Experimental Detection of Unidirectional Topologically-Protected Surface Waves on Gaseous Magnetized Plasma

It has been shown computationally that, due to the nontrivial topology of magnetized plasma bulk electromagnetic wave dispersion bands, there exist topologically protected edge modes of electromagnetic waves that propagate unidirectionally on the boundary between magnetized plasma and other media at band gap frequencies of both the bulk magnetized plasma and the adjacent medium. Topologically protected surface waves are potentially interesting as they propagate unidirectionally and are immune to backscattering, however, prior to our work, they have not been well investigated experimentally. Utilizing gas discharge tubes as a plasma source, we experimentally demonstrate the existence of two different topologically protected surface modes. The first mode travels between the magnetized plasma and metal in a direction perpendicular to the applied magnetic field and is excited with a dipole antenna. The second mode travels between the magnetized plasma and air at an angle to the applied magnetic field and is excited with a metasurface waveguide.