Light extinction and scattering from individual and arrayed high-aspect-ratio trenches in metals

Abstract

S. (2016). Light extinction and scattering from individual and arrayed high-aspect-ratio trenches in metal. Physical Review B (Condensed Matter and Materials Physics), 93(7), [075413]. https://doi.org/10.1103/PhysRevB.93.075413 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.? Users may download and print one copy of any publication from the public portal for the purpose of private study or research. ? You may not further distribute the material or use it for any profit-making activity or commercial gain ? You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access to the work immediately and investigate your claim. We investigate the scattering properties of two-dimensional high-aspect-ratio metal trenches acting as resonators for gap-surface plasmons and show that these resonators are highly efficient scatterers of free waves, reaching at resonance in the perfect-conductor limit the unitary dipolar limit for a two-dimensional scatterer. We construct a simple resonator model which predicts the wavelength-dependent extinction, scattering, and absorption cross section of the trench and compare the model findings with full numerical simulations. Both extinction and scattering cross sections are mainly determined by the wavelength and can reach highly supergeometric values. At wavelengths where the metal exhibits near perfect electrical conductor behavior, such trenches lend themselves to be used as self-normalizing scatterers, as their scattering cross section is independent of their geometry and depend only on the resonance wavelength. For real metals with nonzero absorption, efficient monomaterial absorbers and emitters can be fabricated. We extend the analysis to tapering trenches that can be readily fabricated employing common milling or etching techniques and verify by reflection spectroscopy and two-photon luminescence that the resonant behavior of the vertical trenches is preserved.

Optics of multiple grooves in metal: transition from high scattering to strong absorption

“…4 but for rectangular and tapered (not ultrasharp) grooves and show that the same principles apply for these types of grooves when they are combined in an array of multiple grooves. For these types of grooves, the cross sections are found to be significantly large only for a narrow band of wavelengths, [5][6][7][8] and thus, the optical cross-section spectra are quite different from previous work.…”

“…See Appendix B in Ref. 5 for a description of how the cross sections are calculated using the GFSIEM. The rectangular shape of the grooves is found to give rise to a narrowband resonant behavior in all the cross sections.…”

“…The rectangular grooves have a depth of 500 nm and a width of 50 nm, whereas the tapered grooves have a depth of 350 nm, a top width of 100 nm, and a bottom width of 60 nm, where all the corners are rounded by a circle with a radius of 4 nm as in Ref. 5, implying that the top width of the rectangular grooves is 58 nm. The incident field in Fig.…”

“…The calculations are performed using the Green's function surface integral equation method (GFSIEM) as presented in Appendix B in Ref. 5. See Ref.…”

Engineering 3D Multi-Branched Nanostructures for Ultra- Sensing Applications

“…Within this context, nanostructures endowed with sharp tips/edges and sub-10 nm interparticle separation (IPS) are ideal candidates for nanoscale manipulation of optical energy, promoting nanofocusing of EM radiation into hot-spots [11][12][13][14][15]. In recent years, a great variety of nanostructure geometries, for instance, nanospheres, nanocubes, nanocones, nanoantennas, nanoaggregates and nanostars, have been fabricated by bottom-up and top-down approaches [16][17][18][19][20][21][22][23][24], in order to engineer their plasmonic resonances and increase the field enhancement and hot-spot densities. Control over nanostructure morphology shows promising applications in bio/chemical sensing using the synergistic combination of LSPR and surface-enhanced Raman spectroscopy (SERS) as detection paradigm [9,[25][26].…”