Tunable working bandwidth terahertz switch based on magnetic valley photonic crystal

Terahertz (THz) switches are essential components of THz communication systems. THz switches based on conventional waveguides and photonic crystal structures are sensitive to manufacturing defects and sharp bending, resulting in high scattering losses. In addition, THz switches with tunable working bandwidths have not yet been demonstrated. Here, we design THz switches based on a topological valley photonic crystal (VPC) structure using magnetic materials, which can achieve high forward transmittance based on the unique spin–valley locking effect. The broad working bandwidth allows selective turning on and off at a designed wavelength region by controlling the applied magnetic field. The designed THz switch can achieve an extinction ratio of up to 31.66 dB with an insertion loss of less than 0.13 dB. The 3-dB bandwidth is up to 49 GHz. This tunable THz switch can be experimentally fabricated by current fabrication techniques and thus can find broad applications in THz communication systems.