Nonreciprocal local-resonance induced complex band hybridization

Abstract

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 Im(k) 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 Im(k) instead of the extensively studied real part Re(k). Our finding contradicts the common belief that "spectral nonreciprocity [ω(k)≠ω(-k)] always implies nonreciprocal transmission."