Optical isolator based on surface plasmon polaritons

A new optical isolator mode which is based on the theory of SPP has been designed. A dielectric waveguide and a SPP waveguide are formulated. And there is a gap in the middle of the core in the dielectric waveguide. Low refractive index material is filled into the gap and the total reflection is satisfied at the interface of the two materials. Magneto-optic material is contained in the two waveguides and the two waveguides are stacked together. For the phase matching of the two waveguides and the total reflection at the gap, the light couples from the dielectric waveguides into the SPP waveguides. With the help of the SPP, the light passes the gap successfully and couples into the dielectric waveguide again. However, there is a different situation at the reverse direction. For the effect of the magnetic field, the permittivity of magneto-optic material has been changed and this caused the phase mismatching of the two waveguides. So effective coupling is not able to finish between the two waveguides. With the total reflection at the gap of the core, the light cannot traverse the mode, and the aim that reflected light should be isolated is achieved. The insertion loss value is 1.72dB when the light traverses through the optical isolator in forward direction. In the reverse direction, the isolation value is 34.14dB. And this result is better than the common magneto-optical isolator.