Constructing the Near field and Far field with Reactive Metagratings: Study on the Degrees of Freedom

Abstract

Metamaterials continue to change the way we think about manipulating light. For example, although conventional diffraction gratings are well-studied and widely used, only a few configurations (as in blazed gratings) allow efficient, accurate control of diffraction. The authors show that to construct arbitrary diffraction patterns, each propagating diffraction order requires $e\phantom{\rule{0}{0ex}}x\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y$ two degrees of freedom, represented by structured ``wires'' (in a metamaterial, say). This important result solves an old problem of power management by a diffraction grating. From the physical point of view, it is achieved by accurately adjusting the optical near field scattered from a grating.