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Pereira, Joana P.C. (author), Overbeek, W.J.M. (author), Gudiño Reyes, N.E. (author), Andres Garcia, E. (author), Kapteijn, F. (author), van der Wielen, L.A.M. (author), Straathof, Adrie J.J. (author)Biobased 2-butanol offers high potential as biofuel, but its toxicity toward microbial hosts calls for efficient techniques to alleviate product inhibition in fermentation processes. Aiming at the selective recovery of 2-butanol, the feasibility of a process combining in situ vacuum stripping followed by vapor adsorption has been assessed...journal article 2019
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Konijnenberg, A.P. (author), Pereira, S.F. (author)In this paper we present several algorithms to find pupil functions which give focal fields with different desirable properties, such as a laterally elongated spot, a focal sheet, a spot with increased axial resolution, a lateral array of closely packed spots, and a lateral array of widely spaced diffraction-limited spots. All the algorithms...journal article 2015
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- Petrik, P. (author), Fodor, B. (author), Agocs, E. (author), Kozma, P. (author), Nador, J. (author), Kumar, N. (author), Endres, J. (author), Juhasz, G. (author), Major, C. (author), Pereira, S.F. (author), Lohner, T. (author), Urbach, H.P. (author), Bodermann, B. (author), Fried, M. (author) conference paper 2015
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Ushakova, K. (author), Van den Berg, Q.Y. (author), Pereira, S.F. (author), Urbach, H.P. (author)Spot size reduction is demonstrated by printing focused spots from amplitude-modulated radially polarized light at the wavelength ? = 405 nm on a photoresist. Amplitude modulation is realized by ring illumination and by application of an optimized amplitude distribution function. Amplitude modulation is implemented via spatial light modulator,...journal article 2015
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Konijnenberg, A.P. (author), Pereira, S.F. (author)In this paper we present several algorithms to find pupil functions which give focal fields with different desirable properties, such as a laterally elongated spot, a focal sheet, a spot with increased axial resolution, a lateral array of closely packed spots, and a lateral array of widely spaced diffraction-limited spots. All the algorithms...journal article 2015
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Cisotto, L. (author), Zhu, Y. (author), Pereira, S.F. (author), Urbach, H.P. (author)Finding a fast and precise method to measure the side-wall angle of periodic (or non-periodic) structures is still a very challenging problem in lithographic applications. For this reason, over the years, many techniques have been proposed to circumvent this limitation, with the final goal to give the most precise geometrical description of...conference paper 2015
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Roy, S. (author), Ushakova, K. (author), Van den Berg, Q. (author), Pereira, S.F. (author), Urbach, H.P. (author)A fast noninvasive method based on scattering from a focused radially polarized light to detect and localize subwavelength nanoparticles on a substrate is presented. The technique relies on polarization matching in the far field between scattered and spurious reflected fields. Results show a localization uncertainty of ?10?4?2 is possible for a...journal article 2015
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Roy, S. (author), Assafrao, A.C. (author), Pereira, S.F. (author), Urbach, H.P. (author)Inspection tools for nano-particle contamination on a planar substrate surface is a critical problem in micro-electronics. The present solutions are either expensive and slow or inexpensive and fast but have low sensitivity because of limitations due to diffraction. Most of them are also substrate specific. In this article we report how Coherent...journal article 2014
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Hermosa, N. (author), Rosales-Guzman, C. (author), Pereira, S.F. (author), Torres, J.P. (author)We demonstrate an optical scheme for measuring the thickness of thin nanolayers with the use of light beam’s spatial modes. The novelty in our scheme is the projection of the beam reflected by the sample onto a properly tailored spatial mode. In the experiment described below, we are able to measure a step height smaller than 10 nm, i.e., one...journal article 2014
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Konijnenberg, A.P. (author), Wei, L. (author), Kumar, N. (author), Couto Correa Pinto Filho, L. (author), Cisotto, L. (author), Pereira, S.F. (author), Urbach, H.P. (author)In several optical systems, a specific Point Spread Function (PSF) needs to be generated. This can be achieved by shaping the complex field at the pupil. The Extended Nijboer-Zernike (ENZ) theory relates complex Zernike modes on the pupil directly to functions in the focal region. In this paper, we introduce a method to engineer a PSF using the...journal article 2014
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Pereira, S.P. (author), Vuik, K. (author), Pinho, F.T. (author), Nobrega, J.M. (author)The present work explores the massively parallel capabilities of the most advanced architecture of graphics processing units (GPUs) code named “Fermi”, on a two-dimensional unstructured cell-centred finite volume code. We use the SIMPLE algorithm to solve the continuity and momentum equations that was fully ported to the GPU. The benefits of...conference paper 2013
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Polo, A. (author), Pereira, S.F. (author), Urbach, H.P. (author)We analytically demonstrate that Phase Retrieval (PR) from defocused intensity measurements is achievable using a single measurement plane. Following this approach, the predicted plane is found at a defocus distance of 4? optical unit. Experimental results confirm the theoretical predictionsconference paper 2013
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Polo, A. (author), Pereira, S.F. (author), Urbach, P.H. (author)We study the phase retrieval (PR) technique using through-focus intensity measurements and explain the dependence of PR on the defocus distance. An optimal measurement plane in the out-of-focus region is identified where the intensity distribution on the optical axis drops to the first minimum after focus. Experimental results confirm the...journal article 2013
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El Gawhary, O. (author), Wiegmann, A. (author), Kumar, N. (author), Pereira, S.F. (author), Urbach, H.P. (author)Through-focus phase retrieval methods aim to retrieve the phase of an optical field from its intensity distribution measured at different planes in the focal region. By using the concept of spatial correlation for propagating fields, for both the complex amplitude and the intensity of a field, we can infer which planes are suitable to retrieve...journal article 2013
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Kim, M.S. (author), Scharf, T. (author), Da Costa Assafrao, A. (author), Rockstuhl, C. (author), Pereira, S.F. (author), Urbach, H.P. (author), Herzig, H.P. (author)Bessel-Gauss beams are known as non-diffracting beams. They can be obtained by focusing an annularly shaped collimated laser beam. Here, we report for the first time on the direct measurement of the phase evolution of such beams by relying on longitudinal-differential interferometry. We found that the characteristics of Bessel-Gauss beams cause...journal article 2012
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Polo, A. (author), Haber, A. (author), Pereira, S.F. (author), Verhaegen, M.H.G. (author), Urbach, H.P. (author)We carry out performance characterisation of a commercial push and pull deformable mirror with 48 actuators (Adaptica Srl). We present a detailed description of the system as well as a statistical approach on the identification of the mirror influence function. A new efficient control algorithm to induce the desired wavefront shape is also...journal article 2012
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Pereira, S.F. (author), Wiegman, A. (author), Kumar, N. (author), Da Costa Assafrao, A. (author), Polo, A. (author), Wei, L. (author), Van Haver, S. (author)Measurement techniques to determine the aberration of an optical system, by obtaining through-focus intensity images that are produced when the object is a point source at infinity, are shown. The analysis of the aberrations is made using the extended version of the Nijboer-Zernike diffraction theory. This theory provides a semi analytical...conference paper 2012
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Costa Assafrao, A. (author), Wachters, A.J.H. (author), Pereira, S.F. (author), Urbach, H.P. (author)We have found an alternative way of achieving a doughnutlike focused spot by simply melting a subwavelength scatterer in a polycarbonate/ZnS sample. The near-field microscopy technique is used to directly measure the induced doughnut spot in the near-field regime. A numerical model based on rigorous solution of the Maxwell’s equations is...journal article 2012
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Kim, M.S. (author), Assafrao, A.C. (author), Scharf, T. (author), Wachters, A.J.H. (author), Pereira, S.F. (author), Urbach, H.P. (author), Brun, M. (author), Olivier, S. (author), Nicoletti, S. (author), Herzig, H.P. (author)We report on the experimental and numerical demonstration of immersed submicron-size hollow focused spots, generated by structuring the polarization state of an incident light beam impinging on a micro-size solid immersion lens (?-SIL) made of SiO2. Such structured focal spots are characterized by a doughnut-shaped intensity distribution, whose...journal article 2012
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El Gawhary, O. (author), Schilder, N.J. (author), Da Costa Assafrao, A. (author), Pereira, S.F. (author), Urbach, H.P. (author)It was predicted a few years ago that a medium with negative index of refraction would allow for perfect imaging. Although no material has been found so far that behaves as a perfect lens, some experiments confirmed the theoretical predictions in the near-field, or quasi-static, regime where the behaviour of a negative index medium can be...journal article 2012