Nanofotonian

Nanofotonian is a hypothetical quasiparticle describing a bound state between a photon and localized excitations in nanoscale structures. Predicted by theories of strong light-matter coupling in nanophotonics, it would constitute a new collective mode that arises when optical fields couple to nanoscale resonances such as excitons, plasmons, or phonons confined within a nano-scale system. Nanofotonians would be highly localized and their properties could be tuned by geometry and material.

In formal terms, a nanofotonian would be an eigenmode of the coupled light–matter Hamiltonian in the strong coupling regime, with features such as Rabi splitting and altered local density of optical states. Its effective dispersion, lifetime, and group velocity would depend on the nanostructure design and the nature of the underlying excitation, enabling sub-wavelength control of light.

Status and evidence: The nanofotonian remains speculative and not universally accepted as a distinct quasiparticle. Some related ideas describe hybrid modes in nano-cavities or plasmon–exciton polaritons, but a clean experimental demonstration of a standalone nanofotonian separate from existing polaritons has not yet been established. Challenges include losses, definition in open systems, and distinguishing unambiguous signatures.

Potential applications include ultracompact light sources, nanoscale sensing, and advances in quantum information processing and nonlinear optics at the nanoscale. The concept sits at the intersection of nanophotonics, cavity quantum electrodynamics, plasmonics, and metamaterials.