High-Aspect-Ratio LiNbO3 Ridge Waveguide With Vertical Buffer Layer and Enhanced Electro-Optical Efficiency

As high aspect ratio ridges are not easy to process with standard lithographic techniques we propose alternative solutions based on atomic layer deposition and precise dicing to allow both uniform coating of the relief surface and a selective lift-off at the top of the ridges. The techniques are successfully employed to demonstrate an electro-optical (EO) low-loss tapered ridge waveguide with 90% of EO overlap coefficient, and a Fabry-Perot-based 150 μm long intensity modulator with a figure of merit 8 times better than a standard Ti-indiffused EO modulator. Furthermore, enhancement is even expected by optimizing the manufacturing of the Fabry-Perot cavity inside the ridge. These developments open the way to active three-dimensional microstructures, not only for optical applications but also for MEMS, acoustic or microfluidic devices.