Studies On Performances Of THz Waves Emitted By Photoconductive Antenna Under Strong Excitation

Because of the special situation of the THz radiation in electromagnetic wave spectrum and its outstanding performances, the relative research on the THz radiation generation and application has become a hot spot. In practical application terahertz radiation wave should have wide bandwidth and greater radiation power. Large aperture optical antenna can meet these requirements and has larger optical conversion efficiency. The use of antenna arrays can emit even high power terahertz radiation. Therefore, using photoconductive antenna to generate terahertz radiation has become one of the most applied practical technologies.Currently, mode-locked fiber lasers can generate high-repetition - rate femtosecond pulses. Their performances have achieved the level of Ti: sapphire femtosecond lasers. So fiber laser is expected to generate THz radiation pulse with high repetition frequency. However, the theoretical analysis of high-repetition - rate femtosecond laser pulse exciting photoconductive switches to generate THz radiation pulse has not been seen.Based on the numerical analysis of various processes and parameters using the large aperture optical antenna to generate terahertz radiation, we discussed how they impact the time-domain waveform, the peak amplitude and the detection of the THz radiation. We simulated performances of the photoconductive antenna under the optical pulse excitation with a high applied electric field, high-repetition frequency. This work could be useful for the future research.The main research work summarized as follows:First, we summarized the mechanism of terahertz radiation, terahertz radiation and detection methods based on photonics.Secondly, on the basis of studying theoretical models using large aperture optical antenna to generate THz radiation, we have done some modifications of the model to make it suitable for analyzing the process of the large aperture optical antenna terahertz radiation when it is exited by high modulated applied electric fields with high-energy optical pulses and high pulse-repetition-rates. Through lots of simulation calculation, we inspected that how the applied electric field, luminous flux and photoconductive material parameters affect on terahertz radiation. And we analyzed the saturation phenomena of the THz radiation generated by large aperture photoconductive antennas systemically. We found that THz radiation characteristics are closely related to the above-mentioned factors. So they should be considered entirely when a terahertz radiation system is designed and optimized.At last, we forecasted the possibilities of using fiber laser instead of mode-locked Ti: sapphire laser to produce new THz radiation system with compact configuration and lower cost.