Olaf T. A. Janssen

Coupling Bright and Dark Plasmonic Lattice Resonances

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.

Controlling the directional emission of light by periodic arrays of heterostructured semiconductor nanowires.

We demonstrate experimentally the directional emission of light by InAsP segments embedded in InP nanowires. The nanowires are arranged in a periodic array, forming a 2D photonic crystal slab. The directionality of the emission is interpreted in terms of the preferential decay of the photoexcited nanowires and the InAsP segments into Bloch modes of the periodic structure. By simulating the emission of arrays of nanowires with the emitting segments located at different heights, we conclude that the position of this active region strongly influences the directionality and efficiency of the emission. Our results will help to improve the design of nanowire based LEDs and single photon sources.

Extended Nijboer-Zernike (ENZ) based mask imaging: efficient coupling of electromagnetic field solvers and the ENZ imaging algorithm

Results are presented of mask imaging using the Extended Nijboer-Zernike (ENZ) theory of diffraction. We show that the efficiency of a mask imaging algorithm, derived from this theory, can be increased. By adjusting the basic Finite Difference Time Domain (FDTD) algorithm, we can calculate the near field of isolated mask structures efficiently, without resorting to periodic domains. In addition, the calculations for the points on the entrance sphere of the imaging system can be done separately with a Fourier transformed Stratton-Chu nearto- far-field transformation. By clever sampling in the radial direction of the entrance pupil, the computational effort is already reduced by at least a factor of 4.

On the modeling of optical systems containing elements of different scales

In optical systems often components of widely varying scales occur. The scale, expressed in units of wavelength, determines what kind of model is needed for the component. For objects with size of the order of the wavelength, rigorous electromagnetic models are required. We discuss several home-made rigorous methods such as the Finite Element Method, the Finite Difference Time Domain Method and the Rigorous Coupled Wave Method and describe our experience with them. For lenses of high numerical aperture, the Extended Nijboer Zernike method is considered. An important issue is how to propagate the field from the exit plane of one component to the entrance plane of the other. We explain a numerical integration method by which the diffraction integral can be computed with an error that is independent of the propagation distance.