A novel design for a compact integrated optical isolator based on a unidirectional bandgap in a 2D magnetophotonic crystal

The absence of a miniaturized integrated version of an optical isolator is an issue that is becoming increasingly important in view of the always higher levels of integration in photonic integrated circuits. It has been shown that the intrinsic strength of the magneto-optical (MO) effects, necessary to induce optical non-reciprocity (NR), can be strongly enhanced in photonic crystals (PhC) [1–3]. Yu et al. have proven that an even stronger NR effect is obtained if the time reversal breaking leads to the appearance of a band gap only for the backward wave [4]. Their structure is a 1D Bragg-type MOPhC with two antisymmetrically magnetized MO layers and one isotropic layer in the unit cell. It leads to a very compact unidirectional mirror (or thus isolator). However as 1D device it is not integrated and moreover the need for a magnetic domain wall repeated over several periods with nanometric precision is technologically unfeasible. We improve on this work by proposing a 2D integratedMOPhC version of a unidirectional mirror without the need for antiparallel magnetic domains.