Microwave index engineering for slow-wave coplanar waveguides

Microwave index engineering has been investigated in order to properly design slow-wave coplanar waveguides suitable for a wide range of applications in microwave, photonics, plasmonics and metamaterials. The introduction and optimization of novel capacitive and inductive elements is proposed as a design approach to increase the microwave index while keeping the impedance close to 50 Ω to ensure the compatibility with external electronic devices. The contribution of inductive and capacitive elements and their influence on the performance of the slow-wave coplanar waveguide has been systematically analyzed. As a result, a microwave index as high as 11.6 has been experimentally demonstrated in a frequency range up to 40 GHz which is, to the best of our knowledge, the largest microwave index obtained so far in coplanar waveguides.