Photonic Generation and De-Chirping of Broadband THz Linear-Frequency-Modulated Signals

In this letter, we propose and experimentally demonstrate photonic generation and de-chirp processing of terahertz (THz) linear-frequency-modulated (LFM) signals using coherent photonic super-heterodyne based on frequency quadrupling and photo mixing. In the experiment, a 340-380-GHz LFM signal with 40-GHz bandwidth is successfully generated with a temporal period of 1 μs. As a result, a range resolution of 5 mm is successfully enabled, which is close to the theoretical limit. Benefited from photonic de-chirp processing, the requirements of receiving instantaneous bandwidth and sampling rate are reduced. Moreover, the proposed scheme features high stability, and the measured performance of the system has not deteriorated within 2 hours in the experiment. Therefore, our proposed system has a great potential in THz ranging and imaging applications.