title: Plasmon-enhanced depolarization of reflected light from arrays of nanoparticle dimers.
abstract: Using spectroscopic ellipsometry and analytical multiple scattering theory, we demonstrate significant depolarization of far-field reflected light due to plasmonic near-field concentration in dimer arrays of metallic nanoparticles fabricated by electron beam lithography. By systematically investigating dimer arrays with varying sub-wavelength interparticle separations, we show that the measured depolarization presents a sharp peak at the Rayleigh cutoff condition for efficient in-plane diffraction. Moreover, by investigating the depolarization of reflected light as a function of the excitation angle, we demonstrate that maximum depolarization occurs in the spectral regions of plasmon-enhanced near-fields. Our results demonstrate that far-field reflection measurements encode information on the near-field spectra of complex nanoparticle arrays, and can be utilized to experimentally determine the optimal conditions for the excitation of sub-wavelength plasmonic resonances. The proposed approach opens novel opportunities for the engineering of nanoparticle arrays with optimized enhancement of optical cross sections for spectroscopic and sensing applications.
authors: Department of Electrical and Computer Engineering & Photonic Center, Boston University, 8 Saint Mary’s Street, MA 02215, USA.
authors: Gary F
authors: GF
authors: Walsh
authors: Carlo
authors: C
authors: Forestiere
authors: Luca
authors: L
authors: Dal Negro
mesh_terms: D019281:Dimerization; D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D008855:Microscopy, Electron, Scanning / Q000379:methods; D015233:Models, Statistical; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D055095:Optics and Photonics / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold