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  • 301.
    Fredenberg, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Cederström, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Energy filtering with x-ray lenses: Optimization for photon-counting mammography2010Ingår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, s. 339-342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chromatic properties of the multi-prism and prism-array x-ray lenses (MPL and PAL) can potentially be utilized for efficient energy filtering and dose reduction in mammography. The line-shaped foci of the lenses are optimal for coupling to photon-counting silicon strip detectors in a scanning system. A theoretical model was developed and used to investigate the benefit of two lenses compared to an absorption-filtered reference system. The dose reduction of the MPL filter was 15% compared to the reference system at matching scan time, and the spatial resolution was higher. The dose of the PAL-filtered system was found to be 20% lower than for the reference system at equal scan time and resolution, and only 20% higher than for a monochromatic beam. An investigation of some practical issues remains, including the feasibility of brilliant-enough x-ray sources and manufacturing of a polymer PAL.

  • 302.
    Fredenberg, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Cederström, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Nillius, Peter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Ribbing, Carolina
    Uppsala Univ..
    Karlsson, Staffan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    A low-absorption x-ray energy filter for small-scale applications2009Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, nr 14, s. 11388-11398Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an experimental and theoretical evaluation of an x-ray energy filter based on the chromatic properties of a prism-array lens (PAL). It is intended for small-scale applications such as medical imaging. The PAL approximates a Fresnel lens and allows for high efficiency compared to filters based on ordinary refractive lenses, however at the cost of a lower energy resolution. Geometrical optics was found to provide a good approximation for the performance of a flawless lens, but a field-propagation model was used for quantitative predictions. The model predicted a 0.29 ΔE/E energy resolution and an intensity gain of 6.5 for a silicon PAL at 23.5 keV. Measurements with an x-ray tube showed good agreement with the model in energy resolution and peak energy, but a blurred focal line contributed to a 29% gain reduction. We believe the blurring to be caused mainly by lens imperfections, in particular at the periphery of the lens.

  • 303.
    Fredenberg, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Cederström, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Åslund, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Nillius, Peter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    An efficient pre-object collimator based on an x-ray lens2009Ingår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 36, nr 2, s. 626-633Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multiprism lens (MPL) is a refractive x-ray lens with one-dimensional focusing properties. If used as a pre-object collimator in a scanning system for medical x-ray imaging, it reduces the divergence of the radiation and improves on photon economy compared to a slit collimator. Potential advantages include shorter acquisition times, a reduced tube loading, or improved resolution. We present the first images acquired with a MPL in a prototype for a scanning mammography system. The lens showed a gain of flux of 1.32 compared to a slit collimator at equal resolution, or a gain in resolution of 1.31–1.44 at equal flux. We expect the gain of flux in a clinical setup with an optimized MPL and a custom-made absorption filter to reach 1.67, or 1.45–1.54 gain in resolution.

  • 304.
    Fredenberg, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Cederström, Björn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    Åslund, Magnus
    Ribbing, Carolina
    Uppsala universitet.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk avbildning.
    A Tunable Energy Filter for Medical X-Ray Imaging2008Ingår i: X-Ray Optics and Instrumentation, ISSN 1687-7632, Vol. 2008Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multiprism lens (MPL) is a refractive X-ray lens, and its chromatic properties can be employed in an energy filtering setup to obtain a narrow tunable X-ray spectrum. We present the first evaluation of such a filter for medical X-ray imaging. The experimental setup yields a 6.6 gain of flux at 20 keV, and we demonstrate tunability by altering the energy spectrum to center also around 17 and 23 keV. All measurements are found to agree well with ray-tracing and a proposed geometrical model. Compared to a model mammography system with absorption filtering, the experimental MPL filter reduces dose 13–25% for 3–7 cm breasts if the spectrum is centered around the optimal energy. Additionally, the resolution is improved 2.5 times for a 5 cm breast. The scan time is increased 3 times but can be reduced with a slightly decreased energy filtering and resolution.

  • 305.
    Friberg, Ari T.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Dändliker, R.
    Advances in information optics and photonics2008Samlingsverk (redaktörskap) (Övrigt vetenskapligt)
    Abstract [en]

    This volume is the sixth in a series of books initiated in 1989 by the International Commission for Optics (ICO). These books highlight the advances and trends in the research and development of optical sciences, technologies, and applications at the time of their publication. In this age of the photon, information optics and photonics represent the key technologies to sustain our knowledge-based society. New concepts in classical and quantum-entangled light, coherent interaction with matter, and novel materials and processes have led to remarkable advances in today's information science and technology. The ICO is closely involved with information optics, as exemplified by the ICO topical meeting on Optoinformatics/Information Photonics (St. Petersburg, Russia, 2006), the ICO/ICTP Winter College on Quantum and Classical Aspects of Information Optics (Trieste, Italy, 2006), and the many ICO Prizes recently awarded on outstanding contributions on these topics. This book is in part based on these ICO activities. This volume contains a collection of 32 chapters from internationally leading scientists and research groups on a variety of topics in information optics and photonics, including the 2003-2006 ICO Prize winners. The chapters are divided into 7 sections: Beam Optics; Laser Photonics and Components; Electromagnetic Coherence; Imaging, Microscopy, Holography, and Materials; Photonic Processing; Quantum Information and Matter; and Communications and Networks.

  • 306.
    Friberg, Ari T.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Turunen, Jari
    Univ Eastern Finland, Dept Math & Phys, FI-80101 Joensuu, Finland..
    Optics communications special issue "electromagnetic coherence and polarization"2010Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 283, nr 22, s. 4423-4426Artikel i tidskrift (Övrigt vetenskapligt)
  • 307. Frise, Anton E.
    et al.
    Edri, Eran
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi (stängd 20110630).
    Furo, Istvan
    Regev, Oren
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi (stängd 20110630).
    Protein Dispersant Binding on Nanotubes Studied by NMR Self-Diffusion and Cryo-TEM Techniques2010Ingår i: JOURNAL OF PHYSICAL CHEMISTRY LETTERS, ISSN 1948-7185, Vol. 1, nr 9, s. 1414-1419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carbon nanotubes can be dispersed by a variety of molecules. We investigate the dynamics of protein-assisted carbon nanotube dispersion in water. We find that in equilibrium only a small fraction of the dispersants is indeed adsorbed to the nanotube Surface, while there is a fast exchange process between the adsorbed and free protein molecules. Self-diffusion NMR spectroscopy in combination with cryo-transmission electron microscopy imaging are employed.

  • 308.
    Fu, Hongyan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ou, Haiyan
    Zhu, Kun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Tunable all-optical microwave notch filter with a negative tap based on a semiconductor optical amplifier and a dispersive medium2009Ingår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 41, nr 3, s. 213-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A tunable all-optical microwave notch filter with a negative tap based on a semiconductor optical amplifier and a dispersive medium is demonstrated. A negative tap is realized through the cross gain modulation in the semiconductor optical amplifier. The free spectrum range of the notch filter can be tuned by tuning the wavelength of one of the two laser sources. The influence of the amplitude mismatch of the two lasers on the performance of the filter is analyzed. The present notch filter is easy to implement and cost-effective.

  • 309.
    Färm, Petra
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Dubrova, Elena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Tenhunen, Hannu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Logic optimization technique for molecular cascades2005Ingår i: Nanotechnology II / [ed] Lugli, P; Kish, LB; Mateos, J, SPIE - International Society for Optical Engineering, 2005, Vol. 5838, s. 95-104Konferensbidrag (Refereegranskat)
    Abstract [en]

    Molecular cascades introduced in(1) provide new ways to exploit the motion of individual molecules in nanometer-scale structures. Computation is performed by purely mechanical means similarly to the toppling of a row of standing domino. A specific feature of molecular cascades is that an inverter cannot be build, because it would require that all molecules in the inverter's output untopple when the input cascade topples. This is not possible because an untoppled state has higher energy than a toppled one. As a solution, we propose to avoid the need for inverters by representing signals by the dual-rail convention. As a basic building block we use a molecular block, which has four inputs x(1),...,x(4) such that x(3) = x(1)', x(4) = x(2)', and two outputs f(1) = x(1) . x(2) and f(2) = x(3) + x(4). If input variables are available in both complemented and non-complemented form, then any Boolean function can be implemented by a composition of such molecular blocks. We present an experimental tool which first uses a rule-based randomized search to optimize a Boolean network and then maps it into a network of interconnected molecular blocks.

  • 310.
    Gaiarin, Simone
    et al.
    DTU Fotonik, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark.
    Pang, Xiaodan
    Acreo Swedish ICT AB, Isafjordsgatan 22, Kista, 164 40, Sweden.
    Ozolins, Oskars
    Acreo Swedish ICT AB, Isafjordsgatan 22, Kista, 164 40, Sweden.
    Jones, Rasmus T
    DTU Fotonik, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark.
    Da Silva, Edson Porto
    DTU Fotonik, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark.
    Schatz, Richard
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Westergren, Urban
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Popov, Sergei
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Jacobsen, Gunnar
    Acreo Swedish ICT AB, Isafjordsgatan 22, Kista, 164 40, Sweden.
    Zibar, Darko
    DTU Fotonik, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark.
    High speed PAM-8 optical interconnects with digital equalization based on neural network2016Ingår i: Asia Communications and Photonics Conference, Optical Society of America, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    We experimentally evaluate a high-speed optical interconnection link with neural network equalization. Enhanced equalization performances are shown comparing to standard linear FFE for an EML-based 32 GBd PAM-8 signal after 4-km SMF transmission.

  • 311.
    Gallego-Marcos, Ignacio
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnenergiteknik.
    Grishchenko, Dmitry
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnenergiteknik.
    Kudinov, Pavel
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnenergiteknik.
    Thermal stratification and mixing in a Nordic BWR pressure suppression pool2019Ingår i: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 132, s. 442-450Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The pressure suppression pool of a Nordic Boiling Water Reactor (BWR) serves as a heat sink to condense steam from the primary coolant system in normal operation and accident conditions. Thermal stratification can develop in the pool when buoyancy forces overcome the momentum created by the steam injection. In this case, hot condensate forms a hot layer at the top of the pool, reducing the pool cooling and condensation capacity compared to mixed conditions. The Effective Heat Source and Effective Momentum Source (EHS/EMS) models were previously proposed to model the large-scale pool behavior during a steam injection. In this work, we use CFD code of ANSYS Fluent with the EHS/EMS models to simulate the transient behavior of a Nordic BWR pool during a steam injection through spargers. First, a validation against a Nordic BWR pool test with complete mixing is presented. Prediction of the pool behavior for other possible injection scenarios show that stratification can occur at prototypic steam injection conditions, and that the hot layer temperature above the injection point can be non-uniform. In cases with significant steam condensation inside the sparger pipes, the 95 degrees C pool temperature limit for the Emergency Core Cooling System (ECCS) pumps was reached similar to 7 h after the beginning of the blowdown.

  • 312.
    Gallo, Katia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Nonlinear wave dynamics in 2D periodically poled waveguides2009Ingår i: 2009 IEEE/LEOS WINTER TOPICALS MEETING SERIES (WTM 2009), NEW YORK: IEEE , 2009, s. 162-163Konferensbidrag (Refereegranskat)
    Abstract [en]

    An overview of recent results on spatial solitons in purely nonlinear 2D lattices is presented. Theory and experiments highlight new possibilities for multicolour soliton excitation and control via planar nonlinear structures in periodically poled materials.

  • 313.
    Gallo, Katia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Spatial Wave Dynamics in 2-D Periodically Poled LiNbO3 Waveguides2009Ingår i: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 45, nr 11, s. 1415-1420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent results on parametric spatial solitary waves arising from multiple resonances in purely nonlinear 2-D lattices are presented. Theory and experiments highlight new possibilities for light self-confinement and steering via engineered planar nonlinear structures in periodically poled materials.

  • 314.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Assanto, Gaetano
    Spatial solitons in chi(2) planar photonic crystals2007Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, nr 21, s. 3149-3151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analyze light self-confinement induced by multiple nonlinear resonances in a two-dimensional 2 photoniccrystal. With reference to second-harmonic generation in a hexagonal lattice, we show that the systemcan not only support two-color (1+1)D solitary waves with enhanced confinement and steering capabilitiesbut also enable novel features such as wavelength-dependent soliton routing.

  • 315.
    Gallo, Katia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Baghban, Mohammad Amin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Recent Developments on the Lithium Niobate Material Platform: The Silicon of Nonlinear Optics?2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The talk addresses current challenges and future prospects in combining nanotechnology, ferroelectric domain structuring and integrated optics in LiNbO3 materials to develop small-footprint devices for telecom and quantum optics, and potentially also life-science, applications.

  • 316.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Codemard, Christophe
    Gawith, Corin
    Broderick, Neil
    Smith, Peter
    Nilsson, Johan
    Richardson, David
    Guided-Wave Second Harmonic Generation in Hexagonally Poled RPE:LiNbO32005Ingår i: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2005, s. 1568014-Konferensbidrag (Refereegranskat)
  • 317.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Codemard, Christophe
    Gawith, Corin
    Nilsson, Johan
    Smith, Peter
    Broderick, Neil
    Richardson, David
    Guided-wave second-harmonic generation in a LiNbO3 nonlinear photonic crystal2006Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, nr 9, s. 1232-1234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate twin-beam second-harmonic generation from telecommunications wavelengths in an optimized buried reverse proton exchanged planar waveguide made in 2D hexagonally poled LiNbO3. Experiments carried out with a nanosecond narrow-bandwidth, high-power fiber source thoroughly explored the response of the nonlinear photonic crystal device in terms of its power, wavelength, and angle tunability.

  • 318.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Codemard, Christophe
    Gawith, Corin
    Smith, Peter
    Nilsson, Johan
    Broderick, Neil
    Richardson, David
    Buried slab waveguides in LiNbO3 nonlinear photonic crystals2005Ingår i: Proceedings of WFOPC 2005: 4th IEEE/LEOS Workshop on Fibres and Optical Passive Components / [ed] RivaSanseverino, S; Artiglia, M, 2005, s. 36-40Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present an efficient integrated device for SHG at telecom wavelengths in Hexagonally Poled LiNbO3, based on the reverse proton exchange waveguide technology. We discuss its nonlinear response in terms of power, wavelength and angle tunability and use the experimental SHG data to infer also information on the linear properties of the waveguide.

  • 319.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Gawith, C.B.E.
    Wellington, I.T.
    Mailis, Sakellaris
    Eason, Robert
    Smith, Peter
    Richardson, David
    Kostritskii, Sergey
    Ultraviolet writing of channel waveguides in proton-exchanged LiNbO32007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 1, s. 014110-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on a direct ultraviolet (UV) writing method for the fabrication of channel waveguides at 1.55 mu m in LiNbO3 through UV irradiation of surface and buried planar waveguides made by annealed proton exchange and reverse proton exchange. A systematic study of the guidance properties as a function of the UV writing conditions is presented.

  • 320.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Gawith, Corin
    Prawiharjo, Jerry
    Broderick, Neil
    Smith, Peter
    Mailis, Sakellaris
    Eason, Robert
    Richardson, David
    UV-written channel waveguides in proton-exchanged Lithium Niobate2004Ingår i: Conference on Lasers and Electro-Optics, CLEO, 2004, s. 557-559Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report on the direct UV-writing of channel waveguides in annealed proton-exchanged (APE) and reverse proton-exchanged (RPE) layers in LiNbO 3 and demonstrate efficient guiding within single mode channels at telecom wavelengths.

  • 321.
    Gallo, Katia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Jeong, Yoonchan
    Taira, Takunori
    Jiang, Shibin
    Ilday, F. Omer
    Focus issue introduction: Advanced Solid-State Lasers (ASSL) 20152016Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, nr 5, s. 5674-5682Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The editors introduce the focus issue on "Advanced Solid-State Lasers (ASSL) 2015", which is based on the topics presented at a congress of the same name held in Berlin, Germany, from October 4 to October 9, 2015. This focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 23 contributed papers (17 for Optics Express and 6 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the congress and have extended their work into complete research articles. We hope this focus issue offers a good snapshot of a variety of topical discussions held at the congress and will contribute to the further expansion of the associated research areas.

  • 322.
    Gallo, Katia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Levenius, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Parametric generation in 2D nonlinear photonic crystals2010Ingår i: 4th EPS-QEOD EUROPHOTON CONFERENCE on "Solid-State, Fibre, and Waveguide Coherent Light Sources", 2010Konferensbidrag (Övrigt vetenskapligt)
  • 323.
    Gallo, Katia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Levenius, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Twin-beam Optical Parametric Generation in Nonlinear Photonic Crystals2011Ingår i: Advanced Solid-State Photonics, 2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    We demonstrate dual-beam optical parametric generation in hexagonally poled LiTaO3.The experimental results indicate a coherent contribution to the parametric gain arising frommultiple resonances in the nonlinear lattice.

  • 324.
    Gallo, Katia
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Levenius, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Vermersch, Benoit
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Parametric frequency Downconversion devices in periodically poled Mg-doped stoichiometric Lithium Tantalate2011Ingår i: 2010 12th International Conference on Transparent Optical Networks, ICTON 2010, 2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This paper provides an overview of our work on nonlinear optical devices in MgO-doped nearly stoichiometric LiTaO3. We present experimental results for optical parametric oscillation and broadband generation obtained with one- and two- dimensional periodically poled structures.

  • 325.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Pasquazi, Alessia
    University of Roma Tre.
    Stivala, Salvatore
    Assanto, Gaetano
    Light self-confinement via second harmonic generation in a 2D nonlinear photonic crystal waveguide2007Ingår i: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2007, s. 4386855-Konferensbidrag (Refereegranskat)
  • 326.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Pasquazi, Alessia
    University of Roma Tre.
    Stivala, Salvatore
    Assanto, Gaetano
    Quadratic solitons in 2D nonlinear photonic crystals2007Ingår i: Quadratic solitons in 2D nonlinear photonic crystals, 2007, s. 4431579-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report on the first observation of spatial solitons in a 2D nonlinear photonic crystal. The experiments were performed in an hexagonally poled LiNbO3 waveguide designed for second harmonic generation from ∼1.55 μm.

  • 327.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Pasquazi, Alessia
    Stivala, Salvatore
    Assanto, Gaetano
    Spatial solitons in quadratic 2D nonlinear photonic crystals2007Ingår i: ICTON 2007: Proceedings of the 9th International Conference on Transparent Optical Networks, 2007, s. 170-173Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report on the first investigations into parametric solitary-wave formation in 2D nonlinear photonic crystals and present experimental results obtained in an hexagonally poled LiNbO3 waveguide designed for twin-beam second harmonic generation at telecom wavelengths.

  • 328.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Stivala, Salvatore
    Pasquazi, Alessia
    Assanto, Gaetano
    Parametric solitons in nonlinear photonic crystals2007Ingår i: 2007 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, 2007, s. 622-623Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present theoretical and experimental investigations on the soliton dynamics associated to multiple second harmonic generation resonances in two-dimensional nonlinear photonic crystals, highlighting a wealth of new possibilities for soliton management in such structures.

  • 329.
    Gallo, Katia
    et al.
    Optoelectronics Research Centre, University of Southampton.
    Stivala, Salvatore
    Pasquazi, Alessia
    Assanto, Gaetano
    Spatial Soliton Dynamics in Two-Dimensional Quadratic Photonic Crystals2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a theoretical and experimental investigation of soliton dynamics associated to twin-beam second harmonic generation in a purely nonlinear two-dimensional planar photonic lattice in LiNbO.

  • 330. Gao, Bin
    et al.
    Zhong, Jun
    Song, Li
    Wu, Zi-Yu
    Xie, Sishen
    Qian, Haijie
    Dong, Yuhui
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Studies of bromine modified single-walled carbon nanotubes using photoelectron spectroscopy and density-functional theory2006Ingår i: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, Vol. 75, nr 11, s. 1939-1942Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many applications based on single-walled carbon nanotubes (SWNTs) require chemical modification of carbon nanotube to optimize the functionalities of the device. In this contribution we discuss the properties of SWNTs immersed in a hydrobromic acid (HBr) solution. Changes of atomic and electronic structures of bromine modified SWNTs were investigated using photoelectron spectroscopy (PES). Spectra of SWNTs before and after immersion in the HBr solution exhibit different features. To understand the mechanism of interaction between SWNTs and bromine, we performed density-functional theory calculations to reveal the structural changes, adsorption energy and chemical bonding information of SWNTs interacting with bromine. In addition, based on the Gelius model, from the molecular orbitals (MOs), we calculated ultraviolet photoelectron spectra (UPS) of SWNTs with and without functionalizing and compared them with the experiment. The present study is a first step in the understanding of the functionalization mechanism of carbon nanotubes.

  • 331.
    Gao, Shiming
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Yang, Changxi
    Two channels of entangled twin photons generated by quasi-phase-matched spontaneous parametric down-conversion in periodically poled lithium niobate crystals2008Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 25, nr 5, s. 734-740Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose the generation of two-channel time-energy entangled twin photons based on two simultaneous first-order quasi-phase-matched (QPM) spontaneous parametric down-conversion processes in a periodically poled lithium niobate (PPLN) with a monochromatic pump. The theoretical model for the generation of the entangled photons is established, and the analytical solution is obtained in a lossless crystal with an undepleted pump assumption. The generated condition of entangled photons is achieved in terms of the QPM grating period and the pump wavelength. It is shown that two channels of entangled twin photons with different wavelengths can be created by suitably choosing the PPLN grating period once the pump wavelength is fixed, which provides the potential to introduce the wavelength division multiplexed technique into quantum information systems.

  • 332.
    Garcia-Carrasco, Alvaro
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Grzonka, J.
    Gilbert, M. R.
    Fortuna-Zalesna, E.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Impact of helium implantation and ion-induced damage on reflectivity of molybdenum mirrors2016Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molybdenum mirrors were irradiated with Mo and He ions to simulate the effect of neutron irradiation on diagnostic first mirrors in next-generation fusion devices. Up to 30 dpa were produced under molybdenum irradiation leading to a slight decrease of reflectivity in the near infrared range. After 3×1017 cm-2 of helium irradiation, reflectivity decreased by up to 20%. Combined irradiation by helium and molybdenum led to similar effects on reflectivity as irradiation with helium alone. Ion beam analysis showed that only 7% of the implanted helium was retained in the first 40nm layer of the mirror. The structure of the near-surface layer after irradiation was studied with scanning transmission electron microscopy and the extent and size distribution of helium bubbles was documented. The consequences of ion-induced damage on the performance of diagnostic components are discussed.

  • 333.
    García-Cortés, A.
    et al.
    CSIC, Madrid, Spain.
    Serrano, M. D.
    CSIC, Madrid, Spain.
    Zaldo, Carlos
    CSIC, Madrid, Spain.
    Cascales, Concepción
    Strömqvist, Gustav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Nonlinear Refractive Indices in Disordered NaT(XO4)2T = Y, La, Gd, Lu and Bi, X = Mo, W Laser Crystals2008Konferensbidrag (Refereegranskat)
  • 334.
    Gatti, Alessandra
    et al.
    CNR, Ist Foton & Nanotecnol, Piazza Leonardo Da Vinci 32, Milan, Italy.;Univ Insubria, Dipartimento Sci & Alta Tecnol, Via Valleggio 11, Como, Italy..
    Brambilla, Enrico
    Univ Insubria, Dipartimento Sci & Alta Tecnol, Via Valleggio 11, Como, Italy..
    Gallo, Katia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Jedrkiewicz, Ottavia
    CNR, Ist Foton & Nanotecnol, Piazza Leonardo Da Vinci 32, Milan, Italy.;Univ Insubria, Dipartimento Sci & Alta Tecnol, Via Valleggio 11, Como, Italy..
    Golden ratio entanglement in hexagonally poled nonlinear crystals2018Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 98, nr 5, artikel-id 053827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work analyzes the quantum state of twin photons and twin beams generated by parametric down-conversion in a hexagonally poled photonic crystal, characterized by the simultaneous presence of two nonlinear processes sustained by two vectors of the reciprocal lattice. In those special points of the fluorescence spectrum where the two processes coexist, we show that a tripartite entangled state is realized, equivalent to a single parametric process followed by a beam splitter. By proper angle tuning, a peculiar resonance condition is reached, with a transition to a four-mode entanglement, dominated by the golden ratio of the segment phi = (1 + root 5)/2. A maximal coherence between the two nonlinear processes is established here, as the overall process is shown to be equivalent to two independent parametric processes followed by a beam splitter. We offer an interpretation of the occurrence of the golden ratio in this system based on an analogy between the evolution of the light modes and the Fibonacci sequence.

  • 335.
    Gavrilyuk, Sergey
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Molecular electronic,  vibrational and rotational motion in optical and x-ray fields2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The subject of this theoretical  study is the role ofelectronic structure as well as of rotational and vibrational motionson interactions between molecules and electromagnetic radiation,ranging from optical to x-ray. The thesis concerns both linear and nonlinear regimes of the light-matter interaction. The first part of the thesis is devoted to propagation of opticalpulses with different time-structure through various nonlinear absorbers.First we explain the double-exponential decay of fluorescence caused by photobleaching of pyrylium  salt irradiated by a train of short (100 fs) optical pulses. The main reason for this effect is the transversal inhomogeneity of the light beam which makes the dynamics of the photobleaching differ in the core of the pulse and on its periphery. We also explore the optical power limitingof C60 fullerene irradiated by either microsecond optical pulses or a picosecond pulse trains. Enhancement of nonlinear absorption is caused by strong triplet-triplet absorption that becomes important due toelongation of the interaction time.Here we show the importance of the repetitionrate for the optical power limiting performance.The second part of the thesis addresses the interaction of optical and x-rayfields with rotational degrees of freedom of molecules. In this part the main attention is paid to the rotational heating caused by the recoil, experienced by molecules due to the ejection of photoelectrons. We have quantitatively explained two qualitatively different experiments with the N2 molecule.We predict the interference modulation of the recoil-induced shift,which is a shift of the photoelectron line caused by the rotational recoil effect, as a function of the photon energy.The developed theory also explains the rotational heating ofmolecules observed in the optical fluorescence induced by x-ray radiation.Based on this explanation, we suggest a new scheme of the optical fluorescence induced by x-rays that allows to detect the recoil effect via the recoil-inducedsplitting of the optical resonance.The last part of the thesis focuses on multi-mode nuclear dynamics of the resonant Auger scattering from the C2H2 molecule, that was the subject of a recent experimental study.Here we develop a theory that explains the observed vibrationalscattering anisotropy. We have found that three qualitatively different mechanisms are responsible for this phenomenon. The first mechanism is the interference of the direct and resonance scattering channels. The second mechanismis the interference of the resonant scattering channels through core excitedstate with the orthogonal orientation of the vibrational modes of core excitedstate. The Young's double slit like interference of the quantum pathways through the double-well potential of the bending motion of core excited state is the third mechanism of the vibrational scattering anisotropy.

  • 336.
    Gel'mukhanov, Faris
    et al.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Salek, Pawel
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Ågren, Hans
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Vibrationally resolved core-photoelectron spectroscopy as an infinite-slit interferometry2001Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 64, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During a molecular vibration, an atom changes continuously its position. Just as the emitted photoelectron waves, the electromagnetic waves absorbed by the atom in the different positions are strictly coherent and have different well-defined phases. These phases depend on the relation between the instantaneous internuclear distance and the photoelectron, respectively, photon wavelengths. We predict that the interference of these coherent waves strongly influences the vibrational profile of the photoelectron spectra of core electrons in a molecule. This effect increases with increasing x-ray photon frequency and results in a deformation and broadening of the vibrational profile. In the case of surface adsorbed molecules, the vibrational profile depends strongly on the direction of the photoelectron ejection and photon momentum, and the orientational sensitivity of a vibrational profile can even be used as a tool to define the orientation of adsorbed molecules.

  • 337.
    Gel'mukhanov, Faris
    et al.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Ågren, Hans
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Salek, Pawel
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Doppler effects in resonant x-ray Raman scattering1998Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 57, nr 4, s. 2511-2526Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Theory for Doppler effects in resonant x-ray Raman scattering (RXS) is presented. It is shown that the "electron" Doppler effect is important in nonradiative RXS for decay transitions between continuum nuclear states lying above the dissociation threshold, and that the averaging of the RXS cross section over molecular orientations can lead to strong non-lorentzian broadenings of the atomiclike resonances. The Doppler effect is found to give a unique possibility to distinguish dissociating identical atoms, because different peaks correspond to atoms with opposite Doppler shifts. Spectral features of the atomiclike profile are predicted and analyzed. Strong oscillations of the RXS cross section will occur as a consequence of the interference of the Auger electrons. Due to the Doppler effect and the interference, the atomiclike profile can be associated with supernarrow spectral features, the width of which goes below the lifetime broadening and is practically independent of the spectral distribution of the incident radiation. As another consequence of the oscillations and strong anisotropy caused by the interference, we predict parity selection rules for Auger decay transitions in both bound and dissociative systems. The corresponding experiments can be realized by measurements of resonant Auger of surface adsorbed molecules and for molecules by the electron-ion coincidence technique.

  • 338. Genty, Goery
    et al.
    Surakka, Minna
    Turunen, Jari
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Complete characterization of supercontinuum coherence2011Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 28, nr 9, s. 2301-2309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using second-order coherence theory of nonstationary light we examine in detail the coherence properties of supercontinuum radiation generated in nonlinear fibers. We show that the supercontinuum can be divided into quasi-coherent and quasi-stationary parts and that the relative contributions depend on the dynamics involved in the spectral broadening process. We establish the correspondence between the quasi-coherent part of the two-frequency correlation function of the second-order theory and the usual Dudley-Coen degree of coherence used to characterize the shot-to-shot stability of supercontinuum sources. Experimental implementation for measuring separately the quasi-coherent and quasi-stationary contributions is further addressed. Our results open the route for complete characterization of supercontinuum coherence.

  • 339. Gerasimov, V. S.
    et al.
    Ershov, A. E.
    Karpov, S. V.
    Gavrilyuk, A. P.
    Zakomirnyi, Vadim I.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Rasskazov, I. L.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Polyutov, S. P.
    Thermal effects in systems of colloidal plasmonic nanoparticles in high-intensity pulsed laser fields [Invited]: publisher's note (vol 7,pg 555, 2017)2017Ingår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 7, nr 3, s. 799-799Artikel i tidskrift (Refereegranskat)
  • 340. Gharibi, Arash
    et al.
    Shen, Jian Qi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Gu, Jing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Tunable transient evolutional behaviours of a four-level atomic vapour and the application to photonic logic gates2009Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 42, nr 5, s. 055502-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evolutional optical behaviours (turn-on dynamics) of a four-level N-configuration atomic system are considered based on the transient solution to the equations of motion of atomic probability amplitudes. It is shown that the quantum interference between the signal and control fields can lead to the controllable absorption and transparency properties of the atomic vapour. One of the most remarkable properties of the present scheme is that the absorption (or transmittance) of the probe light in the atomic vapour depends on the intensity ratio of the signal field to the control field, and thus the tunable optical features (transparency or opaqueness to the probe light) can be realized by tuning the quantum interferences between the signal and control fields. The present mechanism can be applicable to designs of some new photonic and quantum optical devices such as logic and functional devices as well as optical switches. Two typical photonic logic gates (NOT and NOR gates) designed based on the tunable four-level optical responses are presented as illustrative examples.

  • 341. Ghiu, Iulia
    et al.
    Bjoerk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Marian, Paulina
    Marian, Tudor A.
    Probing light polarization with the quantum Chernoff bound2010Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, nr 2, s. 023803-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We recall the framework of a consistent quantum description of polarization of light. Accordingly, the degree of polarization of a two-mode state. (rho) over cap of the quantum radiation field can be defined as a distance of a related state (rho) over cap (b) to the convex set of all SU(2)-invariant two-mode states. We explore a distance-type polarization measure in terms of the quantum Chernoff bound and derive its explicit expression. A comparison between the Chernoff and Bures degrees of polarization leads to interesting conclusions for some particular states chosen as illustrative examples.

  • 342. Giuliani, G.
    et al.
    Donati, S.
    Villafranca, A.
    Lasobras, J.
    Garces, I.
    Chacinski, Marek
    Dipartimento di Elettronica, Università di Pavia, Pavia, Italy.
    Schatz, Richard
    Dipartimento di Elettronica, Università di Pavia, Pavia, Italy.
    Kouloumentas, C.
    Klonidis, D.
    Tomkos, I.
    Landais, P.
    Escorihuela, R.
    Rorison, J.
    Pozo, J.
    Fiore, A.
    Moreno, P.
    Rossetti, M.
    Elsasser, W.
    Von Staden, J.
    Huyet, G.
    Saarinen, M.
    Pessa, M.
    Leinonen, P.
    Vilokkinen, V.
    Sciamanna, M.
    Danckaert, J.
    Panajotov, K.
    Fordell, T.
    Lindberg, A.
    Hayau, J. -F
    Poette, J.
    Besnard, P.
    Grillot, F.
    Pereira, M.
    Nelander, R.
    Wacker, A.
    Tredicucci, A.
    Green, R.
    Round-Robin Measurements of Linewidth Enhancement Factor of Semiconductor Lasers in COST 288 Action2007Ingår i: Lasers and Electro-Optics, 2007 and the International Quantum Electronics Conference. CLEOE-IQEC 2007. European Conference on, 2007, s. 4385967-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Round-robin measurements on the linewidth enhancement factor are carried out in many laboratories participating to EU COST 288 Action. Up to 7 different techniques are applied to DFB, VCSELs, QCL, and QD lasers, and results are compared.

  • 343. Goenka, Chhavi
    et al.
    Semeter, Joshua
    Noto, John
    Baumgardner, Jeffrey
    Riccobono, Juanita
    Migliozzi, Michael
    Dahlgren, Hanna
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marshall, Robert
    Kapali, Sudha
    Hirsch, Michael
    Hampton, Donald
    Akbari, Hassanali
    LiCHI - Liquid Crystal Hyperspectral Imager for simultaneous multispectral imaging in aeronomy2015Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, nr 14, s. 17772-17782Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A four channel hyperspectral imager using Liquid Crystal Fabry-Perot (LCFP) etalons has been built and tested. This imager is capable of making measurements simultaneously in four wavelength ranges in the visible spectrum. The instrument was designed to make measurements of natural airglow and auroral emissions in the upper atmosphere of the Earth and was installed and tested at the Poker Flat Research Range in Fairbanks, Alaska from February to April 2014. The results demonstrate the capabilities and challenges this instrument presents as a sensor for aeronomical studies. (C) 2015 Optical Society of America

  • 344. Goenka, Chhavi
    et al.
    Semeter, Joshua
    Noto, John
    Baumgardner, Jeffrey
    Riccobono, Juanita
    Migliozzi, Mike
    Dahlgren, Hanna
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marshall, Robert
    Kapali, Sudha
    Hirsch, Michael
    Hampton, Donald
    Akbari, Hassanali
    Multichannel tunable imager architecture for hyperspectral imaging in relevant spectral domains2016Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 12, s. 3149-3157Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a technique for dimensionality reduction in hyperspectral imaging during the data collection process. A four-channel hyperspectral imager using liquid crystal Fabry-Perot etalons has been built and used to verify this method for four applications: auroral imaging, plant study, landscape classification, and anomaly detection. This imager is capable of making measurements simultaneously in four wavelength ranges while being tunable within those ranges, and thus can be used to measure narrow contiguous bands in four spectral domains. In this paper, we describe the design, concept of operation, and deployment of this instrument. The results from preliminary testing of this instrument are discussed and are promising and demonstrate this instrument as a good candidate for hyperspectral imaging.

  • 345.
    Goncharov, Alexander
    et al.
    National University of Ireland, Galway.
    Burvall, Anna
    National University of Ireland, Galway.
    Dainty, Christopher
    National university of Ireland, Galway.
    Systematic design of anastigmatic lens axicon2007Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 24, s. 6076-6080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an analytical method for systematic optical design of a double-pass axicon that shows almost no astigmatism in oblique illumination compared to a conventional linear axicon. The anastigmatic axicon is a singlet lens with nearly concentric spherical surfaces applied in double pass, making it possible to form a long narrow focal line of uniform width. The front and the back surfaces have reflective coatings in the central and annular zones, respectively, to provide the double pass. Our design method finds the radii of curvatures and axial thickness of the lens for a given angle between the exiting rays and the optical axis. It also finds the optimal position of the reflecting zones for minimal vignetting. This method is based on ray tracing of the real rays at the marginal heights of the aperture and therefore is superior to any paraxial method. We illustrate the efficiency of the method by designing a test axicon with optical parameters used for a prototype axicon, which was manufactured and experimentally tested. We compare the optical characteristics of our test axicon with those of the experimental prototype.

  • 346. Gong, Chensheng
    et al.
    Zhang, Jianhao
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Hybrid unidirectional meta-coupler for vertical incidence to a high-refractive-index waveguide in telecom wavelength2017Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, nr 24, s. 5098-5101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Unidirectional optical manipulation, especially the coupling from a vertical light beam to a waveguide unidirectionally, is desirable in photonic integration. We first propose a hybrid unidirectional meta-coupler for vertical incidence to a high-refractive-index waveguide in telecom wavelength, a periodic plasmonic metasurface composed of metal-insulator-metal unit cells is used for phase matching. Three designs are given for devices working around wavelengths 0.85, 1.31, and 1.55 mu m. The simulated coupling efficiencies are all around 70%, and the 1 dB coupling bandwidths are 29, 82, and 105 nm, respectively. Our approach paves the way for the applications of optical metasurfaces to planar lightwave circuits. (C) 2017 Optical Society of America

  • 347.
    Gonzalez, Delia Rodriguez De Liera
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    A programmable baseband chain for a WCDMA/WLAN(802.11b)multi-standard zero-IF receiver2005Ingår i: VLSI Circuits and Systems II, Pts 1 and 2 / [ed] Lopez, JF; Fernandez, FV; LopezVillegas, JM; DelaRosa, JM, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2005, Vol. 5837, s. 396-403Konferensbidrag (Refereegranskat)
    Abstract [en]

    As we move towards convergent 4G Wireless encompassing both 3G cellular (WCDMA) for wide area networks and Wireless LAN for "hot-spots", the development of low power, low cost multi-band multi-standard wireless chipset solutions is a must. To this end this paper presents a programmable architecture for an analog baseband chain intended for use in a zero-IF multi-standard WCDMA/WLAN(802.11b) radio receiver. It also addresses the DC offset cancellation in the baseband chain. This is one of the major impairments in zero-IF receivers whose simplicity makes them suitable for single-chip multi-standard designs but where DC offset can reduce the receiver performance if a proper DC offset cancellation scheme is not devised. System level design of the baseband chain is given leading to design specifications of the different blocks in the chain. Extensive simulations carried out in MATLAB/SimuLink at the system level and in Cadence design tools at the circuit level show the performance of the system. The circuits will be fabricated in a 0.18 mu m CMOS process for a 1.8 V power supply.

  • 348.
    Goobar, E.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Gillner, L.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    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.
    Broberg, B.
    Tanbun-Ek, T.
    Nilsson, S.
    Measurement of a VPE-transported DFB laser with blue-shifted frequency modulation response from DC to 2 GHz1988Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 24, s. 746-747Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The frequency modulation characteristics of a VPE-transported 1.53 mu;m wavelength GaInAsP-InP DFB semiconductor diode laser was measured. Below approximately 0.7 mW optical output power per facet, it exhibited a smooth, blue-shifted, frequency modulation response from DC to 2 GHz. In the modulation frequency range of 10 MHz to 100 MHz it exhibited a | Delta;f/ Delta;I| of 0.5-1.8 GHz/mA, depending on the biasing level

  • 349.
    Goobar, E.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    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.
    Broadband measurements of frequency noise spectrum in two section DBR laser1991Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 27, s. 289-291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dependence of the frequency noise on the output power, the tuning current and the current modulation has been measured in a two electrode DBR laser from 30 MHz to 8 GHz. The frequency noise spectrum was fairly flat and decreased with increased output power at a rate faster than 1/P. At certain biasing levels, the noise increased and the relaxation peak was shifted towards lower frequencies when current was injected into the passive waveguide. Furthermore, the frequency noise was not affected by the current modulation.

  • 350.
    Goobar, E.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    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.
    Broberg, B.
    Nilsson, S.
    Pure frequency modulation or intensity modulation with suppressed frequency chirp using active Bragg reflector integrated laser1989Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 25, s. 304-305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The modulation properties of a laser structure which consists of an active Bragg reflector (300 mu m) integrated with an uncorrugated gain region (600 mu m) have been measured. The laser exhibited a flat FM response and very low spurious intensity modulation when modulating the current in the Bragg reflector. Furthermore, broadband intensity modulation with suppressed frequency chirp could also be achieved. An inhomogeneous linewidth enhancement factor alpha caused by the uneven carrier density distribution between the two sections gives a qualitative explanation to our results.

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