Broadband photonic crystal antireflection

Abstract

Broadband antireflection layers have been fabricated by two dimensional (2D) photonic crystals (PCs) with tapered pillars on the Si substrate. These PCs have been produced by interference lithography and reactive ion etching (RIE) techniques. The effect of depth and the filling factor (FF) of the PCs on the reflectance magnitude and bandwidth has been investigated. The obtained reflectance was less than 1% in the broad spectral range from 400 to 2100 nm. Our numerical simulation shows the PC pillars slope has an essential effect in the reduction of the reflection. However, our results show that the existence of RIE grasses in the PCs, which are created in the RIE process, does not influence the performance of the antireflection layer. This leads to a simpler fabrication process.