Observation of near-field coupling in metal nanoparticle chains using far-field polarization spectroscopy

Far-field polarization spectroscopy on chains of Au nanoparticles reveals the existence of longitudinal (L) and transverse (T) plasmon-polariton modes. The experimental results provide support for the validity of a recently published dipole model for electromagnetic energy transfer below the diffraction limit along chains of closely spaced metal nanoparticles. The key parameters that govern the energy transport are determined for various interparticle spacings using measurements of the resonance frequencies of L and T modes, yielding a bandwidth of 1.4 × 10¹⁴ rad/s and a maximum group velocity of v_g=4.0×10⁶ m/s for a 75 nm-spacing.