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  • 51. Baev, A
    et al.
    Salek, Pawel
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Gelmukhanov, Faris
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Ågren, Hans
    KTH, Tidigare Institutioner                               , Bioteknologi.
    de Brito, N
    Bjorneholm, O
    Svensson, S
    Picturing molecular femtosecond processes through an ultra-fast controllable X-ray shutter2003Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 289, nr 1, s. 51-56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that frequency detuning in a resonant X-ray scattering experiment acts as an X-ray camera shutter by regulating the duration time of the scattering process. The camera shutter can be used to select processes at different time scales for observation. This is illustrated by a resonant Auger study of the ultra-fast dissociation of the core-excited HF molecule. We present experimental results and first principle simulations of the molecular fraction in the resonant Auger spectra of HF which is a dynamical parameter that well illustrates X-ray shutter controlled dissociation.

  • 52. Baev, Alexander
    et al.
    Prasad, Paras N.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Samoc, Marek
    Wegener, Martin
    Metaphotonics: An emerging field with opportunities and challenges2015Ingår i: Physics reports, ISSN 0370-1573, E-ISSN 1873-6270, Vol. 594, s. 1-60Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Metaphotonics is an emerging multidisciplinary field that deals with manipulation of electro-magnetic fields in nanoengineered (meta)materials using both electric and magnetic interactions and their cross-coupling. It offers unprecedented control of both linear and nonlinear optical functions for applications ranging from optical switching, to negative- and near-zero refractive index metamaterials, to chiral bioimaging, to cloaking. However, realization of such applications requires physics-guided nanoengineering of appropriate artificial media with electro-magnetic properties at visible and infrared wavelengths that are tailored to surpass those of any naturally-occurring material. Here, we review metaphotonics with a broadened vision and scope, introduce potential applications, describe the role of theoretical physics through multiscale modeling, review the materials development and current status, and outline opportunities in this fertile emerging field.

  • 53.
    Baggioli, Matteo
    et al.
    UAM, CSIC, Inst Fis Teor, C Nicolas Cabrera 13-15, Madrid 28049, Spain..
    Gran, Ulf
    Chalmers Univ Technol, Dept Phys, Div Theoret Phys, SE-41296 Gothenburg, Sweden..
    Alba, Amadeo Jimenez
    UAM, CSIC, Inst Fis Teor, C Nicolas Cabrera 13-15, Madrid 28049, Spain..
    Tornso, Marcus
    Chalmers Univ Technol, Dept Phys, Div Theoret Phys, SE-41296 Gothenburg, Sweden..
    Zingg, Tobias
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Holographic plasmon relaxation with and without broken translations2019Ingår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 9, artikel-id 013Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the dynamics and the relaxation of bulk plasmons in strongly coupled and quantum critical systems using the holographic framework. We analyze the dispersion relation of the plasmonic modes in detail for an illustrative class of holographic bottom-up models. Comparing to a simple hydrodynamic formula, we entangle the complicated interplay between the three least damped modes and shed light on the underlying physical processes. Such as the dependence of the plasma frequency and the effective relaxation time in terms of the electromagnetic coupling, the charge and the temperature of the system. Introducing momentum dissipation, we then identify its additional contribution to the damping. Finally, we consider the spontaneous symmetry breaking (SSB) of translational invariance. Upon dialing the strength of the SSB, we observe an increase of the longitudinal sound speed controlled by the elastic moduli and a decrease in the plasma frequency of the gapped plasmon. We comment on the condensed matter interpretation of this mechanism.

  • 54.
    Bagheri, Shervin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Liu, Q.ingyun
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Bergstrand, Jan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Pu, R.
    Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information.
    Zhan, Q.
    Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information.
    Ara, M. H. M.
    Photonics Laboratory, Physics Department, Kharazmi University, Tehran, Iran.
    Ågren, Hans
    KTH, Tidigare Institutioner (före 2005), Bioteknologi. KTH, Tidigare Institutioner (före 2005), Kemi. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Liu, Haichun
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Change in the emission saturation and kinetics of upconversion nanoparticles under different light irradiations2019Ingår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 97, artikel-id 109389Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nd3+-sensitized upconversion nanoparticles (UCNPs) can be excited by both 980 and 808 nm light, which is regarded as a particularly advantageous property of these particles. In this work, we demonstrate that the nanoparticles can exhibit significantly different response when excited at these two excitation wavelengths, showing dependence on the intensity of the excitation light and the way it is distributed in time. Specifically, with 808 nm excitation saturation in the emitted luminescence is more readily reached with increasing excitation intensities than upon 980 nm excitation. This is accompanied by delayed upconversion luminescence (UCL) kinetics and weaker UCL intensities. The different luminescence response at 808 and 980 nm excitation reported in this work is relevant in a manifold of applications using UCNPs as labels and sensors. This could also open new possibilities for multi-wavelength excitable UCNPs for upconversion color display and in laser-scanning microscopy providing selective readouts and sub-sectioning of samples.

  • 55. Bai, Songang
    et al.
    Li, Qiang
    Zhang, Han
    Chen, Xingxing
    Luo, Si
    Gong, Hanmo
    Yang, Yuanqing
    Zhao, Ding
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Large third-order nonlinear refractive index coefficient based on gold nanoparticle aggregate films2015Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, nr 14, artikel-id 141111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Au nanoparticles show large third-order nonlinear effect and ultra-fast response. Here a high nonlinear aggregate film based on self-assembled gold nanoparticles is reported and its third-order nonlinear refractive index coefficient is measured by Z-scan experiment. The third-order nonlinear refractive index coefficient of the Au nanoparticle aggregate film (gamma(1) = 9.2 x 10(-9) cm(2)/W) is found to be larger than that of an 8-nm-thick sputtered Au film (gamma(2)= 6.5 x 10(-9) cm(2)/W). This large nonlinear effect can be attributed to the strong field enhancement due to localized plasmon resonances between Au nanoparticles. The result shows that the self-assembled Au nanoparticle aggregate film could be a promising candidate as a third-order nonlinear optical material.

  • 56. Bandelow, U.
    et al.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Wunsche, H. -J
    A correct single-mode photon rate equation for multisection lasers1996Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 8, s. 614-616Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is shown that not the photon number but photon number divided by the square root of the excess factor of spontaneous emission must be used in the photon rate equation for single-mode lasers when the longitudinal field distribution changes with time. The importance of using the correct dynamic quantity is illustrated with two examples.

  • 57. Bao, Fanglin
    et al.
    Evans, Julian S.
    Fang, Maodong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Zhejiang University, China; South China Normal University, China .
    Inhomogeneity-related cutoff dependence of the Casimir energy and stress2016Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 93, nr 1, artikel-id 013824Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Casimir stress and energy density are widely used to study the Casimir force, but they diverge in inhomogeneous systems, making the force seem to be infinite as well. Here we characterize the asymptotic behavior of the Casimir stress and energy density in inhomogeneous systems. We show an unambiguous map of all cutoff-dependent terms in the asymptotic expansion to the pressure and the surface tension through the insertion of multiple boundary layers. This result reveals an elegant subtraction to retrieve a finite stress that yields a cutoff-independent force.

  • 58.
    Barday, R.
    et al.
    Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany..
    Tashenov, Stanislav
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik. Stockholm Univ, Dept Atom Phys, SE-10691 Stockholm, Sweden.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Eckardt, C.
    Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany..
    Enders, J.
    Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany..
    Goeoek, A.
    Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany..
    Khaplanov, Anton
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Poltoratska, Y.
    Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany..
    Schassburger, Kai-Uwe
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Surzhykov, A.
    Heidelberg Univ, Phys Inst Heidelberg, D-69120 Heidelberg, Germany..
    Wagner, M.
    Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany..
    ELECTRON BEAM POLARIMETRY AT LOW ENERGIES AND ITS APPLICATIONS2011Ingår i: POLARIZED SOURCES, TARGETS AND POLARIMETRY / [ed] Ciullo, G Contalbrigo, M Lenisa, P, WORLD SCIENTIFIC PUBL CO PTE LTD , 2011, s. 105-112Konferensbidrag (Refereegranskat)
    Abstract [en]

    Low energy (E-k similar to 100 keV) Mott scattering polarimetry is a widely established technique to measure the polarization of an electron beam. We analyze the feasibility of Mott scattering at energies up to 20 MeV. For further studies of the electron spin dynamics in the scattering process a correlation between the linear polarization of bremsstrahlung radiation and the electron beam polarization has been measured for the first time using a planar HPGe Compton polarimeter at the 100 keV source of polarized electrons at TU Darmstadt.

  • 59.
    Baryshnikov, Gleb V.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Sunchugashev, Dmitry A.
    Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Valiev, Rashid R.
    Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Minaev, Boris F.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Vibronic absorption spectra of the angular fused bisindolo- and biscarbazoloanthracene blue fluorophores for OLED applications2018Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 513, s. 105-111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An in-depth analysis of the vibronic absorption spectra for the recently synthesized blue-fluorescent OLED emitters bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3',4'-h]anthracene has been carried out computationally at the density functional theory level within the Franck-Condon approximation. These molecules are characterized by extended and rich electronic absorption spectra with most absorption bands being of vibronic origin. The first excited singlet state of bis[(1,2)(5,6)]indoloanthracene compound demonstrates a clear observable double-peak vibronic progression for two different active modes in the absorption spectrum, while the S-2 state is vibronically inactive. In contrast, for the larger biscarbazolo[3,4-a:3',4'-h]anthracene compound the S-0 -> S-2 transition demonstrates well-resolved intense vibronic bands which overlap the less intense progressions of few modes in the S-0 -> S-1 transition. We have also found, that even the higher-lying and very intense S-0 -> S-4 and S-0 -> S-5 transitions for bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3',4'-h]anthracene, respectively, are characterized by clear vibronic progressions in excellent agreement with experimental spectra.

  • 60.
    Basset, F. Basso
    et al.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Rota, M. B.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Schimpf, C.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Tedeschi, D.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Zeuner, Katharina
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    da Silva, S. F. Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Reindl, M.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Jöns, Klaus D.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Rastelli, A.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Trotta, R.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Entanglement Swapping with Photons Generated on Demand by a Quantum Dot2019Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 123, nr 16, artikel-id 160501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test of quantum mechanics and an essential resource to the realization of quantum networks. Probabilistic sources of nonclassical light were used for seminal demonstration of entanglement swapping, but applications in quantum technologies demand push-button operation requiring single quantum emitters. This, however, turned out to be an extraordinary challenge due to the stringent prerequisites on the efficiency and purity of the generation of entangled states. Here we show a proof-of-concept demonstration of all-photonic entanglement swapping with pairs of polarization-entangled photons generated on demand by a GaAs quantum dot without spectral and temporal filtering. Moreover, we develop a theoretical model that quantitatively reproduces the experimental data and provides insights on the critical figures of merit for the performance of the swapping operation. Our theoretical analysis also indicates how to improve stateof-the-art entangled-photon sources to meet the requirements needed for implementation of quantum dots in long-distance quantum communication protocols.

  • 61.
    Basso, Simone
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnkraftssäkerhet.
    Konovalenko, Alexander
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnkraftssäkerhet.
    Kudinov, Pavel
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnkraftssäkerhet.
    Effectiveness of the debris bed self-leveling under severe accident conditions2016Ingår i: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 95, s. 75-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Melt fragmentation, quenching and long term coolability in a deep pool of water under the reactor vessel are employed as a severe accident mitigation strategy in several designs of light water reactors. The success of such strategy is contingent upon the natural circulation effectiveness in removing the decay heat generated in the porous debris bed. The maximum height of the bed is one of the important factors which affect the debris coolability. The two-phase flow within the bed generates mechanical energy which can change the geometry of the debris bed by the "self-leveling" phenomenon. In this work.we developed an approach to modeling of the self-leveling phenomenon. Sensitivity analysis was carried out to rank the importance of the model uncertainties and uncertain input parameters i.e. the conditions of the accident scenario and the debris bed properties. The results provided some useful insights for further improvement of the model and reduction of the output uncertainties through separate-effect experimental studies. Finally, we assessed the self-leveling effectiveness, quantified its uncertainties in prototypic severe accident conditions and demonstrated that the effect of self-leveling phenomenon is robust with respect to the considered input uncertainties.

  • 62.
    Bayer, Christian
    et al.
    Weierstrass Institute for Applied Analysis and Stochastics.
    Hoel, Håkon
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Kadir, Ashraful
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Plechac, Petr
    Dept. of Mathematical Sciences, University of Delaware.
    Sandberg, Mattias
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Szepessy, Anders
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Tempone, Raul
    Division of Mathematics, King Abdullah University of Science and Technology.
    How accurate is molecular dynamics?2012Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Born-Oppenheimer dynamics is shown to provide an accurate approximation of time-independent Schrödinger observables for a molecular system with an electron spectral gap, in the limit of large ratio of nuclei and electron masses, without assuming that the nuclei are localized to vanishing domains. The derivation, based on a Hamiltonian system interpretation of the Schrödinger equation and stability of the corresponding hitting time Hamilton-Jacobi equation for non ergodic dynamics, bypasses the usual separation of nuclei and electron wave functions, includes caustic states and gives a different perspective on theBorn-Oppenheimer approximation, Schrödinger Hamiltonian systems and numerical simulation in molecular dynamics modeling at constant energy.

  • 63.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Imaging through light scattering eye media: letter identification1994Ingår i: Proc.SPIE, Vol. 2079, s. 2079-2079Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of intraocular light scatter on letter identification in the absence and presence of glaring light is studied through computer simulations and simple experiments on healthy test subjects wearing diffusive glasses with known light scattering properties. An explicit expression for the point-spread function of a cataractous eye is used to calculate retinal images. For estimating resolution in the calculated images an assumed neural contrast sensitivity function is needed. The function used is derived from measurements by Campbell and Green. Experimental results are in agreement with theory. The analysis shows that visual acuity is quite insensitive even to substantial diffusive scattering provided that glare sources are not present in the field of view. Comparing measurements of ‘letter size’ with measurements of ‘letter contrast’ the latter method is found to measure intraocular light scattering more sensitively.

  • 64.
    Beckman, Claes
    University of Waterloo.
    The influence of increased interocular lightscatter on the contrast in a confocal scanning laserophthalmoscope image1995Ingår i: Vision Science and Its Application, Vol. 1 of 1995 OSA Technical Digest Series (Optical Society of America, 1995) / [ed] Optical Society of America, Washington, 1995, Vol. 1, s. 106-109Konferensbidrag (Refereegranskat)
    Abstract [en]

    the influence of increased intraocular light scatter on image quality in a confocal scanning laserophthalmoscope (CSLO) is quntified through computer simulations and model eye experiments.

  • 65. Beckman, Claes
    et al.
    Jörgen, Thaung
    Göteborgs Universitet.
    Johan, Sjöstrand
    Göteborgs Universitet.
    In vitro Lens Scatter Measurements and Glare Testing1994Ingår i: The Association for Research in Vision and Ophthalmology Annual Meeting. Sarasota, Florida, May 1-6, 1994. Abstracts. Investigative Ophthalmology & Visual Science March 1994, Vol.35, 1254-2383., 1994, Vol. 35, s. 1803-Konferensbidrag (Refereegranskat)
  • 66. Bellotti, R
    et al.
    Boezio, M
    Volpe, Francesca
    KTH.
    Clustering analysis and supervised methods for antiparticle studies in the PAMELA experiment2004Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 525, nr 1-2, s. 412-416Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study a new approach to pattern recognition problems in astroparticle physics is presented. The context in which this work has been developed is the satellite borne experiment PAMELA, whose principal aim is antiparticle studies. In particular the classification problem of the PAMELA imaging calorimeter has been taken into account. This detector is designed for particle identification; due to its high granularity, both in the transversal and in the longitudinal direction, the calorimeter is suitable for reconstructing the spatial development of a shower. For each event the calorimeter is able to provide a 3D image that can be used to discriminate between hadrons and leptons. In this work the available information for each kind of image event class has been pre-processed representing each event by means of discriminating variables. A clustering analysis has been applied to a data set and the classification has been performed using supervised algorithms. Results from simulated data from the PAMELA prototype calorimeter will be shown.

  • 67. Beltran, M
    et al.
    Deng, L
    Pang, Xiaodan
    RISE ACREO AB.
    Zhang, X
    Arlunno, V
    Zhao, Y
    Yu, X
    Llorente, R
    Liu, D
    Tafur Monroy, I
    Single- and Multiband OFDM Photonic Wireless Links in the 75-110 GHz Band EmployingOptical Combs2012Ingår i: IEEE Photonics Journal, Vol. 4, nr 5, s. 2027-2036Artikel i tidskrift (Refereegranskat)
  • 68. Beltrán, Marta
    et al.
    Deng, Lei
    Pang, Xiaodan
    RISE ACREO AB.
    Zhang, Xu
    Arlunno, Valeria
    Zhao, Ying
    Yu, Xianbin
    Llorente, Roberto
    Liu, Deming
    Tafur Monroy, Idelfonso
    38.2-Gb/s Optical-Wireless Transmission in 75-110 GHz Based on Electrical OFDM with Optical Comb Expansion2012Ingår i: Optical Fiber Communication Conference, 2012Konferensbidrag (Refereegranskat)
  • 69. Bengtsson, M.
    et al.
    Wallström, Stina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gronlund, R.
    Anderson, B.
    Sjoholm, M.
    Larsson, A.
    Kroll, S.
    Svanberg, S.
    Development of a tool for remote detection of fungi and algae on electrical insulators using laser induced fluorescence combined with principal component analysis2005Ingår i: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2005, s. 427-Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study a combination of laser induced fluorescence (LIF) and principal component analysis (PCA) is used in an attempt to develop a method to detect fungal growth on silicone rubber. Field experiments on aged insulators have been carried out to test whether LIF combined with PCA can give useful information about the fungal growth.

  • 70.
    Berrier, Audrey
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Mulot, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Malm, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Anand, Srinivasan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Electrical conduction through a 2D InP-based photonic crystal - art. no. 63220J2006Ingår i: Tuning the Optic Response of Photonic Bandgap Structures III / [ed] Braun, PV; Weiss, SM, 2006, Vol. 6322, s. J3220-J3220Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work investigates the current transport across two-dimensional PhCs dry etched into InP-based low-index-contrast vertical structures using Ar/Cl-2 chemically assisted ion beam etching. The electrical conduction through the PhC field is influenced by the surface potential at the hole sidewalls, which is modified by dry etching. The measured current-voltage (I-V) characteristics are linear before but show a current saturation at higher voltages. This behaviour is confirmed by simulations performed by ISE-TCAD software. We investigate the dependence of the conductance of the PhC area as a function of the geometry of the photonic crystal as well as the material parameters. By comparing the experimental and simulated conductance of the PhC, we deduce that the Fermi level is pinned at 0.1 eV below the conduction band edge. The method presented here can be used for evaluating etching processes and surface passivation methods. It is also applicable for other material systems and sheds new light on current driven PhC tuning.

  • 71.
    Berrier, Audrey
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Mulot, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Talneau, A.
    Anand, Srinivasan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Feature size effects in Ar/Cl-2 chemically assisted ion beam etching of InP-based protonic crystals2006Ingår i: 2006 International Conference on Indium Phosphide and Related Materials Conference Proceedings, NEW YORK: IEEE , 2006, s. 341-344Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work addresses feature size effects (the lag-effect and roughness development) in chemically assisted ion beam etching (CAIBE) etching of InP-based photonic crystals. Photonic crystal fields The slope of the etch,with varying hole size and periods were etched with different etching times. depth versus diameter cures (lag-curves) reveals an aspect ratio dependence, with an etch limiting aspect ratio of the order of 25. A model of the etch rate specific to Ar/Cl-2 CAIBE is proposed. We calculate the etch rate using a physico-chemical model which takes in to account the effect of Ar-ion sputtering and surface chemical reactions. lit addition, it combines the aspect ratio dependence of the gas conductance of the etched holes. Finally, the bottom roughness of the etched holes is examined; its origin and evolution are discussed.

  • 72.
    Berrier, Audrey
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Mulot, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Talneau, A.
    Ferrini, R.
    Houdre, R.
    Anand, Srinivasan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Feature size effects in chemically assisted ion beam etching of InP-based photonic crystals - art. no. 6327072006Ingår i: Nanoengineering: Fabrication, Properties, Optics, and Devices III / [ed] Dobisz, EA; Eldada, LA, BELLINGHAM, WA: SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6327, s. 32707-32707Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work addresses feature size effects (the lag-effect and roughness development) in chemically assisted ion beam etching (CAIBE) etching of InP-based photonic crystals. Photonic crystal fields with varying hole size and periods were etched with different etching times. The slope of the etch depth versus diameter curves (lag-curves) reveals a hole size dependence, with a critical aspect ratio higher than 25. A model for the etch rate specific to Ar/Cl-2 CAIBE is proposed. We calculate the etch rate using a physico-chemical model which takes in to account the effect of Ar-ion sputtering and surface chemical reactions. In addition, it combines the aspect ratio dependence of the gas conductance of the etched holes. The origin and evolution of the bottom roughness of the etched holes is examined. The impact of the feature size dependence of the etching on the photonic crystal optical properties is then assessed by measuring the quality-factor of one-dimensional Fabry-Perot cavities using the Internal Light Source method, and discussed in terms of hole shape and depth. A systematic trend between the determined quality factor (Q) and the lag-effect is evidenced: Q decreases from about 250 to 60 when the hole depth drops from 5 mu m to 2 mu m.

  • 73. Berrill, Mark
    et al.
    Alessi, David
    Wang, Yong
    Domingue, Scott R.
    Martz, Dale H.
    Electrical and Computer Engineering Department, Colorado State University.
    Luther, Brad M.
    Liu, Yanwei
    Rocca, Jorge J.
    Improved beam characteristics of solid-target son x-ray laser amplifiers by injection seeding with high harmonic pulses2010Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 35, nr 14, s. 2317-2319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Injection seeding of solid-target soft x-ray laser amplifiers with high harmonic pulses is shown to dramatically improve the far-field laser beam profile and reduce the beam divergence. Measurements and two-dimensional simulations for a 13.9 nm nickel-like Ag amplifier show that the amplified beam divergence depends strongly on the seed and can therefore be controlled by selecting the divergence of the seed. The near-field beam size of both the seeded and unseeded lasers is shown to be determined by the size of the gain region and the divergence of the amplified beams.

  • 74.
    Bertilson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Laboratory soft x-ray microscopy and tomography2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Soft x-ray microscopy in the water-window (λ = 2.28 nm – 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x‑ray facilities, thereby limiting their accessibility for a wider scientific community.

    This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments are supported by extensive numerical modelling for improved understanding of partially coherent image formation and stray light in soft x-ray microscopes. The models are useful tools for studying effects of zone plate optics or optical design of the microscope on image formation and quantitative accuracy in soft x-ray tomography.

  • 75.
    Bertilson, Michael C.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Takman, Per A. C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Zone plate efficiency measurements with a laser-plasma source2007Ingår i: Advances in X-Ray/EUV Optics and Components II / [ed] Khounsary, AM; Morawe, C; Goto, S, 2007, Vol. 6705, s. F7050-F7050Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate a compact instrument for rapid and accurate measurements of the absolute and local efficiency of soft x-ray zone plates in the water window [M. Bertilson, et al, Rev. Sci. Instrum 78, 026103 (2007)]. The arrangement is based on a new single-line lambda = 2.88 nm liquid-nitrogen-jet laser-plasma source. The versatility of the instrument enables micro and condenser zone plates with focal lengths in the range from similar to 200 mu m to similar to 100 mm to be measured. We demonstrate an accurate local efficiency map of a in-house fabricated micro zone plate. Furthermore, we show how this compact instrument allows rapid feedback to the fabrication process which is important for future improvements.

  • 76.
    Bertilson, Michael
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    von Hofsten, Olov
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Numerical model for tomographic image formation in transmission x-ray microscopy2011Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, nr 12, s. 11578-11583Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a numerical image-formation model for investigating the influence of partial coherence, sample thickness and depth-of-focus on the accuracy of tomographic reconstructions in transmission x-ray microscopes. The model combines wave propagation through the object by finite difference techniques with Fourier methods. We include a ray-tracing model to analyse the origin of detrimental stray light in zone plate-based x-ray microscopes. These models allow optimization of x-ray microscopy systems for quantitative tomographic imaging of thick objects. Results show that both the depth-of-focus and the reconstructed local absorption coefficient are highly dependent on the degree of coherence of the optical system.

  • 77.
    Bertilson, Michael
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    von Hofsten, Olov
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Christakou, Athanasia E.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Laboratory soft-x-ray microscope for cryotomography of biological specimens2011Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 36, nr 14, s. 2728-2730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a lambda = 2.48nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to similar to 100nm.

  • 78. Bierlein, J. D.
    et al.
    Bindloss, W.
    Laurell, Fredrik
    Lee, J. D.
    Segmented waveguides having selected Bragg reflection characteristics1991Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Segmented waveguides for wavelength conversion (e.g., waveguides comprising alternating sections of crystalline substrate having the formula K1-x Rbx TiOMO4 where x is from 0 to 1 and M is P or As and sections of substrate material in which cations of said substrate have been partially replaced) and devices and processes employing segmented waveguides for wavelength conversion are disclosed wherein a periodic structure along the waveguide provides a Bragg reflection having a wavelength essentially equal to the wavelength of the input wave used for wavelength conversion. Also disclosed is a process for preparing a channel waveguide for a wavelength conversion system wherein areas along a portion of a crystal substrate surface used for forming the desired channel are alternately masked and unmasked during cation replacement by immersion in a molten salt.

  • 79. Bin Abdul Rahim, H. R.
    et al.
    Bin Lokman, M. Q.
    Harun, S. W.
    Hornyak, G. L.
    Sterckx, K.
    Mohammed, W. S.
    Dutta, Joydeep
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Applied light-side coupling with optimized spiral-patterned zinc oxide nanorod coatings for multiple optical channel alcohol vapor sensing2016Ingår i: Journal of Nanophotonics, ISSN 1934-2608, Vol. 10, nr 3, artikel-id 036009Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The width of spiral-patterned zinc oxide (ZnO) nanorod coatings on plastic optical fiber (POF) was optimized theoretically for light-side coupling and found to be 5 mm. Structured ZnO nanorods were grown on large core POFs for the purpose of alcohol vapor sensing. The aim of the spiral patterns was to enhance signal transmission by reduction of the effective ZnO growth area, thereby minimizing light leakage due to backscattering. The sensing mechanism utilized changes in the output signal due to adsorption of methanol, ethanol, and isopropanol vapors. Three spectral bands consisting of red (620 to 750 nm), green (495 to 570 nm), and blue (450 to 495 nm) were applied in measurements. The range of relative intensity modulation (RIM) was determined to be for concentrations between 25 to 300 ppm. Methanol presented the strongest response compared to ethanol and isopropanol in all three spectral channels. With regard to alcohol detection RIM by spectral band, the green channel demonstrated the highest RIM values followed by the blue and red channels, respectively.

  • 80.
    Bjurshagen, Stefan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Brynolfsson, Patrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Parreu, I.
    Pujol, M. C.
    Peña, A.
    Aguiló, M.
    Díaz, F.
    Crystal growth, spectroscopic characterization, and eye-safe laser operation of erbium- And ytterbium-codoped KLu(WO4)22008Ingår i: Applied Optics, ISSN 1559-128X, Vol. 47, nr 5, s. 656-665Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Erbium (Er)- and Ytterbium (Yb)-codoped monoclinic KLu(WO4) 2 single crystals were grown by top seeded solution growth-slow cooling method for several different doping concentrations. Growth parameters have been optimized to obtain macrodefect-free single crystals. Er energy levels involved in the 4I13/2 → 4I 15/2 were determined by 6 K polarized optical absorption. The maximum emission cross section for this electronic transition has been evaluated, being 2.85 × 10-20 cm2 for E||Nm at 1535 nm. Laser oscillation in the 1.5 μm range was obtained by pumping the Yb ion at 980 nm and sensitizing Er. The maximum output power achieved was 152 mW, with 1.2% slope efficiency.

  • 81.
    Bjurshagen, Stefan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Koch, R
    Hoffman, H J
    946-nm Nd: YAG laser under ground-state direct diode-pumping at 869 nm2005Ingår i: 2005 Conference on Lasers & Electro-Optics (CLEO), Vols 1-3, WASHINGTON, DC: OPTICAL SOC AMERICA , 2005, s. 328-330Konferensbidrag (Refereegranskat)
    Abstract [en]

    We have demonstrated, what we believe is for the first time, direct diode-pumping at 869 rim into the emitting level of a quasi-three-level Nd:YAG laser operating at 946 nm.

  • 82.
    Bjurshagen, Stefan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Parreu, I.
    University of Tarragona.
    Pujol, M. C.
    University of Tarragona.
    Aguiló, M.
    University of Tarragona.
    Diaz, Francesc
    University of Tarragona.
    Crystal Growth, Spectroscopic Characterisation and Eye-Safe Laser Operation of Er and Yb Doped KLu(WO4)22008Konferensbidrag (Refereegranskat)
    Abstract [en]

    High quality Er:Yb:KLu(WO4)2have been grown using TSSG method and spectroscopically investigated . The laser performance is compared with that in Er:Yb:KY(WO4)2. Role of upconversion processes and optimum doping concentrations have been estimated.

  • 83.
    Björk, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    20th Central European Workshop on Quantum Optics, Stockholm, June 16-20, 2013: Book of Abstracts2013Proceedings (redaktörskap) (Övrigt vetenskapligt)
  • 84.
    Björk, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Information gain when measuring an unknown qubit2018Ingår i: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 39, nr 1, artikel-id 015403Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In quantum information the fundamental information-containing system is the qubit. A measurement of a single qubit can at most yield one classical bit. However, a dichotomous measurement of an unknown qubit will yield much less information about the qubit state. We use Bayesian inference to compute how much information one progressively gets by making sucessive, individual measurements on an ensemble of identically prepared qubits. Perhaps surprisingly, even if the measurements are arranged so that each measurement yields one classical bit, that is, the two possible measurement outcomes are a priori equiprobable, it takes almost a handful of measurements before one has gained one bit of information about the gradually concentrated qubit probability density. We also show that by following a strategy that reaps the maximum information per measurement, we are led to a mutually unbiased basis as our measurement bases. This is a pleasing, although not entirely surprising, result.

  • 85.
    Björk, Gunnar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    de Guise, H.
    Klimov, A. B.
    de la Hoz, P.
    Sanchez-Soto, L. L.
    Classical distinguishability as an operational measure of polarization2014Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 90, nr 1, s. 013830-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We put forward an operational degree of polarization that can be extended in a natural way to fields whose wave fronts are not necessarily planar. This measure appears as a distance from a state to the set of all of its polarization-transformed counterparts. By using the Hilbert-Schmidt metric, the resulting degree is a sum of two terms: one is the purity of the state and the other can be interpreted as a classical distinguishability, which can be experimentally determined in an interferometric setup. For transverse fields, this reduces to the standard approach, whereas it allows one to get a straight expression for nonparaxial fields.

  • 86.
    Björk, Gunnar G.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Kothe, Christian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Bourennane, M.
    Inoue, S.
    Limits to the efficiency of quantum lithography2011Ingår i: Conf. Lasers Electro-Opt. Europe Eur. Quantum Electron. Conf., CLEO EUROPE/EQEC, 2011, s. 5943416-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Quantum lithography promises, in principle, unlimited feature resolution, independent of wavelength. The price to be paid is that the lithographic film must consist of a multi-photon absorbing material. If N photons are absorbed, the minimum feature resolution goes from roughly /2 to /2N. However, there has been a discussion in the literature as to what is the probability of N photons in a lithographic exposure field to hit the same detector pixel, thereby enabling the needed N-photon absorption. On one hand it has been claimed that If the optical system is aligned properly, the probability of the first photon arriving in a small absorptive volume of space time is proportional to [the field intensity]. However, the remaining N-1 photons are constrained to arrive at the same place at the same time [1]. On the other hand it has been argued that it is not true that the first arriving photon greatly constrains the arrival location of the following ones Very few photons will be absorbed in one point since they typically arrive far apart. [2]. The answer to this dispute dictate very much the practical feasibility of quantum lithography, because if the few photons in the entangled state are spread out over the exposed area, the probability will quickly become negligible that they arrive at the same spot (causing a N-photon detection event). This will render quantum lithography very inefficient, albeit still feasible in principle.

  • 87.
    Björk, Gunnar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Man'ko, Margarita
    20th Central European Workshop on Quantum Optics Preface2014Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T160, s. 010301-Artikel i tidskrift (Refereegranskat)
  • 88.
    Björk, Gunnar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Shabbir, Saroosh
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Reply to comment on ‘non-monotonic projection probabilities as a function of distinguishability’2014Ingår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, nr 11, artikel-id 118004Artikel i tidskrift (Refereegranskat)
  • 89.
    Björk, Gunnar
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Söderholm, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Sanchez-Soto, Luis L.
    Klimov, Andrei B.
    Ghiu, Iulia
    Marian, Paulina
    Marian, Tudor A.
    Quantum degrees of polarization2010Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 283, nr 22, s. 4440-4447Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We discuss different proposals for the degree of polarization of quantum fields. The simplest approach, namely making a direct analogy with the classical description via the Stokes operators, is known to produce unsatisfactory results. Still, we argue that these operators and their properties should be basic for any measure of polarization. We compare alternative quantum degrees and put forth that they order various states differently. This is to be expected, since, despite being rooted in the Stokes operators, each of these measures only captures certain characteristics. Therefore, it is likely that several quantum degrees of polarization will coexist, each one having its specific domain of usefulness.

  • 90. Blazhev, A.
    et al.
    Gorska, M.
    Grawe, H.
    Nyberg, J.
    Palacz, M.
    Caurier, E.
    Cederwall, Bo
    KTH, Tidigare Institutioner, Fysik.
    et al,
    Observation of a core-excited E4 isomer in Cd-982004Ingår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 69, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A core-excited I-pi=(12(+)) spin-gap isomer was identified in Cd-98 in an experiment at EUROBALL IV. It was found to feed the known I-pi=(8(+)) seniority isomer by an E4 transition. Half-lives of T-1/2=0.23 ((+4)(-3)) mus and 0.17 ((+6)(-4)) mus were measured for the two states at E-x=6635 keV and 2428 keV, respectively. From the excitation energy of the core-excited isomer a Sn-100 shell gap of 6.46(15) MeV is inferred. The measured E4 and E2 strengths, Sn-100 core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An E2 polarization charge for protons of deltae(pi)

  • 91.
    Bogdanowicz, Janusz
    et al.
    IMEC, Kapeldreef 75, B-3000 Leuven, Belgium.
    Gilbert, Matthieu
    IMEC, Kapeldreef 75, B-3000 Leuven, Belgium.
    Innocenti, Nicolas
    KTH, Skolan för datavetenskap och kommunikation (CSC), Beräkningsbiologi, CB. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Koelling, Sebastian
    IMEC, Kapeldreef 75, B-3000 Leuven, Belgium.
    Vanderheyden, Benoit
    4 Institut Montefiore, Sart-Tilman B28, B-4000 Liege, Belgium.
    Vandervorst, Wilfried
    IMEC, Kapeldreef 75, B-3000 Leuven, Belgium.
    Light absorption in conical silicon particles2013Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, nr 3, s. 3891-3896Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of the absorption of light by a nanoscale dielectric cone is discussed. A simplified solution based on the analytical Mie theory of scattering and absorption by cylindrical objects is proposed and supported by the experimental observation of sharply localized holes in conical silicon tips after high-fluence irradiation. This study reveals that light couples with tapered objects dominantly at specific locations, where the local radius corresponds to one of the resonant radii of a cylindrical object, as predicted by Mie theory.

  • 92. Bolanos, Western
    et al.
    Carvajal, Joan J.
    Mateos, Xavier
    Cinta Pujol, Maria
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lifante, Gines
    Aguilo, Magdalena
    Diaz, Francesc
    Epitaxial layers of KY1-x-yGdxLuy(WO4)(2) doped with Er3+ and Tm3+ for planar waveguide lasers2010Ingår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 32, nr 3, s. 469-474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Here we show the results we obtained in the fabrication of planar wave guide lasers based on monoclinic double tungstates doped with Er3+ and Tm3+. We have successfully introduced these ions into the lattice matched KY0.59Gd0.19Lu0.22(WO4)(2) epitaxial layers grown on KY(WO4)(2) substrates without loss of optical quality and keeping a high refractive index contrast between the epitaxial layer and the substrate. We characterized the waveguiding properties of these epitaxial layers at lambda = 632.8 nm by dark modes spectroscopy, and we showed that these waveguides can support several TE and TM modes. Spectroscopic characterization of the active lanthanide ions in these crystals is also presented.

  • 93. Bolaños, W.
    et al.
    Carvajal, J.J.
    Mateos, X.
    Pujol, M.C.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Aguiló, M.
    Díaz, F.
    Fabrication and characterization of epitaxial layers of the KY1-x-yGdxLuy(WO4)2 system for waveguide lasers2009Konferensbidrag (Refereegranskat)
  • 94.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Intermodulation spectroscopy as an alternative to pump-probe for the measurement of fast dynamics at the nanometer scale2019Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 90, nr 1, artikel-id 013705Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an alternative approach to pump-probe spectroscopy for measuring fast charge dynamics with an atomic force microscope (AFM). Our approach is based on coherent multifrequency lock-in measurement of the intermodulation between a mechanical drive and an optical or electrical excitation. In response to the excitation, the charge dynamics of the sample is reconstructed by fitting a theoretical model to the measured frequency spectrum of the electrostatic force near resonance of the AFM cantilever. We discuss the time resolution, which in theory is limited only by the measurement time, but in practice is of order 1 ns for standard cantilevers and imaging speeds. We verify the method with simulations and demonstrate it with a control experiment, achieving a time resolution of 30 ns in ambient conditions, limited by thermal noise.

  • 95.
    Bornefalk, Hans
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Proposal and validation of a method to construct confidence intervals for clinical outcomes around FROC curves for mammography CAD systems2005Ingår i: MEDICAL IMAGING 2005: IMAGE PROCESSING, PT 1-3 / [ed] itzpatrick, JM; Reinhardt, JM, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2005, Vol. 5747, s. 675-682Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces a method for constructing confidence intervals for possible clinical outcomes around the FROC curve of a mammography CAD system. Given the architecture of a CAD classifying machine, there is one and only one system threshold that will yield a desired sensitivity on a certain population. The limited training sample size leads to a sampling error and an uncertainty in determining the optimal system threshold. This leads to an uncertainty in the operating point in the direction along the FROC curve which can be captured by a Bayesian approach where the distribution of possible thresholds is estimated. This uncertainty contributes to a large and spread-out confidence interval which is important to consider when one is intending to make comparisons between CAD algorithms trained on different data sets. The method is validated using a Monte Carlo method designed to capture the effect of correctly determining the system threshold.

  • 96.
    Bornefalk, Hans
    KTH, Tidigare Institutioner, Fysik.
    Use of phase and certainty information in automatic detection of stellate patterns in mammograms: IMAGE PROCESSING, PTS 1-32004Ingår i: MEDICAL IMAGING 2004: IMAGE PROCESSING, PTS 1-3 / [ed] Fitzpatrick, JM; Sonka, M, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2004, Vol. 5370, s. 97-107Konferensbidrag (Refereegranskat)
    Abstract [en]

    Detection of stellate patterns is a very important step in computer-aided detection schemes designed for mammography. We introduce a new way of finding these regions based on the use of quadrature filters. The method allows extraction of a certainty measure for each orientation estimate. This makes the method of finding the areas the spicules seem to emanate from more robust than simply basing it on the orientation estimates themselves. The local phase extracted from the filter outputs allows us to discriminate between orientation estimates from edges and dark lines from those generated by bright line structures, i.e. spicules. This makes the method more specific. We also show how the method can be modified for finding non-spiculated masses in digitized mammograms.

  • 97.
    Bornefalk, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Hemmendorff, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Hjarn, Torbjorn
    Dual-energy imaging using a digital scanned multi-slit system for mammography: evaluation of a differential beam filtering technique - art. no. 61422O2006Ingår i: Medical Imaging 2006: Physics of Medical Imaging, Pts 1-3 / [ed] Flynn, MJ; Hsieh, J, BELLINGHAM, WA: SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6142, s. O1422-O1422Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes a method for single exposure contrast-enhanced dual-energy imaging of tumors utilizing a scanned multi-slit system for digital mammography. This photon counting system employs an array of silicon strip detectors in an edge-on geometry. In the multi-slit setup, the line detectors and pre-collimator slits are aligned orthogonal to the scan direction. This geometry is advantageous to dual-energy imaging, since it allows differential filtering of the x-ray beam in the pre-collimator slits. A high-energy image is constructed from those lines where the filter material has been chosen to harden the x-ray beam and the low-energy image from the lines with a filter producing softer beams. Both images are obtained in the same scan, eliminating the need to change tube voltages and anode materials and minimizing the risk of motion artifacts. The method is illustrated on a purpose-built phantom and logarithmic subtraction of the images produces images essentially free of anatomical clutter with the contrast-enhanced targets clearly visible.

  • 98.
    Bornefalk, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Lundqvist, Mats
    Dual-energy imaging using a photon counting detector with electronic spectrum-splitting - art. no. 61421H2006Ingår i: Medical Imaging 2006: Physics of Medical Imaging, Pts 1-3 / [ed] Flynn, MJ; Hsieh, J, 2006, Vol. 6142, s. H1421-H1421Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a dual-energy imaging technique optimized for contrast-enhanced mammography using a photon counting detector. Each photon pulse is processed separately in the detector and the addition of an electronic threshold near the middle of the energy range of the x-ray spectrum allows discrimination of high and low energy photons. This effectively makes the detector energy sensitive, and allows the acquisition of high- and low-energy images simultaneously. These high- and low-energy images can be combined to dual-energy images where the anatomical clutter has been suppressed. By setting the electronic threshold close to 33.2 keV (the k-edge of iodine) the system is optimized for dual-energy contrast-enhanced imaging of breast tumors. Compared to other approaches, this method not only eliminates the need for separate exposures that might lead to motion artifacts, it also eliminates the otherwise deteriorating overlap between high- and low-energy spectra. We present phantom dual-energy images acquired on a prototype system to illustrate that the technique is already operational, albeit in its infancy. We also present a theoretical estimation of the potential gain in tumor signal-difference-to-noise ratio when using this electronic spectrum-splitting method as opposed to acquiring the high- and low-energy images separately with double exposures with separate x-ray spectra. Assuming ideal energy sensitive photon counting detectors, we arrive at the conclusion that the signal-difference-to-noise ratio could be increased by 145% at constant dose. We also illustrate our results on synthetic images.

  • 99.
    Bortot, Sara
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Suvdantsetseg, E.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    BELLA: a multi-point dynamics code for safety-informed design of fast reactors2015Ingår i: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 85, s. 228-235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the multi-point dynamics code BELLA and its benchmarking with respect to SAS4A/SASSYS-1 is described for a small fast reactor cooled with natural convection of lead (ELECTRA). It is shown that BELLA is capable of reproducing the magnitude of mass-flow, reactivity, power and temperature excursions during design extension conditions with an accuracy better than 10%. Hence, the BELLA code can be used for safety-informed design and stability analyses of fast reactor systems, permitting to isolate essential phenomena and trends of significance for their safety assessment. (C) 2015 Elsevier Ltd. All rights reserved.

  • 100. Boyko, A. A.
    et al.
    Marchev, G. M.
    Petrov, V.
    Pasiskevicius, Valdus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kolker, D. B.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kostyukova, N. Y.
    Intracavity-pumped, cascaded Mid-IR optical parametric oscillator based on AgGaSe22015Ingår i: Advanced Solid State Lasers, ASSL 2015, Optical Society of America, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report on an AgGaSe2 optical parametric oscillator (OPO), intracavity pumped by the 1.85-μm signal pulses from a 1.064-μm pumped Rb:PPKTP OPO. It operates at 100 Hz with idler tunability from 5.8 to 8.3 μm.

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