Phase-sensitive spectroscopy of surface plasmons in individual metal nanostructures

A. A. Mikhailovsky, M. A. Petruska, Kuiru Li, M. I. Stockman, V. I. Klimov
2004 Physical Review B  
We analyze both theoretically and experimentally the response of individual gold nanoparticles and nanoparticle dimers to a near-field excitation with broad-band radiation ͑a femtosecond white-light continuum͒ delivered through a subwavelength aperture. Because of the coherent superposition of the field emitted by the aperture and the secondary field reemitted by the nanostructure, the signals detected in the far zone exhibit a pronounced dependence on the phase of plasmon oscillations excited
more » ... cillations excited in the nanostructure. This phase sensitivity allows us to accurately determine positions of plasmon resonances not distorted by dielectric losses in a metal. In the near-field extinction spectra of individual nanoparticles, the plasmon resonance is observed as the "zero-extinction" point in which the transition from constructive ͑lower spectral energies͒ to destructive ͑higher spectral energies͒ interference occurs. By using spatially selective near-field excitation with a femtosecond white-light continuum, we are able to detect slight asymmetries in dimers composed of nominally identical nanoparticles.
doi:10.1103/physrevb.69.085401 fatcat:tf4fjog5nvhz5jhktljbcirk64