Room-temperature source for metrological grade terahertz spectroscopy

The terahertz (THz) spectral window, that is generally considered to span from 1 to 10 THz, is nowadays crucial for plenty of every-day-life and scientific applications, as homelandsecurity,environmentmonitoring,qualityinspectionoffoodandbiomedicine. Among these applications,high precision THz spectroscopy of rotational molecular transitions promises to deliver many novel physical insights. But, despite its primary importance, a considerable technological gap still separes this region from the rest of the electromagnetic spectrum. In particular, the lack of room-temperature sources and detectors makes high-precision frequency measurements of molecular transitions an open challenge. Although recent technologies (as frequency multipliers, photo-mixers and quantum-cascade-lasers) already provided accurate frequency measurements on different molecular transitions in the lower part of the THz spectrum (<4THz), the only continuous-wave (CW) sources spanning the whole Terahertz window dates back to the mid 80s years, being represented by the Tunable Far-Infrared Lasers (TuFir) approach based on difference frequency generation (DFG). However, the low reliability and very low emitted powers of that very bulky instrumentation, hampered for decades its widespread use. The work described in the present dissertation just regards the building from scratch of a room-temperature CW THz spectrometer and its application to high precision spectroscopy in the 1-7.3 THz range.