  Continuous Wave (CW) Terahertz spectroscopy enabled by photomixing is a
promising high precision spectroscopic tool for the examination of a wide
variety of samples including biological, chemical, and solid state. However,
often it would be of interest to examine isolated samples free from bulk
effects that broaden spectral features. In this form samples with low
concentrations of absorbers have a reduced cross section making coupling to an
external driving field a challenge. By utilising THz metamaterials one can
borrow the concepts of surface enhanced Raman spectroscopy to confine and
concentrate the THz fields to increase sensitivity for samples with a small
cross section. Our work combines high-speed photodiode technology and THz
metamaterials to offer a solution to this challenge. We present here a proof of
concept on-chip THz spectrometer integrated with a metamaterial waveguide.
