Experimental demonstration of spectral non-reciprocity and unidirectionality in volumetric and printed magnetic photonic crystals

We present experimental confirmation of spectral non-reciprocity and unidirectional propagation in magnetic photonic crystals. The unique dispersion properties of such periodic anisotropic/magnetic media were also emulated on simpler printed structures. We outline two designs that exhibit non-reciprocal dispersion diagrams (i.e. ω(K) ≠ ω (-K)) in volumetric and printed magnetic photonic crystals. Due to spectral non-reciprocity, unidirectional propagation properties were experimentally observed. These designs can also be tuned such that a stationary inflection point is achieved within the first propagation band, where ω\´= ω"= ω"\´=0 (where ω\´=∂ω/∂K). This special mode is referred to as the “frozen mode” (i.e. zero group velocity). Correspondingly, a significantly longer group delay is observed in experiments. These measurements constitute the first experimental demonstration of the unique properties of the subject magnetic photonic crystals.