InP-based planar photonic crystals infiltrated with solid polymers and liquid crystals

The filling is reported of the air holes of an InP-based two-dimensional photonic crystal with solid polymer and withliquid crystal 5CB. The polymer filling is obtained by thermal polymerization of an infiltrated liquid monomer,trimethylolpropane triacrylate. The filling procedure for both the monomer and liquid crystal relies on the capillaryaction of the liquid inside the ~ 200 nm diameter and > 2.5 ?m deep air holes. The solid polymer infiltration result wasdirectly inspected by cross-sectional scanning electron microscopy. It was observed that the holes are fully filled to thebottom. The photonic crystals were optically characterized by transmission measurements around the 1.5 ?mwavelength band both before and after infiltration. The observed high-frequency band edge shifts are consistent withclose to 100% filling, for both the polymer and the liquid crystal. No differences were observed for filling under vacuum or ambient, indicating that the air diffuses efficiently through the liquid infiltrates, in agreement with estimates based on the capillary pressure rise.