Independent determination of the complex refractive index and wave impedance by time-domain terahertz spectroscopy

We present a method for simultaneous determination of the refractive index and wave impedance – or equivalently of the dielectric permittivity and magnetic permeability – of bulk samples. Two independent complex spectroscopic quantities required for an unambiguous evaluation are experimentally obtained by temporal windowing of time domain waveforms measured in the transmission or reflection geometry. We discuss several approaches that can be used for the evaluation of the complex refractive index and wave impedance; three are quantitatively analyzed and compared. Successful evaluation of the dielectric and magnetic dispersion then crucially depends on the accuracy of the wave impedance measurements.