  We present an integrated THz spectroscopy and sensing platform featuring low
loss, vacuum-like dispersion, and strong field confinement in the fundamental
mode. Its performance was characterized experimentally for frequencies between
0.1 THz and 1.5 THz. While linear THz spectroscopy and sensing gain mostly from
low loss and an extended interaction length, nonlinear THz spectroscopy would
also profit from the field enhancement associated to strong mode confinement.
Moreover, the vacuum-like dispersion allows for a reshaping-free propagation of
broadband single- to few-cycle pulses in gas-phase samples or velocity matching
between THz pump and visible to infrared probe pulses. Our platform is based on
a metallic structure and falls in the category of double ridged waveguides. We
characterize essential waveguide properties, for instance, propagation and
bending losses, but also demonstrate junctions and interferometers, essentially
because those elements are prerequisites for integrated THz waveform synthesis,
and hence, for coherently controlled linear and nonlinear interactions.
