3D-ANALYSIS OF SPATIAL ANISOTROPY FOR LINEAR ELECTRO-OPTIC EFFECT IN CRYSTAL MATERIALS: GEOMETRY DETERMINATION OF THE MOST EFFICIENT ELECTRO-OPTIC COUPLING

摘要

The electro-optic (EO) properties of pure and MgOdoped LiNbO_3 crystals are characterized by indicative surfaces (IS) describing the spatial anisotropy of the longitudinal and transverse linear EO effects. By analyzing the IS and their stereographic projections we have determined the geometries with maximum EO coupling. The maximum magnitudes of the linear EO effect are revealed in the longitudinal and transverse geometries along the directions which substantially deviate from the principal crystallographic axes of both crystals. Spatial analysis of the IS thus gives a set of the optimized sample geometries recommended for designers that develop EO modulators or deflectors. Just by switching from the standard cell geometry to the optimized cell geometry, as determined in present work, one may improve almost three times the modulation efficiency of EO devices based on lithium niobate crystals. This results to a corresponding reduction of their driving voltages being evidently of great practical importance for many applications.