Terahertz sources for spectroscopy and imaging applications

The generation of TeraHertz (THz) radiation via photoconductive excitation of semiconducting materials and optical rectification was described. As an excitation source of optical pulse, a mode-locked Ti:Sapphire femtosecond laser was used. Using modern integrated circuit techniques, micron-sized dipole antenna has been fabricated on a low-temperature grown GaAs (LT-GaAs) wafer for photoconductive antenna. As for optical rectification method, 1 mm thick ZnTe (110) crystal was used. The features of above two method of THz pulse generation are compared. In case of the PhotoConductive Antenna (PCA) method, ultra-wide band THz radiation with frequencies between 0.1 THz and 2.5 THz was obtained. Compared with the PCA method, THz field intensity of the optical rectification was smaller. But the full width at half maximum of frequency spectrum of optical rectification was much larger than the PCA method. The terahertz pulses obtained by both the methods can be used to THz time-domain spectroscopy (THz-TDS) and spectroscopic pulse imaging applications