We show that a near-field scanning thermal microscope, which essentially detects the local density of states of the thermally excited electromagnetic modes at nanometer distances from some material, can be employed for nanoscale imaging of structures on that material's surface. This finding is explained theoretically by an approach which treats the surface structure perturbatively

We study the radiative heat transfer between a spheroidal metallic nanoparticle and a planar metallic sample for near-and far-field distances. In particular, we investigate the shape dependence of the heat transfer in the near-field regime. In comparison with spherical particles, the heat transfer typically varies by factors between 1/2 and 2 when the particle is deformed such that its volume is kept constant. These estimates help to quantify the deviation of the actual heat transfer recorded by a near-field scanning thermal microscope from the value provided by a dipole model which assumes a perfectly spherical sensor.

We theoretically investigate lasing action in plasmonic crystals incorporating optically pumped four-level gain media. By using detailed simulations based on a time-domain generalization of the finite-element method, we show that the excitation of dark plasmonic resonances (via the gain medium) enables accessing the optimal lasing characteristics of the considered class of systems. Moreover, our study reveals that, in general, arrays of nanowires feature lower lasing thresholds and larger slope efficiencies than those corresponding to periodic arrays of subwavelength apertures. These findings are of relevance for further engineering of active devices based on plasmonic crystals. DOI: 10.1103/PhysRevB.91.041118 PACS number(s): 78.67. Pt, 73.20.Mf, 78.45.+h Coherent light generation at the nanoscale is one of the critical stepping stones for the ultimate control of the light fields. In this context, plasmonic structures have recently emerged as versatile platforms for achieving lasing action at length scales well below the diffraction limit [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Very recently, it has been demonstrated that plasmon-assisted lasing action is not restricted to single nanocavity systems, but can be also observed in structures supporting extended plasmonic resonances, such as periodic arrays of metallic nanoparticles [17] and periodic arrays of subwavelength apertures milled in a metallic film [18]. These works reported independently on the unique ability of the corresponding metallic periodic structure (plasmonic crystal) to collect all the lasing light produced at the nanoscale and emit it to the far field in the form of a collimated beam. Although in a closely related context a detailed study of the spatiotemporal dynamics of lasing in gain-enhanced plasmonic nano-fishnet structures has been reported [19], a general study that explores the lasing properties of plasmonic crystals from a unified perspective is-to our knowledge-still lacking. In this work we address this issue and present a fundamental theoretical analysis of the dynamics and steady-state characteristics of lasing action in plasmonic crystals consisting of periodic arrays of metallic nanowires and subwavelength apertures embedded in an optically pumped four-level gain medium.The insets of Figs. 1(a) and 1(b) render schematic views of the two model systems under study. For simplicity, we consider plasmonic crystals displaying one-dimensional periodicity along the x direction and continuous translational symmetry along the z direction (see the axes definition in the insets of Fig. 1). These structures support surface electromagnetic modes that resemble those decorating their two-dimensionally periodic counterparts [20] (this is particularly the case for thin-film plasmonic crystals, as the ones studied below). Therefore, the considered model systems are able to capture the fundamental physical phenomena governing the interaction of those surface modes with a four-level gain medium.The first analyzed configuration [in...

In the present work, we check the applicability of the effective medium model (EMM) to the problems of radiative heat transfer (RHT) through so-called wire metamaterials (WMMs)composites comprising parallel arrays of metal nanowires. It is explained why this problem is so important for the development of prospective thermophotovoltaic (TPV) systems. Previous studies of the applicability of EMM for WMMs were targeted by the imaging applications of WMMs. The analogous study referring to the transfer of radiative heat is a separate problem that deserves extended investigations. We show that WMMs with practically realizable design parameters transmit the radiative heat as effectively homogeneous media. Existing EMM is an adequate tool for qualitative prediction of the magnitude of transferred radiative heat and of its effective frequency band. V

We show that a helically grooved metal wire supports chiral surface plasmon polaritons (SPPs) that carry nonzero orbital angular momentum (OAM). This OAM can be tuned to have integer or fractional values by adjusting the mode wave vector. The dispersion relation and angular characteristics of the chiral modes are determined numerically and explained with the help of an effective mode index. Chiral SPPs offer the possibility to control both the chirality and the OAM of electromagnetic fields at the subwavelength scale.