Understanding Plasmonic Nanoantennas

Optical nanoantennas are capable of controlling the absorption, emission, and scattering of light at the nanoscale [1]. Nanoantennas are generally made up of metals like aluminum, silver, or gold that are known to support plasmonic resonances in the near-infrared/visible/ultraviolet spectral regime, and which can be modified by varying size and shape.

Optical nanoantennas have immense potential in a wide range of applications. Their light-directing and light-harvesting properties can be utilized in:

  • Nanoscale sensing
  • Spontaneous emission control
  • Light trapping in solar cells and anti-reflection coatings
  • Fast-writing in magnetic hard disks and localized heating for targeted medicine
  • Low-threshold steam generation
  • Surface-enhanced Raman scattering
  • Color filters for CMOS imaging sensors

Characterization of plasmonic nanoantenna properties presents a challenge in itself which can be attributed to their nanoscale nature. Here, the advanced SPARC cathodoluminescence (CL) system can be used to retrieve optical characteristics with a deep-subwavelength resolution, including:

  • Measurement of emission polarization
  • Measurement of the angular profile for studying directionality
  • Measurement of spatial and spectral distribution of plasmon resonances in a structure with nanoscale spatial resolution

Figure 1 shows an example of how the SPARC CL system can be used in the context of antennas.

Understanding Plasmonic Nanoantennas

Figure 1. (a) Normalized CL spectrum for an Au nanodisk on Si with a diameter of 100 nm and a height of 80 nm. An SEM image is shown as an inset (scale bar: 50 nm). The spectrum is taken by averaging the CL spectrum over the particle. A two-dimensional CL excitation map at λ0 = 560 nm is shown as an inset. The dashed lines indicate the edge of the structure taken from the SEM image. (b) Normalized CL intensity as a function of azimuthal (θ) and zenithal (φ) angles taken at λ0 = 600 nm for excitation on the left side of the structure. The geometry is indicated by the diagram at the right [2].

References

  1. L. Novotny, and N. van Hulst. Antennas for light. Nat. Photon. 5, 83–90 (2011).
  2. T. Coenen et al. Directional emission from a single plasmonic scatterer. Nat. Commun. 5, 3250 (2014).

This information has been sourced, reviewed and adapted from materials provided by Delmic B.V.

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