Holographic realization of hexagonal two dimensional photonic crystal structures with elliptical geometry

Abstract

A complete investigation of holographic photonic crystal structures has been conducted. From both theoretical and experimental results, profiles of resultant patterns under different process conditions can be estimated and controlled. The use of antireflection layers is crucial for realizing submicron photonic crystals with good uniformity over a large area. We successfully realize submicron-scale photonic crystal templates on silicon substrates with an aspect ratio of 2.5 and good quality by a laser holography technique. The samples are highly uniform in an area of >2×2 cm2 and present good reproducibility. A lift-off process is performed to transfer inversed pillar patterns into a chromium hard mask for the following dry etching into silicon substrates. A single-step deep reactive ion etching with controlled mixture of Ar/SF6/C4F8 gases is used to directly transfer pillar patterns into silicon. Transferred patterns with a high aspect ratio and vertical sidewalls (no scalloping) are demonstrated over a large area.