High-aspect-ratio electro-optical ridge waveguide made by precise dicing and atomic layer deposition

Abstract

The development of all-optical, acousto-optical or electro-optical (EO) waveguides represents a stimulating challenge for the production of advanced functionalities in compact optical devices. In particular, high aspect ratio LiNbO3 ridge waveguides have attracted much interest over the past decade, due to their ability to enhance electro-optic effects while ensuring insertion losses lower than 3 dB [1, 2]. However, the large depth and high verticality of the ridge-based waveguides make the electrode deposition difficult to achieve. In particular, a thin and uniform dielectric buffer layer is needed between the ridge waveguide and the metallic electrode to avoid optical losses, but its deposition along deep ridges is highly challenging. Here we show how conformal dielectric buffer layers can be deposited along the ridge edges by Atomic Layer Deposition [3]. An innovative lift-off technique is also proposed, to provide well-defined electrodes.