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研究了Ga As工型偶极子光电导天线(PCA)结构参数对THz辐射特性的影响。首先利用DL(Drude-Lorentz)模型得到了光电导天线的电流解析解,结合时域有限差分(FDTD)进行半解析半数值仿真,有效地解决了纯解析解(通过光电流对时间求导数可以得到辐射的THz的相对强度)无法和PCA结构直接对应的仿真问题,也较直接全波FDTD方法计算效率高。接着,利用偶极子光电导天线的等效电路模型和等效源阻抗公式,结合实际的PCA参数,分别得到了PCA阻抗和源阻抗,说明了由于源阻抗很低,导致匹配效率较低。最后,综合考虑数值仿真结果和理论计算结果可证明,工型偶极子光电导天线的辐射效率会随着其长宽比的增加而相应增加,该结论与相关文献实测结果吻合,从而也验证了文中FDTD仿真结果、理论模型及计算结果的有效性。
The influence of structure parameters of GaAs dipole photoconductive antenna (PCA) on THz radiation characteristics was studied. First, the current analytical solution of photoconductive antenna is obtained by using DL (Drude-Lorentz) model. Semi-analytic semi-numerical simulation is performed by FDTD, which can effectively solve the pure analytic solution The relative intensity of radiation THz) can not directly correspond to the simulation problem of PCA structure, and also more efficient than the direct full-wave FDTD method. Then, using the equivalent circuit model of dipole photoconductive antenna and the equivalent source impedance formula, combined with the actual PCA parameters, the PCA impedance and the source impedance are obtained respectively, which shows that the matching efficiency is low due to the low source impedance. Finally, considering the numerical simulation results and theoretical calculation results, it can be proved that the radiation efficiency of the dipole type photoconductive antenna increases with the increase of the aspect ratio, which is in agreement with the measured results of the relevant literature and thus verifies In this paper, the FDTD simulation results, the theoretical model and the effectiveness of the calculation results.