Bulk and surface excitations in magnetoactive periodic semiconductor heterostructures

We have theoretically investigated the dispersion characteristics of bulk and surface excitations in a magnetoactive periodic semiconductor heterostructure (PSH) using a local theory in the nonretardation limit (c → ∞). The computation has been performed treating the unit cell of the heterostructure as made up of an array of alternate n-type GaAs (in A-type region) and n-type InSb (in B-type region) slabs of equal widths. The presence of the high magnetostatic field (B₀) gives a rich spectrum of the bulk excitations. A new type of surface polariton mode is found in a complete analogy with the one occurring at the surface of a semiconductor superlattice as predicted by Giuliani and Quinn. The frequency-dependent inverse penetration depth for this new magnetoplasma surface polariton has also been computed as a function of wave vector component parallel to the layers. We discuss our analytical and numerical results in the light of the recent work on heterostructures/superlattices.     

Acoustically induced stark effect for excitons in intrinsic semiconductors

A Stark effect for excitons parametrically driven by coherent acoustic phonons is proposed. Our scheme refers to a low-temperature intrinsic semiconductor or semiconductor nanostructure pumped by an acoustic wave (frequency band nu(ac) approximately equal to 1-40 GHz and intensity range I(ac) approximately equal to 10(-2)-10(2) W/cm(2)) and probed by low-intensity light. Tunable optical band gaps, which strongly change the spectral shape of the exciton line, are induced in the polariton spectrum by acoustic pumping. We develop an exactly solvable model of the acoustic Stark effect and apply our results to GaAs driven by bulk or surface acoustic waves.     

Effect of quantizing magnetic field on the spectrum and damping of polaritons in double two-dimensional electronic systems

Nonradiative (surface and bulk) polaritons in a semiconductor structure composed of two heterojunctions GaAs/Al_xGa_1?x As are investigated under the integer quantum Hall effect (IQHE) conditions. The dispersive, polarization, and energy characteristics of these polaritons are determined including energy dissipation in the two-dimensional electron semiconductor layers. The phase and group velocities of surface and bulk polaritons are shown to be quantized under the IQHE conditions. It is found that resonance coupling of two surface polariton modes may occur in double GaAs/Al_xGa_1?x As heterojunctions. Possible experimental observation of nonradiative polaritons is discussed.     

Thermostimulated polariton emission of zinc selenide films on metal substrate

Angular dependences of the spectral radiance for bulk and surface polaritons in ZnSe films on an aluminium mirror have been investigated both experimentally and theoretically. A shift of a surface polariton branch to low frequencies has been observed. The difference between the surface polariton and the transverse optical phonon frequencies turned to be inversely proportional to the metal substrate conductivity. Theoretical results obtained are in good agreement with the experiment.     

The effect of the nonparabolicity of the free carriers dispersion law on the propagation of surface polaritons in a semiconductor-metal structure

The results of a study on the influence of the nonparabolicity of the free carriers dispersion law on the propagation of surface polaritons (SPs) located near the interface between an n-type semiconductor and a metal arc reported. The semiconductor plasma is assumed to be warm and nonisothermal. The nonparabolicity of the electron dispersion law has two effects. The first one is associated with nonlinear self-interaction of the SPs. The nonlinear dispersion equation and the nonlinear Schrodinger equation for the amplitude of the SP envelope are obtained. The nonlinear evolution of the SP is studied on the base of the above mentioned equations. The second effect results in third harmonics generation. Analysis shows that these third harmonics may appear as a pure surface polariton, a pseudosurface polariton, or a superposition of a volume wave and a SP depending on the wave frequency, electron density and lattice dielectric constant.     

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 polaritons at the magnetized semiconductor-dielectric interface

Conditions for the existence of a surface polariton at the semiconductor-dielectric interface have been analyzed. With allowance for the gyrotropy and the resonance frequency dispersion of the semiconductor, which manifests itself in an external magnetic field, the dispersion relation, the characteristic frequencies determining the existence region of a surface polariton, the wave fields, and the energy flux distribution in each of the interfacing media have been obtained. A numerical analysis of the influence of the external field and absorption, which lead to the manifestation of nonreciprocal properties of the polariton and to a substantial reconstruction of the spectrum, has been performed.     

Sapphire surface polariton splitting due to resonance with magnesium oxide film phonon

Surface polariton spectra of magnesium oxide films (of thickness ranging from 10 to 300 nm) prepared by chemical vapor deposition technique on sapphire substrates have been studied. The splitting of the dispersion curve of the sapphire surface polariton appears near 700 cm⁻¹ due to the resonance interaction of the sapphire substrate surface polariton with the film optical phonon. This splitting is proportional to the square root of the film thickness. Optical constants of ultrathin magnesium oxide films have been obtained from surface polariton spectra measurements. For the thinnest film (10 nm) they appear to be close to the bulk crystal values.     

Controlled switching between quantum states in the exciton–polariton condensate

Optically controlled switching between modes of a polariton laser having different symmetries has been demonstrated experimentally. The microscopic shift of the optical excitation spot dramatically changes the shape of the polariton condensate formed in a cylindrical micropillar on the basis of the planar semiconductor microcavity. Switching between the ring and lobed condensate is achieved owing to the violation of the cylindrical symmetry of the effective potential formed by the lateral surface of the pillar and by the cloud of incoherent excitons created by optical pumping.     

Quantum Theory of Surface Polaritons in Semi-Infinite Dielectric Systems

The interaction system of a semi-infinite diatomic dielectric and the electromagnetic field propagating parallelly to the surface is studied. The long-wave optical phonon modes of the semi-infinite dielectric are calculated including the electronic polarizability by a quantum-mechanical theory. Retardation effects are neglected. A quantum field theory method of surface polaritons is developed to calculate the operator describing the interaction between a photon and the phonon polarization fields of the semi-infinite crystal, with explicit inclusion of surface effects. The dispersion relations of the surface phonon-polaritons are derived and discussed. The results are in good agreement with those obtained by the conventional, macroscopic dielectric theory of surface polaritons and experimental ATR (attenuated total reflection) spectra. The dispersion cuwes of polariton leaking modes caused by the interaction between bulk TO mode with surface effect and photons are presented in a graphical form. The k_||-dependence of the electric field strength in each polariton branch is calculated and presented also in a graphical form. We also research the spatial dependence of the field strength in each polariton branch. It is found that these properties are influenced and modulated by the surface phonons because of the interaction between photons and the surface phonon modes of the semi-infinite dielectric system. Hence the divergent nature (diffraction effect) of light propagating along the fib& and waveguides is restrained. We present a method how to use the boundary conditions in the quantum theory, which will be discussed in detail.     

Magneto-phonon polaritons in two-dimension antiferromagnetic/ion-crystalic photonic crystals

Magneto-phonon polaritons in a two-dimension photonic crystal (PC) are discussed. This PC is constructed by embedding a periodical square lattice of ionic-crystal cylinders into an antiferromagnet. The two media are dispersive, with their individual resonant frequencies near each other. We first set up an effective-medium method to obtain the effective magnetic permeability and dielectric permittivity of the PC, followed by the dispersion relations of surface and bulk polaritons. There are a number of new surface polaritons, and two new distinctive bulk polariton bands in which the negative refraction and left-handedness can appear. The numerical calculations are based on the example, FeF₂/TlBr PC.     

Phonon polariton modes in semiconductor superlattices

Phonon polariton modes in semiconductor superlattices are studied. Polariton electric fields and the dispersion relation are derived by electromagnetic theory, and due to periodicity in the direction normal to the superlattice layers, Bloch's theorem is applied. Polariton modes are found to exist between the TO and LO phonon frequencies, and approach the surface polariton frequency in the limit of large tangential wave vectors. The frequencies are also strongly dependent on the ratio of the layer thicknesses. Results are illustrated by a GaAsGaP superlattice.     

Quantum Theory of Surface Polaritons on a Rough Surface

In this paper, we present the quantum field theory of the surface phonon-polaritolis on a rough polar crystal surface. The dispersion relations of the surface phonon-polaritons and the dispersion relations of polariton leaking modes owing to the interaction between bulk TO mode with the surface effect and photons are derived. We also study the k-dependence of the electric field strength in each polariton branch. The numerical calculations for the dispersion relations and the k-dependence of the electric field strength are carried out for a stepped Gap surface. The results show that the surface roughness depressed the frequency of the surface phonon-polariton below its values in the absence of the surface roughness. For the frequencies of the polariton leaking modes, the photon-like one is enhanced by the surface roughness and the phonon-like one b depressed. Our evaluations also illustrate that the surface roughness introduces a strong dependence on the k-dependence of the electric field strength in each polariton branch.     

含单负材料三明治结构的电磁隧穿特性

在理论分析的基础上,结合实验研究了单负材料/正折射率材料(或单负材料)/单负材料三明治结构的电磁隧穿性质.这种结构的电磁隧穿来源于入射平面波与结构的表面或体极化激元的耦合,从理论上讨论并计算了正入射情况下这种结构中的极化激元的色散关系.发现:由单负材料作为边界而正折射率材料为中间层的三明治结构具有体极化激元,这种极化激元的共振频率随着中间层厚度的增加向低频移动;由不同性质的单负材料构成的三明治结构具有两条色散曲线,这两条色散曲线随着中间层厚度的增加而简并.随后基于L-C传输线技 关键词： 单负材料 极化激元 隧穿 L-C传输线')" href="#">L-C传输线     

Quantum theory of the polariton of the bounded semiconductor

The quantization of the polariton field is carried out for the semiconductor bounded by the surface. The orthonormalized set of the normal mode of the vacuum-semiconductor system is explicitly given for the case of the excitonic polarization field with the standard form of the spatial dispersion and the additional boundary condition of the elastic type. The scheme is employed to interpret the several experiments: optical reflectance and transmission, resonant Raman and Brillouin scattering, and the induced absorption of the polariton. Particularly, a recent experiment on CuCl which shows the existence of correlation among the polaritons and reflected light is discussed in view of the quantum picture.     

Surface modes of a degenerate polar pomiconductor with a surface depletion layer

Surface polariton modes of a degenerate semiconductor which has a low carrier concentration surface layer are studied in the hydrodynamic approximation. In particular, the effect of the polar phonons on the higher multipole excitats of the surface is analyzed in the long wavelength non-retarded limit.     

Virtual excitation type surface polaritons on anisotropic media

We discuss the nature of a new type of surface polariton which occurs on anisotropic media, involving a photon coupled to a surface virtual excitation. Dispersion curves are calculated for α-quartz, where both real excitation type and virtual excitation type surface polaritons are predicted. The dispersion curves for virtual excitation surface polaritons are found to remain at small wavevector, and the endpoints of the dispersion curves terminate on the bulk polariton dispersion curves in the two media. The virtual excitation surface polaritons which occur on gyromagnetic and gyrodielectric media are also noted.     

The mechanism of light emission from statistically rough tunnel junctions

Its is found that the spectrum of the light emitted by statistically rough tunnel junctions in the range 400–700 nm correlates with the calculated damping of the fast surface plasmon polariton mode of the tunnel junction structure. It is deduced that the radiative decay of this mode is responsible for the bulk of the light emission. It is shown that the view of existing theory that emission from statistically rough junctions is mediated by the slow surface plasmon polariton mode is untenable. Our deductions firmly consolidate a suggestion due to Kroo, Szentirmay and Felszerfalvi.     

All-optical switching of the transmission of electromagnetic radiation through subwavelength apertures

Unprecedented optical control of the surface plasmon polariton assisted transmission of terahertz radiation through subwavelength apertures is rendered possible by carrier-induced changes to the dielectric properties of a semiconductor grating. Although the study presented is static, the extension of our approach to dynamic switching and tuning is deemed straightforward, opening the way for the realization of ultrafast surface plasmon based devices.     

Polariton Modes in Three-Tile Quasiperiodic Superlattices

The polariton modes in three-tile quasiperiodic superlattices are investigated and evaluatednumerically with a transfer matrix method. The results show that the distribution of the polaritonmodes depends obviously on the structure of the quasiperiodic superlattice. Specially,the number of the bulk modes and the number of the surface modes are related to the numberof layers and the number of interfaces contained within the quasiperiodic superlat tice.