Large-aperture Photoconductive Antenna And Its Terahertz Radiation

The terahertz (THz, 1 THz=1012 Hz) wave, categorized between the microwave and the infrared light in the electromagnetic spectrum, with the frequency lying in 0.1 THz and 10 THz. THz imaging and sensing technologies can provide the information that difficult to be obtained by the conventional methods such as microwave and X-ray techniques. It is believed that THz technique has a good future in many different fields, such as physics, chemistry, biomedicine, communication, radar, security inspection, and so on. In the last decade, the generation techniques of THz wave made rapid progress. Photoconductive antenna (PCA) of the large aperture can provide reasonably good peak power and spectral width of THz generation. In this thesis, we carried out a series of experiments to improve the radiation performance of PCA. The fabrication process of PCA was given in detail, several kinds of PCAs with different electrode geometric structure and semiconductor material were introduced. We presented a high efficient, temperature controlled THz time-domain spectroscopy (TDS) system. Using this system, the experimental comparison of seven PCAs with different electrode geometric structures was drawn. The PCA with I-shaped geometric structure has the best performance during the comparison. Using I-shaped geometric structure, we measured three PCAs with different photoconductive materials. In the experiment, we find that the THz radiation performance of the PCA with multi-layer grown GaAs material is comparatively better than others.Base on the experimental results above, the experiment research of THz radiation properties was conducted by the high efficient THz TDS using the PCA with I-shaped geometric structure and multi-layer grown GaAs material. The results show that, the peak of THz electric field and the peak frequency of spectrum increase linearly as a function of bias field, and tend to saturation as a function of pump power. These experimental results are explained by the corresponding theory.In summary, the comprehensive analyses about fabrication process and THz radiation performance of PCA were done. In this thesis, not only did we obtain the optimized parameters and valuable laws, but also summarized correlative research thoughts and methods. This work is a good reference for investigating and fabricating the high efficient THz radiation source by the large aperture PCA.