Local field enhancement and thermoplasmonics in multimodal aluminum structures

Abstract

Aluminum nanostructures have recently been at the focus of numerous studies due to their properties including oxidation stability and surface plasmon resonances covering the ultraviolet and visible spectral windows. In this article, we reveal a new facet of this metal relevant for both plasmonics purpose and photo-thermal conversion. The field distribution of high order plasmonic resonances existing in two-dimensional Al structures is studied by nonlinear photoluminescence (nPL) microscopy in a spectral region where electronic interband transitions occur. The polarization sensitivity of the field intensity maps shows that the electric field concentration can be addressed and controlled ondemand. We use a numerical tool based on the Green dyadic method to analyze our results and to simulate the absorbed energy that is locally converted into heat. The polarization-dependent temperature increase of the Al structures is experimentally quantitatively measured, and is in an excellent agreement with theoretical predictions. Our work highlights Al as a promising candidate for designing thermal nanosources integrated in coplanar geometries for thermally assisted nanomanipulation or biophysical applications.Metallic nanostructures sustain localized and delocalized Surface Plasmon (SP) resonances when they are excited under specific conditions. These resonances are giving rise to large enhancement of the electromagnetic field, subwalength confinement, and plasmon propagation in structures with low dimensionalities 1,2 . Owing to their remarkable optical properties, SP resonances have led to a large number of direct applications including high-precision biological sensing 3 , light manipulation by metasurfaces 4 , design of integrated devices for information processing 5 , and highly localized heat sources 6,7 . Due to the large negative real part of the dielectric function in the visible spectrum, gold or silver, either as lithographed patterns or as colloidal nanoparticles, represent the bulk of plasmonic devices so far. Although both metals exhibit complementary features that have fostered the fast development of plasmonics as a technology, these two noble metals also suffer from drawbacks; namely bulk oxidation for silver and an important interband absorption for gold at energies above 2.25 eV. Moreover, both are expensive materials limiting their systematic and massive use in commercial systems. These considerations triggered a rising interest for non-conventional plasmonic materials 8,9 . In this context, while discarded for a long time for plasmonic applications due to its high losses in the red part of the visible spectrum, aluminum has recently demonstrated its potential for applications in the blue-ultraviolet energy range 1,[10][11][12][13][14][15][17][18][19][20] . The main asset of Al over other noble metals stems mainly from a * Corresponding author: aurelien.cuche@cemes.fr plasma frequency ω p situated at a higher energy. In addition to its intrinsic electronic properties, the optical response of aluminum is ...

pyGDM—A python toolkit for full-field electro-dynamical simulations and evolutionary optimization of nanostructures

“…If the temperature increase is evaluated at sufficiently large distances to the nano-object, Eq. ( 44) is usually a good approximation also for larger metallic nano-objects [54]. "Sufficiently large distances" could mean comparable to, or larger than the size of the nanoparticle.…”

Surface Plasmon Resonances and Local Field Enhancement in Aluminum Nanoparticles Embedded in Silicon Nitride

“…27,[36][37][38][39][40] It is also worth noting that, despite -or thanks to -its IT around 800 nm (1.55 eV) and high losses in the NIR, aluminum nanoparticles are suggested as a promising alternative for light absorption and near-field enhancement in this spectral region, as well as for designing efficient integrated thermoplasmonic devices. 17,21,26,41 Several approaches have been reported to fabricate aluminum plasmonic nanostructures like lithographic methods, [19][20][21][22][23][24][25][26][27][28][29][30][31] physical vapor deposition, [33][34][35][36]39,40,[42][43][44] cluster beam depo-sition, 45 laser ablation in liquids, 46 and wet-chemical synthesis. 37,47 However, still to this day, technical challenges make it difficult to achieve the production of ultrafine aluminum nanoparticles (< 20 nm) with controlled morphology and composition.…”

“…Apart from its cheapness and natural abundance, the advantages of aluminum are substantial both from fundamental and applied points of view: aluminum is characterized by a great amenability to manufacturing processes and compatibility with semiconductor and nanoelectronics technologies. Moreover, owing both to its high-energy plasma frequency and the absence of IT in the visible and ultraviolet (UV) ranges, aluminum nanoparticles exhibit SPR that can be tuned over a broad spectral range from the NIR down to the deep UV (below 200 nm) with a strong size and shape dependence of the SPR wavelength. − Compared to noble metals, these properties make aluminum an appealing and practical material for UV-plasmonics applications ,,,− such as, for example, broadband light trapping in thin-film photovoltaic devices. ,− It is also worth noting that despiteor thanks toits IT around 800 nm (1.55 eV) and high losses in the NIR, aluminum nanoparticles are suggested as a promising alternative for light absorption and near-field enhancement in this spectral region as well as for designing efficient integrated thermoplasmonic devices. ,,, …”

Aluminum Metasurface with Hybrid Multipolar Plasmons for 1000-Fold Broadband Visible Fluorescence Enhancement and Multiplexed Biosensing

“…[15][16][17] One way to overcome this issue could be utilizing higher order plasmonic modes of large aluminum nanoantennae with lower radiative and interband-damping over the optical spectra. 15,18 However, higher order plasmons are dark (sub-radiant) in nature with almost zero netdipole moment, i.e. they don't easily couple with incident photons, and therefore they are not preferred in optical applications.…”

“…Al especially has the potential to become an excellent alternative due to its abundance, sustainability, and simple processing requirements. ,, Most importantly, Al leads over other noble metals in terms of plasma frequency that lies at a higher energy. Despite their promise, Al nanoantennae have mostly been limited to biosensing applications in the ultraviolet (UV) to blue wavelength regimes due to the inherently low quality factors ( Q ) of dipolar surface plasmons resonances ( Q : ∼ 2) in the visible range as compared to Ag ( Q : 5–10) and Au ( Q : 10–20 in red). − One way to overcome this issue could be utilizing higher order plasmonic modes of large aluminum nanoantennae with lower radiative and interband damping over the optical spectra. , However, higher order plasmons are dark (subradiant) in nature with almost zero net-dipole moment, that is, they do not easily couple with incident photons, and therefore they are not preferred in optical applications . Very recently, it has been shown that the plasmonic dark modes can be bright (super-radiant) and radiative in the far-field of tightly spaced nanostructures caused by symmetry breaking, allowing us to observe strong light–matter coupling at a single molecule level. − …”