Absorption Of Light In Arrays Research Articles

Polarization-Induced Tunability of Plasmonic Light Absorption in Arrays of Sub-Wavelength Elliptical Disks

Polarization-independent plasmonic light absorbers have been widely investigated in the past decades. Nevertheless, the feasibility for artificial manipulation of the optical properties by controlling the polarization state is desirable for numerous applications including the coloring, displaying, filtering, etc. Here, we present a straightforward method to achieve tunable multiple narrowband light absorption by using the polarization-dependent plasmonic cavity resonances in a common metal-dielectric-metal structure consisting of an elliptical disk array. Multiple light absorption bands with the maximal absorption of 98 % are achieved. Moreover, by controlling the illumination polarization state, artificial spectral modulation depth of these light absorption bands can be up to 90 % based on this structure platform. In addition, since this multispectral polarization-manipulated absorber is realized in such a common sub-wavelength plasmonic structure, it will open up a simple and universal approach for multispectral nanophotonic devices including the high-compact polychromatic color filtering, imaging, and detecting.

Strong Geometrical Dependence of the Absorption of Light in Arrays of Semiconductor Nanowires

We demonstrate experimentally that arrays of base-tapered InP nanowires on top of an InP substrate form a broad band and omnidirectional absorbing medium. These characteristics are due to the specific geometry of the nanowires. Almost perfect absorption of light (higher than 97%) occurs in the system. We describe the strong optical absorption by finite-difference time-domain simulations and present the first study of the influence of the geometry of the nanowires on the enhancement of the optical absorption by arrays. Cylindrical nanowires present the highest absorption normalized to the volume fraction of the semiconductor. The absolute absorption in layers of conical nanowires is higher than that in cylindrical nanowires but requires a larger volume fraction of semiconducting material. Base-tapered nanowires, with a cylindrical top and a conical base, represent an intermediate geometry. These results set the basis for an optimized optical design of nanowire solar cells.