Testing And Characterization Of The Performance Of Photoconductive Antenna

Terahertz wave(THz)is an electromagnetic pulse whose frequency between microwave and infrared,it has very important research value and broad application prospect in many fields.The photoconductive antenna(PCA)is the most mature researched and the most widely used generators of the terahertz wave,it is widely used in terahertz spectroscopy and plays a very important role in the performance of terahertz time domain spectroscopy.But the power of THz wave produced by it is too low and there are still some problems in terms of stability and life.The performance of photoconductive antenna is mainly determined by the trigger source,the photoconductive materialand the structure of the antenna.In addition,some external conditions are also the important factors which affect the intensity of THz radiation by antenna,such as the power of the pump laser,the bias voltage of the antenna and so on.The relationship between the performance and parameters of the antenna has been obtaind through the test and comparison to several antennas with different materials and structures and the performances of the antennas have been characterized by the parameters.The main work of this paper are summarized as follows:(1)Achieved the optimum working conditions of photoconductive antenna through the deeply 'research on the breakdown mechanism of photoconductive antenna,those are the maximum safe voltage and saturated laser energy.First of all,tested the maximum THz electric fields radiated by the photoconductive antennas at different pump laser energy and finally determined the saturated laser energy.Then,increased the bias voltage gradually and made the volt-ampere characteristics curve of the antenna,the maximum safe voltage of antenna is that the point of the curve where the slope increase suddenly.It proved by the experient and theory that only under the optimum conditions can the signal-to-noise ratio(SNR)of THz wave radiated by PCA be the highest and the PCA would not breakdown.(2)Using the terahertz time-domain spectroscopy system,tested several PCA with different materials and structures,contrasted the waveform of the terahertz wave radiated by these PCA on their respective conditions,analysised the relationship between the performance and the parameters of PCA detailedly and characterized the antenna by the parameters.