Engineering of energy band and its impact on light transmission in non-reciprocal Hermitian hourglass lattice

We study a quasi-one-dimensional non-reciprocal Hermitian hourglass photonic lattice that can accomplish multiple functions. Under the effect of non-reciprocal coupling, this lattice can produce an energy isolation effect, two kinds of flatbands, and energy band inversion. The excitation and propagation of a single energy band and multiple energy bands can be realized; in the flatband condition, the system has compact localized states, and the flatbands can be excited by a straightforward method. Our findings advance the theory of energy band regulation in artificial photonic lattices.