can be utilized to match the impedance of environment (air) to the substrate (semiconductor material) in the optical range (or acmally any other range) directly by optimizing their particles design. Thus one can obtain perfect black surfaces denoted as superabsorbers [229, 230]. Such nanostructured surfaces are able to absorb light in a wide bandwidth regardless of its polarization and for literally any incident angle. 

Basically, all superabsorbers proposed until now were metal-dielectric-metal sandwiches where the top metal layer of the sandwich is nanostructured to obtain a desired wave impedance. 

Another stmcture represents ID trapezoidal or crossed 2D arrays (Fig. 2.32). The basic form of this super absorber is again metal-dielectric-metal [232]. 

As far as photodetectors are concerned, superabsorber stmctures were described within the context of photovoltaic solar ceU enhancement [232]. However, other wavelength ranges can be covered by changing the dimensions of the elements of the superabsorber. 

Technologically, the metal-dielectric-metal sheet with satisfactory properties can be fabricated utilizing conventional radioffequent sputtering. Nanostmcturing of the 

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