Large tuning range THz synthesiser by means of photomixing

Photomixing is an attractive solution for high resolution spectroscopy, nevertheless it has suffered from a lack of frequency metrology to determine the line centre frequencies. Frequency combs can provide excellent metrology of lasers, hence we propose a photomixing source that is phase locked to a frequency comb to overcome this problem. The resulting instrument has an accuracy of Δν_THz/ν_THz = 10^-8, a spectral purity in the order of 50 kHz and can be continuously tuned over 200 MHz.