Terahertz Parallel-beam Experimental Platform Based On THz-TDS

At present, terahertz, as a whole new band between microwave and light wave, has not yet been fully developed. The conventional terahertz time-domain spectrometry (THz-TDS) system is unable to carry out the research based on parallel beam. In order to overcome the shortcomings of the existing system, advanced terahertz devices are combined to design and set up the terahertz parallel-beam experimental platform based on THz-TDS. THz generation and detection is essentially a pump/probe experiment, where the pump beam generates the THz radiation and the probe beam is used to measure it. To sample the entire THz waveform, the propagation time between the pump and the probe beams is swept while sampling the probe beam. This can be achieved by either delaying the probe beam or advancing the pump beam or a combination of both. Since the efficiency of the THz-TDS system can be as low as1E-7, a highly sensitive acquisition device is required. Modulating the THz generation and demodulating using a lock-in amplifier is required in most cases. The signal-to-noise ratio and beam spot size of the system are analysed. We studied the impact of the change in the power of the probe light chopping frequency and ZnTe angle on the terahertz signals. In addition, the refractive index of the high-resistivity silicon based on the system is measured. From the data analysis, this system has a high efficiency.