Laterally asymmetric particle arrays for one-way guiding

A general theory for one-way optical guiding in periodic particle arrays is developed. Conditions on the asymmetry properties of the structure's period that are necessary to obtain asymmetric dispersion are derived. The two-type rotation principle, presented and studied in previous works on one-way guiding in particle chains, is viewed as a special design that achieves the necessary violation of the period's symmetries. Specific examples of periodic strips that consist of circular particles and support one way guiding, are provided.