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 photonicsbased 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 freespace 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.