Optical, electro-optical, and structural properties of H:LiNbO 3 , H:LiTaO 3 , and Cs:KTP waveguides

Abstract

ABSTRACT In this work we present the results of a systematic study of H:LiNbO3, H:LiTaO3 and Cs:KTPwaveguides obtained by combining measurements of propagation constants, optical profiles, and Ramanscattering of the exchanged layers. Also, we present direct measurements of the r33 coefficients in protonexchanged (PE) and annealed proton exchanged (APE) waveguides in LiNbO3 and LiTaO3 obtained bymeans of phase modulation technique and quantitative relations between the waveguide characteristics andthe doping level in the Cs:KTP layers. Keywords: Planar Optical Waveguides, Ferroelectric Materials 1. INTRODUCTION Ion exchange is widely used for producing optical waveguides in electrooptic ferroelectricsmaterials such as LiNbO3 and LiTaO3 (Li-H substitution or the so-called proton exchange) and KTiOPO4(K-Rb or K-Cs substitution). The fabrication process can provide good quality optical waveguides but italso induces many problems which should be solved before using in practice the waveguide devices. Infact, protonated waveguides, H:LiNbO3 and H:LiTaO3 waveguides, have a complex behavior. Postexchange annealing is required in order to eliminate compositional instabilities and to restore materialproperties. However the refractive index distribution in PE layers is strongly dependent upon the appliedannealing conditions.To optimise the optical device design, it is important to understand the changes of waveguidecharacteristics with the hydrogen concentration during the annealing. Also, a successful utilisation of