This PDF file contains the front matter associated with SPIE Proceedings Volume 8093, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Guided waves in metamaterials are attracting attention, even though, experimentally, there remain some substantial questions about the fabrication of wave guides. Nonlinear guided optical waves have always been attractive for their device potential, so the development of nonlinear waves in metamaterials is an important direction to take and this is the basis of the discussion put forward by this paper. Given an effective medium starting point, it is possible to highlight the metamaterial influences upon both exact nonlinear waves and the soliton behaviour that is characteristic of the weakly nonlinear regime. This paper progresses through a number of priorities that have been discussed in the literature. The outcomes are rapidly reviewed from the point of view of putting the field into the context of both strongly nonlinear waves and spatial solitons, since both scenarios emphasise the role of metamaterial control. Finally, the possibility of using magneto-optics as an external control to modify the metamaterial influences is briefly displayed.

The nonlinear electromagnetic response is one of the foundations of modern technology and it arises in natural materials at the atomic scale. We briefly present some of the fundamentals of nonlinearity in natural materials and then we present experimental studies of analogous behavior in meta-atoms, the fundamental building block of metamaterials. Specifically tunnel-diode loaded, microwave split-ring resonators are shown to enable various nonlinear phenomena including self-sustained oscillation, harmonic/comb generation, frequency locking/pulling, and quasi-chaos generation. We discuss the possible adaptation of these unit cells to create bulk nonlinear metamaterials.

The extraordinary properties of nonlinear optical propagation processes in double-domain positive/negative index metamaterials are reviewed. These processes include second harmonic generation, three- and four-wave frequency mixing, and optical parametric amplification. Striking contrasts with the properties of the counterparts in ordinary materials are shown. We also discuss the possibilities for compensating strong losses inherent to plasmonic metamaterials, which present a major obstacle in numerous exciting applications, and the possibilities for creation of unique ultracompact photonic devices such as data processing chips and nonlinear-optical sensors. Finally, we propose similar extraordinary three-wave mixing processes in crystals based on optical phonons with negative dispersion.

The electromagnetic properties of metamaterials can be engineered to achieve substantially more flexibility and variety than those available from conventional materials. Adding some degree of external control or power to metamaterials enables another level of functionality. We describe our recent efforts to develop an approach for realizing powered and nonlinear metamaterials in which each unit cell contains embedded active or nonlinear elements. We demonstrate experimentally how such active and nonlinear metamaterials enable properties such as gain, nonreciprocity, and phase conjugation.

Experimental investigations reveal significant nonlinear responses from metallodielectric stacks (MDSs) with constituent metal films of silver (Ag), gold (Au) or copper (Cu). In particular, the Cu dielectric MDS exhibited large non-linear absorption. Nevertheless, there is a need to investigate these materials with more faithful numerical techniques in order to account for the underlying physical processes observed in the experiments. We apply a Finite Element Method (FEM) with radial symmetry to numerically solve for the Z-scan experiment of a MDS using the corresponding nonlinear Maxwell equations. The amplitude and the phase of the electromagnetic field at the exit interface of the MDS are used for transforming to the far-field regime.

Novel mechanism of suppression losses in plasmonic subsystem in metals and semiconductors is suggested. If two parametrically coupled fields are applied to a metal plasma, a non-linearity of the transport equation affects the electric response, or the permittivity. If the coupling constant between the probe wave and the support wave is small, the permittivity, at the frequency of the probe wave, is still Drude-like, with the re-normalized plasmon frequency. In the case of a strong coupling, unusual response effects are possible (the induced transparency and the considerable suppression of the plasmon losses), with profoundly non-Drude permittivity function.

The behavior of spontaneous emission of emitters embedded inside metamaterials with hyperbolic dispersion has been investigated. A simple technique has been developed to fabricate lamellar metal-dielectric hyperbolic metamaterials on substrates which can be flat, flexible or curvilinear in geometry. Moreover, this method opens up the possibility of functionalizing the dielectric layers by dye molecules. Utilizing this technique, we study the spontaneous emission kinetics of emitters placed either on top, or embedded inside hyperbolic metamaterials. While we observe a reduction in the radiative lifetimes in both cases, owing to the singularity in the density of photonic states, the effect is much stronger when the dye molecules are inside the metamaterial, rather than on its surface.

The development of electromagnetic (EM) metamaterials for perfect lensing and optical cloaking has given rise to novel multilayer bandgap structures using stacks of positive and negative index materials. Propagation of a collection of TE or TM plane waves, comprising the angular plane wave spectrum, through such structures is analyzed by using the transfer matrix method (TMM) on every plane wave component. Results obtained from this TMM approach for a Gaussian spectrum are compared with those using standard FEM techniques.

We review the foundations of transformation optics (the realization of a certain class of coordinate transformations through appropriate metamaterial design), from the perspective of covariant electromagnetic theory. Whilst reproducing the well-known parameter design for a spatial electromagnetic cloak, the covariant approach allows a greater design flexibility, in that coordinate transformation that explicitly include the time coordinate can be addressed. An example of the latter is the so-called spacetime cloak, in which events are concealed from distant observers through the manipulation of light's speed in both space and time. Covariant approaches have also yielded new insights to acoustics in which it has been shown that the underlying geometry of acoustic waves can be expressed as a (pseudo-)Riemanian metric in 4-dimensional spacetime. The role of the underlying velocity field of the medium is emphasized as a key and novel design parameter. The role of curvature in transformation theory is briefly reviewed. Finally, we speculate on the existance of a transformation formalism that can embrace several areas of physics.

Coherent excitation in optical spectroscopy and control of photo-induced processes like second harmonic generation depend on the temporal properties of ultrafast pulses. In particular, the generation of coherent pulse trains with high repetition rate from femtosecond sources increases both nonlinear signals and the coherent excitation of resonances in molecules. In this work, we explore a Fano resonance type of metamaterial that has very large spectral dispersion properties that can be designed based on the geometry. These properties can affect both the temporal envelope and phase of each spectral component of an ultrafast pulse in useful ways and potentially lead to a means of generating high repetition rate pulse trains.

Membrane projection lithography (MPL) has been demonstrated as a fabrication method for creation of layers of 3D unit cell metamaterials. Here we report an extensive modeling study of the electromagnetic behavior of split ring resonator (SRR) based metamaterial layers using rigorous coupled wave analysis, with particular attention to the MPL fabrication related aspects.

Metamaterials operating at optical frequencies, referred to as optical or photonic metamaterials, require features fabricated at a subwavelength scale from 50 nm to 1000nm. In this work a planar gradient index metamaterial is designed and demonstrated at optical frequencies by numerical simulation through a finite-difference time domain method in conjunction with an electromagnetic retrieval technique. We confirm the gradient by simulating the deflection of a light beam passing through a multilayer silver (Ag) and magnesium fluoride (MgF₂) slab featured with specially designed nano-rectangular holes. The planar gradient index photonic metamaterials we propose can be fabricated by available nano-fabrication technologies. Optical tests can be performed since the designs are also based on the consideration of the frequency range available for evaluation.

We have studied the ability of a lamellar near-field superlens to transfer an enhanced electromagnetic field to the far side of the lens. In this work, we have experimentally and numerically investigated superlensing in the visible range. By using the resonant hot-spot field enhancements from optical nanoantennas as sources, we investigated the translation of these sources to the far side of a layered silver-silica superlens operating in the canalization regime. Using near-field scanning optical microscopy (NSOM), we have observed evidence of superlens-enabled enhanced-field translation at a wavelength of about 680 nm. Specifically, we discuss our recent experimental and simulation results on the translation of hot spots using a silver-silica layered superlens design. We compare the experimental results with our numerical simulations and discuss the perspectives and limitations of our approach.

Two resonant surfaces, which allow the propagation of surface plasmon polaritons (SPPs) can mimic negative index materials (NIM). Hence, it is possible to recreate the near-field imaging effects known from Pendry's perfect lens. The metallic meander structure is a well-suited candidate for such a resonant surface due to the excitation and tunability of the short (SRSPP) and long range surface plasmon (LRSPP) frequencies. Furthermore, the Fano-type pass band between the SRSPP and LRSPP frequencies of a single meander sheet retains its dominant role when being stacked. We demonstrate how a stack consisting of two meander structures can perfectly image within this pass band region and propose a stack of meander structures with successively increasing periodicity. Such a stack might be capable to decrease the lateral wave vector until near-field to far-field transformation is achieved. The frequency shift of the pass band for each sheet can be compensated by changing other geometrical parameters. We rigorously calculate the spectra of various meander designs and show that meander stacks transfer energy resonantly over large distances with a high transmission.

Recently, there has been a lot of interest in electromagnetic analogues of general relativistic effects. Using the techniques of transformation optics, the material parameters of table-top devices have been calculated such that they implement several effects that occur in outer space, e.g., the implementation of an artificial event horizon inside an optical fiber, an inhomogeneous refractive index profile to mimic celestial mechanics, or an omnidirectional absorber based on an equivalence with black holes. In this communication, we show how we have extended the framework of transformation optics to a time-dependent metric-the Robertson-Walker metric, a popular model for our universe describing the cosmological redshift. This redshift occurs due to the expansion of the universe, where a photon of frequency ω_em emitted at instance tem, will be measured at a different frequency ω_obs at time t_obs. The relation between these two frequencies is given by ω_obsa(t_obs) = ω_ema(t_em), where a(t) is the time-dependent scale factor of the expanding universe. Our results show that the transformation-optical analogue of the Robertson-Walker metric is a medium with linear, isotropic, and homogeneous material parameters that evolve as a given function of time. The electromagnetic solutions inside such a medium are frequency shifted according to the cosmological redshift formula. Furthermore, we have demonstrated that a finite slab of such a material allows for the frequency conversion of an optical signal without the creation of unwanted sidebands. Because the medium is linear, the superposition principle remains applicable and arbitrary wavepackets can be converted [V. Ginis, P. Tassin, B. Craps, and I. Veretennicoff Opt. Express 18, 5350-5355 (2010)1].

Metamaterials offer opportunities to explore curved-spacetime scenarios which would otherwise be impractical or impossible to study. These opportunities arise from the formal analogy that exists between light propagation in vacuous curved spacetime and in a certain nonhomogeneous bianisotropic medium, called a Tamm medium. As the science and technology of nanostructured metamaterials continues its rapid development, the practical realization of Tamm mediums is edging ever closer. We considered two particular curved spacetimes associated with: (a) spinning cosmic strings, and (b) the Alcubierre drive. For both examples, a Tamm medium formulation was developed which is asymptotically identical to vacuum and is therefore amenable to physical realization. A study of ray trajectories for both Tamm mediums was undertaken, within the geometric optics regime. For the spinning cosmic string, it was observed that: (i) rays do not cross the string's boundary; (ii) evanescent waves are supported in regions of phase space that correspond to those regions of the string's spacetime wherein closed timelike curves may arise; and (iii) a non-spinning string is nearly invisible whereas a spinning string may be rather more visible. For the Alcubierre drive, it was observed that: (i) ray trajectories are highly sensitive to the magnitude and direction of the warp bubble's velocity, but less sensitive to the thickness of the transition zone between the warp bubble and its background; and (ii) the warp bubble acts as a focusing lens for rays which travel in the same direction as the bubble, especially at high speeds.

In earlier work, noncollinear acousto-optic (AO) interaction has been analyzed in an acoustic metamaterial modeled by a simple dispersion relation. Here we investigate nominally collinear AO interaction in an acoustic metamaterial. We show that phase matching between the undiffracted and diffracted orders, not normally achievable in collinear conventional AO (CAO), can be satisfied using the dispersive acoustic behavior in meta-acousto-optics (MAO). We develop a theory for detailed analysis of collinear interaction between light and CW and multi-frequency (pulsed) acoustic waves in acoustic metamaterials. Application of collinear MAO to AO tunable filters is also investigated.

We investigate the lateral displacement (Goos-Hänchen lateral shift) of a linearly polarized Gaussian beam reflected from a corrugated surface between a conventional dielectric and a homogeneous isotropic metamaterial with a negative index of refraction. We pay particular attention to effects associated with the resonant excitation of surface plasmon polaritons. The dependence of the lateral displacement on the incident beam parameters is examined in detail and discussed in different situations among which is the total reflection case. We compare these characteristics with the limiting case of reflection of a beam from a surface with infinitely periodic corrugations.

Existing in the "gray area" between perfectly periodic and purely randomized photonic bandgap structures are the socalled aperoidic structures whose layers are chosen according to some deterministic rule. We consider here a onedimensional photonic bandgap structure, a quarter-wave stack, with the layer thickness of one of the bilayers subject to being either thin or thick according to five deterministic sequence rules and binary random selection. To produce these aperiodic structures we examine the following sequences: Fibonacci, Thue-Morse, Period doubling, Rudin-Shapiro, as well as the triadic Cantor sequence. We model these structures numerically with a long chain (approximately 5,000,000) of transfer matrices, and then use the reliable algorithm of Wolf to calculate the (upper) Lyapunov exponent for the long product of matrices. The Lyapunov exponent is the statistically well-behaved variable used to characterize the Anderson localization effect (exponential confinement) when the layers are randomized, so its calculation allows us to more precisely compare the purely randomized structure with its aperiodic counterparts. It is found that the aperiodic photonic systems show much fine structure in their Lyapunov exponents as a function of frequency, and, in a number of cases, the exponents are quite obviously fractal.

We study local field energy density enhancement in planar metamaterials at normal incidence based on the finite element method. The microwave metamaterials composed of asymmetric resonators with/without quartz substrates are utilized to investigate the resonant response to incident electromagnetic waves. The trapped-mode resonant feature results from the excitation of an antisymmetric current mode due to the broken symmetry between two resonators and the quality factor and local field energy density enhancement strongly depend on the asymmetry. The proposed metamaterial on glass substrate shows the high possible quality factor of about 1000 and energy density enhance factor of up to 150000. To reduce losses of metamaterials further, freestanding metallic structure is considered being treated as perfect electric conductor and real-loss metal respectively. Real metallic metamaterial provides a very sharp trapped-mode resonance having the quality factor of up to 1500.

We characterize slab and cylindrical waveguides with a dielectric core and a metamaterial cladding (metamaterial-dielectric guide). We use the lossy Drude model to describe the permittivity of the metamaterial and a lossy Lorentz-like model for the permeability. We identify the possible modes and examine various related quantities, such as dispersion and attenuation, for metamaterial-dielectric waveguides. We find that at certain frequencies the modes of the metamaterial-dielectric guides differ from metal-dielectric or dielectric-dielectric guides. Our results also point to the possibility of having a metamaterial-dielectric waveguide with lower loss than a metal-dielectric waveguide.

We investigated the data transmission performance of indium antimonide (InSb) nanowires (NWs) synthesized on InSb (100) substrate using chemical vapor deposition (CVD) having diameters below 20 nm. The data transmission measurement was accomplished over the NW field effect transistors (NWFETs) fabricated on Si/SiO2 substrates. Digital data stream is randomly generated and then uploaded to a waveform generator which generates the stream and transmits it repeatedly with the desired frequency. The signal was applied on the sources of the NWFETs and collected from the drains of the same devices. Collected data was first filtered with a low pass filter (LPF), and then the output of the filter was used to create the eye diagrams of the NWs. Bit error rate (BERs), attenuation , quality factor (Q-factor) and maximum data transmission are extracted from eye diagrams. The results indicate that the data transmission performance of NWs suffer from low mobility values on the order of 10-to-15 cm2V-1s-1 because of their small diameters, crystal defects and oxidation occurs during growth and cooling. 20 nm NWs can sustain data rates up to 10 mega bits per second (Mbps) and the data rate is directly proportional to the diameter of the NWs.

Here we report on preparation of planar optical waveguides based on chitosan (DD=80.5%, MW=500kDa) in different salt forms, chitosan/gold nanoparticles, chitosan/gold nanoparticles/silica hybrids with layered structure and modification of Na/K ion-exchange waveguides with thin chitosan/carrageenan multilayers. Chitosan-based optical waveguides with thickness of 0.5- 1.5 μm were obtained on quartz, glass and MgF₂ substrates by spin-coating and dip-coating. For investigation of optical properties, light (wavelength 632 or 532 nm) was coupled into the planar waveguide via the flint glass prism using goniometer. A number of modes, effective refractive index, waveguide propagation losses were determined for all samples in the range of relative humidity 10-99%.

Metamaterials promise the possibility to tailor the propagation properties of light at the nano-scale. With this contribution we explore the possibility to combine the concept of metamaterials with integrated optics. We investigate a system consisting of a one-dimensional array of double cut-wires (two very thin gold sheets separated by a dielectric spacer) placed on top of a dielectric slab waveguide, which supports only the fundamental TE and TM mode in the near infrared spectral region around 1550 nm. Strong coupling of the waveguide modes to the plasmonic eigenmodes of the double cut-wire is achieved via the longitudinal component of the electric field, being relatively large for an asymmetric refractive index profile. By tuning the length of the double cutwires, we can tune the spectral position of the occurring hybrid resonance. We will show by rigorous calculations, that the resonance is anti-symmetric and hence produces artificial magnetism at optical frequencies in this simple scheme. To further explore the physics of the system, we investigate the dispersion relation of a periodic array of double cut-wires with varying lattice periods. The slab waveguide mode leads to a coupling of the individual plasmonic nanostructures. We find that for short lattice periods the dispersion closely resembles that of the slab waveguide. However when the Bragg frequency approaches the plasmonic resonance frequency, a strong interaction takes place and leads to a back-bending of the dispersion relation with regions of negative group velocity near to the band edge while an avoided crossing of both resonances takes place.

We present a polarization insensitive and omnidirectional broadband near perfect metamaterial absorber in the near infrared regime. The electromagnetic response of the metamaterial absorber is theoretically investigated. The bandwidth of absorption spectrum can be effectively expanded. The broadband metamaterial absorber is polarization insensitive and the absorption remains high even at large incident angles for both transverse electric and transverse magnetic configurations.

We report the results of a study to model the behavior of nonlinear metamaterials in the microwave frequency range composed of arrays of split-ring resonators combined with nonlinear circuit elements. The overall model consists of an array of coupled damped oscillators whose inter-element coupling is a function of signal amplitude, similar to that which exists in the Fermi-Pasta-Ulam system. [8] We note the potential occurrence of classical nonlinear effects including parametric coupling, FPU recurrence and chaos. These effects lead to nonlinear waves on the array which are a type of soliton particular to the form of nonlinearity that has been incorporated. We have studied, in particular, the nonlinear effects that arise from tunnel diodes embedded in the resonant circuits. We carry out simulations of the resulting circuit frequency response.

The toroidal as well as magnetic spectral responses at optical frequencies by integrating four gold U-shaped split-ring resonators (SRRs) are numerically studied. We study two kinds of toroidal structures; the first one is consisted of four-up U-shaped SRRs. The second kind, two of the four U-shaped SRRs is reversed showing two-up-two-down configuration. By reversing two SRRs of toroidal structure, their toroidal resonance and magnetic resonance are also reversed between higher and lower ones. The optical properties of toroidal resonance are also investigated in this paper.

An attempt is made to study the Einstein relation for the diffusivity-mobility ratio (DMR) in nonlinear optical and Optoelectronic compounds on the basis of a newly formulated electron energy spectrum. The results for ternary, III-V and quaternary types of optoelectronic materials form a special case of our generalized investigation. I have also studied the DMR in II-VI, Bi, IV-VI and stressed materials on the basis of various band models as applicable for such focused materials. It has been found taking n-Cd3As2, n-CdGeAs2, n-InAs, n-InSb, n-Hg1-xCdxTe, n-In1-xGaxAsyP1-y lattice matched to InP, CdS, Bi, PbS, PbTe, PbSe and stressed InSb as examples of the aforementioned compounds that the DMR increases with increasing electron concentration in various manners for different band constants of the said materials and the rates of variation are totally band structure dependent. Now the well-known results for non-degenerate wide gap optical and Optoelectronic materials have been obtained as special cases of our generalized theory under definite limiting background.

The wavelength-selection trapezoid gratings which can improve the infrared absorptance contrast are demonstrated. The spectral absorptance of silicon trapezoid grating is studied by using the rigorous coupled-wave analysis (RCWA) numerical scheme. The optical performance of the trapezoid gratings with different side-wall slopes on the groove ridge is calculated and analyzed. According to the analyzed results, the side-wall slope of the trapezoid grating plays an important role for enhancing the contrast of the infrared absorptance. It is found that the absorptance peak is located at the wavelength of 7.0 μm, which is equal to the period of the trapezoid grating. The maximum spectral absorptance contrast is given at the proper side-wall slope of groove ridge of the trapezoid gratings. The influences of the oblique incident light are also analyzed. When the incident angle increases, the absorptance peak deviates from the original location of the normal incident condition. The absorptance peak not only decreases its magnitude but also be split.

Extraordinary transmission properties are demonstrated in the UV range for GaAs gratings with sub-wavelength apertures under TM-polarization excitation. The metal-like response below 270nm, typical of several semiconductors such as GaAs or GaP, in fact may be used to excite surface waves that lead to enhance transmission in the linear regime and for novel nonlinear optical phenomena in the UV and soft X-ray ranges. An investigation of the linear transmission as a function of geometrical parameters of the grating reveals the formation of surface waves and relatively high transmission values even in regimes where the nominal absorption is significant. Strong field localization in subwavelength cavities and on the surface of the grating can be achieved under proper excitation conditions leading to the enhancement of harmonic generation. Nonlinear contributions to harmonic generation arise from symmetry breaking, the nonlinear magnetic Lorentz force, and from intrinsic, dipolar volume contributions. Preliminary results show promising nonlinear conversion efficiencies at wavelengths below 100nm, and demonstrate cross-coupling of TE and TM polarizations for pump and harmonic signals. A down-conversion process that can re-generate pump photons of polarization orthogonal compared to the incident pump field is also demonstrated.

We present a study on nonlinear optical processes in GaAs gratings, made by perforating a single layer of GaAs with very narrow slits. Large enhancement of conversion efficiency, for both second and third harmonic generation, is predicted when a TE-polarized pump field excites the guided mode resonances of the grating. At the onset of these modes the spectrum near the pump wavelength shows abrupt changes of linear transmission and reflection that follow a typical Fano-like shape. Under these circumstances, the grating provides dramatic enhancement of local fields and fosters favorable conditions for harmonic generation processes, even in regimes of strong linear absorption at the harmonic wavelengths. In a GaAs grating pumped at 1064nm, we predict second (532nm) and third (354nm) harmonic conversion efficiencies several orders of magnitude larger than conversion rates achievable in either bulk or etalon structures made of the same material. These efficiencies are not influenced by linear absorption, and they are unrelated to grating thickness. We discuss the influence of self-phase modulation on the harmonic generation conversion efficiencies. Finally, we also analyze self phase modulation effects on resonant gratings tuning the input signal at guided mode resonances, demonstrating the possibility of triggering optical bistability at relatively low switching intensities.

The Talbot effect (or the self-imaging effect) can be observed for a periodic object with a pitch larger than the diffraction limit of an imaging system, where the paraxial approximation is applied. In this paper, we show that the super Talbot effect can be achieved in an indefinite metamaterial even when the period is much smaller than the diffraction limit in both two-dimensional and three-dimensional numerical simulations, where the paraxial approximation is not applied. This is attributed to the evanescent waves, which carry the information about subwavelength features of the object, can be converted into propagating waves and then conveyed to far field by the metamaterial, where the permittivity in the propagation direction is negative while the transverse ones are positive. The indefinite metamaterial can be approximated by a system of thin, alternating multilayer metal and insulator (MMI) stack. As long as the loss of the metamaterial is small enough, deep subwavelength image size can be obtained in the super Talbot effect.

A plasmonic Raman sensor using periodic hole arrays was investigated numerically and experimentally. In previous work, we fabricated a hole array in a thin metal film on a dielectric substrate using focused ion beam lithography and succeeded in observing surface plasmon resonance. We demonstrated the effectiveness of hole shape dependency (i.e., cylindrical or tapered hole structures) for electric field enhancement, transmittance, and reflectance spectra obtained by numerical simulation using the finite-difference time-domain method. Those simulation results for an array of tapered holes agreed well with experimental results. Moreover, we numerically determined the optimized structure in terms of metal film thickness, tapered hole diameter, and hole period. However, optimal structure of a tapered hole array provides insufficient sensitivity (i.e., electric field enhancement) for measuring surface-enhanced Raman scattering. Therefore, we enhanced the electric field by using further structural parameters such as differs from tapered and incident light direction, which we expected to would give us a larger electric field. When the incident light coming from Si3N4 side, the electric field enhancement was increased markedly. The electric field enhancement was more likely to be uninvolved in metal film thicknesses using 300 nm and 500 nm.