Screening Effect Suppression and Radiation Performance Improvement in Photoconductive Terahertz Emitters with Metallic Nanoarray Structure

As core components of terahertz (THz) radiation sources, photoconductive antennas (PCAs) suffer from performance limitations due to inefficient carrier generation/transport and space-charge shielding effects. This study first introduced cylindrical Au nanoarray structures within the electrode gaps of photoconductive antennas to enhance radiation performance. A combination of the finite element method solver and COMSOL Multiphysics was implemented to refine the model by accounting for the shielding field, which is often neglected in the calculations. Guided by the theoretical and simulation model, the generated current, THz radiation power and the shielding field were comparatively studied in the plasmonic nanoarray PCA and traditional PCA without the plasmonic nanoarray structure. The results demonstrate that emitters with the cylindrical nanoarray structures achieve a radiation power 3.81 times higher than that of the traditional structure, along with a 50% broader bandwidth. Further optimization of photogenerated carrier distribution through engineered metallic nanoarray structures reveals that plasmonic photoconductive THz emitters with triangular nanoarrays reduce the space-charge shielding field by 28.7% compared to the cylindrical structures while enhancing the radiation field intensity by a factor of 1.21. This work presents an effective approach to designing high-performance photoconductive THz emitters, holding significant theoretical and practical significance.