Design Of High-Power THz Photoconductive Antennas

Because of its unique characters, THz wave has grand scientific value and wide applied perspective in many fields, such as imaging, entironment supervising, medical diagnosis, radio astronomy, broad band mobile communications, satellite communications and martial radar etc. But lacking in high-power THz sources has seriously blocked the progress of THz technology.In this paper, we detailedly introduced the characters of THz wave, the methods of generation and detection, and the progress of THz time domain spectrum detection, THz imaging and the applications in the biology technology and information technology in the recent ten years. How to improve the power of THz radiation, which is generated by photoconductive antennas, is mainly studied in this paper.Firstly we analyzed the theory of photoconductive antenna material's breaking down, and then we did the following design to improve the maximal biased voltage such as unsharping the electrodes, surface passivation, and encapsulation by gel; and drilled a hole in the back of Teflon base to reduce the losing of THz wave. By contrasting the designed antennas and the bare antennas by experiments, we found the maximal biased voltage and the outcoming THz's intensity can be improved one order after being designed when triggered by light pulse with the same energy.In order to finding the effects of the characters of photoconductive materials to the THz power, we simulated the time domain curves of the near field and far field by thecurrent surge model. Because the microcosmic dynamics factor such as the life and mobility of carriers and the characters of the light such as pulse width and fluence were taken into account in the model, we can change these factors to study the effect to THz intensity. Those modeling results are important, because they can be used to guide the design of photoconductive materials and the design of new experiments to generate high-power THz radiation by photoconductive dipole antenna.