| In this dissertation, active control and sensing application of terahertz surface Plasmon have been presented. The main contents in this dissertation are classified as follows:1. Based on Maxwell equations and boundary conditions of electromagnetic wave, the dispersion relation, penetration depth and propagation length of surface Plasmon polaritons (SP) wave have been deduced. Then several experimental approaches of SP excitation have been introduced to provide the necessary wave vector conservation between incident electromagnetic waves and SP wave, including attenuated total internal reflection (ATIR) prisms, gratings, and waveguides. At last, the mechanism and dependence of localized surface Plasmon has been presented and the similarities and differences are discussed between optical band and terahertz band.2. Based on basic theory of surface Plasmon and localized surface Plasmon, the experiments and dependence of terahertz transmission and reflection properties of periodic subwavelength metallic arrays has been repeated. Base on this, all-optical, active control of terahertz SP has been demonstrated, including the change of dielectric function of photo-excited silicon, terahertz annihilation switching and terahertz changeover switching.3. Based on novel anisotropic property of high temperature superconductor at terahertz frequencies, transmission properties of superconducting YBCO periodic subwavelength array has been presented. First, we deduced the existence of surface wave in anisotropic material. Then we measured terahertz conductivity of YBCO thin film under different temperatures. At last, we achieved thermal active control of terahertz band-pass and band-stop filters in experiments and simulation.4. At last, we discussed the sensing application of freestanding, periodic subwavelength metallic array. Using this kind of array, we distinguished between four isotopes of Methanol. And the potential of qualitative and quantitative sensing has been presented.
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