Left-handed Layers Research Articles

A Metal-Free Helical Covalent Inorganic Polymer: Preparation, Crystal Structure and Optical Properties.

Helical morphologies are widely observed in nature, however, it is very challenging to prepare artificial helical polymers. Especially, precisely understanding the structure information of artificial metal-free helical covalent inorganic polymers via single-crystal X-ray diffraction (SCXRD) analysis is rarely explored. Here, we successfully prepare a novel metal-free helical covalent inorganic polymer ({[Te(C6 H5 )2 ] [PO3 (OH)]}n , named CityU-10) by introducing angular anions (HOPO3 2- ) into traditional tellurium-oxygen chains. The dynamic reversibility of the reaction is realized through the introduction of organic tellurium precursor and the slow hydrolysis of polyphosphoric acid. High-quality and large-size single crystals of CityU-10 have been successfully characterized via SCXRD, where the same-handed helical inorganic polymer chains form a pseudo-two-dimensional layer via multiple hydrogen-bonding interactions. The left-handed layers and right-handed layers alternatively stack together through weak hydrogen bonds to form a three-dimensional supramolecular structure. The single crystals of CityU-10 are found to display promising optical properties with a large birefringence. Our results would offer new guidelines for designing and preparing new crystalline covalent polymers through tellurium-based chemistry.

Sensitivity Analysis of GaAs-Metamaterial Nanocavity as a Tunable Surface Plasmon Resonance Sensor

Background: The paper reports on typical characteristics of resonant electromagnetic modes propagation through interfaces of a multilayer device. Methods: Using the transfer matrix method, p-reflectance is analyzed in angular interrogation for a symmetrical cavity performed with left-handed metamaterial layer mediated with GaAs. Results: An advantage of SPR sensor is demonstrated in terms of optimal performances by controlling thicknesses, refractive indices and dielectric gap layers of the media involved. Conclusion: The functionality of the proposed design, as a tunable filter, has been also identified.

Universal approach for appending double-negative materials to magneto-optics in multilayer structures

We express a general formalism to describe light propagation in multilayers including both left-handed and normal magnetic materials. In this order, we employ propagation and boundary matrices which are applicable to any configuration of media, incident angle of light and orientation of magnetization in each ferromagnetic layer. We calculate the Kerr and Faraday rotation in some given magneto-optical multilayers and show that this universal approach can thoroughly illustrate spectral broadening by the left-handed layers, even in presence of dispersion effect.

On the properties of non-Bragg gaps of one-dimensional metamaterial superlattices

We present a theoretical study of the nature of photonic band gaps of one-dimensional photonic crystals containing dispersive materials. Within the transfer-matrix formalism, we calculate the photonic band structure, transmission spectra and electric field profile for multilayered structures constituted by the periodic repetition of polaritonic and left-handed layers. It is suggested that the prediction of the existence of the 〈n〉=0, plasmon-polariton, and ϕeff non-Bragg gaps, according to the frequency dependence of the permittivity and permeability of both layers, may be made simpler through the definition of more convenient quantities such as the generalized impedance and optical path length.

Resonant tunneling of a wave through a structure that contains a layer with a negative refractive index

We have investigated the transmission ability of a layered structure the central layer of which is made of a “left-handed” material (its refractive index is negative) and is separated by two air slabs from a “right-handed” dielectric medium that surrounds the structure. We consider tunneling of energy fluxes through the structure and determine conditions for the complete (reflectionless) transmission of the power of the incident wave through it. We show that this effect is resonant and is observed when the tangential component of the wave vector of the incident wave coincides with the longitudinal wave vector of one of waveguiding eigenmodes of the left-handed layer.

Nonlinear Tunneling of Surface Plasmon Polaritons in Periodic Structures Containing Left-Handed Metamaterial Layers

The transmission of surface plasmon polaritons through a one-dimensional periodic structure is considered theoretically by using the transfer matrix approach. The periodic structure is assumed to have alternate left-handed metamaterial and dielectric layers. Both transverse electric and transverse magnetic modes of surface plasmon polaritons exist in this structure. It is found that, for nonlinear wave propagation, tunneling structures are formed to transform nontransmitting frequencies into transmitting frequencies and hence transmission bistability is observed. It is further observed that the structure shows sensitivity with respect to the polarization of the electromagnetic field for this phenomenon.

Growth surface topography of kaolinite-group minerals and their simulation based on the regular sequence of enantiomorphic layers

The regularities of manifestation of polytypism in a number of kaolinite-group minerals (kaolinite, dickite, halloysite, and nacrite) have been investigated by transmission electron microscopy and vacuum decoration. Growth patterns of elementary layers with a thickness of 7 A, individual for each polytype, were observed on (001) faces of microcrystals. Specific features of the growth patterns of polytypes have been revealed by comparing them with simulated patterns constructed based on a packing of regularly alternating right- and left-handed (enantiomorphic) kaolinite layers. The new approach to the consideration of the polytypism of kaolinite minerals is substantiated by the absence of symmetry elements in the 7-A-thick layer, which determines their structure; the formation of enantiomorphic forms of kaolinite; the presence of grazing-reflection planes in the growth patterns; and the structure of polytypes with a two-layer period. Packing of enantiomorphic layers may yield eight structures, two of which correspond to the right- and left-handed forms of kaolinite, one is for dickite, two are for halloysite, and three are for nacrite. It is shown that the simulated and real growth patterns of these minerals are in good correspondence.

Investigation of Band Gap Width in Ternary 1D Photonic Crystal with Left-Handed Layer

In this paper, we investigate the variation of band gap width in a ternary 1D photonic crystal with a left-handed layer versus variation of thicknesses and refractive index of second layers. We study these variations in two states, normal and oblique incidents for both TE and TM polarizations. We observe that the variations of band gap width versus thickness of layers are sensitive to the refractive index of second layers. For oblique incident both of variations are shifted towards the large/small frequencies by increasing the incident angles in TE/TM polarization, respectively.

Positively and negatively large Goos–Hänchen lateral displacements from a single negative layered structure

We study the electromagnetic beam reflection from layered structures that include the so-called ε-negative and the μ-negative materials, also called single negative materials. We predict that such structures can demonstrate a giant lateral Goos-Hänchen shift of the resonant excitation of surface waves at the interface between the conventional and single negative materials, as well as due to the excitation of leaky modes in the layered structures. Then we replace the conventional layer with a left-handed layer (a material with both ε<0 and μ<0). We show that the Goos-Hänchen shift can be positive and negative depending on the type of this layer (conventional or LH material), which can support TE or TM surface waves.

Optical properties of a stack of right- and left-handed layers of a cholesteric liquid crystal

We have studied the optical properties of a stack that consists of right- and left-handed layers of a cholesteric liquid crystal (CLC). The problem has been solved using the modified Ambartsumyan layer-summation method. We have examined particular features of the reflection spectra of this system and have shown that, as distinct from a single CLC layer, this system has multiple photonic band gaps. Particular features of the spectra of the photonic density of states have been considered. We have shown that this system has unique polarization characteristics; thus, in particular, if the number of sublayers is even, the eigenpolarizations of the system are degenerate (both eigenpolarizations coincide) and, as distinct from ordinary gyrotropic media, the rotation of the plane of polarization can decrease with increasing thickness of the system, the sign of the rotation depends on the sign of the chirality of the first sublayer of the system, the system is very sensitive to the variation in the number of sublayers, etc. We have investigated how the sublayer thickness, the angle of incidence, the local dielectric anisotropy, and the pitch of helix of sublayers affect the reflection spectra and other optical characteristics of the system.

Investigation of Photon Radiation in a Microsphere with Left-Handed Layers

Se estudió numéricamente la radiación electromagnética de nanoemisores colocados en una microesfera multicapas con metamateriales con dispersión (materiales izquierdos LH). Dicha investigación no puede hacerse analíticamente, sino que requiere intensivas simulaciones numéricas con el uso de la técnica tensor de Green y algoritmos específicos para las funciones esféricas. Todo esto lleva a un intenso consumo de recursos de computo. Como resultado de los experimentos numericos se encuentra que en el rango de frecuencia donde las capas de LH tienen un índice de refracción negativo el espectro de frecuencia del campo consiste en una serie de resonancias estrechas y bien separadas. En la banda de estos picos, gran parte de la energía del campo se encuentra en una capa de LH y prácticamente no sale de la microesfera. Estas conclusiones se obtuvieron como resultado no sólo de simulaciones, sino también de una interacción persona-ordenador. Se discuten los aspectos avanzados de la Interacción Persona-Ordenador con la interfaz gráfica y usabilidad que se han desarrollado en nuestro estudio y que nos ha permitido explorar a fondo un nanosistemas complejos.

Band gap properties of one-dimensional aperiodically deterministic multilayer structure containing left-handed materials

By using the transfer-matrix method and effective medium theory, we have theoretically investigated band gap properties of one-dimensional aperiodically deterministic (quasiperiodic) structure composed of left-handed material and right-handed material layers. The proposed multilayer structure is ordered according to the Fibonacci sequence constituted of two blocks A and B. It is found that this structure possesses a new type of photonic band gap which is invariant with a change of thickness scale, and sensitive to the incident angle and wave polarization. It is also found that for TE (TM) polarization, moving away from normal incidence to oblique incidence shows that the width of the band gap increases (decreases). More interestingly, our numerical results show that for angles of incidence greater than 50° the band gap for TM mode is eliminated. Moreover, for incident angles less than 50° the structure works as a tunable band edge filter.

Suppression of Anderson localization of light in one-dimensional disordered photonic superlattices

The localization properties of electromagnetic modes in one-dimensional disordered photonic superlattices are theoretically studied. The multilayered system is considered to be composed of alternating stacks of two different random-thickness slabs, characterized by nondispersive and/or frequency-dependent electric permittivities and magnetic permeabilities. Results for the localization length are evaluated by using an analytical model for weakly disordered systems as well as its general definition through the transmissivity properties of the heterostructure. Good agreement between both results is observed only for small amplitudes of disorder. The critical frequencies at which the localization length diverges are correctly predicted in the whole frequency spectrum by the analytical model and confirmed via the corresponding numerical calculations. The ${\ensuremath{\lambda}}^{2}$ dependence of the localization length, previously observed in disordered heterostructures made of material of positive refractive indexes, are confirmed in the present work. In addition, new ${\ensuremath{\lambda}}^{4}$ and ${\ensuremath{\lambda}}^{\ensuremath{-}4}$ dependencies of the localization length in positive-negative disordered photonic superlattices are obtained, under certain specific conditions, in the long and short wavelength limits, respectively. The asymptotic behavior of the localization length in these limits is essentially determined by the particular frequency dispersion that characterizes the metamaterial used in the left-handed layers. When the effects of absorption are considered, then a divergence of the localization length is still observed, under some conditions, in the short wavelength limit.

Suppression of Anderson localization in a graphene sheet applied by a random voltage pattern

We theoretically study the transport of electronic waves through a graphene sheet applied by a random voltage pattern in which the magnitudes and/or the widths of the voltages are random. When the magnitudes of the voltages exceed the electronic energy, the applied region can be considered as left-handed (LH) layers. Compared to the disordered structures with right-handed (RH) layers only, the spectra of the (average) density of states and the localization lengths in mixed random structures with RH and LH layers all show the suppression of Anderson localization, owing to the phase compensation effect of LH layers that reduces the long-range interference in the random system.

Anderson localization and Brewster anomalies in photonic disordered quasiperiodic lattices

A comprehensive study of the properties of light propagation through one-dimensional photonic disordered quasiperiodic superlattices, composed of alternating layers with random thicknesses of air and a dispersive metamaterial, is theoretically performed. The superlattices consist of the successive stacking of N quasiperiodic Fibonacci or Thue-Morse heterostructures. The width of the slabs in the photonic superlattice may randomly fluctuate around its mean value, which introduces a structural disorder into the system. It is assumed that the left-handed layers have a Drude-type dispersive response for both the dielectric permittivity and magnetic permeability, and Maxwell's equations are solved for oblique incidence by using the transfer-matrix formalism. The influence of both quasiperiodicity and structural disorder on the localization length and Brewster anomalies are thoroughly discussed.

Effect of uniaxial anisotropy of left-handed layers on created surface waves in a one dimensional photonic crystal

We investigate theoretically the creation conditions of TE and TM polarized surface waves created at the interface between a homogeneous medium and one dimensional photonic crystal (1D PC). The 1D PC is composed of uniaxially anisotropic left-handed (LH) and isotropic right-handed (RH) layers. We show that the characteristics of surface waves created in the 1D PC are significantly different from those created in the structure composed of isotropic LH and RH layers. We also prove that the coexistence of TE and TM surface waves at the interface is possible in the same frequency domain. Moreover, it is shown that in this structure backward and forward surface waves are created in wider ranges of frequency and angle of incident light, in comparison with the structure in which the left-handed layers are isotropic.

The surface mode supported by an asymmetrical waveguide containing left-handed materials

The propagating characteristics of surface mode supported by an asymmetrical three-layer waveguide containing left-hand materials are studied in detail. The forward and the backward surface modes have been identified respectively through the slope of dispersion curve and the total energy flux of the structure. Research shows that anti-symmetry mode corresponds to forward surface wave. Furthermore, to symmetry mode, the type of surface mode depends on the distribution of the electric field in the left-handed layer. It is found that, the conversion between backward surface wave and forward surface wave is realizable by varying the thickness of the left-handed layer and the permittivity of the substrate.

Polarization-independent filters for luminescent solar concentrators

The efficiency of luminescent solar concentrators could be enhanced by use of wavelength-selective filters, reducing the amount of luminescent light lost. To accomplish this, polarization-independent filters with reflectivity &amp;gt;97% were made by combining layers of cholesteric liquid crystals, either a right- with a left-handed layer, or two right-handed layers with a half-lambda waveplate. Normal cholesteric filters have a reflection bandwidth which is narrower than the spectral and angular range of the luminescent emission. The reflection band is broadened from 80 to 200 nm by employing a pitch gradient in the cholesteric layer. The measured transmission bands compare well with calculations.

Absorption effects on plasmon polaritons in quasiperiodic photonic superlattices containinga metamaterial

Absorption effects on plasmon–polariton excitations in quasiperiodic (Fibonacci andThue–Morse) one-dimensional stacks composed of layers of right- and left-handed materialsare theoretically investigated. A Drude-type dispersive response for both the dielectricpermittivity and magnetic permeability of the left-handed layer is considered. Maxwell’sequations are solved for oblique incidence by using the transfer matrix formalism,and the reflection coefficient as a function of the frequency and incidence angleis obtained. The Fibonacci (or Thue–Morse) quasiperiodic structure leads to aCantor-like photonic spectra for the plasmon–polariton modes. Moreover, results for thephotonic band structure, density of states and reflection coefficient indicate thatplasmon–polariton modes are robust in the presence of low and moderate levels ofabsorption.

The Confinement of Electromagnetic Radiation of Nanoemitters in a Multilayered Microsphere with Left-Handed Layers

The electromagnetic radiation of nanoemitters placed into a multilayered microsphere with dispersive left-handed (LH) layers included is studied numerically. It is found that in the frequency range where LH layers have a negative refraction index the field frequency spectrum consists of a series of narrow and well separated resonances. In the band of such peaks, the great part of the field energy is located in a LH layer and practically does not leave the microsphere.