Spectrum of surface plasmons excited by spontaneous quantum dot transitions

We consider quantum fluctuations of near fields of a quantum emitter (two-level system (TLS) with population inversion sustained by incoherent pumping) in the near-field zone of a plasmon (metallic) nanoparticle. The spectrum of surface plasmons excited by spontaneous transitions in the quantum emitter is obtained below the lasing threshold of such a system (spaser) in the approximation of a small number of plasmons. It is shown that the relaxation rate is the sum of the quantum emitter’s rates of relaxation to its thermal reservoir and the plasmon cavity. The resulting dependence of the average number of plasmons on the pump intensity indicates the nonthreshold nature of the process.     

Surface plasmon photodetectors and their applications

Surface plasmon photodetectors are of vigorous current interest. Such detectors typically combine a metallic structure that supports surface plasmons with a photodetection structure based on internal photoemission or electron‐hole pair creation. Detector architectures are highly varied, involving surface plasmons on planar metal waveguides, on metal gratings, on nano‐particles, ‐islands, or ‐antennas, or involving plasmon‐mediated transmission through one or many sub‐wavelength holes in a metal film. Properties inherent to surface plasmons, such as sub‐wavelength confinement and their ability to resonate on tiny metallic structures, are exploited to convey useful characteristics to detectors in addressing applications such as low‐noise high‐speed detection, single‐plasmon detection, near‐ and mid‐infrared imaging, photovoltaic solar energy conversion, and (bio)chemical sensing. The operating principles behind surface plasmon detectors are reviewed, the literature on the topic is surveyed, and avenues that appear promising are highlighted.     

Microcavity plasmonics: strong coupling of photonic cavities and plasmons

The understanding of light‐matter interactions at the nanoscale lays the groundwork for many future technologies, applications and materials. The scope of this article is the investigation of coupled photonic‐plasmonic systems consisting of a combination of photonic microcavities and metallic nanostructures. In such systems, it is possible to observe an exceptionally strong coupling between electromagnetic light modes of a resonator and collective electron oscillations (plasmons) in the metal. Furthermore, the results have shown that coupled photonic‐plasmonic structures possess a considerably higher sensitivity to changes in their environment than conventional localized plasmon sensors due to a plasmon excitation phase shift that depends on the environment.     

On the plasmon contribution to the surface energy of metals

The agreement between a recently propounded theory of metallic surface energies and experiment is a consequence of the arbitrary choice of the same plasmon cut-off wave-vector, k_c, for both bulk and surface plasmons. With a more reasonable choice of k_c's, the ‘plasmon theory’ predicts negative surface energies.     

Propagating anti-symmetrically coupled plasmons generation by electron beams

Propagating anti-symmetrically coupled plasmons that usually cannot be excited with incident light and radiate to far field can be efficiently generated by electron beams. An electron beam is proposed as a practical propagating anti-symmetrically coupled plasmon source due to that it couples differently to the surface plasmons than free radiation. Specifically, whispering-gallery anti-symmetrically coupled plasmons with the character of symmetrical coupled dipoles are excited by an electron beam in a nested ringlike waveguide, which is consistent with the dispersion of electron excited plasmons in an infinite-long nanowire pair.     

Negative role of surface plasmons in the transmission of metallic gratings with very narrow slits

It is generally admitted that the extraordinary transmission of metallic grating with very narrow slits is mainly due to the excitation of surface plasmons on the upper and lower interfaces of the grating. We show that the surface plasmon contribution is not the prime effect and that waveguide mode resonance and diffraction are responsible for the extraordinary transmission. Additionally and surprisingly, we reveal that the transmittance of subwavelength metallic gratings is always nearly zero for frequencies corresponding to surface plasmon excitation. This finding implies that surface plasmons play a negative role in the transmission.     

Electromagnetic renormalization of the plasmon spectrum in a laterally screened two-dimensional electron system

It is demonstrated theoretically that the effects of lateral electromagnetic screening of plasmons in a two-dimensional electron system by side metallic electrodes modify the plasmon spectrum. The effects of lateral screening become more pronounced at larger values of the plasmon wave vector. This leads to the deviation of the dispersion of laterally screened plasmons from the square-root dispersion law characteristic of unscreened plasmons. The results allow interpreting the recent experimental data of other authors on the dispersion of the plasma oscillations in a laterally screened two-dimensional electron system.     

损耗对表面等离子体激元压缩态的影响

表面等离子体激元是金属表面电子集体振荡,它以波的形式在金属和介质之间的界面中传播.近期Huck等证明等离子体激元可以处在压缩态,本文利用量子光学的热库理论,研究金波导损耗对表面等离子体激元压缩态的影响,并对Huck等的实验结果给与理论解释. 关键词： 表面等离子体激元 压缩态 热库理论     

Plasmonic structure and electromagnetic field enhancements in the metallic nanoparticle-film system

We investigate the plasmonic structure of a metallic nanoparticle near a metallic thin film. We show that in the thin film limit, a virtual plasmon resonance composed of delocalized thin film plasmons is induced. We investigate how the physical properties of the virtual state depend on polarization, film thickness and nanoparticle-film separation. We show that the electromagnetic field enhancements associated with the virtual plasmon resonance are large, suggesting applications of metallic nanoparticle/thin film systems as substrates for surface enhanced spectroscopies and surface enhanced scanning probe microscopies. PACS 78.67.Bf; 73.20.Mf; 78.30.-j     

Subwavelength propagation and localization of light using surface plasmons: A brief perspective

Surface plasmons at the metal–dielectric interface have emerged as an important candidate to propagate and localize light at subwavelength scales. By tailoring the geometry and arrangement of metallic nanoarchitectures, propagating and localized surface plasmons can be obtained. In this brief perspective, we discuss: (1) how surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs) can be optically excited in metallic nanoarchitectures by employing a variety of optical microscopy methods; (2) how SPPs and LSPs in plasmonic nanowires can be utilized for subwavelength polarization optics and single-molecule surface-enhanced Raman scattering (SERS) on a photonic chip; and (3) how individual plasmonic nanowire can be optically manipulated using optical trapping methods.     

Plasmon hybridization in metallic nanotubes with a nonconcentric core

We develop a theory of plasmon excitations in a metallic nanotube with a nonconcentric core using the plasmon hybridization method. We apply the two-center cylindrical coordinate system for mathematical convenience and find an explicit form of the dispersion relation for surface plasmons, in terms of interaction between the bare plasmon modes of the individual surfaces of the nanotubes. We present numerical result displaying the effect of the offset distant d of the inner core from the nanotube center, when there is no angular momentum transfer, i.e., m=0. For large offsets, the plasmon shifts is strong, but weak for small offset.     

Waveguide plasmon polaritons in metal-dielectric photonic crystal slabs

The optical properties of arrays of metallic (gold) nanowires deposited on dielectric substrates are studied both theoretically and experimentally. Depending on the substrate, Wood’s anomalies of two types are observed in the transmission spectra of such planar metal-dielectric photonic crystals. One of them is diffraction (Rayleigh) anomalies associated with the opening of diffraction channels to the substrate or air with an increase in the frequency of the incident light. The other type of Wood’s anomaly is resonance anomalies associated with excitation of surface quasi-guided modes in the substrate. Coupling of the quasi-guided modes with individual nanowire plasmons brings about the formation of waveguide plasmon polaritons. This effect is accompanied by a strong rearrangement of the optical spectrum and can be utilized to control the photonic bands of metal-dielectric photonic crystal slabs.     

Extremely narrow plasmon resonances based on diffraction coupling of localized plasmons in arrays of metallic nanoparticles

We experimentally demonstrate extremely narrow plasmon resonances with half-width of just several nanometers in regular arrays of metallic nanoparticles. These resonances are observed at Rayleigh's cutoff wavelengths for Wood anomalies and based on diffraction coupling of localized plasmons. We show experimentally that reflection from an array of nanoparticles can be completely suppressed at certain wavelengths. As a result, our metal nanostructures exhibit pi-jump for the phase of the reflected light.     

Sensitivity enhancement of surface plasmon resonance sensor using continuous film metallic gratings

A surface plasmon resonance (SPR) sensor based on continuous film metallic gratings is numerically investigated for enhance sensitivity. The results calculated by rigorous coupled-wave analysis (RCWA) present that interplays between localized surface plasmons and surface plasmons polaritons contribute to sensitivity enhancement. The sensitivity enhancement factor (SEF), which represents the influence of metallic grating, increased as the grating period decreased. In addition, several reflection dips can be achieved as the period of metallic grating increased. By double-dips method, the sensitivity SPR sensor based on continuous film grating-based is improved into 153.23°/RIU, which is more sensitive than conventional thin film-based SPR sensor in the same condition. The SPR sensor based on continuous film metallic gratings exhibits good linearity.     

Theoretical study of photon emission from single quantum dot emitter coupled to surface plasmons

Motivated by the recent pioneering advances on nanoscale plasmonics and also nanophotonics technology based on the surface plasmons (SPs), in this work, we give a master equation model in the Lindblad form and investigate the quantum optical properties of single quantum dot (QD) emitter coupled to the SPs of a metallic nanowire. Our main results demonstrate the QD luminescence results of photon emission show three distinctive regimes depending on the distance between QD and metallic nanowire, which elucidates a crossover passing from being metallic dissipative for much smaller emitter-nanowire distances to surface plasmon (SP) emission for larger separations at the vicinity of plasmonic metallic nanowire. Besides, our results also indicate that, for both the resonant case and the detuning case, through measuring QD emitter luminescence spectra and second-order correlation functions, the information about the QD emitter coupling to the SPs of the dissipative metallic nanowire can be extracted. This theoretical study will serve as an introduction to understanding the nanoplasmonic imaging spectroscopy and pave a new way to realize the quantum information devices.     

Surface plasmon modes and the Casimir energy

We show the influence of surface plasmons on the Casimir effect between two plane parallel metallic mirrors at arbitrary distances. Using the plasma model to describe the optical response of the metal, we express the Casimir energy as a sum of contributions associated with evanescent surface plasmon modes and propagative cavity modes. In contrast to naive expectations, the plasmonic mode contribution is essential at all distances in order to ensure the correct result for the Casimir energy. One of the two plasmonic modes gives rise to a repulsive contribution, balancing out the attractive contributions from propagating cavity modes, while both contributions taken separately are much larger than the actual value of the Casimir energy. This also suggests possibilities to tailor the sign of the Casimir force via surface plasmons.     

The influence of wire shape on surface plasmon mode distribution

The influence of the nanowire shape on the excitation of surface plasmon polaritons at metallic nanowire arrays is studied numerically. For a system of silver nanowires housed on a polymer substrate, nanowires with rectangular and elliptical cross sections are compared. It was found that in the case of rectangular nanowires the excitation efficiency is higher for surface plasmons at the polymer–metal interface than for surface plasmons at the air–metal interface. Conversely, in the case of elliptical nanowires the air–metal plasmon modes are stronger. Further, it is noted that the nanowire shape directly influences the position of the surface plasmon resonance.     

Foundations of Plasmonics

Plasma physics is a very mature field, studied extensively for well over a century. The cross-disciplinary field of plasmonics (electromagnetics of metallic nanostructures), on the other hand, with its potential for an extraordinary light control through novel class of materials and the resulting applications, has become very fashionable only recently. Inevitably, as a result of this rapid development, the deep connections with the mother discipline, the plasma physics, have sometimes been overlooked. The goal of this work is to review some of these basic connections, which are relevant, and ultimately helpful for researchers in the new field. We focus on the solid-state structured plasmas and address the issue of classical versus quantum treatments. We discuss the little known subtleties of the surface plasmons at metallic surfaces (e.g. multipole plasmons) and their consequences on plasmonics of the textured metallic films. Plasmonics of nanoparticles has been preceded by studies of plasma effects in metallic clusters and semiconducting quantum dots (QDs). In this context, we discuss the little known connection between the Mie resonance in metallic particles and the collective resonance in wide parabolic quantum wells (QWs) and QDs. Researchers dealing with plasmonics of thin films can benefit from earlier studies of plasmons in the semiconductor modulation doped heterojunctions and QWs, with its rich spectrum of intersubband and two-dimensional plasmons. In non-equilibrium plasmonic systems, generation of plasmons can be stimulated, leading to the exciting possibility of the plasmon instability. Extraordinarily complex is the plasmonics of carbon nanotubes and graphene, with its numerous van Hove, one- and three-dimensional plasmons, and we discuss how the plasmonics of metamaterials can benefit from this complexity. Finally, we discuss a few applications, which could directly benefit from plasmonics, including medical and the novel class of solar cells.     

Back focal plane imaging of Tamm plasmons and their coupled emission

The unique optical properties of Tamm plasmons (TPs) – such as flexible wavevector matching conditions including inplane wavevector within the light line, and existing both S‐ and P‐polarized TPs − facilitate them for direct optical excitation. The Tamm plasmon‐coupled emission (TPCE) from a combined photonic–plasmonic structure sustaining both surface plasmons (SPs) and TPs is described in this paper. The sensitivity of TPCE to the emission wavelength and polarization is examined with back focal plane imaging and verified with the numerical calculations. The results reveal that the excited probe can couple with both TPs and SPs, resulting in surface plasmon‐coupled emission (SPCE) and TPCE, respectively. The TPCE angle is strongly dependent on the wavelength allowing for spectral resolution using different observation angles. These Tamm structures provide a new tool to control the optical emission from dye molecules and have many potential applications in fluorescence‐based sensing and imaging.     

Plasmon hybridization in metallic nanotubes

We study theoretical formalism of the plasmon hybridization in a metallic nanotube and find an explicit form of the dispersion relation for surface plasmons, in terms of interaction between the bare plasmon modes of the individual surfaces of the nanotubes. In the special case when the longitudinal wave vector is zero (q=0), the plasmon hybridization of a nanotube has a behavior similar to the spherical nanoshell.