The Study Of Terahertz Wave Generation Using Photoconductive Antennas

In recent years, the investigation of terahertz wave is receiving increasing attention around the world, and exploiting technology of this waveband, which is finally a band has not yet been widely applied in electromagnetic waves, are set to become increasingly important. Terahertz radiation source is one of key factors limiting terahertz wave used in a very diverse range of practical applications. It is now a practical problem needed to solve urgently that how to effectively generate broadband terahertz radiation with high-power, high energy and operating at room temperature in present terahertz research. Photoconductive antenna is the most commonly used method for generating pulse terahertz radiation and will become a hot topic because of its good performance and broad application prospects.In the paper, the radiation process and the spatial distribution of electromagnetic field for the photoconductive antenna generating THz wave were simulated by finite-difference time domain (FDTD) method based on Matlab software, use finite difference time domain (FDTD) method calculate THz wave through a metal slit enhancements. First, system structure and composition of photoconductive antenna generating terahertz radiation were analyzed, it was pointed out that the main factors affecting terahertz radiation power. The micro-mechanism of photoconductive antenna generating THz wave was explained based on "current instantaneous impulse" theoretical model,The calculating formulas of radiation field intensity and power of THz wave generated by photoconductive antenna were obtained. Combining quantum mechanics with statistical physics theory, complex dielectric constant and complex refractive index were calculated according to the Drude model in the interaction of terahertz wave and material. Secondly, from the calculation of antenna radiation characteristics point of view, the basic theory of the electromagnetic wave's finite-difference time domain (FDTD) was introduced, and the related issues needed to consider in the calculations were discussed. Third, the model and program for photoconductive antenna generating terahertz radiation were designed. The simulation results of antenna radiation characteristics were visually displayed in a pseudo-color pattern. In accordance with simulation results, the characteristics parameters of photoconductive antenna were calculated. Finally, based on theoretical analysis and simulation results, improving methods for the antenna's electrode structure and electrode materials were introduced in order to enhance the radiation power. And it was proposed that adding a metal nano-slit on the photoconductive device may be beneficial to enhance the THz electric field intensity, use sub-grid FDTD technology calculate electromagnetic fields and energy enhancement with a slit width of the metals.This paper has made some research results. The work has a certain reference to improve the THz radiation power from photoconductive antenna and the design of antenna structure.