Comparative Analysis of the Near‐ and Far‐Field Optical Response of Thin Plasmonic Nanostructures

Abstract

Nanostructures made of metallic materials support collective oscillations of their conduction electrons, commonly known as surface plasmons. These modes, whose characteristics are determined by the material and morphology of the nanostructure, couple strongly to light and confine it into subwavelength volumes. Of particular interest are metallic nanostructures for which the size along one dimension approaches the nanometer or even the subnanometer scale, since such morphologies can lead to stronger light–matter interactions and higher degrees of confinement than regular three‐dimensional nanostructures. Here, the plasmonic response of metallic nanodisks of varying thicknesses and aspect ratios is investigated under far‐ and near‐field excitation conditions. It is found that, for far‐field excitation, the strength of the plasmonic response of the nanodisk increases with its thickness, as expected from the increase in the number of conduction electrons in the system. However, for near‐field excitation, the plasmonic response becomes stronger as the thickness of the nanodisk is reduced. This behavior is attributed to the higher efficiency with which a near‐field source couples to the plasmons supported by thinner nanodisks. The results of this work advance the understanding of the plasmonic response of thin metallic nanostructures, thus increasing their potential for the development of novel applications.

Analysis of the Limits of the Optical Response of a Metallic Nanoparticle with Gain

“…These are two quantities that are usually employed to characterize respectively the near-and far-field response of plasmonic nanostructure. 72 We define the near-field intensity enhancement η as the ratio between the field intensity produced by the nanoparticle and the probe field intensity. We evaluate η at a point located a distance d from the center of the nanoparticle in the direction perpendicular to the polarization of the probe field, as indicated in the schematics of Figure 1a.…”

Controlling Single-Photon Emission with Ultrathin Transdimensional Plasmonic Films

“…Currently available due to the rapid progress in nanofabrication techniques, [4][5][6][7][8][9][10][11] such materials offer high tailorability of their electronic and optical properties not only by altering their chemical and/or electronic composition (stoichiometry, doping) but also by merely varying their thickness (number of monolayers). [12][13][14][15] Materials like these are indispensable for studies of fundamental properties of the light-matter interaction as it evolves from a single 2D atomic layer to a larger number of layers approaching the 3D bulk material properties. With thickness of only a few atomic layers, ultrathin TD films of metals, doped semiconductors, or polar materials can support plasmon-, exciton-, magnon-, and phonon-polariton eigenmodes.…”

“…With thickness of only a few atomic layers, ultrathin TD films of metals, doped semiconductors, or polar materials can support plasmon-, exciton-, magnon-, and phonon-polariton eigenmodes. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Plasmonic TD materials (ultrathin metallic films) offer controlled light confinement, large tailorability and dynamic tunability of their optical properties due to their thickness-dependent localized surface plasmon (SP) modes, [14][15][16][17][18][19][20][21] which are distinctly different from those of conventional thin films commonly described by either purely 2D or by 3D material properties with boundary conditions imposed on their top and bottom interfaces. [33][34][35][36][37][38][39][40][41] In such systems, the vertical quantum confinement enables a variety of new quantum phenomena, including the thickness-controlled plasma frequency red shift, 2,11 the SP mode degeneracy lifting, 14,18 a series of magneto-optical effects, 13 and even atomic transitions that are normally forbidden, 1,...…”

Far- and Near-Field Heat Transfer in Transdimensional Plasmonic Film Systems

“…[1][2][3][4][5][6][7][8][9][10] Often referred to as transdimensional (TD) quantum materials, [10][11][12][13][14] such films offer high tailorability of their electronic and optical properties not only by altering their chemical and electronic composition (stoichiometry, doping) but also by varying their thickness (the number of monolayers). [14][15][16][17][18][19][20] Plasmonic TD materials (ultrathin metallic films) are irreplaceable for studies of the fundamental properties of the light-matter interaction as it evolves from a single 2D atomic layer to a larger number of layers approaching the 3D bulk material properties. 11,14 They offer controlled light confinement and large tailorability of their optical properties due to their thickness-dependent localized surface plasmon (SP) modes.…”

“…11,14 They offer controlled light confinement and large tailorability of their optical properties due to their thickness-dependent localized surface plasmon (SP) modes. [12][13][14][15][16][17][18][19][20] The strong vertical quantum confinement makes these modes distinct from those of conventional thin films commonly described either by 2D or by 3D material properties with boundary conditions on their top and bottom interfaces. [21][22][23][24][25][26][27][28][29] Their properties can be understood in terms of the confinement-induced nonlocal Drude electromagnetic response theory proposed 15 and verified experimentally 10,30 recently.…”