Tuneable monolithically integrated photonic THz heterodyne system

We report a tuneable heterodyne photonic THz source, monolithically integrated on an InP chip. The system, locked to a comb generator, allows generation of high purity signals and is tuneable from 25 GHz to 1.6 THz. Continuous frequency sweeps of 300 MHz and tuneability between comb lines from 2 GHz to 6 GHz offset are demonstrated. Due to the photonic integration and small dimension, custom-made electronics, the propagation delay in the loop was less than 1.8 ns.