太赫兹GaAs光电导天线阵列辐射特性

Radiation characteristics of terahertz GaAs photoconductive antenna arrays

GaAs光电导天线是太赫兹电磁波的重要辐射源之一,天线阵列可以提高THz波的辐射强度,因而光电导天线及阵列一直以来备受瞩目.本文采用CST Microwave Studio软件对光电导天线阵列辐射太赫兹电磁波的特性进行仿真计算.根据电流瞬冲模型计算了激光入射到GaAs光电导天线时产生的脉冲光电流,并作为激励源对光电导天线的辐射性能进行仿真计算,分析了天线结构和衬底材料对辐射太赫兹波的影响.在此基础上计算了GaAs光电导天线阵列辐射太赫兹波的远场辐射.仿真结果表明:光电导天线阵列辐射太赫兹波的方向性更强,主波瓣宽度减小,其远场辐射符合电场叠加的倍数关系.研制了1×2 GaAs光电导天线阵列,实验测试结果与仿真结论相一致,为制备多阵元太赫兹光电导天线阵列奠定了理论和实验基础.

A GaAs photoconductive antenna is one of the important radiation sources of terahertz electromagnetic waves. Antenna arrays can increase the radiation intensity of terahertz waves. Therefore, photoconductive antennas and arrays have attracted much attention for a long time. In this study, CST Microwave Studio is used to conduct a simulation calculation of the characteristics of a photoconductive antenna array radiating terahertz electromagnetic waves. Using the current transient model, the pulsed photocurrents generated when the laser is incident on the GaAs photoconductive antenna are calculated. With the pulsed photocurrents serving as an excitation source, a simulation calculation of the radiation performance of photoconductive antenna is conducted, and the effects of antenna structure and substrate material on the radiation of terahertz waves are analyzed. Based on this, the far-field radiation of terahertz wave radiated by the GaAs photoconductive antenna array is calculated. The simulation results show that the photoconductive antenna array radiates terahertz waves with stronger directivity. The width of main lobe is reduced, and its far-field radiation conforms to the multiple relationships of electric field superposition. A 1 × 2 GaAs photoconductive antenna array is developed, and the experimental results are consistent with the simulation conclusions, thereby laying a theoretical and experimental basis for fabricating the multielement terahertz photoconductive antenna arrays.