Enhanced broadband extraordinary terahertz transmission through plasmon coupling between metal hemisphere and hole arrays

Enhanced extraordinary optical transmission (EOT) is generated by a gold hole array with a concentric hemisphere in the terahertz (THz) region. By introducing hemispherical particles and using the plasmon coupling effects of surface plasmon polaritons and localized surface plasmon resonances, it can be found that not only the transmission intensity is greatly enhanced to 0.97 and the bandwidth is nine times wider than that of a non-particle in a hole, but also the size of the structure can be significantly reduced. Additionally, optical characteristics of the hemisphere-in-hole structure are thoroughly analyzed by the schematic diagram, transmission spectra, and optical field distribution. In addition, with the diameter of the hemisphere increasing, the transmission peak maintains at a high value and the peak position redshifts correspondingly. Finally, we alter the shapes and sizes of the central particles to verify the influence on the enhanced THz EOT. Our results provide a reference for theoretical understanding and expand the application prospects for many THz plasmonic devices.