Broadband negative refraction based on a pair of anti-parity-time structures

Abstract An anti-parity-time(A-PT) symmetric system, of which the refractive index satisfies n( - x) = - n*(x), can present intriguing scattering properties like continuous coherent perfect absorption(CPA) spectrum and laser spectrum, which are symmetric to each other in the parameter space. In this work, an acoustic parity-time(PT) symmetric system consisting of two A-PT symmetric structures is introduced to realize a broadband negative refraction. When the two A-PT symmetric structures are at their CPA mode and laser mode respectively, the PT symmetric system can display its unidirectional negative refraction property. As the two A-PT structures we design here have a broadband CPA and laser modes, the PT symmetric negative refraction system would be broadband. Besides, the exceptional point(EP) of the proposed PT-symmetric system corresponds to the CPA point and laser point of its two components, and it's unidirectionally transparent on broadband as well.