The effect of strongly nonreciprocal reflected phase behavior on waveguiding structures containing antiferromagnets

We investigate how nonreciprocal waveguiding structures using antiferromagnets in the terahertz range should be possible within the magnon reststrahl region of such materials. Application of a external magnetic field should make these structures nonreciprocal. In particular, we relate this nonreciprocity to strong nonreciprocity in the phase of radiation reflected off an antiferromagnet at oblique incidence. We confirm the effect using simulations for a copper–vacuum–Mn F 2 waveguide structure at low temperature, and show that only a small applied field is necessary to induce nonreciprocal propagation in the waveguide. We consider how such a waveguide may be used as a two-way optical switch or a reversible optical diode, and show how damping effects may be minimized.