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); and 2) creation of localised structural defects embedded in, and in registration with, a 3D photonic crystal by direct two-photon laser writing, 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