Enhanced Band Gap and Defect Structure of Low Dielectric Photonic Crystals Using ALD Coatings

We propose a method for enhancing the photonic band gap and maximizing the gap to mid-gap ratio of photonic crystals fabricated on low dielectric substrates. By depositing materials of higher dielectric constants around the air holes of two dimensional photonic crystals TE band gap can be increased, and the gap position can be shifted to lower frequencies. Two examples using TiO2 interfacial layers in AAO and SiO2 substrates are presented. In the case of AAO/TiO2 the gap to mid-gap ratio can be increased from 10.4 % to 25.2 % whereas SiO2/TiO2 structure has a larger enhancement, from 1.9 % to 23.4%. It is also demonstrated that in SiO2/TiO2 structure defect states can be brought into the band gap by introducing a single defect