The non-reciprocal circular dichroism and Faraday rotation effect for terahertz (THz) waves in longitudinally magnetized InSb were investigated by the theoretical and experimental studies in the THz regime, which indicated its ability for THz circular polarized isolator, THz circular polarizer, tunable polarization converter, and polarization modulator by the manipulation of the different magnetic fields. Furthermore, we demonstrated the InSb plasmonics based on its magneto-optical effects combined with artificial microstructure. We found the magneto-optical enhancement mechanisms in this magneto plasmonic structure, achieving broadband perfect orthogonal linear polarization conversion modulated by the weak magnetic field in the experiment. Moreover, the magneto-optical modulation with modulation depth of 95% and one-way transmission with the isolation of 33dB can be achieved by this device under a weak magnetic field of 150mT. InSb and its magnetoplasmonic device have broadly potentials for THz isolator, magneto-optical modulator, and polarization convertor in the THz application systems.
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