Research On Terahertz Transmission Through Subwavelength Array Structure Based On Surface Plasmon

This article mainly studies the anomalous resonant terahertz transmission through metal-dielectric-metal structure, whose both metallic layers were patterned with a periodic array of subwavelength air circular loop.Utilizing numerical simulations, in the terahertz transmittance of this structure there appeared two resonant peaks caused by surface plasmon. The electric field distributions of the two resonances in transmission spectra confirmed the confinement of surface plasmon and presented the propagation mechanism of surface electromagnetic waves and process of energy flow. Calculated dispersion relations along the plane of array showed that these two resonant peaks were resulted from propagating surface plasmon and localized surface plasmon, respectively. And these modes of surface plasmon were not any simple mode of surface plasmon but the results of interactions and couplings among them. If varying the relative parameters of the structure, tendencies of resonant frequency deviations verified the two surface plasmon modes and indicated that coupling of SP modes as well as quasi-rectangular waveguide effect generated in the air loop significantly together modified the terahertz transmission.The experimental results were obtained by measuring the terahertz transmission of the sample fabricated by technologies of magnetron sputtering and laser. Via analyses, FP effect appearing in the reference signal was caused by the ZnTe plate in the THz-TDS and the properties of terahertz transmittance of the sample showed the enhancement of surface plasmon on the transmission. In a word, good agreement was found between the measured and calculated transmittance, qualitatively confirming the validity of the analysis.Finally, combining the features of the structure and terahertz functional devices, we presented the designs of terahertz filter and modulator based on the structure.