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Adam, A.J.L. (author), Zuidwijk, T. (author), Urbach, Paul (author)The Optics Group of Delft University of Technology plays a major role in teaching optics to bachelor and master students. In addition, the group has a long record of introducing, demonstrating and teaching optics to quite diverse groups of people from outside of the university. We will describe some of these activities and focus on a recently...conference paper 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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Dwivedi, P. (author), Konijnenberg, A.P. (author), Pereira, S.F. (author), Urbach, Paul (author)For high resolution imaging, X-rays and electron beams are being used. However, for such a short wavelength, imaging with lenses becomes difficult as lenses absorb a part of radiation and lenses with very low aberrations must be used. Ptychography is a lens-less imaging technique which uses intensity information of the multiple diffraction...conference paper 2017
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Ezerskaia, A. (author), Pereira, S.F. (author), Urbach, Paul (author), Varghese, Babu (author)Skin barrier function relies on well balanced water and lipid system of stratum corneum. Optimal hydration and oiliness levels are indicators of skin health and integrity. We demonstrate an accurate and sensitive depth profiling of stratum corneum sebum and hydration levels using short wave infrared spectroscopy in the spectral range around...conference paper 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
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- Nemati, M. (author), Urbach, Paul (author), Bhattacharya, N. (author) journal article 2016
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Ezerskaia, A. (author), Pereira, S.F. (author), Urbach, Paul (author), Varghese, Babu (author)Skin health characterized by a system of water and lipids in Stratum Corneum provide protection from harmful external elements and prevent trans-epidermal water loss. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin health; a right balance between these components is an indication of...conference paper 2016
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Wei, L. (author), Urbach, Paul (author)The focal field properties of radially/azimuthally polarized Zernike polynomials are studied. A method to design the pupil field in order to shape the focal field of radially or azimuthally polarized phase vortex is introduced. With this method, we are able to obtain a pupil field to achieve a longitudinally polarized hollow spot with a depth of...journal article 2016
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Ezerskaia, A. (author), Pereira, S.F. (author), Urbach, Paul (author), Varghese, B. (author)Skin health is characterized by heterogeneous system of water and lipids in upper layers providing protection from external environment and preventing loss of vital components of the body. Skin hydration (moisture) and sebum (skin surface lipids) are considered to be important factors in skin health; a right balance between these components...conference paper 2016