Fig. 4: Multi-color and bidirectional perfect absorptions.
a Schematic diagram of the experimental setup. Two YIG spheres are integrated at different positions along the SSPP waveguide and subjected to a common vertical bias magnetic field (B-field). The magnon mode frequencies of the two YIG spheres are independently tuned via local magnetic field adjustments (B + δB1(2)) using two separate coils. b, c Evolution of the measured transmission and absorption spectra when the magnon mode frequency of YIG 2 is tuned. Red and blue curves correspond to rightward and leftward propagating microwaves, respectively. The top inset schematically illustrates the transverse spin directions of the SSPP waveguide modes at the locations of the two YIG spheres for each propagation direction. All spectra are measured under conditions of perfect chiral coupling and critical coupling for both YIG spheres.
