Showing papers on "Plasmon published in 1994"
TL;DR: In this article, the authors measured the Ramaman spectra of n-type gallium nitride with different carrier concentrations and found that the phonon band shifted towards the high frequency side and broadened with an increase in carrier concentration.
Abstract: Raman spectra of n‐type gallium nitride with different carrier concentrations have been measured. The LO phonon band shifted towards the high‐frequency side and broadened with an increase in carrier concentration. Results showed that the LO phonon was coupled to the overdamped plasmon in gallium nitride. The carrier concentrations and damping constants were determined by line‐shape fitting of the coupled modes and compared to values obtained from Hall measurements. The carrier concentrations obtained from the two methods agree well. As a result, the dominant scattering mechanisms in gallium nitride are deformation‐potential and electro‐optic mechanisms.
344 citations
TL;DR: In this paper, the authors synthesized a silica glass with dispersed colloid Au particles by ion implantation and found that the third-order nonlinear optical susceptibility χ(3) of this glass was inversely proportional to the third power of the radius of the colloid particles.
Abstract: Silica glass with dispersed colloid Au particles was synthesized by ion implantation. Colloid Au particles were found to grow through an Ostwald ripening mechanism controlled by diffusion in the silica glass. The third‐order nonlinear optical susceptibility χ(3) of this glass was found to be proportional to the fourth power of the radius of the colloid particles or the fourth power of the absorption coefficient at the peak of a plasmon band when the total volume of the colloid particles was constant. Furthermore, χ(3) of the glass was inversely proportional to the third power of the total volume of colloid particles when the absorption coefficient of the plasmon band was constant.
228 citations
TL;DR: In this article, the optical properties of carbon nanotubes were studied within the gradient approximation, and the calculated dielectric function exhibits many divergent structures, due to the divergencies in its density of states.
Abstract: The optical properties of carbon nanotubes are studied within the gradient approximation. The calculated dielectric function exhibits many divergent structures, due to the divergencies in its density of states. As a result, the electron-energy-loss spectrum has many peak structures, including a prominent one at \ensuremath{\sim}6 eV, which is identified as the collective excitations of the \ensuremath{\pi}-band electrons. This plasmon is found to be insensitive to both radius and chiral angle, due to the unique one-dimensional band structure of carbon nanotubes. The result is consistent with the experimental measurements. The reflectance also exhibits many interesting features, including a weak but sharp plasmon edge at \ensuremath{\sim}6 eV.
223 citations
TL;DR: The experimental and theoretical study of a Au/Co/Au model structure demonstrates that the resonant coupling of the $p$ component of the light electric field with the gold surface plasmons results in an enhancement of the magneto-optical response of the system, both in the reflected light and in the evanescent mode.
Abstract: Magneto-optical properties of noble-metal-ferromagnetic-metal multilayer thin films have been investigated in the total reflection condition. The experimental and theoretical study of a Au/Co/Au model structure demonstrates that the resonant coupling of the $p$ component of the light electric field with the gold surface plasmons results in an enhancement of the magneto-optical response of the system, both in the reflected light and in the evanescent mode.
167 citations
TL;DR: In this paper, the size and size distributions of the Cu clusters were measured by transmission electron microscopy, and were found to be determined by the ion-beam current during implantation.
Abstract: Cu clusters of nanometer dimensions were created by implantation of Cu ions into pure fused silica substrates at energies of 160 keV. The sizes and size distributions of the Cu clusters were measured by transmission electron microscopy, and were found to be determined by the ion‐beam current during implantation. Optical‐absorption spectra of these materials show the size‐dependent surface plasmon resonance characteristic of noble‐metal clusters. There are also significant size‐dependent effects in both the nonlinear index of refraction and two‐photon absorption coefficients. The distinctive variations in linear and nonlinear optical properties with Cu nanocluster sizes and size distributions affords potentially interesting possibilities for using these materials in nonlinear optical devices.
150 citations
TL;DR: Calculated spectra were found to be in good agreement with measured data and comparison between calculated results and experimental data extracted from reflected electron-energy-loss spectra showed good agreement.
Abstract: Electron differential inverse mean free paths for volume-plasmon excitations and differential probabilities for surface-plasmon excitations have been calculated using dielectric response theory. A model dielectric function which satisfied sum rules and agreed with optical data was established for these calculations. In surface-plasmon calculations, we considered electron-impact emissions of the reflected electron-energy-loss spectroscopy. Formulations were made for obliquely incident electrons with the recoil effect and without the small-scattering-angle assumption. For volume-plasmon excitations, we evaluated corrections due to the exchange and ${\mathit{Z}}_{1}^{3}$ effects. Comparison between calculated results and experimental data extracted from reflected electron-energy-loss spectra showed good agreement. Calculated differential cross sections have been used to solve the transport equation for the angular and energy flux spectra of reflected electrons. Contributions to the spectra from single and plural plasmon excitations were analyzed. It was found that calculated spectra were in good agreement with measured data.
141 citations
TL;DR: In this paper, the authors demonstrate how to obtain the ultimate lateral resolution in surface plasmon microscopy (SPM) (diffraction limited by the objective) by determining the optimal depth values for wavelengths ranging from 531 to 676 nm.
Abstract: In this article we demonstrate how to obtain the ultimate lateral resolution in surface plasmon microscopy (SPM) (diffraction limited by the objective). Surface plasmon decay lengths are determined theoretically and experimentally, for wavelengths ranging from 531 to 676 nm, and are in good agreement. Using these values we can determine for each particular situation which wavelength should be used to obtain an optimal lateral resolution, i.e., where the plasmon decay length does not limit the resolution anymore. However, there is a trade‐off between thickness resolution and lateral resolution in SPM. Because of the non‐optimal thickness resolution, we use several techniques to enhance the image acquisition and processing. Without these techniques the use of short wavelengths results in images where the contrast has vanished almost completely. In an example given, a 2.5 nm SiO2 layer on a gold layer is imaged with a lateral resolution of 2 μm, and local reflectance curves are measured to determine the laye...
124 citations
TL;DR: It is concluded that carbon nanotubes should be semimetallic, as is graphite, because the first few graphitic sheets of nanotube structures act as if they are effectively decoupled electronically, and as the radius of curvature increases then the interlayer structures approach the structure of graphite as do the electronic properties.
Abstract: Electron energy loss spectroscopy and high-resolution images of carbon nanotubes, obtained using a 2 nm probe and energy resolution of 0.5 eV, revealed a 15 eV surface plasmon for tubes containing [le]12 cylindrical graphitic sheets. As the number of sheets increases further the 24 eV bulk plasmon quickly dominates the low-loss spectra. It is concluded that carbon nanotubes should be semimetallic, as is graphite. The first few graphitic sheets of nanotube structures act as if they are effectively decoupled electronically. As the radius of curvature increases then the interlayer structures approach the structure of graphite, as do the electronic properties. The present results do not exclude the possibility that the electronic structure of carbon nanotubes is the same as that of graphite, due to the operation of a conformal invariance principle.
87 citations
TL;DR: In this article, the optical extinction by a dilute dispersion of metal nanoclusters in GaAs is calculated using the optical theorem and Maxwell-Garnet theory with complex dielectric functions for Cr, Fe, Ni, Cu, Ag, Au, Er, and As.
Abstract: Optical extinction by a dilute dispersion of metal nanoclusters in GaAs is calculated using the optical theorem and Maxwell–Garnet theory with complex dielectric functions for Cr, Fe, Ni, Cu, Ag, Au, Er, and As. The large dielectric function of the semiconductor host shifts the surface plasmon resonance frequencies from the ultraviolet to the near infrared. The noble metals have well‐defined resonances with significant absorption and Rayleigh scattering at photon energies compatible with diode lasers and semiconductor electro‐optic modulators. Interband transitions in metals such as As, Cr, Fe, Ni, and Er strongly damp the surface plasmon modes, quenching the resonant absorption by the particles, but providing significant absorption to wavelengths longer than 1.5 μm. Metal‐semiconductor composites may arise during growth or processing of materials, such as GaAs:Er for fiber‐optic applications, and GaAs:As in which metallic precipitates of As form in GaAs after low temperature growth of GaAs using molecula...
79 citations
TL;DR: A time-dependent plasmon pole approximation is derived and shown to give an excellent description of the dynamics of screening after a resonant femtosecond pulse.
Abstract: The screened Coulomb Keldysh propagator is evaluated in the time-domain for ultra-short-pulse laser excitation of a semiconductor using the nonequilibrium Green-function technique. The buildup of screening in the time interval during and shortly after the pulse excitation is treated. A time-dependent plasmon pole approximation is derived and shown to give an excellent description of the dynamics of screening after a resonant femtosecond pulse.
62 citations
TL;DR: By means of a Green-function, volume-integral-equation approach, the scattering of a surface plasmon polariton at a planar vacuum-metal interface by dielectric and metallic defects that are either embedded in the metal substrate or are situated in the vacuum region on the substrate is studied.
Abstract: By means of a Green-function, volume-integral-equation approach we study numerically the scattering of a surface plasmon polariton at a planar vacuum-metal interface by dielectric and metallic defects that are either embedded in the metal substrate or are situated in the vacuum region on the substrate. We calculate the transmission and reflection coefficients for the surface plasmon polariton, as well as the efficiency of its conversion into volume electromagnetic waves in the vacuum propagating away from the surface. We also compute the near field in the vicinity of the surface defect.
TL;DR: In this article, the authors measured the transmission electron energy-loss spectra of single-shell carbon nanotubes and compared them with those of multishell carbon nano-tubes and graphite.
Abstract: Transmission electron energy-loss spectra of single-shell carbon nanotubes were measured and compared with those of multishell carbon nanotubes and graphite. Two peaks due to the π plasmon and the π+σ plasmon were observed at 5.8 eV and 20.6 eV, respectively. The energy of the π plasmon takes a value between those of two kinds of multishell tubes. The energy of the π+σ plasmon is lower than those of multishell tubes and graphite by 2 eV and 6 eV, respectively. The 1s→π* and 1s→σ* transition peaks of the single-shell tubes are much broader than those of the multishell tubes and graphite. The reason for the broadening may be due to the strong curving of the graphitic sheets.
TL;DR: In this article, the energy loss spectra and plasmon dispersions of the alkali metals Na, K, Rb, and Cs within the random phase approximation, including band structure effects and core electrons as well as local field effects.
Abstract: We present ab initio calculations of the energy loss spectra and plasmon dispersions of the alkali metals Na, K, Rb, and Cs within the random phase approximation, including band structure effects and core electrons as well as local field effects, due to inhomogeneity in the induced charge density. Band structure effects are found to cause a negative dispersion in Cs.
TL;DR: The frequency and wave-vector dependent dielectric function of Al is calculated for both the real and imaginary parts within the random-phase approximation and good agreement of the calculated plasma frequencies with experiments is found.
Abstract: We investigate the optical properties and the dielectric response of Al through self-consistent ab initio pseudopotential calculations. The frequency and wave-vector dependent dielectric function of Al is calculated for both the real and imaginary parts within the random-phase approximation. The accuracy of the calculations is tested using Kramers-Kr\"onig relations and sum rules. In the limit q\ensuremath{\rightarrow}0, we find major optical peaks at 0.5 and 1.5 eV, which originate from the electronic structure, in good agreement with experimental data. For the wave vectors along the [100] direction, the electron-energy-loss function is calculated to examine the plasmon mode. Considering the exchange-correlation and core polarization effects, we find good agreement of the calculated plasma frequencies with experiments. The anisotropy of the plasmon dispersion is also investigated.
Patent•
13 May 1994
TL;DR: In this paper, a surface plasmon high efficiency HDTV projector employs voltage-induced color-selective absorption with surface plasmons at metal/liquid crystal interface, which is very high optical efficiency.
Abstract: A surface plasmon high efficiency HDTV projector employs voltage-induced color-selective absorption with surface plasmons at metal/liquid crystal interface. When a collimated p-polarized white light (9) is incident at metal (2) and liquid crystal (6) interface, surface plasmon resonance can be excited, certain frequencies of photons will be absorbed without reflection, and the reflected light shows the complementary color. This resonance frequency depends on the dielectric constant of both the metal film and the liquid crystal. If a voltage (8) is applied on the liquid crystal (6) to change its dielectric constant, then the absorption spectrum can be controlled by this voltage. When the p-polarized white light is reflected three times at three interfaces which are set a surface plasmon resonance at blue, green and red respectively, any color can be generated by switching these resonances. Because this device only takes the unwanted colors out of the spectrum, the wanted color almost all pass through, the optical efficiency of this device is very high.
TL;DR: In this article, an intrinsic fiber-optic sensor is described which utilizes the surface plasmon effect to monitor the chemical environment surrounding the fiber, which is constructed by polishing a short section of the lateral surface of a single-mode fiber to within the evanescent field surrounding the core.
Abstract: An intrinsic fiber-optic sensor is described which utilizes the surface plasmon effect to monitor the chemical environment surrounding the fiber. The device is constructed by polishing a short section of the lateral surface of a single-mode fiber to within the evanescent field surrounding the core. Then one or more tin films are deposited onto the polished surface, beginning with a thin metallic film which acts as the support for the plasmon. A highly refractive dielectric overlay is deposited on the metal film to allow the monitoring of a wide range of chemical sample indices of refraction. The final layer applied to the device is the chemical sample of interest
TL;DR: In this article, a multitarget sputtering method was applied to prepare Ag particles embedded in SiO2 glass thin films, and the absorption peak due to the surface plasmon resonance of Ag particles was clearly observed at the wavelength of 390-406 nm.
Abstract: A multitarget sputtering method was applied to prepare Ag particles embedded in SiO2 glass thin films. In the optical absorption spectra of the films, the absorption peak due to the surface plasmon resonance of Ag particles was clearly observed at the wavelength of 390–406 nm. The full width at half-maximum of the absorption band is decreased with increasing diameter of Ag particles. The third-order nonlinear susceptibility at 400 nm was estimated to be 1.6×10-8 esu for the film with 9.0 at% of Ag by means of a degenerated four-wave mixing.
TL;DR: In this article, the authors investigated the dimensionality crossovers of plasmons in carbon nanotubes, modeled as curved layered electron-gas superstructures, and showed that the number of graphitic shells increases with number of nodes, leading to a transition from a one-dimensional to a three-dimensional character.
Abstract: Dimensionality crossovers of plasmons in carbon nanotubes, modeled as curved layered electron-gas superstructures, are investigated. For small wave vectors, the \ensuremath{\sigma} plasmons exhibit a transition from a one- to a three-dimensional character as the number of graphitic shells increases, in correspondence with recent experiments. For large wave vectors, plasmons of two-dimensional character are predicted.
TL;DR: In this paper, the far-infrared response of electron systems confined in a parabolic potential is investigated experimentally and compared with theoretical results based on a generalization of Kohn's theorem.
Abstract: The far-infrared response of electron systems confined in a parabolic potential is investigated experimentally We present recent studies on cyclotron resonance, intersubband resonance and hybrid modes using various experimental techniques and geometries and compare our experimental findings with theoretical results based on a generalization of Kohn's theorem We also focus on the far-infrared spectrum of so-called imperfect parabolic wells with intentionally induced deviations from ideal parabolicity Here, new symmetry-forbidden resonances are observed which yield a sensitive test for a theoretical description At finite wavevector, intrasubband plasmonic excitations are also possible We study their dispersion and investigate their interaction with the intersubband modes If subjected to an in-plane magnetic field, the intrasubband plasmon exhibits a strongly anisotropic dispersion which can be directly related to so-called one-dimensional plasmons Due to the simplicity of the confining potentials, most of our experimental results can be explained in straightforward ways Many of our results as well as the theoretical descriptions directly apply to recent investigations of lateral nanostructures and thus may also serve for a better understanding of this rapidly developing field
TL;DR: In this paper, a modulator with micron dimensions, capable of optical modulation and switching in an integrated waveguide, is proposed, which uses surface plasmon resonance and an electro-optic polymer to modulate light.
Abstract: A modulator with micron dimensions, capable of optical modulation and switching in an integrated waveguide, is proposed. The proposed modulator uses surface plasmon resonance and an electro-optic polymer to modulate light which is guided in an integrated waveguide. Theoretical analysis of the modulator is presented for wavelengths of light in the visible and near infrared. Design criteria and dimensions of the modulator are discussed. >
TL;DR: An analysis of collective longitudinal electrostatic plasma excitations in quasi-one-dimensional degenerate plasmas is presented using the dielectric function in the random phase approximation to compute the complete spectrum of the collective excitations, including frequencies and damping or growth rates.
Abstract: An analysis of collective longitudinal electrostatic plasma excitations in quasi-one-dimensional degenerate plasmas is presented using the dielectric function in the random phase approximation. Analytical continuation of the dielectric function into the lower energy half plane allows us to compute the complete spectrum of the collective excitations, including frequencies and damping or growth rates. In contrast to two- and three-dimensional plasmas, a multicomponent quasi-one-dimensional system at zero temperature is found to exhibit one undamped plasmon mode for each component. The conditions for the occurrence of unstable modes are investigated and the influence of temperature and collisions on the results is discussed.
TL;DR: In this article, a multi-purpose sensor based on surface plasmon polariton resonance in a Schottky barrier structure is presented, where information is obtained directly as an electric signal across the barrier.
Abstract: A new multi-purpose sensor concept based on surface plasmon polariton resonance in a Schottky barrier structure is given. Information is obtained directly as an electric signal across the barrier. High potentialities of the sensor are experimentally confirmed by the examples of measuring sucrose concentration in water and magnetic field sensing.
TL;DR: In this paper, the behavior of the intrasubband plasmon mode of a two-dimensional electron gas undergoing lateral drift in an applied electric field was studied, and the data clearly showed the expected Doppler shifts of the modes traveling up and downstream, together with the expected dependence on the wave vector.
Abstract: We present the first Raman‐scattering studies of the behavior of the intrasubband plasmon mode of a two‐dimensional electron gas which is undergoing lateral drift in an applied electric field. The data clearly show the expected Doppler shifts of the modes traveling up‐ and downstream, together with the expected dependence on the wave vector, but at higher drift velocities, the expected linear shift is distorted because of electron heating effects.
TL;DR: In this article, high purity polycrystalline samples of C60 and C70 were obtained and studied by the electron energy-loss spectroscopy in the reflection mode, and the spectra were used for determination of the loss functions of fullerenes.
Abstract: High purity polycrystalline samples of C60 and C70 were obtained and studied by the electron energy-loss spectroscopy in the reflection mode. The spectra were used for determination of the loss functions of fullerenes. Loss functions of the fullerenes were compared with those of graphite. It was established that the relative intensities of the peaks corresponding to (σ+π)- and π-plasmons depended on the primary electron energy, while the (σ+π)-plasmon energies did not depend on the primary electron energy and were equal to 25.0 eV for C60 and 24.8 eV for C70. The conclusion on the space localization for plasma occilations in fullerenes was made on the base of the study of the energy dependent loss functions.
TL;DR: In this article, a double barrier semiconductor structure is biased near a tunneling resonance, and the coupling between this two dimensional electron gas and the tunneling current is investigated, showing that a plasmon excitation has remarkably similar structure.
Abstract: When a double barrier semiconductor structure is biased near a tunneling resonance, charge can accumulate in the quantum well. Coupling between this two dimensional electron gas and the tunneling current is investigated. Experimental data taken inside a region of apparent bistability in one device reveal a satellite on the high energy side of the current resonance in the I(V) characteristic. A theoretical model based on the many-body transfer Hamiltonian formalism shows that a plasmon excitation has remarkably similar structure. Magnetic field data support the plasmon satellite interpretation.
TL;DR: The creation of a Cooper-pair mass spectroscopy is suggested for investigation of two-dimensional plasmons in semiconductor microstructures and polaritons in condensed-matter physics.
Abstract: The creation of a Cooper-pair mass spectroscopy is suggested. The plasmons in low-dimensional superconductor structures (layers or wires in the dielectric background) are theoretically considered for this purpose. The Cooper-pair mass [ital m][sup *] (the parameter [ital m][sup *] in London electrodynamics) can be determined by measurements of the Doppler shift of the plasmon frequency when a direct current is applied through the superconductor. The plasmons with frequency [omega] lower than the superconducting gap 2[Delta] can be detected by the same far-infrared absorption technique and grating coupling used previously for investigation of two-dimensional plasmons in semiconductor microstructures and polaritons in condensed-matter physics.
TL;DR: In this paper, surface plasmon resonance studies have been used to characterize the response of a thin film of 18-crown-6 metal-free phthalocyanine upon exposure to NO2.
Abstract: In this work surface plasmon resonance studies have been used to characterize the response of a thin film of 18-crown-6 metal-free phthalocyanine upon exposure to NO2. The phthalocyanine was deposited by spin coating onto a gold film which supported the surface plasmon resonance. By fitting angle dependent reflectivity data to the Fresnel theory for a range of wavelengths it has been possible to obtain the real and imaginary parts of the optical permittivity of the material over the visible part of the spectrum. This procedure has been conducted both before and after exposure to the gas giving an accurate characterization of the changes brought about by the NO2. Thereby the wavelength at which the system's sensitivity to NO2 is an optimum has been calculated. As a secondary measure, the optical parameters derived from the surface plasmon resonance experiments have been compared to data obtained by ultraviolet-visible spectroscopy.
TL;DR: In this paper, the collective electronic excitations of cylindrical quantum-well wires, the intrasubband and intersubband plasmons in the random-phase approximation were studied theoretically.
Abstract: We study theoretically the collective electronic excitations of quasi-one-dimensional cylindrical quantum-well wires, the intrasubband and intersubband plasmons in the random-phase approximation. Using a two-subband model we calculate the dispersion curves for the case that two subbands are occupied. We study the influence of the image forces on the intrasubband and intersubband plasmons in detail. These modes are split in two branches. The intrasubband plasmon branches can be classified in an optical and an acoustic branch which are influenced quite differently by the image forces. The intersubband plasmon branches behave like acoustic plasmons.