270-360 GHz tunable beat signal light generator for photonic local oscillator

A new millimetre- and submillimetre-wave generation method is proposed. The method employs three techniques, namely the modulation of CW light by an electroabsorption modulator, pulse spectrum expansion through higher-order soliton compression, and spectrum filtering by using tunable fibre Bragg gratings. With this method, a continuously tunable beat signal from 270 to 360 GHz with no frequency fluctuation was obtained experimentally. In addition, the method requires only one laser source, and generates a beat spectrum with a linewidth of less than 10 Hz. By using optical filters with a sufficiently wide tuning range, it is possible to generate a beat signal at any frequency from 100 GHz to 1 THz