A Coplanar Strip Slow Wave Structure for the Optical Directional Coupler Modulators

A design of a coplanar stripline (CPS) slow wave structure, which has for the first time both series inductive and shunt capacitive sections, has been developed. It has been designed to match the RF/microwave modulation signal phase velocity to the optical wave velocity in GaAs optical waveguides. In this design, the CPS with series inductances and shunt capacitances retains the characteristic impedance at 50 ¿ . This slow wave structure provides flexibility of design for narrow gap CPS structures. The effective refractive index and characteristic impedance of this design have been measured in the frequency range of up to 45 GHz and compared to simulations.