Cw THz spectrometer with high SNR and MHz frequency resolution

We developed an all-fiber-based continuous-wave terahertz spectrometer based on optoelectronic signal generation and detection. The spectrometer has a very high spectral resolution in the MHz range over the whole tuning range from 50 GHz to 1750 GHz. The signal-to-noise ratio is ≈ 80 dB at 100 GHz and still 50 dB at 1 THz, using a lock-in time constant of 300 ms. We applied the spectrometer to absorption measurements of a-lactose monohydrate and demonstrate the suitability of the instrument to determine the area density of paper samples.