Study on the super transmission in a typical dielectric structure

Abstract

Reflection is a natural phenomenon that occurs when light passes the interface between materials with different refractive index. In many applications, such as solar cells, introduction of a substrate will result in an increase in reflection. There are many ways to reduce the reflection from a substrate, which have been investigated so far, including dielectric interference coatings, surface texturing, adiabatic index matching, and scattering from plasmonic nanoparticles etc. Here we present an entirely new concept to eliminate reflection from a silicon wafer, which makes use of much simpler method than the ones reported before, and can be applied to any high-index material. Finite-difference-time-domain (FDTD) method and auxiliary differential equations are used in this paper to simulate a new structure that can suppress the reflection of light from a silicon surface over a broad spectral range. A two-dimensional periodic array of subwavelength silicon nanocylinders is designed, which possesses a phenomenon strongly substrate-coupled to the Mie resonances, and which can produce an extraordinary transmission phenomenon similar to the metal surface plasmon that yields almost zero total reflectance over the entire spectral range from ultraviolet to near-infrared. This new antireflection concept relies on the strong forward scattering that occurs when a scattering structure is placed in close proximity to a high-index substrate with a high optical density of states. For a detailed description of the problem, we have carried out some simulations. From the results, one can see that although nano-pillar covers only 30% of the substrate surface area, it can reduce the reflection from the surface from 30% to under 10% at the Mie resonance. For the purpose of reducing reflection from the substrate, this new structure designed may provide a reference for the actual solar cells and optical antenna design.