We study the complex band hybridization induced by nonreciprocal local resonances in photonic crystals. Composed of trimer unit cells, a two-dimensional magnetophotonic crystal with an analytically obtainable solution is considered. We find that a nonreciprocal spectral gap may appear without nonreciprocal transmission and that the imaginary parts of the complex wave vectors $\text{Im}\left(\mathbf{k}\right)$ may blow up at resonance to give extreme nonreciprocal transmission. We further show that, for a subwavelength lattice, the isolation ratio for the nonreciprocal transmission is determined solely by $\text{Im}\left(\mathbf{k}\right)$ instead of the extensively studied real part $\text{Re}\left(\mathbf{k}\right)$. Our finding contradicts the common belief that “spectral nonreciprocity $\left[\omega \right(\mathbf{k})\ne \omega (-\mathbf{k}\left)\right]$ always implies nonreciprocal transmission.”

Close

PrevNext

View figure in article

• Magneto-optics
• Non-reciprocal transmission
• Photonic crystals
• Topological effects in photonic systems
• Band structure methods