To analyze the carrier lifetime of Si, a 0.4 mm thickness high-resistivity silicon had been investigated by the optical-pump-terahertz-probe (OPTP) system. The terahertz time domain curve and frequency spectrum (bandwidth of > 6THz) of Si are achieved by the time domain spectroscopy mode, and its characteristic parameters, including refractive index and absorption coefficient, were obtained. And the carrier lifetime of Si was measured by the OPTP mode, the result is about 905 ps.
The ultrafast photoconductive characteristics of GaAs were investigated by the optical-pump terahertz-probe (OPTP) method at room temperature. In our experiment, a significant decrease of the terahertz transmittance has been observed when the time delay between the optical pump pulse and the terahertz probe pulse was adjusted. When the optical excitation occurred on the surface of GaAs, the free carriers increase. Results regressed the experimental curve and obtained the carrier lifetime is 681ps.