Double-nonlinear metamaterials

We study a double-nonlinear metamaterial composed of a mixture of both nonlinear electric and nonlinear magnetic resonators. We predict multistable behavior in such metamaterial with the possibility to control the effective index of refraction by the electromagnetic field intensity. In contrast to the structure with just one type of nonlinear inclusions, our composite material may switch properties between the transparent negative index and the transparent positive index regimes.Authors would like to acknowledge the support from the Australian Research Council, from the National Natural Science Foundation of China Grant No. 60878008, from the New Teacher Foundation of Ministry of Education of China Grant No. 200801081014, and from the Natural Science Foundation of Shanxi Province Grant No. 2008012002-1

Exact dipole solitary wave solution in metamaterials with higher-order dispersion

We present an exact dipole solitary wave solution in a mutual modulation form of bright and dark solitons for a higher-order nonlinear Schrödinger equation with third- and fourth-order dispersion in metamaterials (MMs) using an ansatz method. Based on the Drude model, the formation conditions, existence regions and propagation properties are discussed. The results reveal that the solitary wave may exist in a few parameter regions of MMs, different from those in optical fibres, and its propagation properties can be controlled by adjusting the frequency of incident waves in each existence region

Plasmon induced transparency like transmission properties in compact MIM waveguide side-coupled with U-cavity

Surface plasmon polaritons (SPPs) can overcome the limitation of diffraction and control light at nanoscale, thus becoming a hotspot in recent years. SPPs based metal-insulator-metal (MIM) plasmonic waveguides using U-cavity and slot cavity are designed. The transmission characteristics are numerically simulated and verified by the coupled mode theory (CMT). Meanwhile, the effects of changing the geometric parameters on the transmission characteristics are also studied. Single and double plasmon induced transparency (PIT) effects are realized through the coupling and the destructive interfering between the transmission paths. Furthermore, characteristics of the refractive index sensing as well as the slow light and fast light effects are also investigated. We hope the designed waveguide structures along with their transmission characteristics have potential application prospects in the area of nanoscale integrated optical devices, such as filters, sensors, switches, slow/fast light devices, and other optoelectronic circuits

Gray solitary-wave solutions in nonlinear negative-index materials

We predict the existence of gray (dark) solitary waves in negative-index materials on the basis of a derived higher-order nonlinear Schrödinger equation. The conditions for the formation of three cases of gray solitary waves and exact analytical express

Tunable Fano resonance in MDM stub waveguide coupled with a U-shaped cavity

A new compact metal-dielectric-metal waveguide system consisting of a stub coupled with a U-cavity is proposed to produce sharp and asymmetric Fano resonance. The transmission properties of the proposed structure are numerically studied by the finite element method and verified by the coupled mode theory. Simulation results reveal that the spectral profile can be easily tuned by adjusting the geometric parameters of the structure. One of the potential application of the proposed structure as a highly efficient plasmonic refractive index nanosensor was investigated with its sensitivity of more than 1000 nm/RIU and a figure of merit of up to 5500. Another application is integrated slow-light device whose group index can be greater than 6. In addition, multiple Fano resonances will occur in the broadband transmission spectrum by adding another U-cavity or (and) stub. The characteristics of the proposed structure are very promising for the highly performance filters, on-chip nanosensors, and slow-light devices

Tunable modulation instability in metamaterials with pseudo-quintic nonlinearity, self-steepening effect and delayed Raman response

Modulation instability (MI) in metamaterials induced by pseudo-quintic nonlinearity, self-steepening effect along with delayed Raman response (DRR) is investigated and expression for MI gain is presented by linear stability method. Compared to the previous results with saturable nonlinearity, it is found that the MI without DRR may occur in four primary cases with different threshold behaviors depending on the combination of dispersion and nonlinearity and the competition of pseudo-quintic nonlinearity and self-steepening effect. This implies that we may manipulate or tune the MI by adjusting the power and frequency of incident waves at will. In addition, we consider the influence of DRR on MI and find that the DRR leads to additional regions where it entirely governs the MI gain, besides the primary ones where the self-steepening and the pseudo-quintic nonlinearity dominate the MI gain. Moreover, the DRR makes MI happen in three new cases exhibiting monotonous growth with perturbation frequency, which means that it is possible to observe MI at arbitrary high frequency. Finally, we confirm the analytical results by numerical simulations. The obtained results may be useful for manipulating or tuning the MI in metamaterials and provide more ways to generate ultrashort pulses with ultrahigh repetition rate

Tunable quad-band perfect metamaterial absorber on the basis of monolayer graphene pattern and its sensing application

In this paper, a classic three-layer metamaterial absorber (MA) is designed to achieve quad-band perfect absorption. The unit cell of the top graphene pattern layer is made up of a periodically arranged graphene split-ring nested with a cross-like graphene structure formed by four L-shaped strips. The middle dielectric spacer layer is SiO2 and the ground layer is gold. Simulation results show that four absorption bands with near unity peak absorption rate will occur in the interested frequency range of 3–11 THz. The absorption mechanism and the parameter dependency are discussed at first, which will provide guiding significances for the actual fabrication. Meanwhile, when the Fermi level of graphene is increased, the four absorption bands will have different degrees of blue-shift, and when the relaxation time of graphene is increased, the four absorption peaks will increase first and then decreases. As a result, dynamical tunability of the absorption properties can be achieved by changing the Fermi level or the relaxation time of the graphene without changing the geometry of the proposed MA. Further investigation indicates that the proposed absorber is independent of the polarization of the input electromagnetic (EM) wave and can maintain well absorption properties when the incident angle is changed within a broader range. Considering the potential sensing applications, it is shown that the proposed MA can be operated as a type of refractive index sensor with highest sensitivity of 2.97THz/RIU, and the maximum figure of merit (FOM) is 47.5. In terms of these unique performances, the proposed MA has broad application prospects in multispectral optical stealth, optical filtering, integrated photo detecting, sensing and so on

Coaxial multi-layer hybrid plasmonic waveguide at subwavelength scale

A new type of a coaxial multi-layer plasmonic waveguide is proposed. The mode propagation properties are analyzed at the communication working wavelength. Theoretical investigations reveal that the enhanced optical confinement can be achieved in the two low-index dielectric media layers. The mode size can be sub- or deep sub-wavelength scale. The mode propagation loss can be well compensated by replacing the high-index dielectric media with gain material to achieve longer propagation length with better mode confinement. The comparisons of the mode properties between the proposed waveguide and waveguides studied in the published literatures are also considered. These investigations potentially lay the groundwork for the further applications of nanowire type multilayer hybrid structures. This structure could also enable various applications such asnanophotonic waveguides, high-quality nanolasers, and optical trapping and biosensors

Exact similariton solution families and diverse composite waves in coherently coupled inhomogeneous systems

Seeking analytical solutions of nonlinear Schrödinger (NLS)-like equations remains an open topic. In this paper, we revisit the general inhomogeneous nonautonomous NLS (inNLS) equation and report on exact similaritons under generic constraint relationships by proposing a novel generic self-similar transformation, which implies that there exist a rich variety of highly-controllable solution families for inhomogeneous systems. As typical examples, richly controllable behaviors of the self-similar soliton (SS), self-similar Akhmediev breather (SAB), self-similar Ma breather (SMB), and self-similar rogue wave (SRW) are presented in a periodic distribution nonlinear system. With the aid of a linear transformation, these novel similariton solutions are deployed as a basis for constructing two-component composite solutions to a pair of coherently coupled inNLS equations including four-wave mixing. The diverse composite waves thatemerge, including SS SS, SAB SMB, and SRW SRW families, are investigated in some detail. The family of similariton solutions presented here may prove significance for designing the controland transmission of nonlinear waves