A straight hybrid plasmonic waveguide (HPW) with concentric nanoring and nanodisk is numerically investigated based on a three-dimensional finite-difference time-domain method. It shows that the straight HPW and the nanoring with variational geometry parameters possess different coupling efficiencies at the telecommunication wavelengths. With different coupling processes, effective coupling can be achieved which provides a way to achieve optimal transmittance. Under an appropriate geometry parameter regime, the HPW could simultaneously offer a large split ratio and provide subwavelength field confinement and long propagation distance. The wavelength responses show that the HPW has good wavelength toleration around 1550 nm, indicating that it may be employed as an optical device with the desired performance for optical communications.
Through using the standard split-step Fourier method, it is found that the transverse modulation instability (MI)can
develop when beams copropagate in the positive- and the negative-index region of the metamaterials (MMs) respectively
and it is equivalent with the temporal MI in the case of two pulses copropagate in the anomalous and normal dispersion
regions of the optical fibers respectively, which is meaning that bright and dark electromagnetic spatial solitons may
generate simultaneously. Furthermore, it is confirmed that the bright and dark electromagnetic spatial solitons may even
generate simultaneously when beams copropagate in MM, which is a new way to generate spatial soliton pair for there is
only leading to the generation of bright or dark spatial solitons in conventional material when two beams copropagate.
Absorption or loss is inevitable for the metal-based metamaterials (MMs) due to the intrinsic loss of the metal, and
constitutes a major hurdle to the practical realization of most applications such as a sub-wavelength lens. Thus, to reduce
the losses becomes one of the major challenges in the MM field. However, the inevitable loss can also be harnessed to
take a positive role in the applications of MMs such as stealth technology or other types of cloaking devices. In this
presentation, after a brief review of the advances in MMs-based absorbers, we present several schemes to fulfill the
desired electromagnetic absorption properties, both linear and nonlinear. For linear absorption, we have experimentally
demonstrated that the absorption performance of an ordinary microwave absorbing material can be evidently improved
by using the electric resonance resulting from an array of subwavelength metallic circuit elements. For nonlinear
absorption, we show theoretically that the active linear magnetic permeability induces a nonlinear absorption, similar to
the two-photon absorption (TPA), of electric field in a lossy MM with a Kerr-type nonlinear polarization.
It is well known that the omnidirectional photonic bandgap (zero-n bandgap) can be realized in the one-dimensional
photonic crystals containing metamaterials. However, these omnidirectional photonic bandgaps are not tunable. In this
manuscript, we show that the electrically tunable omnidirectional photonic bandgap can be obtained in one-dimensional
photonic crystal with third-order nonlinear composite materials and linear metamaterials. It is demonstrated this photonic
crystal possesses electrically tunable photonic band structures based on the fact that the effective refractive index of
nonlinear composite material has electric-field dependence due to the existence of third-order nonlinear responses.
Moreover, we also showed that the photonic bandgap of this photonic crystal can be tuned by controlling the filling
fraction f of the composite.
Metamaterials (MMs) are artificial structures, which can be engineered to satisfy the prescribed requirements. The most
important difference between an ordinary medium and a MM is that the former has a constant permeability, while the latter
has a dispersive and controllable permeability. MMs can extend the electromagnetic properties of conventional materials,
and the study of the nonlinear propagation of ultrashort pulses in MMs could lead to completely new electronic and optical
devices. In this paper, the research advances on the propagation of electromagnetic pulses in MMs with third-order nonlinear
response are briefly described. Special effort is focused on the typical nonlinear optical phenomena such as modulation
instability, bright and dark solitons.
Two kinds of novel spatial filters constructed by metamaterials and their possible applications in high-power laser
systems have been investigated. The first one can be constructed by forming a compensating bilayer of indefinite
metamaterials. It is shown that the cutoff wave vector of the low-pass spatial filter can be adjusted desirably. The second
kind of low-pass spatial filter is based on the controllable dispersion characteristics of photonic crystals. With proper
design, the higher spatial frequency components, which are incident to the filter with angles exceed a critical value, are
reflected totally because no Bloch waves of the photonic crystals can be excited. However, the lower spatial frequency
components are coupled to the self-collimating modes and permeate with high transmission. The applications of the two
novel kinds of metamaterials-based low-pass spatial filter in high-power lasers are discussed.
We investigate the Goos-Hanchen (GH) shifts from an asymmetric configuration with single-negative materials by means of the stationary phase theory. The transmission and reflection coefficients for both TE- and TM-polarized incident beams are obtained using the transfer matrix method. A large GH shift was observed in the asymmetric configuration with single-negative materials when the surface polariton is properly excited for the TM polarization. The GH shift of the reflected beam is not equal to that of the transmitted beam. Furthermore, it is found that there is an optimum thickness and an optimum incident angle for the maximum GH shift time. The GH shift of the reflected beam can be detectable due to its large value and high reflectivity.
The guided optical modes in the asymmetric slab waveguide with a core of the normal dielectric surrounded by two single-negative (SNG) materials are investigated. The condition for occurring surface waves in the SNG material is analyzed. It is found that the epsilon-negative (ENG) waveguide supports both oscillating and surface guided modes, which is a new feature that the conventional waveguide does not possess. The oscillating guided modes of TM polariton are absent of fundamental mode, while the TE polariton can support the fundamental mode. For higher frequency, larger slab thickness and constitutive parameters, the ENG waveguide accommodates more oscillating guided modes. Furthermore, it is found that the ENG waveguide only supports TM surface guided modes, while the mu-negative (MNG) waveguide only supports TE surface guided modes. The existence of various stable solutions to the surface guided modes depends on the combination of the different constitutive parameters and the structures of waveguide. Finally, the transverse profiles of the surface guided modes in three different regions are obtained.
We study the transmission of a one-dimensional ternary left-handed photonic crystal which is consisting of three alternating slabs in the form of {ABC}, where A and C represent two kinds of positive- refractive-index materials, and B represents the negative-refractive-index material. Firstly, we obtain the dispersion equation based on the boundary conditions and Bloch theorem. By construing the obtained dispersion relation theoretically we demonstrated that a zero averaged refractive index (ZARI) gap which is around the frequency where the average refractive index vanishes appears. Secondly, we investigate the dependence of the transmission on the thickness of slabs by changing the thickness of slab A, B and C respectively. We find that the transmission of such a structure can be made tunable. This novel property may be very useful in designing tunable filters because the position of band gaps in such a structure can be chosen expediently. Furthermore, we study the property of defect mode of such a structure, and find that the defect mode doesn't always appear simultaneously in both Bragg and ZARI gaps of the transmission spectrum. It can be selected to appear either in the Bragg gap or in the ZARI gap.
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