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  • 1251.
    Viotti, Anne Lise
    KTH, Skolan för teknikvetenskap (SCI).
    Cascaded supercontinuum in mid-IR with periodically structured KTiOAsO4 and KTiOPO42016Konferensbidrag (Refereegranskat)
  • 1252.
    Viotti, Anne-Lise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Nonlinear optics in KTiOPO4 for spectral management of ultra-short pulses in the near- and mid-IR2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    I den här avhandlingen undersöks möjligheterna att kontrollera ickelinjära optiska processer iferroelektriska material. Detta för att kunna anpassa bandbredden hos ultrakorta pulser i piko- ochfemtosekundsområdena. Processerna kontrolleras genom kvasifasmatchning, vilket innebär attmaterialets spontana polarisation alterneras på ett sätt som ger upphov till olika domäner. Arbetetsom presenteras här avser främst användandet av kristallen KTiOPO4 (KTP), då den har en högoptisk ickelinjäritet, en bred transmission i de nära- och mellan-infraröda områdena samt en högskadetröskel. Dessutom möjliggör KTP tillverkning av uniforma samt finstrukturerade domänermed hög kontrast och kvalitet. Dessa egenskaper gör KTP till ett attraktivt material för en stormängd tillämpningar och har möjliggjort mycket av arbetet i denna avhandling.Utbredning av ultrakorta pulser i domänstrukturerade ferroelektriska material studeradesnumeriskt med en modell som baserades på en ickelinjär amplitudekvation. Modellen tar hänsyntill materialets absorption och dispersion så väl som andra- och tredje ordningens ickelinjäriteter.Superkontinuumgenerering i det nära- och mellan-infraröda området undersöktes för periodisktstrukturerat KTP i fallet med femtosekundspulser vid 1.5 μm. Beräkningarna visade att pulsernakan genomgå självkomprimering i samband med en oktavsträckande spektral breddning. Dessaprocesser möjligörs av kaskaderade andra ordningens ickelinjäriteter och kan anpassas medkvasifasmatchningsparametrarna, vilka bestäms av strukturens periodicitet. Designen sompresenteras i detta arbete gav upphov till en negativ effektiv ickelinjär Kerr-koefficient med enstorlek på 1.651014 cm2/W i det positiva dispersionsområdet, vilket är en storleksordning högreän den naturliga Kerr-koefficienten i KTP. Karaktäriseringen av ett enkelpasseringsexperimentmed en 128 fs-puls vid 1.52 μm propagerandes genom en periodiskt strukturerad KTP-kristall,med en periodicitet på 36 μm, presenteras också. Resultaten visar på en spektral breddning från1.1 μm till 2.7 μm samt en komprimering ner till 18.6 fs, vilket således verifierar de numeriskaresultaten.Möjligheten att anpassa bandbredden för ultrakorta infraröda pulser studerades även ipikosekundsområdet med s.k. baklängesvågs-optiska parametriska oscillatorer (BWOPO). Denhär sortens system bygger på domänstrukturer med sub-mikrometerperioder för att genereramotpropagerande signal- och komplementärsignalvågor. I dessa system får den framåtgenereradevågen samma fasmodulation som pumpvågen, medan den bakåtgenererade vågen är intrinsisktsmalbanding och i stort sett okänslig för ändringar i pumpvåglängden. I detta arbete studeraskaskaderade BWOPO-system, där den framåtgenererade vågen används som pump i enenkelpasseringskonfiguration. Problemet med att ändra våglängden på den smalbandigabakåtpropagerande signalen löstes genom att passera den genom en bredbanding optiskparametrisk förstärkare, vilket möjliggjorde ett frekvensskift på 2.7 THz för en våglängd kring1.87 μm med en bandbredd på 28 GHz. Den koherenta fasöverföringen från pumpen till denframåtpropagerande BWOPO-vågen undersöktes även genom pulskomprimering. I dettaexperiment så överfördes 220 GHz bandbredd från 800 nm till en 150 ps lång puls vid 1.4 μm,vilken kunde komprimeras till 1.3 ps i en enkel-gitterkompressor med μJ energi.

  • 1253.
    Viotti, Anne-Lise
    et al.
    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.
    Supercontinuum generation and self-compression of femtosecond pulses at 1030 nm in KTP crystals2018Konferensbidrag (Refereegranskat)
  • 1254.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Coherent phase transfer and pulse compression at 1.4 µm in a backward-wave OPOManuskript (preprint) (Övrigt vetenskapligt)
  • 1255.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Coherent phase transfer and pulse compressionat 1.4μm in a backward-wave OPO2019Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 44, nr 12, s. 3066-3069Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The frequency modulation transfer property of a backward-wave optical parametric oscillator (BWOPO) is investigated in the context of near-IR pulse compression. The maximum transferrable bandwidth from the pump to the forward wave in a BWOPO is determined by the group dispersion mismatch. In comparison, the third-order phase introduced in a single-grating compressor setup is more detrimental to achieve optimum compression of the BWOPO forward wave. Nevertheless, we demonstrate a 220 GHz bandwidth transfer from 800 nm to 1.4 μm, with a compression factor of 115, leading to near-IR pulses as short as 1.3 ps with μJ energy.

  • 1256.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Coherent Temporal Phase Transfer in Backward Wave Parametric Oscillator at 1.4 mu m2019Ingår i: 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), IEEE , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The frequency modulation transfer property of a backward wave optical parametric oscillator is employed to generate compressed near-IR pulses at 1.4 mu m with 1.3ps duration. Limitations to the linear frequency modulation transfer in BWOPO are investigated.

  • 1257.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Coherent temporal phase transfer in backward wave parametric oscillator at 1.4 µm2019Ingår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The frequency modulation transfer property of a backward wave optical parametric oscillator is employed to generate compressed near-IR pulses at 1.4µm with 1.3ps duration. Limitations to the linear frequency modulation transfer in BWOPO are investigated.

  • 1258.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    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.
    Mid-Infrared Supercontinuum generation in χ(2)-structured KTP and KTA using cascaded soliton self-compression2017Konferensbidrag (Refereegranskat)
  • 1259.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Budriunas, Rimantas
    Kucinskas, Dainius
    Stanislauskas, Tomas
    Canalias, Carlota
    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.
    Mid-IR supercontinuum generation and cascaded soliton self-compression in χ^((2))-modulated KTiOPO42018Ingår i: NorthernOptics2018 proceedings   Photonics Sweden, 2018Konferensbidrag (Refereegranskat)
  • 1260.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Budriunas, Rimantas
    Vilnius Univ, Laser Res Ctr, 10 Sauletekio Ave, LT-10222 Vilnius, Lithuania.;Light Convers Ltd, 2B Keramiku St, LT-10223 Vilnius, Lithuania..
    Kucinskas, Dainius
    Vilnius Univ, Laser Res Ctr, 10 Sauletekio Ave, LT-10222 Vilnius, Lithuania.;Light Convers Ltd, 2B Keramiku St, LT-10223 Vilnius, Lithuania..
    Stanislauskas, Tomas
    Light Convers Ltd, 2B Keramiku St, LT-10223 Vilnius, Lithuania..
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Supercontinuum generation and soliton self-compression in chi((2))-structured KTiOPO42018Ingår i: Optica, ISSN 2334-2536, Vol. 5, nr 6, s. 711-717Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultrafast sources in the mid-IR are indispensable research tools for spectroscopic and medical applications and can also potentially be used to generate attosecond pulses. We investigated a route to directly achieve self-compressed supercontinuum pulses with an octave-exceeding spectrum extending into the mid-IR by employing self-defocusing nonlinearities obtained through cascaded chi((2)) interactions in domain-structured ferroelectrics. A model was developed based on a single-wave nonlinear envelope equation that accounts for cascaded chi((2)) nonlinearities, the native Kerr response from the third-order nonlinear polarization, and the delayed Raman response. Experimental validation of the model was carried out by using an in-house fabricated, periodically poled, Rb-doped KTiOPO4 crystal with a period of 36 mu m. A supercontinuum spectrum spanning from 1.1 to 2.7 mu m was achieved, as well as self-compression down to 18.6 fs, from a 128 fs pump pulse at 1.52 mu m. Using the actual pump pulse and sample parameters, excellent agreement was reached between the model and the experimental results, thus proving the validity of the model. As periodically poled KTiOPO4 can be obtained with large apertures, this approach is energy scalable and hence promising for future development in the field.

  • 1261.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Mutter, Patrick
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Tidigare Institutioner (före 2005), Materialvetenskap. KTH, Skolan för teknikvetenskap (SCI), Fysik. KTH, Tidigare Institutioner (före 2005), Fysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Fysik. KTH, Tidigare Institutioner (före 2005), Fysik. KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Degenerate Mirrorless Optical Parametric Oscillator2019Konferensbidrag (Refereegranskat)
  • 1262.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Cascaded supercontinuum in mid-IR with structured KTP and KTA2016Konferensbidrag (Refereegranskat)
  • 1263.
    Viotti, Anne-Lise
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicus, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Generation of widely-tunable narrowband infrared radiation by PPRKTP mirrorless OPO and broadband chirped-pulse OPA2017Ingår i: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2017, Vol. Part F82Konferensbidrag (Refereegranskat)
  • 1264. Virk, Mudassar
    et al.
    Xiong, Kunli
    Svedendahl, Mikael
    Chalmers University of Technology, Sweden.
    Käll, Mikael
    Dahlin, Andreas B.
    A thermal plasmonic sensor platform: resistive heating of nanohole arrays.2014Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, nr 6, s. 3544-3549Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have created a simple and efficient thermal plasmonic sensor platform by letting a DC current heat plasmonic nanohole arrays. The sensor can be used to determine thermodynamic parameters in addition to monitoring molecular reactions in real-time. As an application example, we use the thermal sensor to determine the kinetics and activation energy for desorption of thiol monolayers on gold. Further, the temperature of the metal can be measured optically by the spectral shift of the bonding surface plasmon mode (0.015 nm/K). We show that this resonance shift is caused by thermal lattice expansion, which reduces the plasma frequency of the metal. The sensor is also used to determine the thin film thermal expansion coefficient through a theoretical model for the expected resonance shift.

  • 1265.
    Vogt, Ulrich
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lindblom, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Jansson, Per A. C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Tuohimaa, Tomi T.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wieland, M.
    Wilhein, M.
    Towards Soft X-Ray Phase-Sensitive Imaging with Diffractive Optical Elements2006Ingår i: Proc. 8th International Conference X-ray Microscopy, 2006, s. 91-93Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this contribution we present the first diffractive optical elements for soft x-ray differential interference contrast microscopy.Due to an improved calculation method the nanofabrication accuracy of these optics is the same as for comparable normal zoneplate optics with the same outermost zone width. Different diffractive optical elements were fabricated with outermost zone widthof 100 nm, different spot separation directions and different phase relations between the two spots. The optics were successfullyused in experiments both at the synchrotron radiation based TWINMIC microscope and at the Stockholm compact liquid-nitrogenlaser-plasma source based microscope.

  • 1266.
    Vogt, Ulrich
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Reinspach, Julia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Uhlén, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nilsson, Daniel
    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.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Diffractive optics for laboratory sources to free electron lasers2013Ingår i: 11th International Conference On X-Ray Microscopy (XRM2012), Institute of Physics (IOP), 2013, Vol. 463, nr 1, s. 012001-Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this contribution we present our recent results in the field of diffractive optics for both soft and hard x-ray radiation, and for laboratory sources to x-ray free electron lasers (XFEL). We developed a laboratory soft x-ray microscope that uses in-house produced zone plate optics as high-resolution objectives. We continuously try to improve these optics, both in terms of efficiency and resolution. Our latest development is the manufacturing of tungsten soft x-ray zone plates with outermost zone widths of 12 nm and 90 nm high structures. For hard x-rays, we investigated the possibility to use metal zone plates on a diamond substrate for nano-focusing of the European X-ray Free Electron Laser. The simulations show that the heat conduction is efficient enough to keep a zone plate well below melting temperature. However, metal zone plates will experience large and rapid temperature fluctuations of several hundred Kelvin that might prove fatal. To test this, we manufactured tungsten on diamond prototype zone plates and exposed them to radiation from the LCLS XFEL. Results show that metal zone plates can survive the XFEL beam.

  • 1267.
    Voigtländer, Christian
    et al.
    Friedrich-Schiller-University Jena.
    Zeil, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thomas, Jens
    Friedrich-Schiller-University Jena.
    Ams, Martin
    Macquarie University.
    Williams, Robert J.
    Macquarie University.
    Withford, Michael J.
    Macquarie University.
    Tünnermann, Andreas
    Friedrich-Schiller-University Jena.
    Nolte, Stefan
    Friedrich-Schiller-University Jena.
    Fs laser induced apodised Bragg waveguides in fused silica2011Ingår i: FRONTIERS IN ULTRAFAST OPTICS: BIOMEDICAL, SCIENTIFIC, AND INDUSTRIAL APPLICATIONS XI / [ed] Heisterkamp, A; Neev, J; Nolte, S, SPIE - International Society for Optical Engineering, 2011, , s. 7Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present apodised Bragg waveguides inscribed in fused silica using a high repetition rate fs laser system. By varying the modulation with a pulse picker, the mean refractive index over the grating length could be kept constant, while the grating strength is varied. Thus, Bragg waveguides with zero crossing Gaussian modulation profile could be demonstrated. The side-lobes were suppressed by about 10 dB compared to a uniform grating.

  • 1268. Voipio, T.
    et al.
    Setälä, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Partial polarization of pulsed light beams2011Ingår i: Proc SPIE Int Soc Opt Eng, 2011, s. 83061C-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We introduce a formalism for characterizing partial polarization in random pulsed electromagnetic beams in time and frequency domains. The connection between the temporal and spectral polarization properties is analyzed, and compared to the analogous relationship in the context of stationary beams. The formalism is demonstrated using as an example a beam whose orthogonal components are delayed copies of the same Gaussian-shaped and Gaussian-correlated linearly polarized pulse. The results show that the temporal and spectral polarization properties are quite different, and the time-dependent polarization behavior of the beam may be tailored by changing the delay between the orthogonal components and their coherence time.

  • 1269. Voipio, Timo
    et al.
    Setala, Tero
    Shevchenko, Andriy
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Polarization dynamics and polarization time of random three-dimensional electromagnetic fields2010Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, nr 6, s. 063807-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the polarization dynamics of random, stationary three-dimensional (3D) electromagnetic fields. For analyzing the time evolution of the instantaneous polarization state, two intensity-normalized polarization autocorrelation functions are introduced, one based on a geometric approach with the Poincare vectors and the other on energy considerations with the Jones vectors. Both approaches lead to the same conclusions on the rate and strength of the polarization dynamics and enable the definition of a polarization time over which the state of polarization remains essentially unchanged. For fields obeying Gaussian statistics, the two correlation functions are shown to be expressible in terms of quantities characterizing partial 3D polarization and electromagnetic coherence. The 3D degree of polarization is found to have the same meaning in the 3D polarization dynamics as the usual two-dimensional (2D) degree of polarization does with planar fields. The formalism is demonstrated with several examples, and it is expected to be useful in applications dealing with polarization fluctuations of 3D light.

  • 1270.
    Volotinen, Tarja
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Fang, Mei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Rao, K. V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Mathematical analysis of the transmission spectrum and photonic band gaps for a low-refractive-index magnetic photonic crystal2011Artikel i tidskrift (Övrigt vetenskapligt)
  • 1271.
    von Hofsten, Olof
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Phase-Contrast and High-Resolution Optics for X-Ray Microscopy2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    X-ray microscopy is a well-established technique for nanoscale imaging. Zone plates are used as microscope objectives and provide high resolution, approaching 10 nm, currently limited by fabrication issues. This Thesis presents zone plate optics that achieve either high resolution or phase contrast in x-ray microscopy. The high-resolution optics use high orders of the zone plate, which alleviates the demands on fabrication, and the phase-contrast optics are single-element diffractive optical elements that produce contrast by Zernike or differential-interference contrast methods. The advantage of phase contrast in x-ray microscopy is shorter exposure times, and is crucial in the hard x-ray regime. Microscopy in the absorption‑contrast region of the water-window (2.34 - 4.37 nm) also benefits from these optics. The development of the optics for a laboratory soft x-ray microscope spans from theoretical and numerical analysis of coherence and stray light to experimental implementation and testing. The laboratory microscope uses laser-produced plasma-sources in the water-window and is unique in its design and performance. It will be shown that the laboratory microscope in its current form is a user-oriented and stable instrument, and has been used in a number of applications. The implementation of a cryogenic sample stage for tomographic imaging of biological samples in their natural environment has enabled applications in biology, and 3D x-ray microscopy of cells was performed for the first time with a laboratory instrument.

     

  • 1272.
    von Hofsten, Olov
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Bertilson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Simulation of partially coherent image formation in x-ray microscopy - art. no. 67050I2007Ingår i: Advances in X-Ray/EUV Optics and Components II, SPIE - International Society for Optical Engineering, 2007, Vol. 6705, s. I7050-I7050Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present the theory and implementation of a numerical model capable of simulating two-dimensional images for an x-ray microscope using partially coherent illumination considerations. Partially coherent illumination is found in all x-ray microscopes and particularly in the latest generation of our in-house compact soft x-ray microscope. This is due to an introduced mismatch in numerical aperture of the condenser and objective zone plate, and will yield diffraction-like artifacts in phase-shifting objects. The numerical model approximates the condenser zone plate as a secondary incoherent source represented by individually coherent but mutually incoherent source emitters, each giving rise to a separate image. A final image is obtained by adding up the image intensities of the individual contributions. The simulation has been a useful tool for investigating the influence of coherence on images in both the mirror and zone plate condenser arrangement of the in-house compact soft x-ray microscope. The latest development included in the program is the effect of astigmatism and partial coherence, where the calculated results show good qualitative agreement with respect to the microscope images.

  • 1273. Wachulak, P.
    et al.
    Grisham, M.
    Heinbuch, S.
    Martz, Dale
    Department of Electrical and Computer Engineering, Colarado State University.
    Rockward, W.
    Hill, D.
    Rocca, J. J.
    Menoni, C. S.
    Anderson, E.
    Marconi, M.
    Interferometric lithography with an amplitude division interferometer and a desktop extreme ultraviolet laser2008Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 25, nr 7, s. B104-B107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a compact interferometric lithography nanopatterning tool based on an amplitude division interferometer (ADI) and a 46.9 nm wavelength desktop size capillary discharge laser. The system is designed to print arrays of lines, holes, and dots with sizes below 100 nm on high resolution photoresists for the fabrication of arrays of nanostructures with physical and biological applications. The future combination of this ADI with high repetition rate tabletop lasers operating at shorter wavelengths should allow the printing of arrays of sub-10 nm size features with a tabletop setup.

  • 1274. Wagner, F.
    et al.
    Rachlew, E.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Study on a hypothetical replacement of nuclear electricity by wind power in Sweden2016Ingår i: The European Physical Journal Plus, ISSN 2190-5444, E-ISSN 2190-5444, Vol. 131, nr 5, artikel-id 173Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Swedish electricity supply system benefits strongly from the natural conditions which allow a high share of hydroelectricity. A complete supply is, however, not possible. Up to now, nuclear power is the other workhorse to serve the country with electricity. Thus, electricity production of Sweden is basically CO2-free and Sweden has reached an environmental status which others in Europe plan to reach in 2050. Furthermore, there is an efficient exchange within the Nordic countries, Nordpol, which can ease possible capacity problems during dry cold years. In this study we investigate to what extent and with what consequences the base load supply of nuclear power can be replaced by intermittent wind power. Such a scenario leads unavoidably to high wind power installations. It is shown that hydroelectricity cannot completely smooth out the fluctuations of wind power and an additional back-up system using fossil fuel is necessary. From the operational dynamics, this system has to be based on gas. The back-up system cannot be replaced by a storage using surplus electricity from wind power. The surplus is too little. To overcome this, further strong extension of wind power is necessary which leads, however, to a reduction of the use of hydroelectricity if the annual consumption is kept constant. In this case one fossil-free energy form is replaced by another, however, more complex one. A mix of wind power at 22.3GW plus a gas based back-up system with 8.6GW producing together 64.8TWh would replace the present infrastructure with 9GW nuclear power producing 63.8TWh electricity. The specific CO2-emission increases to the double in this case. Pumped storage for the exclusive supply of Sweden does not seem to be a meaningful investment.

  • 1275.
    Wallenius, Janne
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Pillon, S.
    Zaboudko, L.
    Fuels for accelerator-driven systems2006Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 562, nr 2, s. 625-629Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In Europe, uranium-free fuels for minor actinide burning in Accelerator-D riven Systems (ADS) are under development in the frame of the CONFIRM, FUTURE and MATINE projects. In the present paper, the status of these projects is reviewed. Transuranium oxide and nitride fuel samples have been fabricated and characterized. Their performance has been modelled under normal operation as well as under accident conditions, using 800 MWth sub-critical cores as a basis. The safety analysis shows that oxide cermet fuels with molybdenum matrix may hold an advantage over the alternatives in terms of a high margin to melt. Oxide cercer fuels based on MgO are more easily fabricated, but should be operated at low linear rating and deep sub-criticality to ensure sufficient safety margins. Nitride fuels with liquid metal bond appear to provide better in pile performance, but are complicated to fabricate.

  • 1276. Wang, Baoju
    et al.
    Zhan, Qiuqiang
    Zhao, Yuxiang
    Wu, Ruitao
    Liu, Jing
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. South China Normal University, China.
    Visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals2016Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, nr 2, s. A302-A311Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Further development of multiphoton microscopic imaging is confronted with a number of limitations, including high-cost, high complexity and relatively low spatial resolution due to the long excitation wavelength. To overcome these problems, for the first time, we propose visible-to-visible four-photon ultrahigh resolution microscopic imaging by using a common cost-effective 730-nm laser diode to excite the prepared Nd3+-sensitized upconversion nanoparticles (Nd3+-UCNPs). An ordinary multiphoton scanning microscope system was built using a visible CW diode laser and the lateral imaging resolution as high as 161-nm was achieved via the four-photon upconversion process. The demonstrated large saturation excitation power for Nd3+-UCNPs would be more practical and facilitate the four-photon imaging in the application. A sample with fine structure was imaged to demonstrate the advantages of visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals. Combining the uniqueness of UCNPs, the proposed visible-to-visible four-photon imaging would be highly promising and attractive in the field of multiphoton imaging.

  • 1277.
    Wang, Jing
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    High-Q Optical Filter Based on Photonic Crystal Surface-Mode Microcavity2009Ingår i: 2009 IEEE/LEOS WINTER TOPICALS MEETING SERIES (WTM 2009), NEW YORK: IEEE , 2009, s. 20-21Konferensbidrag (Refereegranskat)
    Abstract [en]

    An optical filter based on a side-coupled two-dimensional photonic crystal surface mode cavity on crystalline silicon-on-insulator (SOI) structure is presented. The measured system Q and intrinsic Q factor are 6900 and 13700, respectively.

  • 1278.
    Wang, Jing
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Song, Yi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Efficient coupler between silicon waveguide and hybrid plasmonic waveguide2010Ingår i: 2010 Asia Communications and Photonics Conference and Exhibition (ACP), 2010, s. 489-490Konferensbidrag (Refereegranskat)
    Abstract [en]

    We experimentally demonstrate an efficient coupler between a silicon waveguide and a hybrid plasmonic waveguide for the wavelength range 1460-1540 nm. Such compact, efficient plasmonic couplers provide a promising platform for integrated photonic circuits.

  • 1279.
    Wang, Jing
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Song, Yi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Yan, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Efficient coupler between silicon waveguide and hybrid plasmonic waveguide2011Ingår i: OPTOELECTRONIC MATERIALS AND DEVICES V / [ed] oyama, F; Chuang, SL; Duan, GH; Huang, Y, 2011, Vol. 7987Konferensbidrag (Refereegranskat)
    Abstract [en]

    We experimentally demonstrate an efficient coupler between a silicon waveguide and a hybrid plasmonic waveguide for the wavelength range 1460-1540 nm. Such compact, efficient plasmonic couplers provide a promising platform for integrated photonic circuits.

  • 1280.
    Wang, Jing
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Song, Yi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Yan, Wei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    High-Q photonic crystal surface-mode cavities on crystalline SOI structures2010Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 283, nr 11, s. 2461-2464Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-Q side-coupled surface-mode cavities in two-dimensional (2D) photonic crystals on crystalline silicon-on-insulator (SOI) structures are demonstrated. One of the surface-mode cavities has the measured system Q factor and intrinsic Q factor of 6200 and 13,400, respectively. The experimental results show that the value of system Q factor is ten times and the intrinsic Q factor six times higher than those of similar structures on amorphous SOI structures, respectively, due to the intrinsic material loss is much lower for crystalline silicon. The Q factors of cavities can be further improved by spin-on-glass overlayers, for increasing the structural symmetry. After the spin-on-glass process, the system Q factor and the intrinsic Q factor become nearly twice higher. Meanwhile, the drop wavelengths are largely red-shifted. (C) 2010 Elsevier B.V. All rights reserved.

  • 1281. Wang, Nan
    et al.
    Evans, Julian S.
    Mei, Ju
    Zhang, Jianhao
    Khoo, Iam-Choon
    He, Sailing
    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. Zhejiang University, China.
    Lasing properties of a cholesteric liquid crystal containing aggregation-induced-emission material2015Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, nr 26, s. 33938-33946Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate band edge lasing action from a cholesteric liquid crystal (CLC) containing an aggregation-induced-emission (AIE) dye as gain material. AIE materials do not suffer aggregation-caused quenching, have strong resistance to photobleaching, and can show large Stokes shift. The amplified spontaneous emission (ASE) and lasing emission of the dye-doped CLC cell have been characterized, the lasing threshold has been estimated, and its resistance to photobleaching has been measured. AIE materials with their unique properties are especially suitable for acting as gain materials in liquid crystal lasers where defect structures lower the threshold for nanoscale aggregation effects. Our studies have shown that such AIE-dye-doped CLC is capable of lasing action with unusually large Stokes shift at moderate threshold with strong resistance to photobleaching.

  • 1282. Wang, Qing
    et al.
    Zhao, Hang
    Du, Xu
    Zhang, Weichun
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Li, Qiang
    Hybrid photonic-plasmonic molecule based on metal/Si disks2013Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, nr 9, s. 11037-11047Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optical properties of two identical coupled disks forming a "hybrid photonic-plasmonic molecule" are investigated. Each disk is a metal-dielectric structure supporting hybrid plasmonic-photonic whispering-gallery (WG) modes. The WG modes of a molecule split into two groups of nearly-degenerate modes, i.e., bonding and anti-bonding modes. The oscillation of quality factor (Q) with the inter-disk gap d and significant enhancement at certain inter-disk gaps can be observed. An enhanced Q factor of 1821 for a hybrid photonic-plasmonic molecule composed of two 1.2 mu m-diameter disks, compared with that for a single disk, is achieved. The corresponding Purcell factor is 191, making the hybrid photonic-plasmonic molecule an optimal choice for subwavelength-scale device miniaturization and light-matter interactions. Moreover, the far-field emission pattern of the hybrid photonic-plasmonic molecule exhibits an enhanced directional light output by tuning the azimuthal mode number for both bonding and anti-bonding modes.

  • 1283. Wang, Ruoxu
    et al.
    Tang, Ming
    Zhang, Liangjun
    Zhang, Hailiang
    Feng, Zhenhua
    Lin, Rui
    KTH, Skolan för informations- och kommunikationsteknik (ICT). Huazhong University of Science and Technology, China.
    Fu, Songnian
    Liu, Deming
    Shum, Perry Ping
    Demonstration of Programmable In-Band OSNR Monitoring Using LCFBG With Commercial Thermal Printer Head2015Ingår i: IEEE PHOTONICS JOURNAL, ISSN 1943-0655, Vol. 7, nr 4, artikel-id 6802008Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We proposed and experimentally demonstrated a programmable optical signal-to-noise ratio (OSNR) monitoring scheme by using linearly chirped fiber Bragg grating (LCFBG) and a commercial thermal printer head. For the coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission system, the monitor's working wavelength can be flexibly software-controlled from 1530 to 1538 nm to support standard ITU-T grid or flex-grid operation. The linear OSNR monitoring range has been achieved from 9 to 26 dB for a 16-quadrature amplitude modulation (QAM) OFDM transmission system with negligible errors, respectively. Neither chromatic dispersion nor polarization mode dispersion affect the monitoring accuracy of our system.

  • 1284.
    Wang, S.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Karlsson, H.
    Laurell, F.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Type-II quasi-phase matched UV generation in first order periodically poled KTP1999Ingår i: OSA Trends in Optics and Photonics, ISSN 1094-5695, Vol. 26, s. 59-62Artikel i tidskrift (Refereegranskat)
  • 1285.
    Wang, S.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, H.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Karlsson, H.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    First-order type-II quasi-phase matched UV generation in periodically poled KTP1999Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 24, s. 978-980Artikel i tidskrift (Refereegranskat)
  • 1286.
    Wang, Shunhua
    et al.
    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.
    Peculiarities of green light-induced infrared absorption dynamics in PPKTP2004Ingår i: OSA Trends in Optics and Photonics, ISSN 1094-5695, Vol. 94, s. 461-465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-sensitivity thermal lens technique has been used to investigate greenlight-induced infrared absorption (GRIIRA) dynamics in KTP and PPKTP. The higher GRIIRA amplitude and different dynamicsin PPKTP is explained by changes in native defect concentration produced by poling.

  • 1287. Wang, Xu-Dong
    et al.
    Xuan, Chuan-Jin
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Tian, Shan Xi
    Note: Coherent resonances observed in the dissociative electron attachment to carbon monoxide2015Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, nr 6, artikel-id 066101Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Succeeding our previous finding about coherent interference of the resonant states of CO- formed by the low-energy electron attachment [Tian et al. Phys. Rev. A 88, 012708 (2013)], here we provide further evidence of the coherent interference. The completely backward distributions of the O- fragment of the temporary CO- are observed with anion velocity map imaging technique in an electron energy range of 11.3-12.6 eV and explained as the results of the coherent interferences of three resonant states. Furthermore, the state configuration of the interference is changed with the increase of electron attachment energy. © 2015 AIP Publishing LLC.

  • 1288. Wang, Z.
    et al.
    Liang, Y.
    Meng, B.
    Sun, Yan-Ting
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Omanakuttan, Giriprasanth
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Gini, Emilio
    Beck, M.
    Sergachev, I.
    Lourdudoss, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Faist, J.
    Scalari, G.
    Over 2W room temperature lasing on a large area photonic crystal quantum cascade laser2019Ingår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2019, artikel-id SW4N.4Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a large-area (1.5 mm × 1.5 mm) photonic crystal quantum cascade laser, with over 2 W peak power at room temperature (289 K), and symmetrical, narrow (< 1◦), single-lobed surface-emitting beam.

  • 1289.
    Wang, Zhechao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Investigation of New Concepts and Solutions for Silicon Nanophotonics2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Nowadays, silicon photonics is a widely studied research topic. Its high-index-contrast and compatibility with the complementary metal-oxide-semiconductor technology make it a promising platform for low cost high density integration. Several general problems have been brought up, including the lack of silicon active devices, the difficulty of light coupling, the polarization dependence, etc. This thesis aims to give new attempts to novel solutions for some of these problems. Both theoretical modeling and experimental work have been done.

    Several numerical methods are reviewed first. The semi-vectorial finite-difference mode solver in cylindrical coordinate system is developed and it is mainly used for calculating the eigenmodes of the waveguide structures employed in this thesis. The finite-difference time-domain method and beam propagation method are also used to analyze the light propagation in complex structures.

    The fabrication and characterization technologies are studied. The fabrication is mainly based on clean room facilities, including plasma assisted film deposition, electron beam lithography and dry etching. The vertical coupling system is mainly used for characterization in this thesis. Compared with conventional butt-coupling system, it can provide much higher coupling efficiency and larger alignment tolerance.

    Two novel couplers related to silicon photonic wires are studied. In order to improve the coupling efficiency of a grating coupler, a nonuniform grating is theoretically designed to maximize the overlap between the radiated light profile and the optical fiber mode. Over 60% coupling efficiency is obtained experimentally. Another coupler facilitating the light coupling between silicon photonic wires and slot waveguides is demonstrated, both theoretically and experimentally. Almost lossless coupling is achieved in experiments.

    Two approaches are studied to realize polarization insensitive devices based on silicon photonic wires. The first one is the use of a sandwich waveguide structure to eliminate the polarization dependent wavelength of a microring resonator. By optimizing the multilayer structure, we successfully eliminate the large birefringence in an ultrasmall ring resonator. Another approach is to use polarization diversity scheme. Two key components of the scheme are studied. An efficient polarization beam splitter based on a one-dimensional grating coupler is theoretically designed and experimentally demonstrated. This polarization beam splitter can also serve as an efficient light coupler between silicon-on-insulator waveguides and optical fibers. Over 50% coupling efficiency for both polarizations and -20dB extinction ratio between them are experimentally obtained. A compact polarization rotator based on silicon photonic wire is theoretically analyzed. 100% polarization conversion is achievable and the fabrication tolerance is relatively large by using a compensation method.

    A novel integration platform based on nano-epitaxial lateral overgrowth technology is investigated to realize monolithic integration of III-V materials on silicon. A silica mask is used to block the threading dislocations from the InP seed layer on silicon. Technologies such as hydride vapor phase epitaxy and chemical-mechanical polishing are developed. A thin dislocation free InP layer on silicon is obtained experimentally.

  • 1290.
    Wang, Zhixin
    et al.
    Swiss Fed Inst Technol, Inst Quantum Elect, Auguste Piccard Hof 1, CH-8093 Zurich, Switzerland..
    Liang, Yong
    Swiss Fed Inst Technol, Inst Quantum Elect, Auguste Piccard Hof 1, CH-8093 Zurich, Switzerland..
    Meng, Bo
    Swiss Fed Inst Technol, Inst Quantum Elect, Auguste Piccard Hof 1, CH-8093 Zurich, Switzerland..
    Sun, Yan-Ting
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Omanakuttan, Giriprasanth
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Gini, Emilio
    Swiss Fed Inst Technol, FIRST Lab, CH-8093 Zurich, Switzerland..
    Beck, Mattias
    Swiss Fed Inst Technol, Inst Quantum Elect, Auguste Piccard Hof 1, CH-8093 Zurich, Switzerland..
    Sergachev, Ilia
    Wyss Zurich, Weinbergstr 35, CH-8092 Zurich, Switzerland..
    Lourdudoss, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Faist, Jerome
    Swiss Fed Inst Technol, Inst Quantum Elect, Auguste Piccard Hof 1, CH-8093 Zurich, Switzerland..
    Scalari, Giacomo
    Swiss Fed Inst Technol, Inst Quantum Elect, Auguste Piccard Hof 1, CH-8093 Zurich, Switzerland..
    Over 2W room temperature lasing on a large area photonic crystal quantum cascade laser2019Ingår i: 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), IEEE , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a large-area (1.5 mm x 1.5 mm) photonic crystal quantum cascade laser, with over 2 W peak power at room temperature (289 K), and symmetrical, narrow (<1 degrees), single-lobed surface-emitting beam.

  • 1291.
    Wei, Yizhen
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Sun, Bing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wang, Tianshu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Chen, Daru
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Widely tunable L-band brillouin fiber laser incorporating a bismuth-based erbium-doped fiber2009Ingår i: Optics InfoBase Conference Papers, 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    We proposed a widely tunable single-wavelength Brillouin fiber laser (BFL) by employing a bismuth-based erbium-doped fiber (Bi-EDF). The BFL operates in a range from 1555 nm to 1632 nm, which is the widest to the best of our knowledge. It's an attractive narrow linewidth laser source on the L-band.

  • 1292. Werner, Michael
    et al.
    Merenda, Fabrice
    Piguet, Joachim
    Salathé, René-Paul
    Vogel, Horst
    Microfluidic array cytometer based on refractive optical tweezers for parallel trapping, imaging and sorting of individual cells.2011Ingår i: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 11, nr 14, s. 2432-2439Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Analysis of genetic and functional variability in populations of living cells requires experimental techniques capable of monitoring cellular processes such as cell signaling of many single cells in parallel while offering the possibility to sort interesting cell phenotypes for further investigations. Although flow cytometry is able to sequentially probe and sort thousands of cells per second, dynamic processes cannot be experimentally accessed on single cells due to the sub-second sampling time. Cellular dynamics can be measured by image cytometry of surface-immobilized cells, however, cell sorting is complicated under these conditions due to cell attachment. We here developed a cytometric tool based on refractive multiple optical tweezers combined with microfluidics and optical microscopy. We demonstrate contact-free immobilization of more than 200 yeast cells into a high-density array of optical traps in a microfluidic chip. The cell array could be moved to specific locations of the chip enabling us to expose in a controlled manner the cells to reagents and to analyze the responses of individual cells in a highly parallel format using fluorescence microscopy. We further established a method to sort single cells within the microfluidic device using an additional steerable optical trap. Ratiometric fluorescence imaging of intracellular pH of trapped yeast cells allowed us on the one hand to measure the effect of the trapping laser on the cells' viability and on the other hand to probe the dynamic response of the cells upon glucose sensing.

  • 1293. Wersäll, Martin
    et al.
    Verre, Ruggero
    Svedendahl, Mikael
    Chalmers University of Technology, Sweden.
    Johansson, Peter
    Käll, Mikael
    Shegai, Timur
    Directional Nanoplasmonic Antennas for Self-Referenced Refractometric Molecular Analysis2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 36, s. 21075-21080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Localized surface-plasmon resonance (LSPR) sensors are typically based on tracing resonance peak shifts that precisely follow changes in the local refractive index. Such measurements usually require a spectrometer, a stable light source, and an accurate LSPR position tracing technique. As a simple but efficient alternative, we investigated a self-referenced single-wavelength sensing scheme based on angle-dependent and highly directional radiation patterns originating from a monolayer of asymmetric gold nanodimers. We found that one could easily trace a model biotinneutravidin recognition reaction as well as minute bulk refractive index changes, by measuring the intensity ratio between the light scattered in two different directions with respect to the dimers. The refractometric resolution of the methodology was estimated to be on the order of Delta n approximate to 10(-5) RIU. These results may be particularly useful for label-free biosensing applications that require a combination of simple and cost-effective optical readout with a reasonable sensitivity.

  • 1294.
    Westergren, Urban
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Yu, Yichuan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Thylen, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    High-speed travelling-wave electro-absorption modulators2006Ingår i: Workshop on Optical Components for Broadband Communication / [ed] Fonjallaz, PY; Pearsall, TP, BELLINGHAM, WA: SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6350, s. 35004-35004Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electroabsorption modulators (EAM) based on quantum-confined Stark effect (QCSE) in multiple-quantum wells (MQW) have been demonstrated to provide high-speed, low drive voltage, and high extinction ratio. They are compact in size and can be monolithically integrated with continuous-wave (CW) lasers. In order to achieve both high speed and low drive-voltage operation, travelling-wave (TW) electrode structures can be used for EAMs. The inherently low impedance of high-speed EAMs may be transformed to values close to the standard 500hm impedance using periodic microwave structures with a combination of passive transmission lines with high characteristic impedance and active modulator sections with low impedance. Modulation bandwidths of 100GHz (-3dBe) have been accomplished with electrical reflections lower than -10dB in a 500hm system. Transmission at 80Gbit/s with non-return-to-zero (NRZ) code has been demonstrated for InP-based TWEAMs using electronic time-domain multiplexing (ETDM), indicating the possibility of reaching speeds of 100Gbit/s and beyond.

  • 1295.
    Westlund, Robert
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hoffmann, Markus
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Vestberg, Robert
    Hawker, Craig
    Glimsdal, Eirik
    Lindgren, Mikael
    Norman, Patrick
    Eriksson, Anders
    Lopes, Cesar
    Multi-functionalized platinum(II) acetylides for optical power limiting2006Ingår i: Optical Materials in Defence Systems Technology III / [ed] Grote JG; Kajzar F; Lindgren M, SPIE-INT SOC OPTICAL ENGINEERING , 2006, Vol. 6401, s. U87-U94Konferensbidrag (Refereegranskat)
    Abstract [en]

    Preliminary results on the optical power limiting properties of platinum(II) acetylides containing triazole units are presented. It is shown that the triazole units give a positive contribution to the limiting abilities of the platinum(H) acetylide and that this modified chromophore could have potential use in sensor protection devices. Moreover, this paper discusses how the versatile building block 2,2-bis(methylol)propionic acid (bis-MPA) can be used advantageously to functionalize nonlinear optical (NLO) platinum(H) acetylides. The bis-MPA units can be used to prepare dendritic substituents offering site isolation to the chromophore leading to improved clamping. The bis-MPA functionalization also improves the solubility of the platinum(H) acetylides in many organic solvents. The preparation of solid-state optical power limiters, where the NLO chromophore is inserted in an optically transparent matrix, is addressed. Again, the bis-MPA unit can be employed to increase the number of accessible end-groups to which matrix-compatible species can be attached. It is concluded that the hydroxy-functional platinum(II) acetylides can be modified to fit almost any matrix, organic or inorganic. Finally, depending on functionalization, it is possible to prepare doped glasses where the chromophore is either embedded in the matrix, or covalently bonded to the matrix.

  • 1296.
    Westlén, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Impact of ADS on nuclear fuel cyclesIngår i: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100Artikel i tidskrift (Övrigt vetenskapligt)
  • 1297.
    Westlén, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Transmutation of nuclear waste in gas-cooled sub-critical reactors2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 1298.
    Westlén, Daniel
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Neutronic and Safety Aspects of a Gas-Cooled Subcritical Core for Minor Actinide Transmutation2005Ingår i: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 154, nr 1, s. 41-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have designed a gas-cooled accelerator-driven system dedicated to transmutation of minor actinides. Thanks to the excellent neutron economy of the uranium-free fuel employed, the pin pitch to diameter ratio (P/D) could be increased to 1.8. The increased coolant fraction allows for decay heat removal at ambient pressure. The large coolant fraction further results in a low, pressure loss-26 kPa over the core, 35 kPa in. total. Thanks to the large P/D, the elevation of the heat exchanger necessary to remove decay heat by natural circulation is just more than I m. The absence of uranium in conjunction. with the presence of 35% (heavy atom) americium in the fuel results in a low effective delayed neutron fraction and a vanishing Doppler feedback, making subcritical operation mandatory.

  • 1299.
    Westlén, Daniel
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    On TiN-particle fuel based helium-cooled transmutation systems2006Ingår i: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 33, nr 16, s. 1322-1328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have designed a sub-critical helium-cooled core with TiN-coated particle fuel, dedicated to the transmutation of minor actinides. The excellent neutronic properties of helium allows for a low plutonium fraction in the fuel, which yields a low reactivity swing, Delta k = 2600 pcm, for a burnup of 31.2%. Further the neutron spectrum is hard, limiting the buildup of Cm and Cf. The high burnup combined with a minor actinide burning rate of 355 kg/GWth year makes the present design an attractive transmutation system.

  • 1300.
    Widarsson, Max
    Applied Physics, KTH.
    Intra-Cavity Up-Conversion Photon Counting Mid-Infrared Range Determination2019Konferensbidrag (Refereegranskat)
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