Fabrication of 3D high index photonic crystals by holographic lithography and their fidelity

摘要

In order to create three-dimensional (3D) photonic crystals (PCs) with large photonic bandgap properties (PBG), it is necessary to control the 3D fabrication with desired symmetry, high index contrast, and high structural stability. To rational design the 3D photonic structures fabricated by holographic lithography, we have conducted quantitative analysis to study structural distortion during each processing step and their impact to PBG. Because of the relatively low dielectric contrast between typical polymers and air, the directly patterned polymer structures are usually used as templates for backfilling of high-index materials, followed by removal of the polymer template to realize complete PBGs. Therefore, the fidelity of the final PCs is critically dependent on the thermal and mechanical robustness of the polymer templates, the deposition methods (e.g. dry chemical vapor deposition vs. wet chemistry), and the template removal procedure. Here, we address these challenges using different photoresist systems and deposition methods to create Si and titania 3D PCs.