nonradiating

Nonradiating refers to a condition or configuration in physics where an object, field distribution, or process does not emit electromagnetic radiation into the far field, despite having time-varying currents or charges. The concept is central in classical electrodynamics, particularly in the study of structured sources that can produce localized electromagnetic modes without radiative loss. Nonradiating sources were first formalised in the 1960s and 1970s when researchers examined the inverse problem of determining source distributions from far‑field measurements. They showed that there exist non‑unique current configurations that generate identical far‑field patterns, and that one can deliberately construct currents that give zero radiation in the far zone.

Typical examples include superpositions of electric and magnetic multipoles whose far‑field components cancel each other. Another class is the Bessel‑beam or other non‑diffraction‑limited beams that carry energy along a propagation axis without spreading, which, when used to drive currents, can cancel their own radiation. In quantum optics, the notion extends to atoms or quantum dots driven into “dark states”, where destructive interference prevents spontaneous emission.

Nonradiating configurations find practical applications in stealth technology, where antennas or radar signatures are suppressed, and in energy‑trapping devices such as photonic or plasmonic resonators that need to store energy without external radiative loss. They also arise in theoretical studies of electromagnetic cloaking and invisibility, where tailored material responses silence scattering. In condensed‑matter physics, nonradiating excitations play a role in exciton–polaritons and other quasiparticles that maintain coherence without emitting photons. Thus, the study of nonradiating phenomena bridges fundamental electrodynamics, materials science, and applied engineering, offering pathways to manipulate radiation and localisation of electromagnetic energy.