Highly controlled Bloch wave propagation in surfaces with broken symmetry
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We propose and demonstrate reduced symmetry photonic surfaces providing highly controlled Bloch wave propagation. The backward and dual directional propagations have been observed in the proposed low-symmetric periodic structures without variation in the unit-cell filling factor. Frequency-domain analyses present group indices up to negative/positive −237∕ 96 as strong indicators of the observed directional controlled surface waves driven by the orientation angle in the range of 20°–90°. Further verification of the index-based propagation direction has been achieved through detailed time-domain analyses and microwave experiments. Smart management of the propagation direction in low-symmetric surfaces has great potential for next-generation photonic applications.