Effect of the buffer layer on the microwaves properties in the coplanar waveguide for LiNbO3 optical modulators with superconducting electrodes

The effects of a buffer layer on the modulation bandwidth of LiNbO₃ optical modulators with superconducting and normal-conducting electrodes have been deduced by using the transverse resonance method (TRM). The analysis is based on the integral equations and the equivalent network representation of each structure. A high Tc superconducting material Yba₂Cu₃O_7-8 (YBCO) has been used for the super-conducting electrode case. The microwave effective index (N_m) as a function of the thickness and dielectric constant of the buffer layer has been computed. Also the bandwidth-length product (Δf.L) as a function of the thickness and dielectric constant of the buffer layer has been computed. A comparison with published results is also included to check the accuracy of TRM technique´s results.