Spatial localization of an optical near field in one-dimensional nanomaterial system

A model for a pseudo one-dimensional optical near-field probe system is proposed to explain the mechanism of photon localization in space and the experimentally suggested coexistence of photon and phonon fields. Transforming the photon-phonon interaction, light in the probe system can be expressed in terms of photon operators associated with the coherent state of phonons. The photon hopping constants are modified by the localized phonon modes due to the impurities in the system, and become site-dependent. This site-dependence qualitatively allows photons to localize with a finite width around an impurity site. Numerical results show that the localization of an optical near field originates in the competition between the photon hopping constants and the photon-phonon coupling constants, especially the photon-localized phonon coupling constants, as well as the edge effect in the finite system.