Terahertz time-domain spectroscopy (THz-TDS) technology has developed rapidly in the past decades, and it has become an important method in the field of spectral analysis. Traditional THz-TDS can only analyze isotropic materials. But the need to add polarization analysis in THz-TDS is becoming more and more urgent. In this paper, a polarization THz-TDS system is established. The birefringence and polarization dependent loss parameters of YVO<sub>4</sub>, Iceland spar, MgF<sub>2</sub>, quartz in the terahertz band had been measured. Among them, the birefringence parameter of quartz, MgF<sub>2</sub> and Iceland spar at 0.9 THz is in good agreement with the literature. The minimum polarization dependent loss of the four crystals between 0.2THz and 1.5THz are 3.03dB, 4.42dB, 4.4dB and 2.94dB, respectively.
Responsivity is one of the important technical parameters of the detector. With the development of ultraviolet detector technology, ultraviolet focal plane array devices have also been rapidly developed. Therefore, it is increasingly important to accurately measure the response of ultraviolet detectors. This paper analyzes the principle of UV focal plane array response measurement, uses the alternative method to measure the response of the UV focal plane array detection device, and establishes the UV focal plane array response measurement device. The results of uncertainty analysis show that the uncertainty of the UV focal plane array device response measurement system is about 4.2 %, can meet the measurement requirements.
In this paper, a series of experiments on dispersion compensation in terahertz time-domain spectrometers are performed. The Influence of femtosecond laser pulse width on the performance of terahertz time-domain spectrometers is systematically studied. A terahertz time-domain spectroscopy system was constructed using fiber-coupled photoconductive antennas. Through the adjustment of the grating spacing and the replacement of different lengths of fiber cable, the laser pulse width acting on the antenna was multiplexed from 130fs to 2.46ps, and the performance of the terahertz time domain spectroscopy system under different pulse widths was tested. The experimental results show that, with the increase of the femtosecond laser pulse width, the signal intensity of the terahertz time domain waveform and the high frequency part of the terahertz spectrum decrease significantly. Quantitative comparative analysis was performed using the average signal-to-noise ratio, validating the necessity of using dispersion compensation and femtosecond laser pulse width testing in the terahertz time-domain spectroscopy system.
Terahertz technology is getting fast development in scientific research and the characteristics of terahertz beam is of great importance when using a terahertz laser. In this paper we scan the THz beam along its diameter by a slit and a circular aperture to measure the THz beam’s power distribution and thus get its spot’s size. The results show that the beam spot of the THz source we employed is satisfied with Gaussian distribution. The value of the peak power would affect the determination of the spot boundary, the influence of environmental noise will increases when the the peak power become weak and the measured spot diameter will be too large ultimately.