Imaging optical near fields at metallic nanoscale voids

Abstract

Direct imaging of the electromagnetic fields generated by plasmon excitation at gold nanoscale voids is achieved with high spatial resolution using scanning near-field optical microscopy ͑SNOM͒. The spatial intensity distribution of the electromagnetic field in spherical Au void structures strongly depends on the light excitation wavelength and on the diameter and degree of truncation of the voids. Comparing the SNOM results with reflectivity measurements and boundary element calculations allows for a clear identification of the plasmon modes being activated in each case. The unique mapping of the high-field regions provides key information for the use of void nanostructures as substrates for surface-enhanced Raman scattering.

Metamaterial as a controllable template for nanoscale field localization

“…Although justifiable concerns have been raised regarding the disturbance that the SNOM tip could cause to the near-field of the investigated structure, 17,18 SNOM provides a powerful and informative tool for mapping plasmon fields. 15,19,20 Indeed our measurements illustrate that a good qualitative agreement is seen between the field maps measured by the SNOM technique and computed theoretically.…”

Synergetic Light-Harvesting and Near-Field Enhancement in Multiscale Patterned Gold Substrates

“…SSV arrays have been extensively studied since the original work of Bartlett et al, [6][7][8] with detailed studies of the plasmon modes supported by the structure (propagating Bragg plasmons, 13 and localised Mie-type plasmons 11,[14][15][16] ), aided by numerical simulations. 14 The system was found extremely versatile, with possibilities to tune plasmon resonances from the near UV to the near IR ends of the spectrum by varying the sphere size.…”

Dye-doped spheres with plasmonic semi-shells: Lasing modes and scattering at realistic gain levels

“…The excitability of the localized plasmon modes depends on the polar and azimuthal angles of the direction of illumination and on the orientation of the electric field vector. In a recent experimental work, some of the most prominent eigenmodes of metallic voids have been imaged using a near-field microscope [ 14 ]. A further prominent feature of semi-shells with broken symmetry (compared to angularly symmetric shells) is their capability to scatter light preferentially into certain directions [ 15 – 16 ].…”