A brief review is developed of the manner in which forced gyrotropic effects can be exploited through the application of a magnetic field to special classes of materials. Magnetooptics brings controlled complexity into important two- and threedimensional phenomena. These are addressed through the introduction of dissipative-external energy input effects and optical singularities. The latter create edge and screw dislocations with latter being identified with optical vortices. The way in which magnetization distributions control vortex dynamics is discussed.

We fabricated a photonic bandgap material consisting of a stack of containers with steel spheres. In the absence of external magnetic field the particles are in a disordered state. Magnetic field magnetizes the particles and they self-assemble into ordered crystalline state. We study mm-wave transmission through the stack as a function of magnetic field, i.e. for different degrees of order. This system exhibits a well-defined stopband in the ordered state, while in the disordered state the stopband becomes completely smeared. We model our results using the effective-medium approximation. We relate the disappearance of the stopband in the disordered state to the fluctuations in refraction index and admittance of individual layers. These fluctuations arise from the in-plane density fluctuations. Magnetic field suppresses density fluctuations and thus controls electromagnetic wave propagation through teh stack.

We have investigated electrical switching behavior of sol-gel derived SiO₂ films in c-Si(p)/SiO₂/metal structures. The SiO₂ film is fabricated from silicafilm (a soluble Si polymer in dissolved in denatured alcohol) using spin-coating technique. The thickness of the film is in the range of 300~2000 Å which depends on both spinning speed and the degree of dilution. We find that, with Ag as the top contact, when the applied voltage reaches a critical value of 1.5 ~ 2.5 V, current increases rapidly many orders of magnitude higher, and an irreversible switching occurs. The switching is also found to be polarity-dependent. The switching occurs only when the top contact (Ag) is biased positively, indicating the switching involves diffusion or electromigration of Ag. Both switching voltage and current are found to scale with the top contact area of the device. The switching dynamics is studied using voltage-pulse over a duration of 300 ns to 500 ms and amplitude of 2 to 20 V. We find that the switching electrical field is strongly dependent of the delay time prior to switching, and not related to the film thickness.

Decreasing feature sizes due to advances in nanotechnology place a premium on careful treatment of phase, length, and time in optics. All three quantities are intermeshed due to morphology at the nanometer length-scale. Speculation of nanotechnology for optics as a PLT sandwich has emerged from examining the characteristics of the responses of sculptured thin films to optical pulses and beams.

The optical properties of narrow-band Fabry-Perot filters for circulalry polarized light are surveyed theoretically. Here the general filter is considered to be formed by two chiral reflectors each of N turns, one with an abrupt twist of ξ and separated by an isotropic spacer of refractive index n and thickness d. The spacerless filter with d = 0, ξ = π/2 which may be regarded as a special case, is known to suffer from severe limitation of finesse and purity of polarization as N becomes large. However from previous work, there is reason to anticipate that general chiral supercavities with virtually unlimited finesse may be possible. In the presentation performance maps of the degree of polarization and the finesse confirm that chiral supercavities are possible, and conditions on n, d, and ξ are explored.

We present a new method of calculating the reflectances and transmittances associated with axial propagation through a chiral dielectric slab. The method yields simple analytic formulas that are quantitatively well-matched to those calculated using other methods.

An exact matrix polynomial series solution for oblique propagation in chiral sculptured thin films and chiral smectic liquid crystals is analyzed. The convergence of the series is investigated via calculations for a range of wavelengths, incidence angles, and material parameters. Implementation of this method is compared with the piecewise uniform permittivity approximation method.

The circularly polarized wave decomposition of Maxwell's equations for electromagnetic wave propagation in chiral materials is the starting point for this analysis. The Fourier transforms of the Green's functions for the electromagnetic waves on both sides of a flat interface between two semi-infinite chiral materials are derived. These harmonic solutions are expressed in terms of the characteristic right and left circularly polarized waves. Through a path deformation in the complex plane, the Green's functions are converted into alternate, modal, representations that are suitable for the complete expansion of the electromagnetic fields above and below a rough interface between two chiral materials with laterally varying material properties. From these representations, generalized Fourier teransform pairs are derived. The generalized Fourier transforms can be used to obtain two sets of coupled ordinary differential equations for the field transforms in terms of the forward and backward wave amplitudes of the transverse fields. Iterative solutions of these generalized telegraphists equations are found. From these solutions the fields can be found under appropriate assumptions. Since no a priori assumptions are made about the surface height, the frequency of the source, or the material parameter this work could be applied to nanotechnology involving stratified chiral structures.

Analytical theory and numerical calculations for periodic arrays of metal nanoparticles indicate resonant-like enhancement of local electromagnetic field, which can be tuned by varying a ratio of particle diameter to interparticle spacing. For Raman scattering, local field enhancements on the order of 10¹³ and surface-averaged field enhancements on the order of 10¹¹ can be achieved udner optimal conditions. This is several orders of magnitude greater tan that obtaiend in disordered metal-dielectric films, and suggests a new design for engineering plasmonic substrates supporting intense and spatially well-defined field patterns, with direct applications for surface-enhanced Raman scattering (SERS), and surface-enhanced optical nonlinearities.

We make a step towards quantum nanoplasmonics: surface plasmon fields of a nanosystem are quantized and their stimulated emission is considered. We introduce a quantum generator for surface plasmon quanta and consider the phenomenon of surface plasmon amplification by stimulated emission of radiation (spaser). Spaser generates temporally-coherent high-intensity fields of selected surface plasmon modes that can be strongly localized on the nanoscale, including dark modes that do not couple to far-zone electromagnetic fields. Applications and related phenomena are discussed.

Self-assembled Quantum Dots (QDs)have great potential as the active region in semiconductor laser diodes, resonant cavity light emitting diodes and semiconductor optical amplifiers. Yet, after nearly a decade of intense research many of the promised advantages have yet to be fully achieved. In this paper it will be shown that this non-ideal behavior is the result of an inability to control the size, shape and composition of the three dimensional islands during growth and factors such as carrier relaxation, which are fundamental to the lasing process, are not well udnerstood. In addition, the presence of the wetting layer and non-radiative recombination centers incorporated in the barrier material during growth at temperatures below that normally used for high quality material lead to poor performance at high temperatures. The emphasis has recently shifted towards GaAs-based devices operating at telecomms wavelengths where there is the possibility of replacing InP-based emitters and fabricating vertical cavity lasers in the 1.3 and 1.55-micron wavelength regions. The progress here has been steady and it is likely that commercial products will be available soon. There are also encouraging indicators for single photon emitters utilizing single dots and wideband semiconductor optical amplifiers.

Space charge is known to affect current transport in organic light emitting devices (OLEDs). This normally occurs at low bias when current density varies quadratically with the bias voltage. A transition exists when current flow changes from space-charge limited to “recombination” limited. In order to further investigate this transition, we extended our model on exciton formation based on bimolecular recombination [7] to include the existence of space charge. In examining the model characteristics, we found that where the transition occurs depends on the density of the space charge in the active layer and the fraction of it associated with "recombination". This also relates to a parameter a₀ defining the optimal charge separation for "recombination" to take place. Our results indicated that the transition would vary for different organic semiconductors and would be an important factor affecting the device performance. In comparing our model with experimental data, we are of the opinion that space charge effect may be responsible for the occasional occurrence of an "anomalous" current reported in the J-V characteristics of OLEDs.

Stimulated emission can be obtained in small volumes of scattering laser materials without cavity or any special optical design. Such sources of stimulated emission are known as random lasers. In random lasers, amplifying laser medium provides for gain, and scatterers (powder particles, air gaps between particles, etc.) provide for stimulated emission feedback. Above certain threshold pumping energy, the emission characteristics of random lasers change dramatically: the emission spectrum collapses to one or several narrow lines and one or several short emission pulses appear in response to a relatively long pumping pulse. Solid-state random lasers based on rare-earth doped dielectrics, dielectrics with color centers, semiconductors, scattering polymers, etc., offer challenging and not yet completely understood physics as well as promising applications, including express testing of laser materials, identification, and information processing. The focus of our presentation is on optically pumped neodymium random lasers. In particular, we discuss the dependence of the photon mean free path lt, the threshold energy density E_th/S and the slope efficiency in neodymium random lasers as a function of the mean particles size s. The experimental results are compared with the predictions of the developed models.

Materials having both a negative permittivity and a negative permeability allow the free propagation of electromagnetic waves with a negative phase velocity (NPV), i.e., the phase velocity is opposite the direction of energy propagation. An NPV material can be made with a lattice of fine wires cladded in nonmagnetoc insulation and embedded in a magnetic host. The wires give rise to the negative permittivity, the magnetic host supplies the negative permeability, and the nonmagnetic cladding minimizes the coupling between the wires and the magnetic host. This structure is so simple that it has the potential to be made small enough for NPV materials to operate in the far infrared. This presentation describes calculations developed to compare to experiments at microwave frequencies with cladded wires in ferrimagnetic hosts.

Materials with negative real effective permittivity and permeability (also known as "double-negative (DNG)" media) may exhibit interesting features that lead to unconventional phenomena in guidance of electromagnetic waves. As one such class of problems, in some of our earlier works we studied the guided wave propagation in structures containing a layer of DNG material paired with a slab of conventional (i.e., "double-positive (DPS)") material. In particular, we showed that such a DNG-DPS bilayer has unusual properties as a guided-wave structure. For instance, a parallel-plate waveguide filled with a pair of parallel lossless DNG and DPS layers may support dominant TE and TM modes that can propagate even when the waveguide total thickness is electrically very small. In the present work, we underline the possibility to explain some of the unconventional EM characteristics of such paired DPS-DNG waveguides and cavities using the distributed-circuit-element approach with appropriate choice of elements. The negative nature of the real part of permittivity and/or permeability affects the choice of such distributed circuit elements, and in turn the overall circuit structure exhibits certain natural "resonances" that may not be present when conventional materials are employed in such waveguides or cavities. The "circuit-element" approach can also be applied to "single-negative (SNG)" layers, in which only one of the material parameters, not both, has negative real part. Here, we first present a brief overview of our work on modal analysis in waveguides and cavities with DNG or SNG layers, and we then present our results on their distributed-circuit-element modeling.

It has been known for some time (Rothman, 1962) that meta-materials consisting of a network of metal wires share a number of electromagnetic properties with plasma. For example, both have a cutoff frequency at the effective plasma frequency of the mesh below which there is no wave propagation. These ideas have recently been re-discovered (Pendry, 1996) and applied to designing electromagnetic structures that have negative dielectric permittivity and magnetic permeability. The extent to which the electromagnetic properties of wire arrays actually mimics the properties of the plasma is still open to debate. We demonstrate that two-dimensional wire arrays are essentially different from plasmas in all aspects except having a cut-off for a particular wave polarization. On the other hand, three-dimensional wire arrays support the same classes of waves as the plasma: longitudinally polarized plasmons and transversely polarized photons. Electromagnetic properties of two and three-dimensional wire arrays are also expained using equivalent lumped circuits.

There has been a growing interest in the design and fabrication of composite materials to enhance the flexibility in specifying their optical properties for device applications. Here we show that metamaterials composed of metal-dielectric nano-structures can be engineered to have an effective refractive index below unity at optical wavelengths. These materials show intriguing optical properties including total external reflection. Different rigorous and approximate modeling techniques will be compared. We will show a novel approach to derive a realistic value of the effective refractive index from the reflection coefficients of finite slabs. The effect of losses and dispersion will be analyzed in the visible range of frequencies considering the properties of real metals. We explain the differences among ultra-low refractive index metamaterials, photonic bandgap materials, and metals. Finally, we propose the application of these metamaterials to waveguide structures that guide light in air by total external reflection.

Voigt waves are shown to propagate in biaxial composite materials whose component phases do not support the propagation of Voigt waves. The relationship between the orientations of the singular axes (along which Voigt wave propagation can occur) and the distinguished axes of the component phases is investigated by means of both the Maxwell Garnett and the Bruggeman homogenization formalisms.

In the formal development of optical response theory in terms of susceptibilities, proper representation of the optical frequency dependence necessitates modeling both the discrete linewidth and the finite signal enhancement associated with the onset of resonance. Such dispersion behavior is generally accommodated by damping factors, featured in both resonant and non-resonant susceptibility terms. For the resonant terms, the sign of such damping corrections is unequivocal; however the correct choice of sign for non-resonant terms has become a matter of debate, heightened by the discovery that entirely opposite conventions are applied in mainstream literature on Raman scattering and nonlinear optics. Where the two conventions are applied to electro-optical processes in fluids there are significant and potentially verifiable differences between the associated results. Through a full thorough quantum electrodynamical treatment the universal correctness of one convention can be ascertained and flaws in the counter-convention identified. Resolution of the central issue requires consideration of a number of fundamental questions concerning the nature of dissipation in quantum mechanical systems. It is concluded that optical susceptibilities formulated with correct signing of the damping corrections must fulfill several fundamental tests: satisfaction of a new sum rule; invariance of the associated quantum amplitudes under time-reversal symmetry, and a resilience to canonical transformation.

Electromagnetic band-gap structures (EBG) have received considerable attention in the microwave regime, due to their tremendous potential for different applications. In this communication, guided wave propagation in parallel-plate, rectangular and circular waveguides with Kronig-Penney morphology is considered. Propagation modes in these waveguides are classified as either transverse electric (TE) or transverse magnetic (TM) with respect to the propagation direction. At frequencies above the modal cut-off frequencies in the considered waveguides, band gaps exists wherein propagation is forbidden. The allowed and forbidden bands are obtained for the TE and TM propagation modes, after invoking the Bloch theorem. From the study of the ideal EBG structures, the dependencies of the locations and the widths of the band gaps -- on the modal order, the waveguide geometry and dimensions, the permittivity contrast and the relative volumetric proportion of the two materials constituting the unit cell of the EBG structure -- are deduced. Also, propagation in the corresponding real EBG structures, with finite numbers of unit cells, is studied using the scattering matrix technique. As the number of unit cells in a real structure increases, its transmission characteristics converge to those of its ideal EBG analog in the band gaps.

The dynamics of electromagnetic fields in open waveguiding structures whose dielectric properties are changed in time due to rapid plasma creation is considered. The phenomenon of transient coupling between bulk and surface waves is found. The applicability of this phenomenon for input/output of electromagnetic energy is discussed for simple waveguiding structures with both semiconductor and gaseous plasmas. In particular, a component for transient input of an electromagnetic wave into a planar dielectric waveguide covered with a nonstationary semiconductor film is proposed. Using the example of standing waves we show that the transient dynamics is sensitive to the values of the electromagnetic fields at the moment of the plasma density growth. The knowledge of the transient dynamics in rapidly ionized material can be applied for the control of guided modes in open waveguiding structures of integrated optics and (sub)millimeter wave electronics, rapid manipulation by coupling between electromagnetic radiation and guided modes, and ultrafast transient spectroscopy of an electron-hole plasma in semiconductors.

This work presents a spectroscopic ellipsometry study of phonon and polariton modes in zincblende group-III-group-V semiconductor layer structures. Contributions to the dielectric function due to infrared-active polar phonon modes and coupled longitudinal-phonon-plasmon modes are differentiated and quantified upon model lineshape analysis. Interface Fano-, Brewster- and surface-guided modes are assigned upon solution of the surface polariton dispersion relation for layered structures, and addressed by experiment. We explain the physical origin of the Berreman-effect.

The urgent goal of the optical polarimetry of solids is simultaneous and accurate measurements of circular dichroism together with circular birefringence. Needless to say, measurements of circular phenomena are extremely difficult compared with those of linear ones. As for circular birefringence, 170 years elapsed since its discovery by Arago until the development of the HAUP method, by which the accurate measurements of the gyration tensor components of a solid became possible for the first time. Subsequent to appearance of the HAUP method, attempts to extend the HAUP theory to being applicable for measurements of circular dichroism of crystals were followed by several authors. However any applications to real crystal were not fully successful. We completed fresh the theory of the extended HAUP. This paper reports the extended HAUP measurement of both circular birefringence and dichroism of fresnoite Ba₂Si₂TiO₈. It is clearly found that the circular dichroism abruptly appears at the transition temperature, where the crystal changes from the high temperature 4mm phase to the low temperature mm2 phase. It increases with decrease of temperature together with circular birefringence. This is the first proof that the HAUP method provides with sufficiently accurate data of circular dichroism of crystals. It is important to note that the circular dichroism affects only θ₀, which is one of the salient parameter characterizing the HAUP method. It means that the HAUP is an exclusive method for measuring circular dichroism of crystals.

The anisotropic homogenized composite medium (HCM) which arises from particulate component phases based on ellipsoidal geometries is considered. For cubically nonlinear component phases, the zeroth-order strong-permittivity-fluctuation theory (SPFT) (which is equivalent to the Bruggeman homogenizaiton formalism) and second-order SPFT are established and applied to estimate the constitutive parameters of the HCM. The sensitivity of the HCM constitutive parameters to the component phase particulate geometries is investigated. Particular attention is drawn to differences between the estimates of the Bruggeman homogenization formalism and the second-order SPFT. The issue of nonlinearity enhancement is explored.

The most recent approach to the development of novel antimicrobial and antifungal agents is based on the application of synthetic and natural zeolites, because zeolites are known to be the carrier and slow releaser of the heavy metals with olygodynamic properties. The microbiological activity of the ion-exchanged zeolites is attributed to the ionic state of the metal sreleased from the zeolites by ion re-exchange. In the present work we used low cost natural clinoptilolite (Cli) as a substrate for copper and silver in different states. The state of oxidation of the exchanged metal in zeolite with supported Cu and Ag species (in the form of cations, small clusters, sub-coloidal particles, large particles) in order to fit them to fulfill the following criteria: to demonstrate their high protective abilities against fungi and long-term stability. The study of structure of samples with XRD, UV-visible spectroscopy, FTIR, their stability with temperature and during storage was carried out for obtaining the correct correlation with microbiological activity.

The influence of an external magnetic field on to the magneto-optical properties of media with a helical periodical structure is discussed. The case of light normal incidence is considered, and it is assumed that the external magnetic field is directed along medium axis. The transmission and reflection of the light incident normal onto a thin film having helical structure and being in external magnetic field is discussed. It is shown that at certain conditions this system can work as an ideal optical diode or one-sided reflector for polarized light. It is shown that when absorption is present in the system it becomes nonreciprosity for non-polarized light, i.e. a new type of nonreciprocity is appeared.

The procedure followed in analyzing electromagnetic scattering by irregular layered structures, in which the heights of the interfaces as well as the medium parameters fluctuate laterally, is such that all the simplifying assumptions introduced in order to make the rigorous solutions to the problems more tractable, are made a posteriori rather than a prior. In this way the same analysis can be used to obtian the high frequency physical optics solutions that can be applied to structures with scales of roughness that are much larger than the wavelength as well as to obtain the low frequency small perturbation type solutions for structures with scales of roughness without introducing a wavelength. Thus this analysis can be applied to multiple scale structures without introducing an artificial scale parameter that dictates the solution to the problem. In addition the same analysis can be used to obtain the far field approximations suitable for structures with scales of roughness comparable and larger than the wavelength, as well as to obtain the near field approximations that are suitable for structures with subwavelength scales. The analysis accounts for evanescent as well as propagating waves, the lateral waves and the guided, surface waves of the irregular structures. To this end, a full wave approach that is based on the complete expansion of the fields as well as the imposition of exact boundary conditions at the rough interfaces is used in the analysis. Since these complete fields expansions do not necessarily converge uniformly at the irregular interface, careful mathematical procedures must be followed. It is shown that using the far field approximations, the solutions for the scattered fields are expressed as integrals over the spatial variables. On the other hand when the near field approximations are used, the scattered fields are expressed as integrals over the wave vector variables. This fulll wave analysis can also be applied to anisotropic media such as chiral materials.