Surface Polariton Dispersion Curves Research Articles

Surface resonance enhanced Goos–Hänchen shifts for different orientations of antiferromagnets in the presence of an applied magnetic field

When reflection takes place off the surface of antiferromagnets, surface resonances, considered as an extension of surface polariton dispersion curves into the reflection region, can enhance the lateral shift of the reflected beam in the presence of an external magnetic field. The effect was earlier studied for both the applied field and the antiferromagnet easy axis perpendicular to the plane of incidence in the case of a small applied field. Here, using MnF2 as the antiferromagnet, we extend the work to look at how increasing the field and changing the antiferromagnet orientation affects the results, which always display nonreciprocity. We find that, when the antiferromagnet easy axis is parallel to the surface within the plane of incidence, leading to spin canting, enhanced shifts in the reflection region occur in much the same way as when the easy axis is along the applied field direction, but an applied field an order of magnitude higher is needed. However, when the easy axis is perpendicular to the surface even higher fields are necessary, and it is difficult to achieve such enhanced shifts.

Surface Polaritons in GaAs/CdTe/PbTe Multilayer Structures

Infrared spectra of reflection and attenuated total reflection of PbTe thin films deposited by molecular beam epitaxy on a GaAs/CdTe substrate have been measured. The high-frequency dielectric constant, frequencies and oscillator strengths of transverse optical phonons, plasma frequencies, and plasma collision frequencies have been determined for all layers using the dispersion analysis. Attenuated total reflection spectra obtained with silicon and diamond prisms demonstrate surface phonon and plasmon–phonon polaritons. The dispersion curves of surface polaritons have been obtained.

Surface phonon polariton characteristics of wurtzite ZnO thin film grown on silicon substrate

AbstractIn this work, p‐polarized far infrared attenuated total reflection (ATR) with Otto configuration technique is employed to study the surface phonon polariton (SPP) characteristics of wurtzite ZnO thin film grown on Si(111) substrate. One prominent dip corresponding to the leaky SPP mode of the ZnO is detected at 532 cm−1. The obtained result is in good agreement with the calculated ATR spectrum simulated based on the transfer matrix formulation. The origin of the observed dip is verified with the surface polariton dispersion curves based on a three anisotropic layer model (air–ZnO–Si). The results also reveal that the real SPP and the interface phonon polariton modes for this studied structure are barely observable experimentally.

Dispersion of Surface and Interface Phonon Polariton Modes in Wurtzite Based Multilayer System

Dispersion of the surface and interface phonon polariton modes in wurtzite based multilayer system is investigated theoretically. In this study, we present a new formulation of the surface polariton (SP) dispersion relation for wurtzite based multilayer system. The expression is derived through solving Maxwell's electromagnetic equations directly by using algebraic manipulation method. The formulation is general and can be applied on any wurtzite layered structures in which the total number of layers in the system is equal or greater than two. In practice, the theory is employed to simulate the SP dispersion curves for several wurtzite layered structures, i.e., vacuum/ZnO, vacuum/ZnO/6H-SiC and vacuum/ZnO/GaN/6H-SiC. The features of these SP dispersion curves are analyzed and discussed in detail. It is shown that the characteristics of layers and the thicknesses of layers in the system have an important influence on the dispersion properties of the surface and interface phonon polariton modes.

Surface and interface phonon polariton characteristics of wurtzite ZnO/GaN heterostructure

Surface and interface phonon polariton modes in wurtzite ZnO/GaN heterostructure on wurtzite 6H–SiC substrate were investigated by a variable angle p-polarized infrared attenuated total reflection spectroscopy. Three dips corresponding to the surface and interface phonon polariton modes were observed; two of the dips that having a lower intensity level of reflectivity were the leaky modes whereas, another one was a real mode. The observations were verified with the surface polariton dispersion curve simulated based on an anisotropy model for a four-layer system. It was shown that the frequencies of leaky modes are predictable by considering the damping of the substrate.

Studies of surface and interface phonon polariton characteristics of wurtzite ZnO thin film on wurtzite 6H-SiC substrate by p-polarized infrared attenuated total reflection spectroscopy

The surface and interface phonon polariton characteristics of a wurtzite ZnO thin film grown on a wurtzite 6H-SiC substrate are investigated by p-polarized infrared attenuated total reflection spectroscopy. Two absorption dips corresponding to the leaky surface phonon polariton (SPP) mode of ZnO and the interface phonon polariton (IPP) mode of ZnO/6H-SiC are clearly observed at 558 and 916cm−1, respectively. The observations are in good agreement with the results determined from the theoretical surface polariton dispersion curve simulated by means of an anisotropy model. Finally, the effects of the ZnO thin film thickness on the SPP and IPP modes are deduced from the theoretical calculations.

Surface phonon polariton characteristics of bulk wurtzite ZnO crystal

The surface phonon polariton (SPP) mode of bulk wurtzite (α-) zinc oxide (ZnO) crystal is investigated by means of p-polarized infrared attenuated total reflection (ATR) spectroscopy. From the ATR spectrum, a strong absorption dip corresponds to the SPP mode of bulk α-ZnO is clearly observed at 529 cm −1. The experimental SPP mode showed good agreement with the theoretical SPP mode deduced from the surface polariton dispersion curve generated by the semi-infinite anisotropic crystal model.

SURFACE PHONON–POLARITON MODES OF WURTZITE STRUCTURE InN SEMI-INFINITE CRYSTAL

In this paper, theoretical study on the surface phonon–polariton (SPP) modes of wurtzite (α-) structure indium nitride ( InN ) semi-infinite crystal is presented. Based on an anisotropy model, the surface polariton (SP) dispersion curve of α- InN is simulated. The characteristics of this dispersion curve are discussed. The relevant experimental information by attenuated total reflection method is given. For comparison, the SP dispersion curve of cubic (β-) structure InN simulated based on isotropy model is also presented. Due to optical anisotropic, the SP dispersion curve of α- InN exhibits an extra branch as well as an extra SPP mode as compared to α- InN . In addition, the SPP mode of α- InN is found to be 4 cm-1 smaller than that of β- InN .

Conical propagation of a surface polariton across a grating

By the use of the homogeneous form of the reduced Rayleigh equation for the electromagnetic field above and on a two-dimensional rough surface we obtain the dispersion relation for a surface polariton propagating across a classical diffraction grating when the sagittal plane is not perpendicular to the generators of the surface. This dispersion relation is exact within the domain of validity of the Rayleigh hypothesis upon which it is based. It is solved numerically, and dispersion curves are determined for several directions of propagation of the surface polariton for three different choices for the grating profile function. Particular attention is paid to the dependence on the direction of propagation of the position and width of the gap in the surface polariton dispersion curve that occurs at the boundary of the first Brillouin zone defined by the periodicity of the grating. The results obtained are compared with those of a recent experimental determination of this gap.

The Investigation of Plasmon-Longitudinal Optical Phonon Coupling and Surface Polariton Modes in Donor Doped GaAs-Al 0.33 Ga 0.67 As Multi Quantum Wells

Infrared Fourier transform spectroscopy has been used to investigate phonon, plasmon, surface polariton and plasma-longitudinal optical phonon coupling in highly donor doped multi quantum wells (GaAs/Al0.33Ga0.67As) and direct band gap n- type AlXGa1-XAs thin layer on GaAs substrate. Using different samples with different concentration of free carriers. The dispersion equation of coupling modes have been calculated by using the condition which the dielectric functions of samples are zero for longitudinal coupled modes and experimental papameters which have been obtained from the best fit p-polarized oblique incidence far infrared reflection spectra. In MQW samples, the free carriers confined to the well and carriers are quasi two dimensional. So, plasmon- LO phonon coupling occur in the well (GaAs). In n- type AlXGa1-XAs thin layer, the coupled modes consist of three branches of the high, intermediate and low frequency modes. Their frequencies depend on both concentration and alloy composition. To analyses the surface polariton modes we carry out attenuated total reflection (ATR) measurements. In order to support our assignment the magnetic field profiles and surface polariton dispersion curves have been calculated.

Magnetoplasma reflectivity and polaritons in semiconductor superlattices

The expressions for the effective-medium dielectric tensor of a superlattice comprising doped semiconductor layers in the presence of a magnetic field are derived. They are applied to calculations of reflectivity, bulk and surface polariton dispersion curves and attenuated total reflection (ATR). Numerical results are presented for an n-p and for an n-n' superlattice, the latter being a model for delta -doped GaAs.

Splitting of surface polariton dispersion curves due to resonance with magnetoplasma transition layer

We study magnetoplasma polaritons of a thin semiconductor film on a polar-semiconductor substrate. In the vicinity of the hybrid cyclotron-plasmon frequency the surface-phonon polariton dispersion curve exhibits a splitting. The repulsion between the upper and lower branches depends on the intensity of the applied magnetic field. We have considered propagation in directions that are parallel or perpendicular to the magnetic field (itself parallel to the thin film) and find a strong directional effect.

Artificial dielectric films on crystalline quartz

The optical properties of the layers formed when partially oxidized tin was evaporated in a vacuum are reported in this paper. After deposition of the films onto a quartz substrate, measurements of the IR reflectance, the dispersion curves of surface polaritons and the conductivity indicated that the film was a dielectric with a high refractive index. The dependence of the properties of such films on their deposition conditions was investigated. The influence of the films on the reflectance in the crystalline quartz restrahlen band was also studied.

Influence of thermal annealing on the optical properties of crystalline quartz after oxygen and nitrogen ion irradiation

The optical properties of crystal quartz irradiated by N+ and O+ ions after a thermal annealing are investigated. The influence of dose is studied and a comparison is made with the properties of the samples before annealing. The defects created by implantation with a dose 1014 ion cm−2 the reflectance spectra becomes very complicated and dispersion analysis is used to determine the optical constants of the damaged transition surface layer. The surface polariton dispersion curves shift to that of untreated quartz and a splitting on the dispersion curve after the annealing of the samples, irradiated with the dose ≈ 1015 ion cm−2, is obtained. [Russian Text Ignored].

Surface polaritons on metal films with grating surface

We obtained the dispersion relation for surface polaritons propagating across a metal film upon which a periodic grating has been impressed in one face. We employed the method of reduced Rayleigh equations, and found that the surface polariton dispersion curve has an infinite number of branches. Assuming a dielectric function of a free-electron metal for the film and a sinusoidal profile function, numerical solutions were obtained for films with different thicknesses. We observed that the convergence of the method depends on the film thickness.

Surface polaritons along a grating: a linear electromagnetic study

The electromagnetic theory of gratings, previously developed to study the diffracted field, is applied to determine the field inside the material in order to obtain the characteristics of the surface polariton wave. The results predict a large enhancement of the surface polariton intensity and depression of the surface polariton dispersion curve as the groove depth is increased. The former effect is related to the existence of Wood anomalies of gratings. It is shown that one must carefully define the surface polariton dispersion curve in order to obtain correct results. This calculation includes the fact that, in addition to the well known dissipation process, surface polaritons may lose energy by coupling to the other diffracted orders.

Plasmon surface polariton dispersion by direct optical observation

Simple optical techniques are described for the direct visual observation of the plasmon surface polariton dispersion curve, ω vs κ, and of the shift in the dispersion curve from overcoatings of different thicknesses. To see the dispersion curve, a collimated beam of white light is dispersed by a prism, and then focused by a cylindrical lens onto the base of a second prism coated with a thin metal film. With this arrangement the attenuated total reflection spectrum is obtained with all the visible frequencies spatially resolved. The shift of the dispersion curve for coatings of different thicknesses is illustrated in a separate experiment using a specially constructed Langmuir wedge. This demonstrates the usefulness of plasmon surface polaritons for monitoring coatings with thicknesses of the order of nanometers.

Experimental and theoretical study of exciton surface polaritons on organic crystals. II. Highly reflecting faces of CTIP and PTS

Exciton surface polaritons have been observed at room temperature on the highly reflecting crystal faces of CTIP [γ-cyclopropyl-bis (1,3,3-trimethylindolenine-2-yl)pentamethinium fluoroborate] and PTS [poly-2,4-hexadiyne-1,6-diol bis (p-toluene sulfonate)]. These surface modes, which cannot be excited by light incident from air, were detected by measuring the attenuated total reflection (ATR) of a focused laser beam inside a prism separated from the crystal face by a gap of the order of the wavelength of the exciting light. The experimental dispersion curves of the surface modes were obtained by plotting the photon energy against the angle of the reflectance minimum. The surface active component of the complex dielectric tensor was calculated for both cyrstals and found to agree quite well with values obtained from normal incidence reflectivity studies. Several supporting theoretical studies are also reported, including: (i) the calculation of the free exciton surface polariton dispersion curves for the natural faces of CTIP, (ii) model calculations representing the ATR for all energies and angles as a perspective figure, and (iii) an investigation of the stop-point region where the virtual exciton surface polariton intersects the volume polariton modes of the CTIP crystal.

Theory of surface polaritons in germanium

A theoretical investigation has been made of surface polaritons in germanium using experimental values of the complex dielectric constant. The surface-polariton dispersion curve and attenuation length were obtained from these data. In the higher-frequency region, the dispersion curve exhibits backbending. Zenneck modes were found in the small-wave-vector region (i.e., where $k<\frac{\ensuremath{\omega}}{c}$). The use of attenuated total reflection for observing the surface polaritons in Ge is discussed.

Surface polaritons in tetragonal BaTiO 3 and PbTiO 3

For uniaxial PbTiO 3 and BaTiO 3 the upper two surface polariton dispersion curves were measured by attenuated total reflection. Comparison to calculated curves is based on data for the dielectric function which were derived from a Kramers-Kronig analysis of reflectivity spectra. The highest dispersion branch in BaTiO 3 is strongly influenced by interaction of the surface polariton with two phonon bands.