Bjorn Maes
University of Mons
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Publication
Featured researches published by Bjorn Maes.
Journal of Applied Physics | 2009
Honghui Shen; Peter Bienstman; Bjorn Maes
The influence of silver nanoparticles on light absorption in organic solar cells based on poly(3-exylthiophene):(6,6)-phenyl-C61-butyric-acid-methyl ester is studied by means of finite element method simulations. The metallic nanoparticles are embedded directly inside the active layer. We investigate the enhancement mechanism and the influence of factors such as the spacing between neighboring nanoparticles, the particle diameter, and the coating thickness. The plasmonic resonance of the particles has a wideband influence on the absorption, and we observe a rich interaction between plasmonic enhancement and the absorption characteristics of the active layer material. An enhancement with a factor of around 1.56 is observed for nanoparticles with a diameter of 24 nm and a spacing of 40 nm, bringing the structure to the absorption level of much thicker active layers without nanoparticles. In addition, a significant effect of the particle coating thickness is observed.
Nature Nanotechnology | 2009
Joris Roels; Iwijn De Vlaminck; L Lagae; Bjorn Maes; Dries Van Thourhout; Roel Baets
The confinement of light in components with nanoscale cross-sections in nanophotonic circuits significantly enhances the magnitude of the optical forces experienced by these components. Here we demonstrate optical gradient forces between two nanophotonic waveguides, and show that the sign of the force can be tuned from attractive to repulsive by controlling the relative phase of the optical fields injected into the waveguides. The optical gradient force could have applications in optically tunable microphotonic devices and nanomechanical systems.
Journal of The Optical Society of America B-optical Physics | 2005
Bjorn Maes; Peter Bienstman; Roel Baets
Using coupled-mode theory we examine the linear and Kerr nonlinear behavior of multiple consecutive photonic-crystal switches. Two types of resonators are considered, those with the cavity inside and those adjacent to the waveguide. We observe gap solitons in both structures and examine a nonlinear mode with energy localized near the boundaries of the finite system. Finally, we propose a device with two side-coupled resonators and a judiciously chosen intercavity distance that demonstrates switching at low powers. In addition to coupled-mode theory, rigorous simulations are performed for this structure.
Optics Express | 2012
Khai Q. Le; Aimi Abass; Bjorn Maes; Peter Bienstman; Andrea Alù
We theoretically investigate and compare the influence of square silver gratings and one-dimensional photonic crystal (1D PC) based nanostructures on the light absorption of organic solar cells with a thin active layer. We show that, by integrating the grating inside the active layer, excited localized surface plasmon modes may cause strong field enhancement at the interface between the grating and the active layer, which results in broadband absorption enhancement of up to 23.4%. Apart from using silver gratings, we show that patterning a 1D PC on top of the device may also result in a comparable broadband absorption enhancement of 18.9%. The enhancement is due to light scattering of the 1D PC, coupling the incoming light into 1D PC Bloch and surface plasmon resonance modes.
Journal of Applied Physics | 2011
Aimi Abass; Honghui Shen; Peter Bienstman; Bjorn Maes
We explore the optical enhancement of organic photovoltaic cells by incorporating a metallic grating as the back contact. We numerically demonstrate a strongly enhanced light absorption exploiting a complex interplay between multiple electromagnetic wave phenomena, among which surface plasmon polariton (SPP) resonances, waveguide mode resonances, Fabry–Perot modes, and scattering. We focus on a triangular grating structure and describe the particular opportunities to obtain a good angular performance. In addition we introduce a novel multiperiodic geometry that incorporates multiple types of SPP resonances. Our triangular structure shows an increased absorption of 15.6% with the AM1.5G spectrum in the 300–800 nm wavelength range. For the multiperiodic grating case a significant further increase to 20.7% is shown.
Optics Express | 2011
Honghui Shen; Bjorn Maes
We propose an organic solar cell structure with combined silver gratings consisting of both a front and a back grating. This combination provides multiple, semi-independent enhancement mechanisms which act additively, so that a broadband absorption is obtained. Both gratings couple the incident light into various plasmonic modes, showing a more localized or propagating character respectively. In addition, some modes only appear for tilted incident light, and therefore present a complex angle-dependent behavior. We provide extensive numerical simulations, resulting in an optimized period of 490 nm, with front grating elements of 60 by 10nm and back elements of 60 by 30 nm. With these parameters an integrated absorption enhancement factor around 1.35 is observed, with absorption increasing from 48% to 65% under TM polarized light. In addition, the solar cell with combined gratings is much less sensitive to the angle of incident light than the single grating cases. Furthermore, the grating structure does not have a large influence on the TE polarized light absorption.
Physical Review X | 2011
S. R. K. Rodriguez; Aimi Abass; Bjorn Maes; Olaf T. A. Janssen; Gabriele Vecchi; J. Gómez Rivas
We demonstrate the coupling of bright and dark surface lattice resonances (SLRs), which are collective Fano resonances in 2D plasmonic crystals. As a result of this coupling, a frequency stop gap in the dispersion relation of SLRs is observed. The different field symmetries of the low- and high-frequency SLR bands lead to pronounced differences in their coupling to free-space radiation. Standing waves of very narrow spectral width compared to localized surface-plasmon resonances are formed at the high-frequency band edge, while subradiant damping onsets at the low-frequency band edge, leading the resonance into darkness. We introduce a coupled-oscillator analog to the plasmonic crystal, which serves to elucidate the physics of the coupled plasmonic resonances and which is used to estimate very high quality factors for SLRs.
Optics Express | 2013
Bjorn Maes; Jiří Petráček; Sven Burger; Pavel Kwiecien; Jaroslav Luksch; Ivan Richter
High-quality cavities in hybrid material systems have various interesting applications. We perform a comprehensive modeling comparison on such a design, where confinement in the III-V material is provided by gradual photonic crystal tuning, a recently proposed method offering strong resonances. The III-V cavity couples to an underlying silicon waveguide. We report on the device properties using four simulation methods: finite-difference time-domain (FDTD), finite-element method (FEM), bidirectional eigenmode propagation (BEP) and aperiodic rigorous coupled wave analysis (aRCWA). We explain the major confinement and coupling effects, consistent with the simulation results. E.g. for strong waveguide coupling, we find quantitative discrepancies between the methods, which establishes the proposed high-index-contrast, lossy, 3D structure as a challenging modeling benchmark.
Optics Express | 2006
Bjorn Maes; Marin Soljacic; John D. Joannopoulos; Peter Bienstman; Roel Baets; Simon-Pierre Gorza; Marc Haelterman
We describe stable symmetry-breaking states in systems with two coupled nonlinear cavities, using coupled-mode theory and rigorous simulations. Above a threshold input level the symmetric state of the passive Kerr system becomes unstable, and we show how this phenomenon can be employed for switching and flip-flop purposes, using positive pulses only. A device with compact photonic crystal microcavities is proposed by which we numerically demonstrate the principle.
Applied Physics Letters | 2012
Honghui Shen; Bjorn Maes
To achieve non-resonant behavior, we propose a metallic grating device with linearly tapered slits. The tapering provides a gradual impedance variation from the entrance to the exit of the slits, leading to broadband and wide-angle enhanced transmission in the infrared. In addition, the light is strongly localized and enhanced at the slit exits, in contrast with straight slits. We describe the phenomenon with a transmission line model, which is in accordance with rigorous simulations.