Emulating Nonreciprocity with Spatially Dispersive Metasurfaces Excited at Oblique Incidence.

Area of Science:

• Electromagnetics
• Materials Science
• Nanotechnology

Background:

• Ultrathin metasurfaces with transverse surface currents offer precise control over electromagnetic wave front and polarization.
• Engineering nonreciprocal electromagnetic phenomena typically requires complex or non-reciprocal materials.

Purpose of the Study:

• To demonstrate that incorporating longitudinal (normal) surface currents into reciprocal metasurfaces can emulate nonreciprocal electromagnetic phenomena.
• To expand the engineering capabilities of metasurfaces using reciprocal materials.

Main Methods:

• Analytical derivation showing that spatially dispersive metasurfaces are effectively self-biased by the transverse momentum of incident waves.
• Reinvestigation of metasurface reciprocity and derivation of generalized reciprocity relations.
• Design and simulation of metasurfaces to emulate Faraday rotation and optical isolation.

Main Results:

• Metasurfaces with longitudinal currents exhibit inherent spatial dispersion, enabling emulation of nonreciprocal effects.
• Generalized reciprocity relations are derived, redefining metasurface symmetry.
• Designed metasurfaces successfully imitate Faraday rotation and optical isolation for specific incident wave types.

Conclusions:

• Longitudinal surface currents in metasurfaces significantly enhance their functionality by enabling emulation of nonreciprocal phenomena with reciprocal materials.
• These findings pave the way for low-profile devices with unprecedented electromagnetic control and functionality.