Batch process for the fabrication of LiNbO3 photonic crystals using proton exchange followed by CHF3 reactive ion etching

We report a simple process for the batch fabrication of photonic crystals in lithium niobate substrates. By means of proton-exchange (PE) followed by CHF3 reactive ion etching (RIE) we have achieved structures with a diameter of 400 nm and an aspect ratio (depth-to-diameter) of 3:1. Sub-micrometric structures have been fabricated with an 85° angle between the walls and the plane of the substrate. We provide the optimized parameters – and their influence on the aspect ratio, the etching rate and the verticality of the walls. Transversal cross-section micrographs of the etched patterns, for both X-cut and Z-cut substrates, are shown as a clear evidence of the capability developed.