Trapping a magnetic rainbow by using a one-way magnetostatic-like mode

Trapped rainbow effects have been realized in many systems while they are all characterized by electric-field enhancement. The trapped rainbow with strong magnetic-field enhancement has yet to be studied. Here, we achieve the trapped magnetic rainbow effect in a novel metal-air-YIG (yttrium-iron-garnet)-metal (MAYM) waveguide applied with a continuously decreasing magnetic field.

The proposed system supports a one-way propagation feature, leading to the suppressed reflection. We systemically analyze the dispersion and the modal properties, showing the transition from the SMP (surface magnetoplasmon)-like mode to magnetostatic-like mode and the change of the group velocity when decreasing the external magnetic field along the propagation direction of the wave.

We obtain the trapped magnetic rainbow effects as well as magnetic hotspots both in frequency- and time-domain simulations. The trapped rainbow effect with strong magnetic field enhancement paves a promising way for many applications including magnetic sensing to magnetic non-linearity.