Narrow linewidth tunable THz signal generation using a unitravelling carrier photodiode and a dual-mode laser

A dual-frequency laser coupled to a unitravelling carrier photodiode is used to produce a highly coherent THz wave. THz signal is detected by a subharmonic mixer coupled to an electrical spectrum analyzer. All components involved in this experiment operate at room temperature and no active stabilization is used. The measured linewidth is better than 30 kHz and tunable from DC to 1 THz. The dynamic range is 35 dB at 0.683 THz.