Optimization of a nonreciprocal phase shifter comprising a magneto-optic slab waveguide

The problem of a nonreciprocal phase shifter is solved analytically in the framework of first-order perturbation theory. The expression for the differential phase shift ∆β is valid for any set of material parameters. It is shown that an optimal ∆β is achieved for a film thickness smaller than that for maximal power confinement. Using scaled parameters and introducing a normalized nonreciprocal phase shift allow to obtain universal charts for the optimal film thickness and the corresponding nonreciprocal phase shift.