Olaf Theodorus Albertus Janssen

Olaf Theodorus Albertus Janssen
Hogeschool Fontys · Institute of ICT

PhD

About

30
Publications
3,054
Reads
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985
Citations
Citations since 2016
2 Research Items
530 Citations
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
Additional affiliations
April 2013 - November 2018
Hogeschool Fontys
Position
  • Lecturer
January 2007 - December 2010
Technische Universiteit Delft
Education
April 2006 - April 2010
Delft University of Technology
Field of study
  • Optics
January 2006
University of Santiago de Compostela
Field of study
  • Summer School in Micro-Optics Modelling
September 1999 - January 2006
Eindhoven University of Technology
Field of study
  • Applied Physics

Publications

Publications (30)
Article
Full-text available
Don’t think transparency will solve all your AI trust issues, we need more complex AI systems. https://medium.com/@o.t.a.janssen/machine-learning-and-the-whole-transparency-thing-ac85577be382?source=friends_link&sk=dfe8c6368da5356391ad474bda1149fa
Conference Paper
Full-text available
Artificial neural networks can be used to detect emotion from gait and music can act as an agent to influence gait. While the impact of specific musical composition elements may be highly personal (every person has their own preferred running playlist), we hypothesize that using deep learning, it becomes possible to steer individual running techniq...
Article
Full-text available
Light sources based on reliable and energy-efficient light-emitting diodes (LEDs) are instrumental in the development of solid-state lighting (SSL). Most research efforts in SSL have focused on improving both the intrinsic quantum efficiency (QE) and the stability of light emitters. For this reason, it is broadly accepted that with the advent of hi...
Article
Full-text available
We numerically demonstrate that a periodic array of metallic nanorods sustains a maximum near-field enhancement and a far field (FF)-induced transparency at the same energy and in-plane momentum. The coupling of bright and dark plasmonic lattice resonances, and electromagnetic retardation along the nanorod length, are responsible for this effect. A...
Article
Full-text available
We demonstrate that a periodic array of optical antennas sustains a resonant Near-Field (NF) and an anti-resonant Far-Field (FF) at the same energy and in-plane momentum. This phenomenon arises in the context of coupled plasmonic lattice resonances, whose bright and dark character is interchanged at a critical antenna length. The energies of these...
Article
Full-text available
By tuning the radiative coupling of localized surface plasmons to diffracted orders, we demonstrate how stop-gaps in plasmonic crystals of nanorods may be opened and tuned. The stop-gap arises from the mutual coupling of surface lattice resonances (SLRs), which are collective resonances associated with counter-propagating surface polaritons. We pre...
Article
Full-text available
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 t...
Article
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...
Conference Paper
It will be shown that the incoherent emission can be computed very efficiency by applying the reciprocity principle. We shall furthermore consider the optimization of the structures.
Article
We demonstrate experimentally that arrays of base-tapered InP nanowires on top of an InP substrate form a broad band and omnidirectional absorbing medium. These characteristics are due to the specific geometry of the nanowires. Almost perfect absorption of light (higher than 97%) occurs in the system. We describe the strong optical absorption by fi...
Article
We explain how the application of the reciprocity principle can be applied to improve the optimization of structures to maximize the emission by an LED.
Article
Full-text available
The incoherent emission of periodically structured Light Emitting Diodes (LEDs) can be computed at relatively low computational cost by applying the reciprocity method. We show that by another application of the reciprocity principle, the structure of the LED can be optimized to obtain a high emission. We demonstrate the method by optimizing one-di...
Article
Full-text available
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 Metho...
Article
Full-text available
In the next decade, several applications of nanotechnology will change our lives. LED lighting is about to replace the common light bulb. The main advantages are its energy efficiency and long lifetime. LEDs can be much more efficient, when part of the emitted light that is currently trapped in the device, could be radiated out of the device. Other...
Article
Full-text available
We present details of a novel imaging algorithm based on the extended Nijboer-Zernike (ENZ) theory of diffraction. We derive integral expressions relating the electric field distribution in the entrance pupil of an optical system to the electric field in its focal region. The evaluation of these integrals is made possible by means of a highly accur...
Article
Using the reciprocity theorem, we calculate the incoherent emission in a single direction of a periodically structured LED, by performing two small simulations on a single unit cell.
Article
Full-text available
In this paper we introduce a new mask imaging algorithm that is based on the source point integration method (or Abbe method). The method presented here distinguishes itself from existing methods by exploiting the through-focus imaging feature of the Extended Nijboer-Zernike (ENZ) theory of diffraction. An introduction to ENZ-theory and its applica...
Article
Full-text available
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, wit...
Article
Full-text available
In this Letter, we show that the energy equivalent to that incident on a 4.7 microm wide strip can be squeezed through a 50 nm wide slit in a metal film surrounded by grooves. This corresponds to a transmission efficiency of 9400%, which can be even further enhanced by increasing the number of grooves. We use the phase of the magnetic field to expl...
Article
Full-text available
We present a comparison among several fully-vectorial methods applied to a basic scattering problem governed by the physics of the electromagnetic interaction between subwavelength apertures in a metal film. The modelled structure represents a slit-groove scattering problem in a silver film deposited on a glass substrate. The benchmarked methods, a...
Article
Full-text available
The excitation of surface plasmons by subwavelength slits in metal films is studied using a rigorous diffraction model. It is shown that the plasmon is launched by a slit in antiphase with the incident magnetic field. This is true independent of slit width and of the metal used. Using this phase information, maxima and minima in transmission are ex...

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Projects

Projects (4)
Project
Investigate, design, and implement AI solutions for society and our environment. Make them more transparent and explainable. And build those application with good engineering principles.
Project
Understanding what transparency, decision making and trust means in the interaction between users and machine learning systems.
Archived project
Develop a state-of-the-art FDTD electromagnetic field solver to solve a wide range of computational problems and apply it mainly to LED radiation problems.