In this paper, we have reviewed our research on terahertz (THz) isolators and nonreciprocal transmission devices. In addition, we present a new kind of THz isolator based on asymmetry magneto-metasurface. A structured InSb layer coats on the silica substrate in which the numerical simulation shows that this metasurface has isolation over 60dB at 0.646 THz and a 10dB operating bandwidth of 13 GHz under an external magnetic field of 0.3T with an insertion loss less than 2.5dB. This kind of low-loss, high isolation, easy coupling THz magneto-metasurface isolator has broadly potentials for THz application systems. Importantly, we discuss and conclude the necessary conditions of forming THz nonreciprocal transmission in the magneto-material devices, which is strongly related with magneto-material and asymmetric transmission system.
In this work, we present a terahertz (THz) isolator in metal parallel plate waveguide (PPWG). A magneto-optical film with 30μm thickness is coated on one side of the metal plate of PPWG with 100μm width, forming a metal- magnetoair- metal hybrid waveguide. Due to the non-reciprocity of magneto-optical medium and the asymmetry of the waveguide structure, this waveguide show a strong one-way transmission property. The numerical simulation shows that this THz isolator has a maximum isolation of 30dB and a 20dB operating bandwidth of 90GHz under a magnetic field of 0.3T, and its insertion loss is smaller than 0.5dB. Moreover, this operating frequency band can be widely tuned by changing the external magnetic field and temperature. This low-loss, high isolation, broadband tunable nonreciprocal THz waveguide has a great potential for THz application systems.