We demonstrate a free space two-port photonic vector network analyzer capable of measuring the scattering parameters of devices and materials in the terahertz range with a frequency coverage of 0.2 - 2 THz in a single system. It is based on photoconductive terahertz sources and detectors driven by a telecom-wavelength femtosecond laser. Being able to cover a bandwidth of one order of magnitude, the system is capable of performing S-parameter measurements deep into the terahertz range, beyond frequencies reachable by their electronic counterparts. We demonstrate high performance at three application examples, namely S-parameter measurements of a split ring resonator array and a distributed Bragg reflector, as well as material parameter extraction of several materials.
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