Optical Responses From Zero Optical-Path-Length Object.

Optical path length (OPL) is a key concept that determines elementary and advanced optical effects from classical optical components to cutting-edge nanophotonic devices. In this paper, we treat objects with their physical and OPL thickness simultaneously vanishing and show that such objects in principle can produce remarkably strong optical effects under certain conditions associated with dipole-preserving compression of an ordinary three-dimensional medium. Such two-dimensional (2D) sheets essentially produce elementary optical responses of reflection, diffraction, and localization in the same manner as a quantum-mechanical delta-function potential-well problem. On this basis, we propose periodic array structures that enable resonant excitations and versatile spectral features favorable for practical applications taking advantages of their minimally space-occupying and least inertial embodiment. Importantly, the proposed zero-OPL-thickness elements can be effectively created in practice by using strongly polarizing ceramics or 2D materials including graphene and transition-metal dichalcogenide monolayers.