Device Fabrication in High-Index 3D Photonic Crystals

Holographic lithography (HL) is a flexible technique for the fabrication of three-dimensional (3D) photonic crystals with the submicron periodicity required for optical and near-IR applications. We demonstrate two key steps towards the creation of integrated optical devices based on waveguides and microcavities operating within a complete photonic band gap: 1) infiltration of a holographically-defined polymeric 3D photonic crystal template with high-index dielectric by Atomic Layer Deposition (ALD) [1]; and 2) creation of localised structural defects embedded in, and in registration with, a 3D photonic crystal by direct two-photon laser writing [2]. Structural and optical characterisation of TiO2 photonic crystals produced by infiltration and removal of the polymer template demonstrates the high quality of the negative replica. Structural characterisation of photonic crystals with embedded defects shows a faithful rendering of the designed structure in the developed polymer photonic crystal. The combination of these three techniques (HL, two-photon writing and ALD) maps out a clear route to device fabrication in high-index 3D photonic crystals.