Bandwidth Improvement of Coplanar Waveguide for Electro-optic Sampling System

We study and improve the bandwidth of coplanar waveguide (CPW) for electro-optic sampling (EOS) system. Coplanar waveguide is based on LiTaO3 and an electro-optic sampling system is used to measure ultrafast waveform generated by a photodiode (PD). Higher coplanar waveguide bandwidth means more accurate measurement results. Coplanar waveguide design optimizes transmission coefficient (S21) and characteristic impedance based on structure parameters. On-wafer scattering parameters measurement system is employed to validate the bandwidth of fabricated LiTaO3 coplanar waveguide, whose transmission coefficient reduces 1.1dB as frequency up to 170 GHz.