Fabrication method of low-loss large single mode ridge Ti:: LiNbO3 waveguides

We present a method for fabrication of smooth ridge waveguides by wet etching technique, using a special mixture of acids and applying a pretreatment procedure. By implementing this method, we fabricated 4.5 mu m-deep large single mode ridge waveguides with walls and edges roughness comparable with the roughness of the non-etched regions, namely, less than 20 nm. Optical extra losses caused by the ridge creation were measured by the Fabry Perot technique and were 0.2 dB/cm@TM and 0.7 dB@TE for 1550 nm wavelength. Surface roughness, morphology, etching rates and propagation losses are presented and compared to the characteristics achieved by previously reported wet etching recipes. (c) 2006 Elsevier B.V. All rights reserved.