title: Optical frequency mixing at coupled gold nanoparticles.
abstract: We present nonlinear-optical four-wave mixing (4WM) at coupled gold nanoparticles. By decreasing the interparticle distance from large separation to touching contact, the 4WM yield increases by 4 orders of magnitude. The reason for this dramatic enhancement lies in the shift of the localized plasmon resonance to infrared wavelengths as the dimer is formed, making one of the input wavelengths doubly resonant. At the touching point, the 4WM signal changes discontinuously because of a sudden charge redistribution imposed by the formation of a conductive bridge. The 4-wave mixing signal provides an ultrasensitive measure for the contact point between a pair of particles and it can be employed as a spatially and temporally controllable photon source.
authors.affiliation: Institute of Optics, University of Rochester, Rochester, New York USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Danckwerts
authors.forename: Lukas
authors.initials: L
authors.lastname: Novotny
mesh_terms: D015374:Biosensing Techniques; D006046:Gold / Q000737:chemistry*; D007834:Lasers; D053768:Metal Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D006046:Gold