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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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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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Konijnenberg, A.P. (author), Coene, W.M.J.M. (author), Urbach, Paul (author)A noise-robust extension of iterative phase retrieval algorithms that does not need to assume a noise model is proposed. It works by adapting the intensity constraints using the reconstructed object. Using a proof-of-principle ptychographic experiment with visible light and a spatial light modulator to create an object, the proposed method is...journal article 2018
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Shao, Y. (author), Lu, Xingyuan (author), Konijnenberg, A.P. (author), Zhao, C.L. (author), Cai, Yangjian (author), Urbach, Paul (author)The complete characterization of spatial coherence is extremely di cult because the mutual coherence function (MCF) is a complex-valued function of four independent Cartesian coordinates. This di culty limits the ability to control and to optimize the spatial coherence in a broad range of key applications. Here we propose an e cient and...journal article 2018
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Ezerskaia, A. (author), Uzunbajakava, Natallia Eduarda (author), Puppels, Gerwin J. (author), De Sterke, Johanna (author), Caspers, Peter J. (author), Urbach, Paul (author), Varghese, Babu (author)We demonstrate the feasibility of short wave infrared (SWIR) spectroscopy combined with tape stripping for depth profiling of lipids and water in the stratum corneum of human skin. The proposed spectroscopic technique relies on differential detection at three wavelengths of 1720, 1750, and 1770 nm, with varying ratio of the lipid-to-water...journal article 2018
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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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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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van der Sijs, T.A. (author), El Gawhary, O. (author), Urbach, Paul (author)We present the realization of a vectorial perturbation method based on the Born series applied to strong electromagnetic scattering problems. We present the general theoretical formalism and show a semianalytical implementation for scattering by diffraction gratings. We are particularly interested in the strong scattering regime, where the Born...journal article 2024
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Konijnenberg, A.P. (author), Lu, Xingyuan (author), Liu, Leixin (author), Coene, W.M.J.M. (author), Zhao, C.L. (author), Urbach, Paul (author)A novel non-iterative phase retrieval method is proposed and demonstrated with a<br/>proof-of-principle experiment. The method uses a fixed specially designed mask and through-focus intensity measurements. It is demonstrated that this method is robust to spatial partial coherence in the illumination, making it suitable for coherent diffractive...journal article 2018
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Dwivedi, P. (author), Konijnenberg, A.P. (author), Pereira, S.F. (author), Urbach, Paul (author)Ptychography, a form of Coherent Diffractive Imaging, is used with short wavelengths (e.g. X-rays, electron beams) to achieve high-resolution image reconstructions. One of the limiting factors for the reconstruction quality is the accurate knowledge of the illumination probe positions. Recently, many advances have been made to relax the...journal article 2018
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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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Mout, B.M. (author), Flesch, Andreas (author), Wick, Michael (author), Bociort, F. (author), Petschulat, Joerg (author), Urbach, Paul (author)The electric field at the output of an optical system is in general affected by both aberrations and diffraction. Many simulation techniques treat the two phenomena separately, using a geometrical propagator to calculate the effects of aberrations and a wave-optical propagator to simulate the effects of diffraction. We present a ray-based...journal article 2018
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Xi, Z. (author), Urbach, Paul (author)We propose a scheme to retrieve the size parameters of a nanoparticle on a glass substrate at a scale much smaller than the wavelength. This is achieved by illuminating the particle using two plane waves to create rich and nontrivial local polarization distributions, and observing the far-field scattering pattern into the substrate. By using...journal article 2018
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Meng, P. (author), Pham, Hong Liên (author), Pereira, S.F. (author), Urbach, Paul (author)Lateral resolution enhancement is demonstrated in a confocal imaging system with amplitude-modulated radially polarized (RP) light at the wavelength Annular pupil fields and optimized amplitude distribution functions can be realized with a spatial light modulator. By comparing images obtained with full and amplitude modulated apertures of RP...journal article 2020
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Man, Z. (author), Xi, Z. (author), Yuan, Xiaocong (author), Burge, R. E. (author), Urbach, Paul (author)Carrying orbital angular momentum per photon, the optical vortex has elicited widespread interest. Here, we demonstrate that dual coaxial longitudinal polarization vortices can appear upon a nonparaxial propagation of a tightly focused Pancharatnam-Berry tailored Laguerre-Gaussian beam. Most importantly, it is capable of accessing arbitrary...journal article 2020
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Ansuinelli, P. (author), Coene, W.M.J.M. (author), Urbach, Paul (author)The development of actinic mask metrology tools represents one of the major challenges to be addressed on the roadmap of extreme ultra violet (EUV) lithography. Technological advancements in EUV lithography result in the possibility to print increasingly fine and highly resolved structures on a silicon wafer, however the presence of fine–scale...journal article 2020
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Kolenov, D. (author), Urbach, Paul (author), Pereira, S.F. (author)We demonstrate the far field detection of low-contrast nanoparticles on surfaces using a technique that is based on evanescent-wave amplification due to a thin dielectric layer that is deposited on the substrate. This research builds upon earlier results where scattering enhancement of 200 nm polystyrene (PSL) particles on top of a glass...journal article 2020