Kevin Vynck

Graded photonic crystals curve the flow of light: An experimental demonstration by the mirage effect

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 10GHz. 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.

Superlattice for photonic band gap opening in monolayers of dielectric spheres.

Dielectric spheres synthesized for the fabrication of self-organized photonic crystals such as opals offer large opportunities for the design of novel nanophotonic devices. In this paper, we show that a hexagonal superlattice monolayer of dielectric spheres exhibits an even photonic band gap below the light cone for refractive indices higher than 1.93. The use of spheres with refractive index 2.9 and diameter 0.33 mum tunes the photonic band gap to the telecommunications range (lambda=1.55 mum). As a practical example for the use of such a photonic band gap, we demonstrate the possibility of waveguiding light linearly through the monolayer.

Efficient light coupling into a photonic crystal waveguide with flatband slow mode

Abstract 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 ≈ 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%.

Efficient light coupling from integrated single-mode waveguides to supercollimating photonic crystals on silicon-on-insulator platforms

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 1.55μm. This approach constitutes a significant step toward the integration of supercollimating structures on photonic chips.

Broadband single-mode waveguiding in two- and three-dimensional hybrid photonic crystals based on silicon inverse opals

Hybrid 2D-3D heterostructures are a very promising way for waveguiding light in 3D photonic structures. Single-mode waveguiding of light has been demonstrated in heterostructures where a 2D photonic crystal consisting of a triangular lattice of silicon rods in air was intercalated between two silicon inverse opals. In this paper, we show that by using a graphite lattice of rods instead of a triangular one, it is possible to enlarge the maximal single-mode waveguiding bandwidth by more than 70 %, i.e. up to 129 nm centered on 1.55 mum. The sensibility to the 2D layer structure parameters is lower, offering enhanced experimental flexibility in the design of the structure.

Light transport in 2D photonic glasses

The propagation of light in a 2D random medium is studied. The medium is made on dielectric scatterers with a high permittivity allowing for the existence of Mie resonances. It is shown that, according to the polarization, it is possible to obtain conduction bands around the resonances.verligh

2D Photonic Defect Layers in 3D Inverted Opals on Si Platforms

Dielectric spheres synthesised for the fabrication of self-organized photonic crystals such as opals offer large opportunities for the design of novel nanophotonic devices. In this paper, we show a hexagonal superlattice monolayer of dielectric spheres inscribed on a 3D colloidal photonic crystal by e-beam lithography. The crystal is produced by a variation of the vertical drawing deposition method assisted by an acoustic field. The structures were chosen after simulations showed that a hexagonal super-lattice monolayer in air exhibits an even photonic band gap below the light cone if the refractive index of the spheres is higher than 1.93