Abstract
Scattering of electromagnetic waves is related to the inhomogeneity of a photonic system. The inohomogeneity, i.e. the obstacles, can vary between microscopic to macroscopic scales, or even manifest in a synthetic (artificial) manner. I will discuss several recent results on electromagnetic scattering. First, I will present a general framework for nanoscale electromagnetism, demonstrated by far-field scattering measurements. The framework extends the applicability of Maxwell’s equations to the deep nanoscale regime. Second, I will treat free-electron radiation as near-field scattering and derive a universal upper limit to their spontaneous emission and energy loss. Such an upper limit identifies a slow-electron-efficient regime of radiation operation and methods for enhancing the emission probability. Finally, I will discuss a synthetic scattering phenomena. Based on optical mode degeneracy, we break time-reversal symmetry in different manners to synthesize tunable non-Abelian (non-commutative) gauge fields in real space, which enable us to observe the non-Abelian Aharonov—Bohm effect with optical waves.