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Mout, B.M. (author), Wick, Michael (author), Bociort, F. (author), Petschulat, Joerg (author), Urbach, Paul (author)We study a simulation method that uses the Wigner distribution function to incorporate wave optical effects in an established framework based on geometrical optics, i.e., a ray tracing engine. We use the method to calculate point spread functions and show that it is accurate for paraxial systems but produces unphysical results in the presence...journal article 2018
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Meng, P. (author), Pereira, S.F. (author), Urbach, Paul (author)Rigorous vectorial focusing theory is used to study the imaging of small adjacent particles with a confocal laser scanning system. We consider radially polarized illumination with an optimized amplitude distribution and an annular lens to obtain a narrower distribution of the longitudinal component of the field in focus. A polarization...journal article 2018
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Strauch, M. (author), Somers, P.A.A.M. (author), Bociort, F. (author), Urbach, Paul (author)A technique to create aspheric surface shapes on commercially available electrowetting liquid lenses is demonstrated. Based on a previously published surface oscillation model a technique using a Hankel transform is proposed and tested experimentally. An alternating actuation voltage is applied to the liquid lens to stimulate surface...journal article 2018
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El Gawhary, O. (author), Van Mechelen, T. (author), Urbach, Paul (author)Electromagnetic fields carry a linear and an angular momentum, the first being responsible for the existence of the radiation pressure and the second for the transfer of torque from electromagnetic radiation to matter. The angular momentum is considered to have two components, one due to the polarization state of the field, usually called...journal article 2018
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Xu, Xiaosi (author), Konijnenberg, A.P. (author), Pereira, S.F. (author), Urbach, Paul (author)Coherent Fourier scatterometry is an optical metrology technique that utilizes the measured intensity of the scattered optical field to reconstruct certain parameters of test structures written on a wafer with nano-scale accuracy. The intensity of the scattered field is recorded with a camera and this information is used to retrieve the...journal article 2017
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Xi, Z. (author), Urbach, Paul (author)It is generally believed that when a single metallic nanowire is sufficiently small, it scatters like a point electric dipole. We show theoretically when a metallic nanowire is placed inside specially designed beams, the magnetic dipole contribution along with the electric dipole resonance can lead to unidirectional scattering in the far field,...journal article 2017
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Wei, L. (author), Bhattacharya, N. (author), Urbach, Paul (author)We describe a method to control the directional scattering of a high-index dielectric nanosphere, which utilizes the unique focusing properties of an azimuthally polarized phase vortex and a radially polarized beam to independently excite inside the nanosphere a spinning magnetic dipole and a linearly polarized electric dipole mode normal to the...journal article 2017
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Strauch, M. (author), Shao, Y. (author), Bociort, F. (author), Urbach, Paul (author)The increased usage of liquid lenses motivates us to investigate surface waves on the liquid's surface. During fast focal switching, the surface waves decrease the imaging quality. We propose a model that describes the surface modes appearing on a liquid lens and predicts the resonance frequencies. The effects of those surface modes on a...journal article 2017
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- Hänsel, A. (author), Reyes Reyes, A. (author), Persijn, ST (author), Urbach, Paul (author), Bhattacharya, N. (author) journal article 2017
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Roy, S. (author), Pereira, S.F. (author), Urbach, Paul (author), Wei, X. (author), El Gawhary, O. (author)The classical problem of subwavelength particle detection on a flat surface is especially challenging when the refractive index of the particle is close to that of the substrate. We demonstrate a method to improve the detection ability several times for such a situation, by enhancing the "forbidden" evanescent waves in the substrate using the...journal article 2017
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Ezerskaia, A. (author), Ras, Arno (author), Bloemen, Pascal (author), Pereira, S.F. (author), Urbach, Paul (author), Varghese, Babu (author)We demonstrate a low-cost optical method for measuring the gloss properties with improved sensitivity in the low gloss regime, relevant for skin gloss properties. The gloss estimation method is based on, on the one hand, the slope of the intensity gradient in the transition regime between specular and diffuse reflection and on the other on...journal article 2017
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Konijnenberg, A.P. (author), Coene, W.M.J.M. (author), Urbach, Paul (author)We report on a novel non-iterative phase retrieval method with which the complex-valued transmission function of an object can be retrieved with a non-iterative computation, with a limited number of intensity measurements. The measurements are taken in either real space or Fourier space, and for each measurement the phase in its dual space is...journal article 2016
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Konijnenberg, A.P. (author), Coene, W.M.J.M. (author), Pereira, S.F. (author), Urbach, Paul (author)In this article we combine the well-known Ptychographical Iterative Engine (PIE) with the Hybrid Input-Output (HIO) algorithm. The important insight is that the HIO feedback function should be kept strictly separate from the reconstructed object, which is done by introducing a separate feedback function per probe position. We have also...journal article 2016
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Wang, Haifeng (author), Lin, Jian (author), Zhang, Dawei (author), Wang, Yang (author), Gu, Min (author), Urbach, Paul (author), Gan, Fuxi (author), Zhuang, Songlin (author)We present a concealing method in which an anti-point spread function (APSF) is generated using binary optics, which produces a large-scale dark area in the focal region that can hide any object located within it. This result is achieved by generating two identical PSFs of opposite signs, one consisting of positive electromagnetic waves from...journal article 2016
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Xi, Z. (author), Wei, L. (author), Adam, A.J.L. (author), Urbach, Paul (author), Du, L (author)Identifying subwavelength objects and displacements is of crucial importance in optical nanometrology. We show in this Letter that nanoantennas with subwavelength structures can be excited precisely by incident beams with singularity. This accurate feeding beyond the diffraction limit can lead to dynamic control of the unidirectional scattering...journal article 2016
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Mout, B.M. (author), Wick, Michael (author), Bociort, F. (author), Petschulat, Joerg (author), Urbach, Paul (author)We present a method for simulating multiple diffraction in imaging systems based on the Huygens–Fresnel principle. The method accounts for the effects of both aberrations and diffraction and is entirely performed using Monte Carlo ray tracing.We compare the results of this method to those of reference simulations for field propagation through...journal article 2016
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Li, X. (author), Wei, L. (author), Poelma, René H. (author), Vollebregt, S. (author), Wei, J. (author), Urbach, Paul (author), Sarro, Pasqualina M (author), Zhang, Kouchi (author)This paper presents a tuneable binary amplitude Fresnel lens produced by wafer-level microfabrication. The Fresnel lens is fabricated by encapsulating lithographically defined vertically aligned carbon nanotube (CNT) bundles inside a polydimethyl-siloxane (PDMS) layer. The composite lens material combines the excellent optical absorption...journal article 2016
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Nemati, M. (author), Kenjeres, S. (author), Urbach, Paul (author), Bhattacharya, N. (author)The scattering of coherent light from a system with underlying flow can be used to yield essential information about dynamics of the process. In the case of pulsatile flow, there is a rapid change in the properties of the speckle images. This can be studied using the standard laser speckle contrast and also the fractality of images. In this...journal article 2016
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Schmidt, S. (author), Klein, A. E. (author), Paul, T. (author), Gross, H. (author), Diziain, S. (author), Steinert, M. (author), da Costa Assafrao, A. (author), Pertsch, T. (author), Urbach, Paul (author), Rockstuhl, C. (author)Aperture based scanning near field optical microscopes are important instruments to study light at the nanoscale and to understand the optical functionality of photonic nanostructures. In general, a detected image is affected by both the transverse electric and magnetic field components of light. The discrimination of the individual field...journal article 2016
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Zimmerling, J.T. (author), Wei, L. (author), Urbach, H.P. (author), Remis, R.F. (author)We present a Krylov model-order reduction approach to efficiently compute the spontaneous decay (SD) rate of arbitrarily shaped 3D nanosized resonators. We exploit the symmetry of Maxwell’s equations to efficiently construct so-called reduced-order models that approximate the SD rate of a quantum emitter embedded in a resonating nanostructure....journal article 2016