Abstract
A numerical model of x-cut LiNbO3 optical modulator with backside slot structures to satisfy the velocity matching condition without the layer of silicon dioxide is presented. The analysis of microwave properties of the proposed structures is based on the transverse resonance technique. An equivalent circuit is deduced to represent the structures. Generalized trial quantities are introduced as virtual sources in the equivalent network representation of boundary conditions. The lossy conductor of a planar transmission line is represented by a particular two port network. Thus, the metallic losses can be evaluated for any metallization thickness without restricting the conductor modeling to a simple surface impedance approximation. The dependence of the effective microwave index, the characteristic impedance and the product of the drive voltage and the electrode interaction length on the thickness of substrate near the ground electrode is investigated. The optical response of the modulator is computed. The 3-dB optical bandwidth as a function of substrate thickness is also investigated. These types of modulators are more sufficient for the broadband optical transmission systems up to 40 Gb/s. The obtained results are agreed very well with published practical results and theoretical results of finite element method.