Linear and nonlinear optical characterization of aluminum nanoantennas.

We experimentally determine the order of multiphoton induced luminescence of aluminum nanoantennas fabricated on a nonconductive substrate using electron-beam lithography to be 2.11 (±0.10).

Gold nanoantenna resonance diagnostics via transversal particle plasmon luminescence.

We perform two-photon excitation confocal experiments on coupled gold nanoantennas and observe time-integrated luminescence spectra that match plasmonic mode emission in the far-field. We show that the transversal particle plasmon mode can be excited, using excitation light that is cross-polarized with respect to the gold luminescence signal and therefore oriented along the long axis of the dipole gold antenna. We provide evidence for losses in polarization information from the excitation channel to the luminescence response due to the nature of the energy and momentum transfer.

Coupled nanoantenna plasmon resonance spectra from two-photon laser excitation.

We report on the two-photon excitation and subsequent plasmonic mode relaxation of coupled optical gold nanoantennas. Using pulsed laser excitation at a constant wavelength of 810 nm, we observe two-photon-induced plasmon emission spectra, find them to match dark-field microscopy scattering spectra, and show that the emission intensity is enhanced by up to a factor of 65 compared to single gold rods of equal dimensions. This study shows the link of nonlinear optical excitation schemes with radiative relaxation pathways that match plasmonic mode emission of resonant optical gold antennas.

Highly localized non-linear optical white-light response at nanorod ends from non-resonant excitation.

We investigate gold nanorods that are excited non-resonantly using a femtosecond 800 nm pulsed laser beam. We find that they emit very localized white light--two-photon induced photoluminescence (PL)--spatially confined in the optical far-field with a full-width-at-half-maximum of 138 nm (x-y plane) and 328 nm (z-plane). The PL spectrum is characterized to show at least two components--a second-harmonic peak and an intrinsic gold interband transition.

Nanoengineering and characterization of gold dipole nanoantennas with enhanced integrated scattering properties.

In this paper we present our approach for engineering gold dipole nanoantennas. Using electron-beam lithography we have been able to produce arrays of single gold antennas with dimensions from 70 to 300 nm total length with a highly reproducible nanoengineering protocol. Characterizing these gold nanoantenna architectures by optical means via dark-field microscopy and scattering spectroscopy gives the linear optical response function as a figure-of-merit for the antenna resonances, spectral linewidth and integrated scattering intensity.