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Meng, P. (author), Man, Z. (author), Konijnenberg, A.P. (author), Urbach, Paul (author)Optical angular momenta (AM) have attracted tremendous research interest in recent years. In this paper we theoretically investigate the electromagnetic field and angular momentum properties of tightly focused arbitrary cylindrical vortex vector (CVV) input beams. An absorptive particle is placed in focused CVV fields to analyze the optical...journal article 2019
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Chang, J. (author), Esmaeil Zadeh, I.Z. (author), Los, Johannes W.N. (author), Zichi, Julien (author), Fognini, Andreas (author), Gevers, Monique (author), Dorenbos, Sander (author), Pereira, S.F. (author), Urbach, Paul (author), Zwiller, Val (author)In the past decade, superconducting nanowire single-photon detectors (SNSPDs) have gradually become an indispensable part of any demanding quantum optics experiment. Until now, most SNSPDs have been coupled to single-mode fibers. SNSPDs coupled to multimode fibers have shown promising efficiencies but have yet to achieve high time resolution....journal article 2019
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Lu, Xingyuan (author), Shao, Y. (author), Zhao, C.L. (author), Konijnenberg, A.P. (author), Zhu, Xinlei (author), Tang, Y. (author), Cai, Yangjian (author), Urbach, Paul (author)We propose and experimentally demonstrate a noniterative diffractive imaging method for reconstructing the complex-valued transmission function of an object illuminated by spatially partially coherent light from the far-field diffraction pattern. Our method is based on a pinhole array mask, which is specially designed such that the...journal article 2019
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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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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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Ezerskaia, A. (author), Ras, A. (author), Pereira, S.F. (author), Urbach, Paul (author), Varghese, B. (author)We report a low-cost optical method with high sensitivity for the quantitative assessment of the gloss of human skin in the low gloss regime relevant for physiological skin gloss conditions. Using Monte Carlo simulations, experiments on gloss calibration standards and in-vivo skin gloss experiments using an optical prototype, we demonstrate...conference paper 2018
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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), Pereira, S.F. (author), Urbach, Paul (author), Varghese, Babu (author)We show the feasibility of short wave infrared spectroscopy combined with tape stripping as a simple and noninvasive method for the analysis of lipids and the degree of hydration as a function of depth in the stratum corneum. The spectroscopic method utilizes differential detection with three wavelengths 1720, 1750, and 1770 nm, corresponding...conference paper 2018
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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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- Bhattacharya, N. (author), Cui, M. (author), Zeitouny, M. (author), Urbach, Paul (author), van den Berg, S. (author) conference paper 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