Precision broadband spectroscopy near 2 THz: Frequency-stabilized laser sideband spectrometer with backward-wave oscillators

Doppler-limited high-resolution, broadband scanning spectroscopy with microwave accuracy was achieved in the 2 THz region by using backward-wave oscillators (BWO) for sideband generation. The radiation of a newly developed frequency-stabilized far infrared ring-laser system is mixed on an open-structure Schottky barrier diode pumped with phase-stabilized power output from BWO, which is typically about 10-30% of the BWO's center frequency. An instantaneous frequency scanning capability of 10 GHz can be achieved and has been demonstrated by recording the rQ13 branch of the near-prolate asymmetric-top molecule DSSD in the frequency range between 1872 and 1882 GHz.