Parallel plate waveguide terahertz time domain spectroscopy for 2D materials

We demonstrate a parallel plate waveguide (PPWG) based terahertz spectroscopy approach to characterize the electromagnetic properties of two-dimensional (2D) materials. The amount of absorption exponentially increases with the waveguide length, therefore, the minimum detectable conductivity of this method sensitively increases by simply increasing the length of the waveguide along which the THz wave propagates, enabling us to detect low-conductivity carriers in a straightforward, macroscopic configuration that is compatible with any standard time-domain THz spectroscopy setup.