We propose a practical and efficient solution for the coupling of light from integrated single-mode waveguides to supercollimating planar photonic crystals (PhCs) on conventional silicon-on-insulator platforms. The device consists of a rib waveguide, designed to sustain spatially extended single modes and matched to a supercollimating PhC, which has been truncated at its boundary to improve impedance matching between the two photonic components. Three-dimensional simulations show transmission efficiencies up to 96% and reflections below 0.2% at wavelengths close to 1.55 mu m. This approach constitutes a significant step toward the integration of supercollimating structures on photonic chips. (c) 2008 American Institute of Physics.

We report the experimental demonstration of a beam curvature in graded photonic crystals via a spectacular mirage effect. A two-dimensional structure of metallic rods is constructed to produce this effect in the microwave domain near 10 GHz. Experimental results are in excellent agreement with theoretical predictions, thus, proving the versatility of graded photonic crystals in view of their integration in future photonic circuits. (C) 2008 American Institute of Physics.

We show that photonic crystals with ring-shaped holes (RPhCs) exhibit superior properties compared to conventional photonic crystals (PhCs). At low air-fill factors RPhCs can have a larger bandgap than conventional PhCs. Moreover, RPhC waveguides with both high group index and small group velocity dispersion can be designed. RPhC waveguides are also more sensitive to external refractive index changes, which is attractive for sensor applications. Finally we set up a procedure to pattern RPhCs in silicon-on-insulator. (c) 2007 Elsevier B.V. All rights reserved.

We study the coupling of light between strip and rib waveguides and supercollimating photonic crystals on silicon-on-insulator substrates. The dispersive properties of the supercollimating photonic crystal are used to define the design requirements on the excitation waveguide and the boundary of the photonic crystal is optimized to improve the impedance matching between the two structures. By 3D calculations, we find that rib waveguides can yield transmission efficiencies up to about 96 % and reflections lower than 0.2 % at wavelengths close to 1.55 pm, while insuring single-mode propagation. This work therefore constitutes an important step toward the integration of supercollimation- based optical circuits on photonic chips.

We demonstrate an isotropic phase matching condition achieved in nonlinear 2D PhCs that suppresses the incident angle constraint [1]. In addition, we show a backward SH localization effect by combining this unusual all-angle phase matching and left-handed PhC properties. The SH emission is confined in a small area of dimension close to the pump wavelength without the introduction of defect lattices. An analytical model is proposed in order to explain this parametric localization mechanism.

We design an efficient coupler to transmit light from a strip waveguide into the flatband slow mode of a photonic crystal waveguide with ring-shaped holes. The coupler is a section of a photonic crystal waveguide with a higher group velocity, obtained by different ring dimensions. We demonstrate coupling efficiency in excess of 95% over the 8 nm wavelength range where the photonic crystal waveguide exhibits a quasi-constant group velocity v(g) approximate to c/37 and observe a more than 12-fold intensity enhancement in the slow-light waveguide. An analysis based on the small Fabry-Perot resonances in the simulated transmission spectra is used for studying the effect of the coupler length and for evaluating the coupling efficiency in different parts of the coupler. The mode conversion efficiency within the coupler is more than 99.7% over the wavelength range of interest. The parasitic reflectance in the coupler, which depends on the propagation constant mismatch between the slow mode and the coupler mode, is lower than 0.6%. (c) 2008 Elsevier B.V. All rights reserved.

The metamaterials exhibiting negative permittivity and permeability that have been under numerical and experimental study recently generally operate at frequencies between the homogeneous and heterogeneous regimes, a region characterized by the phenomenon of spatial dispersion. However, since many interesting applications such as the superlens rely on nondispersive homogeneous behavior, one needs a means to diagnose spatial dispersion efficiently as well as to explore in more detail the physics of dispersive media. In this work, we put forward and illustrate the notion of an inhomogeneous effective medium model. We use it to explore the spatial dispersion in negative-index composites, and we show that it is an ideal tool for studying the behavior of composite metamaterials in the intermediate-frequency region where homo- geneous effective medium models become spatially dispersive or nonlocal.