A quasi-optical testbed for wideband THz on-wafer measurements

We propose a novel quasi-optical topology to enable ultra-wideband on-wafer characterization in the THz regime. Using quasi-optical components, we implement a high-performance directional coupler and a noncontact probing scheme, to interrogate on-wafer devices and circuits. The use of quasi-optics allows superior signal isolation and wideband operation due to the frequency independent nature of focusing components. Additionally, the simple topology is amenable to integration with photonics-based THz emitters and detectors to enable a true THz testbed for vector measurement capabilities. A proof-of-concept testbed is designed and evaluated in the 300-340 GHz band using free-space and on-wafer measurements. The on-wafer characterization of passive devices shows good agreement with simulated results and repeatability of <2% for reflection coefficient magnitude and <4° for phase deviation.