A new power divider, composed of a novel composite right/left-handed (CRLH) transmission line (TL) unit, is proposed. The properties of the power divider based on four CRLH TL unit cells are investigated theoretically. By adjusting the parameters of the capacitors and the inductors, the power divider shows perfectly symmetric power division at 5.13 GHz, return loss up to −24 dB, with the transmitted power being close to −3.1 dB. The phenomena are demonstrated by simulation results. Being compact in size and low-cost, the proposed power divider is very suitable for microwave and millimeter wave integrated circuits.

In this paper, we summarize some recent activities in the field of metamaterial research at the National University of Singapore (NUS). Integral equations are applied for electromagnetic modelling of supernatural materials. Some special characteristics of the metamaterials are shown. Moreover, quasi-static Lorentz theory and numerical method (i.e., the method of moments for solving the electric field integral equation) and the transmission line theory are both presented to obtain the effective constitutive relations of metamaterials, respectively. Finally, feasibility of fabricating metamaterials based on analysis of equivalent transmission line model in the microwave spectrum and even higher is also shown and correspondingly some broad-bandwidth and low-loss metamaterial structures are designed and synthesized.

The realization of double negative electromagnetic wave media, sometimes called left-handed materials (LHMs) or metamaterials, have drawn considerable attention in the past few years. We will examine the possibility of extending the concept to acoustic waves. We will see that acoustic metamaterials require both the effective density and bulk modulus to be simultaneously negative in the sense of an effective medium. If we can find a double negative (negative density and bulk modulus) acoustic medium, it will be an acoustic analogue of Veselago’s medium in electromagnetism, and share many novel consequences such as negative refractive index and backward wave characteristics. We will give one example of such a medium.

In this paper, numerical modelling of left-handed materials (LHMs) is presented using in-house and commercial software packages. Approaches used include the finite-difference time-domain (FDTD) method, finite element method (FEM) and method of moments (MoMs). Numerical simulation includes verification of negative refraction and “perfect lenses” construction, investigation of evanescent wave behaviour in layered LHMs, reversed Snell’s Law in electromagnetic band gap (EBG)-like structures and construction of LHMs using modified split ring resonators (SRRs). Numerical results were verified to be in good agreement with theory. At the end of this paper, potential applications of LHMs in microwave engineering are discussed.

The feasibility of using metal optics or negative ε materials, with the aim of reducing the transversal extent of waveguided photonic fields to values much less than the vacuum wavelength, in order to achieve significantly higher densities of integration in integrated photonics circuits that is possible today is discussed. Relevant figures of merit are formulated to this end and used to achieve good performance of devices with today’s materials and to define required improvements in materials characteristics in terms of decreased scattering rates in the Drude model. The general conclusion is that some metal based circuits are feasible with today’s matals. Frequency selective metal devices will have Q values on the order of only 10~100, and significant improvements of scattering rates or lowering of the imaginary part of ε have to be achieved to implement narrowband devices. A photonic “Moore’s law” of integration densities is proposed and exemplified.

We utilize the anomalous dispersion of planar photonic crystals near the dielectric band edge to control the wavelength-dependent propagation of light. We typically observe an angular swing of up to 10° as the input wavelength is changed from 1290 nm to 1310 nm, which signifies an angular dispersion of 0.5°/nm (“Superprism” phenomenon). Such a strong angular dispersion is of the order required for WDM systems. By tuning the incident angle, light beams with up to 20° divergence were collimated over a 25 nm (1285 nm to 1310 nm) bandwidth using a triangular lattice (“Supercollimator” phenomenon). The wavelength collimating range can be extended from 25 nm to 40 nm by changing the lattice from triangular to square. These two devices can be realized in the same configuration, simply by tuning the wavelength. Sources of loss are discussed.

The authors numerically investigated the characteristics of surface plasmons excited on a thin metal grating placed in planer or conical mounting. After formulating the problem, the solution method, Yasuura’s method (a modal expansion approach with least-squares boundary matching) was described. Although the grating is periodic in one direction, coupling between TE and TM waves occurs because arbitrary incidence is assumed. This requires the employment of both TE and TM vector modal functions in the analysis. Numerical computations showed: (1) the excitation of surface plasmons with total or partial absorption of incident light; (2) the resonance character of the coefficient of an evanescent order that couples the plasmon surface wave; (3) the field profile and Poynting’s vector. The plasmons excited on the surfaces of a thin metal grating are classified into three types: SISP, SRSP, and LRSP, different from each other in the feature of field profile and energy flow. In addition, the eigenvalue of a plasmon mode was obtained by solving a sequence of diffraction problems with complex-valued angles of incidence and using the quasi-Newton algorithm to predict the real angle of incidence at which the absorption occurs.

In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such resonator, a novel resonant mode with the resonant frequency depending on the length ratio of the RH/LH TL sections occurs as a consequence of the full phase compensation due to the backward wave in the LH TL section. The theoretical circuit-model analyses are supported by simulation and experimental evidence on resonators with different RH/LH length ratios.

New types of Bragg reflectors, multilayered periodic structures, based on alternating left-handed transmission line (LHTL) and right-handed transmission line (RHTL) are proposed. These new structures based on ideal microstrip TLs and L-C lumped elements, are designed and analyzed. We report on unusual narrow transmission bands in such kind of structures. In such multilayered structures both Bragg reflectance and the Fabry-Perot resonance exist and the phenomenon of unusual transmission is a result of competition between these two transmission effects, in which the Fabry-Perot resonance is dominant. According to our simulation results we find that this unusual transmission property exits no matter if the electrical length of the LHTL layer cancels the electrical length of the RHTL layer or not.

A new approach was introduced to analyze composite right/left-handed transmission lines (CRLH TLs). The Bloch impedance and the dispersion relations are directly obtained from the S parameters of the unit cells. The LH and RH frequency bands are then identified by the real parts of the Bloch impedance and the phase delay of the unit cells. The new approach has some advantages over the LC parameters extraction method introduced by Caloz et al.(2004). Based on the new approach, a novel resonator is designed using CRLH TLs. The simulation and experimental results accorded well with the theoretical analysis. The novel resonator may have potential applications in filters with high harmonic suppression and compact structures.

A quasi 0-dB coupler composed of a composite right-/left-handed transmission line (CRLH TL) and a conventional right-handed transmission line (RH TL) is presented. This coupler is shown to exhibit broad bandwidth and tight coupling characteristics. The circuit model and S-parameter results are also demonstrated. Another coupler with properly chosen loaded lumped-elements L_L and C_L in the CRLH TL is proposed to gain further understanding of the coupling mechanism. By adjusting the spacing between the CRLH TL and RH TL from 8 mm to 0.2 mm, it can be shown that backward coupling occurs in the left-handed region.

Based on the analytical solution of electromagnetic scattering by a uniaxial anisotropic sphere in the spectral domain, an analytical solution to the electromagnetic scattering by a uniaxial left-handed materials (LHMs) sphere is obtained in terms of spherical vector wave functions in a uniaxial anisotropic LHM medium. The expression of the analytical solution contains only some one-dimensional integral which can be calculated easily. Numerical results show that Mie series of plane wave scattering by an isotropic LHM sphere is a special case of the present method. Some numerical results of electromagnetic scattering of a uniaxial anisotropic sphere by a plane wave are given.

Thermally poled germanium-doped channel waveguides are presented. Multilayer waveguides containing a silicon oxynitride layer were used as charge trapper in this investigation on the effect of the internal field inside the waveguide. Compared to waveguides without the trapping layer, experimental results showed that the induced linear electro-optic (EO) coefficient increases about 20% after poling, suggesting strongly that the internal field is relatively enhanced, and showed it is a promising means for improving nonlinearity by poling in waveguides.

A transversal mode with zero group velocity and non-zero phase velocity that can exist in chains of silver nano-spheres in the optical frequency range was theoretically studied. It is shown that the external source radiating a narrow-band non-monochromatic signal can excite in the chain a mixture of standing and slowly travelling waves. The standing wave component (named as resonator mode) is strongly dominating. The physical reason of such a regime is a sign-varying distribution of power flux over the cross section of the chain. This situation is similar to the scenario of the propagation of a wave along the boundary between the right-handed and left-handed media where the spatial distribution of the light intensity is vortex. However, in the present case there is no boundary between media and the boundary between the positive and negative power fluxes is a cylindric tube in free space whose axis is the axis of the chain.

The authors’ theoretical investigation on the high-frequency response of magnetized metallic magnetic films showed that magnetic films may become left-handed materials (LHMs) near the ferromagnetic resonance frequency of incident waves with right-handed circular polarization (RCP) and linear polarization (LP). The frequency range where LHM exists depends on the waves polarization, the magnetic damping coefficient, and the ferromagnetic characteristic frequency ω_m of the film. There also exists a critical damping coefficient α_c, above which the left-handed properties disappear completely.

A metamaterial was introduced into the cover of a patch antenna and its band structure was analyzed. The metamaterial cover with correct selection of the working frequency increases by 9.14 dB the patch antenna’s directivity. The mechanism of metamaterial cover is completely different from that of a photonic bandgap cover. The mechanism of the metamaterial cover, the number of the cover’s layers, and the distance between the layers, were analyzed in detail. The results showed that the metamaterial cover, which works like a lens, could effectively improve the patch antenna’s directivity. The physical reasons for the improvement are also given.