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  • 16751.
    Zidane, Mustapha
    et al.
    Mohammed V Univ, Fac Sci, Dept Phys, Lab Condensed Matter & Interdisciplinary Sci, Rabat, Morocco..
    Salmani, El Mehdi
    Mohammed V Univ, Fac Sci, Dept Phys, Lab Condensed Matter & Interdisciplinary Sci, Rabat, Morocco..
    Majumdar, Arnab
    Uppsala Univ, Dept Phys & Astron, Mat Theory Div, SE-75121 Uppsala, Sweden..
    Elmoulat, Meryem
    Univ Mohammed 5, Fac Sci, Res Unit GeoRisk Geol Risks, Battouta Ave, Rabat 10140, Morocco..
    Bghour, Mustapha
    Hassan II Acad Sci & Technol, Rabat, Morocco..
    Labrag, A.
    Univ Ibn Zohr, Fac Sci, Res Team High Crit Temp Superconducting Mat, BP 8106, Agadir, Morocco.;Univ Ibn Zohr, Fac Appl Sci, Natl Rd 10 Cite Azrou, Ait Melloul, Morocco..
    Ez-Zahraouy, Hamid
    Mohammed V Univ, Fac Sci, Dept Phys, Lab Condensed Matter & Interdisciplinary Sci, Rabat, Morocco..
    Benyoussef, Abdelilah
    Mohammed V Univ, Fac Sci, Dept Phys, Lab Condensed Matter & Interdisciplinary Sci, Rabat, Morocco.;Hassan II Acad Sci & Technol, Rabat, Morocco..
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Egenskaper. Uppsala Univ, Dept Phys & Astron, Mat Theory Div, SE-75121 Uppsala, Sweden..
    Thermophysical properties of helium and hydrogen mixtures under high pressure predicted by ab-initio calculations: Implications for Saturn and Jupiter planets2022Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 555, s. 111430-, artikel-id 111430Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thermodynamic and physical properties of Helium (He) and Hydrogen (H) mixtures are crucial form an astrophysical perspective. Nowadays, it is well known that these two elements constitute roughly 95% of the matter in the solar system. The high-pressure equation of He state doped with H is calculated in the framework of density functional theory (DFT) for three crystallographic structures. Namely, the Body Centered Cubic (BCC), Face Centered Cubic (FCC), and hexagonal close packed (HCP) structures have been studied. The equations of state (EOS) are provided for the He0.90H0.10 and He0.70H0.30 mixtures and the energy of the same mixtures are calculated with the earlier structures. The band structure for pressures of 0, 75 and 150 GPa were estimated by our calculations for the presumed crystal structures in the case of pure He and He0.70H0.30 mixture for comparison. The k(x) - k(y) cuts of the Bloch Spectral Functions (BSF) are presented for the pure He and He0.70H0.30 mixture for the three structures to explore the impact of doping on electronic properties. In addition, electrical resistivity calculations of the mentioned structures were carried out for mixtures with 10, 15, 20 and 30% of H. At final stage, the enthalpy (Delta H) of these latest mixtures have been deduced for the three crystal structures.

  • 16752.
    Zidane, Mustapha
    et al.
    Mohammed V Univ, Lab Condensed Matter & Interdisciplinary Sci, Dept Phys, Fac Sci, Rabat, Morocco..
    Salmani, El Mehdi
    Mohammed V Univ, Lab Condensed Matter & Interdisciplinary Sci, Dept Phys, Fac Sci, Rabat, Morocco..
    Majumdar, Arnab
    Uppsala Univ, Dept Phys & Astron, Mat Theory Div, SE-75121 Uppsala, Sweden..
    Ez-Zahraouy, Hamid
    Mohammed V Univ, Lab Condensed Matter & Interdisciplinary Sci, Dept Phys, Fac Sci, Rabat, Morocco..
    Benyoussef, Abdelilah
    Mohammed V Univ, Lab Condensed Matter & Interdisciplinary Sci, Dept Phys, Fac Sci, Rabat, Morocco.;MAScIR Fdn, Rabat Design Ctr, Mat & Nanomat Ctr, Rue Mohamed Al Jazouli Madinat Al Irfane, Rabat 10100, Morocco.;Hassan II Acad Sci & Technol, Rabat, Morocco..
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Egenskaper. Uppsala Univ, Dept Phys & Astron, Mat Theory Div, SE-75121 Uppsala, Sweden..
    Electrical and thermal transport properties of Fe-Ni based ternary alloys in the earth's inner core: An ab initio study (vol 301, pg 106465, 2020)2021Ingår i: Physics of the Earth and Planetary Interiors, ISSN 0031-9201, E-ISSN 1872-7395, Vol. 312, artikel-id 106671Artikel i tidskrift (Refereegranskat)
  • 16753.
    Zidane, Mustapha
    et al.
    Mohammed V Univ, Unite Rech Labellisee CNRST, Lab Condensed Matter & Interdisciplinary Sci LaMC, Rabat, Morocco..
    Salmani, El Mehdi
    Mohammed V Univ, Unite Rech Labellisee CNRST, Lab Condensed Matter & Interdisciplinary Sci LaMC, Rabat, Morocco..
    Majumdar, Arnab
    Uppsala Univ, Dept Phys & Astron, Mat Theory Div, SE-75121 Uppsala, Sweden..
    Syad, Badr Ait
    Mohammed V Univ, Unite Rech Labellisee CNRST, Lab Condensed Matter & Interdisciplinary Sci LaMC, Rabat, Morocco..
    Ez-Zahraouy, Hamid
    Mohammed V Univ, Unite Rech Labellisee CNRST, Lab Condensed Matter & Interdisciplinary Sci LaMC, Rabat, Morocco..
    Benyoussef, Abdelilah
    Mohammed V Univ, Unite Rech Labellisee CNRST, Lab Condensed Matter & Interdisciplinary Sci LaMC, Rabat, Morocco.;Hassan II Acad Sci & Technol, Rabat, Morocco..
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Egenskaper. Uppsala Univ, Dept Phys & Astron, Mat Theory Div, SE-75121 Uppsala, Sweden..
    Determination and comparison of the electrical and thermal transport properties of BCC and FCC Fe-Ni based ternary alloys in the Earth's inner core2022Ingår i: JOURNAL OF EARTH SYSTEM SCIENCE, ISSN 2347-4327, Vol. 131, nr 4, artikel-id 221Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Earth's core contains, in addition to iron, 5-10% nickel and many light elements such as C, O, Si and S, among others. For this work, we consider binary Fe-Ni alloys with 10% Ni as host material, doped with light elements as impurity atoms. The phases considered for the Fe-Ni host alloy are face-centered cubic (fcc) and body-centred cubic (bcc). At different concentrations of 2.5-50%, the impurity atoms C, O, Si and S were placed in the host Fe-Ni alloy to create ternary alloys. The resulting ternary systems are exposed to a pressure equivalent to that existing at the Earth's core. As shown by their formation energies, these alloys are stable and advantageous. The calculation of the resistivity of the impurities was performed with the help of the Kubo-Greenwood formula. Compared to fcc, in the case of bcc, electrical resistivities begin to saturate at about 30% of the atomic concentration of the impurities. Thermal conductivity was also determined from electrical resistivities calculated for varying concentrations and pressures according to Wiedemann-Franz law. In the case of compression, we observe a rise in thermal conductivity of about 1.5% of the core's internal pressure. The reported thermal conductivities support the notion of maintaining a convection-induced geodyanmo.

  • 16754. Zielińska, J. A.
    et al.
    Zukauskas, A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Noyan, M. A.
    Mitchell, M. W.
    Fully-resonant, tunable, monolithic frequency conversion as a coherent UVA source2017Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 25, nr 2, s. 1142-1150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a monolithic frequency converter incorporating up to four tuning degrees of freedom, three temperature and one strain, allowing resonance of pump and generated wavelengths simultaneous with optimal phase-matching. With a Rb-doped periodically-poled potassium titanyl phosphate (KTP) implementation, we demonstrate efficient continuous-wave second harmonic generation from 795 to 397, with low-power efficiency of 72% and high-power slope efficiency of 4.5%. The measured performance shows good agreement with theoretical modeling of the device. We measure optical bistability effects, and show how they can be used to improve the stability of the output against pump frequency and amplitude variations. 

  • 16755.
    Ziemann, Ingvar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Ziemann, Volker
    Uppsala Univ, S-75120 Uppsala, Sweden..
    Noninvasively improving the orbit-response matrix while continuously correcting the orbit2021Ingår i: Physical Review Accelerators and Beams, E-ISSN 2469-9888, Vol. 24, nr 7, artikel-id 072804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on continuously recorded beam positions and corrector excitations from, for example, a closedorbit feedback system we describe an algorithm that continuously updates an estimate of the orbit response matrix. The speed of convergence can be increased by adding very small perturbations, so-called dither, to the corrector excitations. Estimates for the rate of convergence and the asymptotically achievable accuracies are provided.

  • 16756. Zietz, Burkhard
    et al.
    Gabrielsson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Johansson, Viktor
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    El-Zohry, Ahmed M.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Photoisomerization of the cyanoacrylic acid acceptor group - a potential problem for organic dyes in solar cells2014Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 6, s. 2251-2255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic solar cell dyes containing the most common anchoring group, cyanoacrylic acid, are shown to be photolabile and undergo photoisomerization. This may have significant consequences for dye-sensitized solar cells, as isomerisation competes with electron injection and leads to modifications of the dye and surface arrangement.

  • 16757. Zimmermann, J
    et al.
    Scherer, H
    Kamp, M
    Deubert, S
    Reithmaier, J P
    Forchel, A
    Marz, R
    Anand, Srinivasan
    KTH, Tidigare Institutioner (före 2005), Elektronik.
    Photonic crystal waveguides with propagation losses in the 1 dB/mm range2004Ingår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 22, nr 6, s. 3356-3358Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-quality photonic crystal waveguides have been fabricated in the InGaAsP/InP and GaAs/AlGaAs material systems aimed at the communication wavelengths of 1.55 and 1.31 mum. The waveguides consist of omitted rows of holes in a triangular lattice of air holes etched into the semiconductor heterostructures by electron cyclotron resonance reactive ion etching. Efficient waveguiding has been observed in optical transmission measurements, with waveguide losses ranging from 1.5 dB/mm for a waveguide with three missing row of holes (W3) to 0.2 dB/mm for seven missing rows (W7). (C) 2004 American Vacuum Society.

  • 16758. Zisis, G.
    et al.
    Manzo, Michele
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Gallo, Katia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Soergel, E.
    Mailis, S.
    UV laser-induced poling inhibition in proton exchanged LiNbO3 crystals2017Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 123, nr 4, artikel-id 158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The applicability of the UV laser-induced poling inhibition method for ferroelectric domain engineering in proton exchanged lithium niobate planar waveguides is investigated. Our results indicate that intense UV irradiation of proton exchanged lithium niobate samples can, indeed, produce poling inhibited domains in this material under certain irradiation conditions. However, there is strong indication that the temperature gradient that is formed during UV irradiation modifies the local proton concentration leading to changes in the refractive index profile of the original planar waveguide.

  • 16759. Ziss, Dorian
    et al.
    Martin-Sanchez, Javier
    Lettner, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantnanofotonik.
    Halilovic, Alma
    Trevisi, Giovanna
    Trotta, Rinaldo
    Rastelli, Armando
    Stangl, Julian
    Comparison of different bonding techniques for efficient strain transfer using piezoelectric actuators2017Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, nr 13, artikel-id 135303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, strain transfer efficiencies from a single crystalline piezoelectric lead magnesium niobatelead titanate substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely, gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the "soft" SU8 bonding in comparison to the "hard" bonding via gold-thermo-compression. A comparison between the XRD results and FEM simulations allows us to explain this unexpected result with the presence of complex interface structures between the different layers.

  • 16760.
    Zlosnik, Tom
    et al.
    Czech Acad Sci, Inst Phys, CEICO, Slovance 1999-2, Prague 18221, Czech Republic..
    Urban, Federico
    Czech Acad Sci, Inst Phys, CEICO, Slovance 1999-2, Prague 18221, Czech Republic..
    Marzola, Luca
    NICPB, Ravala Pst 10, EE-10143 Tallinn, Estonia..
    Koivisto, Tomi S.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. NICPB, Ravala Pst 10, EE-10143 Tallinn, Estonia.
    Spacetime and dark matter from spontaneous breaking of Lorentz symmetry2018Ingår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 35, nr 23, artikel-id 235003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is shown that a spontaneously-broken gauge theory of the Lorentz group contains Ashtekar's chiral formulation of general relativity accompanied by dust. From this perspective, gravity is described entirely by a connection omega valued in the Lie algebra of the complexified Lorentz group and a Lorentz-charged scalar field tau. The model is 'pre-geometric' in the sense that the spacetime metric may be constructed only in the symmetry-broken regime. We speculate on the extent to which this dust may account for dark matter and on the behaviour of the theory in regimes where the symmetry is not broken.

  • 16761. Zoller, C. J.
    et al.
    Dentoni Litta, Eugenio
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Primetzhofet, D.
    Characterization of high-k dielectrics using MeV elastic scattering of He ions2015Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 347, s. 52-57Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a systematic comparison of two distinct ion-beam based methods for composition analysis of nanometer oxide films: ion-beam channeling and elastic scattering using nuclear resonances, both at MeV energies. Thin films of the technologically highly relevant high-k dielectrics HfO2 and HfAIO are characterized in the present study, with the additional aim of obtaining a better quantification of the Al content for the latter system. We show that both employed ion scattering methods enable a quantitative determination of the oxygen concentrations with typical uncertainties of about 5-10% in the oxygen fraction. The influence of various kinds of systematic inaccuracies in the evaluation procedure are discussed.

  • 16762.
    Zorrilla, Luc
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Beyond high mutation highrecombination limit in statisticalgenetics2021Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I examensarbetet behandlas modeller i populationsgenetik med två alleler per lokus. Modellerna beskiver hur en mängd genom ändras över tid under inflytande av naturligt urval, mutationer, rekombination och genetisk drift. Fokus ligger på en fas icke-egentlig linkagejämvikt (Quasi Linkage Equilibrium, QLE) med härledningar av Neher och Shraiman. Denna fas finns när rekombination är en snabb process relativt det naturliga urvalet, och förenklar dynamiken avsevärt jämfört med det allmäna fallet. Med användning av resultat som gäller i QLE samt direktkopplingsanalys (Direct Coupling Analysis, DCA) kan man härleda urvalslandskapet i vilket en population befinner sig i, särsklit epistaskoefficienter. Med användning av dessa ideer undersöker vi här i detalj ett samband mellan populationsstorlek, rekombantionshastighet och epistasspridning som beskriver var QLE slutar gälla, från ett DCA- inferens-perspektiv. Vi finner att det inte finns något klart samband mellan den kritiska rekombinationshastigheten och populationsstorleken, men som väntat ett linjärt förhållande mellan epistasvariationen och den kritiska rekombinationshastighete.

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  • 16763.
    Zorzato, Alberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Wannier Functions in non-Hermitian Systems2022Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The scope of this thesis is analyzing and characterizing certain gapless states in tight-binding non-Hermitian systems. We start by providing a pedagogical introduction to tight-binding theory, topological phases of matter, Wannier functions as real-space duals of Bloch functions and their properties, non-Hermitian systems and associated differences from standard Hermitian systems. Subsequently we show the possibility of extending pre-existing concepts of Hermitian quantum mechanics to non-Hermitian settings without losing predicting power over some peculiar observables. We conclude by providing numerical evidence for existence of certain topological states in finite one-dimensional and two-dimensional systems, also testing their robustness against symmetry-breaking and disorder.

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  • 16764.
    Zotov, Mikhail
    et al.
    Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
    Capel, Francesca
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Max Planck Institute for Physics, Föhringer Ring 6, Munich, D-80805, Germany.
    Wiencke, Lawrence
    Department of Physics, Colorado School of Mines, Golden, CO, 80401, USA.
    et al.,
    Neural Network Based Approach to Recognition of Meteor Tracks in the Mini-EUSO Telescope Data2023Ingår i: Algorithms, E-ISSN 1999-4893, Vol. 16, nr 9, artikel-id 448Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mini-EUSO is a wide-angle fluorescence telescope that registers ultraviolet (UV) radiation in the nocturnal atmosphere of Earth from the International Space Station. Meteors are among multiple phenomena that manifest themselves not only in the visible range but also in the UV. We present two simple artificial neural networks that allow for recognizing meteor signals in the Mini-EUSO data with high accuracy in terms of a binary classification problem. We expect that similar architectures can be effectively used for signal recognition in other fluorescence telescopes, regardless of the nature of the signal. Due to their simplicity, the networks can be implemented in onboard electronics of future orbital or balloon experiments.

  • 16765.
    Zou, Jiali
    et al.
    KTH.
    Gudowski, Waclaw
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Zhao, J.
    Chmielarz, B.
    Study of minor actinides transmutation in a lead-cooled fast reactor2019Ingår i: International Conference on Nuclear Engineering, Proceedings, ICONE, American Society of Mechanical Engineers (ASME) , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Feasibility studies were performed to investigate minor actinides (MAs) transmutation in a 700MWth lead-cooled fast reactor through SERPENT Monte Carlo code. A mixture of nitrides of MAs, plutonium and depleted uranium was used. The mix was based on the spent fuel of Light Water Reactors (LWRs) with burnup of 33GWd/tHM and cooling for 10 years. A simple fuel method of 83at.% used uranium and 17at.% transuranic waste(TRU) with no separation of plutonium from americium was carried out to burn about 34kg MAs in one 5-year fuel cycle, which indicates that the lead-cooled fast reactor has a great potential to transmute MAs. Different MA contents from 0at.% up to 12at.% in fuel, with the initial plutonium loading mass retained were calculated to investigate the effects on transmutation and core performance. The results show that with the addition of MA loading the initial effective multiplication factor decreases but the burnup reactivity swing is lower. The fuel burnup is prolonged to allow more MA nuclides to burn. It is apparent that increasing MA content can improve the MA transmutation performance. Closer inspection shows that the reduction of MA is mainly attributed to the reduction of neptunium and americium, in contrast, the curium inventory increases. It is known that the MA loading amount in fast reactor is limited by the reactor safety performance degradation. This study focuses on the impact of MA on the effective delayed neutron fraction, which is an important parameter for reactor control operation. It is found that the addition of MAs has a negative influence on the effective delayed neutron fraction, decreasing it approximately linearly to their addition. In summary, efficient MA transmutation can be in the lead-cooled faster reactor achieved even when the effect of MA addition on safety performance is accounted for.

  • 16766.
    Zou, Kai
    et al.
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Hao, Zifan
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Feng, Yifan
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Meng, Yun
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Hu, Nan
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Steinhauer, Stephan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Gyger, Samuel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Hu, Xiaolong
    Tianjin Univ, Sch Precis Instrument & Optoelect Engn, Tianjin 300072, Peoples R China.;Minist Educ, Key Lab Optoelect Informat Sci & Technol, Tianjin 300072, Peoples R China..
    Fractal superconducting nanowire single-photon detectors working in dual bands and their applications in free-space and underwater hybrid LIDAR2023Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 48, nr 2, s. 415-418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a fiber-coupled fractal superconducting nanowire single-photon detector (SNSPD) system with minimum polarization dependence of detection efficiency. Its system detection efficiency (SDE) was maximized at the wavelength of 1540 nm, which was measured to be 91 +/- 4%; furthermore, we observed the second local maximum of SDE at the wavelength of 520 nm, which was measured to be 61 +/- 2%. This dual-band feature of SDE was due to the enhancement of the optical absorptance by two longitudinal resonance modes of the micro-cavity. By using high SDE with minimum polarization dependence in these two bands, we implemented a hybrid LIDAR for imaging the remote objects in free space and under water.

  • 16767.
    Zou, Kai
    et al.
    School of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Optoelectronic Information Science and Technology, Ministry of Education, Tianjin 300072, China.
    Meng, Yun
    School of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Optoelectronic Information Science and Technology, Ministry of Education, Tianjin 300072, China.
    Hu, Nan
    School of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Optoelectronic Information Science and Technology, Ministry of Education, Tianjin 300072, China.
    Feng, Yifang
    School of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Optoelectronic Information Science and Technology, Ministry of Education, Tianjin 300072, China.
    Hao, Zifan
    School of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Optoelectronic Information Science and Technology, Ministry of Education, Tianjin 300072, China.
    Gyger, Samuel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Steinhauer, Stephan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Hu, Xiaolong
    School of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China; Key Laboratory of Optoelectronic Information Science and Technology, Ministry of Education, Tianjin 300072, China.
    Superconducting Nanowire Single-Photon Detectors and Multi-Photon Detectors2022Ingår i: Optics InfoBase Conference Papers, Optica Publishing Group (formerly OSA) , 2022, artikel-id QW3B.1Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present our research progress in superconducting nanowire single-photon detectors (SNSPDs) and multi-photon detectors (SNMPDs), including fractal SNSPDs with reduced polarization sensitivity, two mechanisms of device timing jitter, and SNMPDs integrated with current reservoirs.

  • 16768.
    Zou, Yuqin
    et al.
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Yuan, Shuai
    Renmin Univ China, Dept Chem, Beijing 100872, Peoples R China..
    Buyruk, Ali
    Univ Munich LMU, Chair Phys Chem, Dept Chem, D-81377 Munich, Germany.;Univ Munich LMU, Ctr NanoSci CeNS, D-81377 Munich, Germany..
    Eichhorn, Johanna
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Yin, Shanshan
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Reus, Manuel A.
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Xiao, Tianxiao
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Pratap, Shambhavi
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Liang, Suzhe
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Weindl, Christian L.
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Chen, Wei
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany..
    Mu, Cheng
    Renmin Univ China, Dept Chem, Beijing 100872, Peoples R China..
    Sharp, Ian D.
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Ameri, Tayebeh
    Univ Munich LMU, Chair Phys Chem, Dept Chem, D-81377 Munich, Germany.;Univ Munich LMU, Ctr NanoSci CeNS, D-81377 Munich, Germany..
    Schwartzkopf, Matthias
    DESY, D-22607 Hamburg, Germany..
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. DESY, D-22607 Hamburg, Germany..
    Mueller-Buschbaum, Peter
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat, D-85748 Garching, Germany.;Tech Univ Munich, Heinz Maier Leibnitz Zentrum MLZ, D-85748 Garching, Germany..
    The Influence of CsBr on Crystal Orientation and Optoelectronic Properties of MAPbI(3)-Based Solar Cells2022Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 14, nr 2, s. 2958-2967Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Crystal orientations are closely related to the behavior of photogenerated charge carriers and are vital for controlling the optoelectronic properties of perovskite solar cells. Herein, we propose a facile approach to reveal the effect of lattice plane orientation distribution on the charge carrier kinetics via constructing CsBr-doped mixed cation perovskite phases. With grazing-incidence wide-angle X-ray scattering measurements, we investigate the crystallographic properties of mixed perovskite films at the microscopic scale and reveal the effect of the extrinsic CsBr doping on the stacking behavior of the lattice planes. Combined with transient photocurrent, transient photovoltage, and space-charge-limited current measurements, the transport dynamics and recombination of the photogenerated charge carriers are characterized. It is demonstrated that CsBr compositional engineering can significantly affect the perovskite crystal structure in terms of the orientation distribution of crystal planes and passivation of trap-state densities, as well as simultaneously facilitate the photogenerated charge carrier transport across the absorber and its interfaces. This strategy provides unique insight into the underlying relationship between the stacking pattern of crystal planes, photogenerated charge carrier transport, and optoelectronic properties of solar cells.

  • 16769.
    Zouganelis, I.
    et al.
    ESAC, European Space Agcy, Camino Bajo Castillo S-N, Madrid, Spain..
    Vaivads, Andris
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Rymd- och plasmafysik.
    Zhukov, A. N.
    Royal Observ Belgium, SIDC, Solar Terr Ctr Excellence, Ringlaan 3 Av Circulaire, B-1180 Brussels, Belgium.;Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia..
    et al.,
    The Solar Orbiter Science Activity Plan: Translating solar and heliospheric physics questions into action2020Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 642, artikel-id A3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed.

  • 16770.
    Zrake, Jonathan
    et al.
    Columbia Univ, Phys Dept, 538 West 120th St, New York, NY 10027 USA.;Columbia Univ, Columbia Astrophys Lab, 538 West 120th St, New York, NY 10027 USA..
    Beloborodov, Andrei M.
    Columbia Univ, Phys Dept, 538 West 120th St, New York, NY 10027 USA.;Columbia Univ, Columbia Astrophys Lab, 538 West 120th St, New York, NY 10027 USA.;Max Planck Inst Astrophys, Karl Schwarzschild Str 1, D-85741 Garching, Germany..
    Lundman, Christoffer
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova, Oskar Klein Ctr Cosmoparticle Phys, SE-10691 Stockholm, Sweden..
    Subphotospheric Turbulence as a Heating Mechanism in Gamma-Ray Bursts2019Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 885, nr 1, artikel-id 30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine the possible role of turbulence in feeding the emission of gamma-ray bursts (GRBs). Turbulence may develop in a GRB jet as the result of hydrodynamic or current-driven instabilities. The jet carries dense radiation and the turbulence cascade can be damped by Compton drag, passing kinetic fluid energy to photons through scattering. We identify two regimes of turbulence dissipation: (1) "Viscous"-the turbulence cascade is Compton-damped on a scale l(damp) greater than the photon mean free path l(star). Then turbulence energy is passed to photons via bulk Comptonization by smooth shear flows on scale l(star) < l(damp). (2) "Collisionless"-the cascade avoids Compton damping and extends to microscopic plasma scales much smaller than l(star). The collisionless dissipation energizes plasma particles, which radiate the received energy; how the dissipated power is partitioned between particles needs further investigation with kinetic simulations. We show that the dissipation regime switches from viscous to collisionless during the jet expansion, at a critical value of the jet optical depth, which depends on the amplitude of turbulence. Turbulent GRB jets are expected to emit nonthermal photospheric radiation. Our analysis also suggests revisions of turbulent Comptonization in black hole accretion disks discussed in previous works.

  • 16771.
    Zubayer, Anton
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Ion Dynamics & Magnetic Order in 2D Honeycomb Materials2020Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
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  • 16772.
    Zubkins, Martins
    et al.
    Univ Latvia, Inst Solid State Phys, Kengaraga 8, LV-1063 Riga, Latvia..
    Vibornijs, Viktors
    Univ Latvia, Inst Solid State Phys, Kengaraga 8, LV-1063 Riga, Latvia..
    Strods, Edvards
    Univ Latvia, Inst Solid State Phys, Kengaraga 8, LV-1063 Riga, Latvia..
    Butanovs, Edgars
    Univ Latvia, Inst Solid State Phys, Kengaraga 8, LV-1063 Riga, Latvia..
    Bikse, Liga
    Univ Latvia, Inst Solid State Phys, Kengaraga 8, LV-1063 Riga, Latvia..
    Ottosson, Mikael
    Angstrom Lab, Dept Chem, Lagerhyddsvagen 1, SE-75120 Uppsala, Sweden..
    Hallén, Anders
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektronik och inbyggda system, Elektronik och inbyggda system.
    Gabrusenoks, Jevgenijs
    AGL Technol SIA, Smerla 3, LV-1006 Riga, Latvia..
    Purans, Juris
    Univ Latvia, Inst Solid State Phys, Kengaraga 8, LV-1063 Riga, Latvia..
    Azens, Andris
    AGL Technol SIA, Smerla 3, LV-1006 Riga, Latvia..
    Deposition of Ga2O3 thin films by liquid metal target sputtering2023Ingår i: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 209, s. 111789-, artikel-id 111789Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reports on the deposition of amorphous and crystalline thin films of Ga2O3 by reactive pulsed direct current magnetron sputtering from a liquid gallium target onto fused (f-) quartz and c plane (c-) sapphire sub-strates, where the temperature of the substrate is varied from room temperature (RT) to 800 degrees C. The deposition rate (up to 37 nm/min at RT on f-quartz and 5 nm/min at 800 degrees C on c-sapphire) is two to five times higher than the data given in the literature for radio frequency sputtering. Deposited onto unheated substrates, the films are X-ray amorphous. Well-defined X-ray diffraction peaks of 13-Ga2O3 start to appear at a substrate temperature of 500 degrees C. Films grown on c-sapphire at temperatures above 600 degrees C are epitaxial. However, the high rocking curve full width at half maximum values of X2.4-2.5 degrees are indicative of the presence of defects. A dense and void-free microstructure is observed in electron microscopy images. Composition analysis show stoichiometry close to Ga2O3 and no traces of impurities. The optical properties of low absorptance (<1%) in the visible range and an optical band gap of approximately 5 eV are consistent with the data in the literature for Ga2O3 films produced by other deposition methods.

  • 16773. Zubkov, M.
    et al.
    Stait-Gardner, T.
    Price, W. S.
    Stilbs, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Steady state effects in a two-pulse diffusion-weighted sequence2015Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, nr 15, artikel-id 154201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In conventional nuclear magnetic resonance (NMR) diffusion measurements a significant amount of experimental time is used up by magnetization recovery, serving to prevent the formation of the steady state, as in the latter case the manifestation of diffusion is modulated by multiple applications of the pulse sequence and conventional diffusion coefficient inference procedures are generally not applicable. Here, an analytical expression for diffusion-related effects in a two-pulse NMR experiment (e.g., pulsed-gradient spin echo) in the steady state mode (with repetition times less than the longitudinal relaxation time of the sample) is derived by employing a Fourier series expansion within the solution of the Bloch-Torrey equations. Considerations are given for the transition conditions between the full relaxation and the steady state experiment description. The diffusion coefficient of a polymer solution (polyethylene glycol) is measured by a two-pulse sequence in the full relaxation mode and for a range of repetition times, approaching the rapid steady state experiment. The precision of the fitting employing the presented steady state solution by far exceeds that of the conventional fitting. Additionally, numerical simulations are performed yielding results strongly supporting the proposed description of the NMR diffusion measurements in the steady state.

  • 16774. Zuin, M.
    et al.
    Dal Bello, S.
    Marrelli, L.
    Puiatti, M. E.
    Agostinetti, P.
    Agostini, M.
    Antoni, V.
    Auriemma, F.
    Barbisan, M.
    Barbui, T.
    Baruzzo, M.
    Belli, F.
    Bettini, P.
    Bigi, M.
    Bilel, R.
    Boldrin, M.
    Bolzonella, T.
    Bonfiglio, D.
    Brombin, M.
    Buffa, A.
    Bustreo, C.
    Canton, A.
    Cappello, S.
    Carraro, L.
    Cavazzana, R.
    Cester, D.
    Chacon, L.
    Chitarin, G.
    Cooper, W. A.
    Cordaro, L.
    Palma, M. Dalla
    Deambrosis, S.
    Delogu, R.
    De Lorenzi, A.
    De Masi, G.
    Dong, J. Q.
    Escande, D. F.
    Fassina, A.
    Felici, F.
    Ferro, A.
    Finotti, C.
    Franz, P.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Gaio, E.
    Ghezzi, F.
    Giudicotti, L.
    Gnesotto, F.
    Gobbin, M.
    Gonzalez, W. A.
    Grando, L.
    Guo, S. C.
    Hanson, J. D.
    Hirshman, S. P.
    Innocente, P.
    Jackson, J. L.
    Kiyama, S.
    Komm, M.
    Kudlacek, O.
    Laguardia, L.
    Li, C.
    Liu, B.
    Liu, S. F.
    Liu, Y. Q.
    Lopez-Bruna, D.
    Lorenzini, R.
    Luce, T. C.
    Luchetta, A.
    Maistrello, A.
    Manduchi, G.
    Mansfield, D. K.
    Marchiori, G.
    Marconato, N.
    Marcuzzi, D.
    Martin, P.
    Martines, E.
    Martini, S.
    Mazzitelli, G.
    McCormack, O.
    Miorin, E.
    Momo, B.
    Moresco, M.
    Narushima, Y.
    Okabayashi, M.
    Paccagnella, R.
    Patel, N.
    Pavei, M.
    Peruzzo, S.
    Pilan, N.
    Pigatto, L.
    Piovan, R.
    Piovesan, P.
    Piron, C.
    Piron, L.
    Predebon, I.
    Pucella, G.
    Rea, C.
    Recchia, M.
    Rizzolo, A.
    Rostagni, G.
    Ruset, C.
    Sajo-Bohus, L.
    Sakakita, H.
    Sanchez, R.
    Sarff, J. S.
    Sattin, F.
    Scarin, P.
    Schmitz, O.
    Schneider, W.
    Siragusa, M.
    Sonato, P.
    Spada, E.
    Spagnolo, S.
    Spolaore, M.
    Spong, D. A.
    Spizzo, G.
    Stevanato, L.
    Suzuki, Y.
    Taliercio, C.
    Terranova, D.
    Tudisco, O.
    Urso, G.
    Valente, M.
    Valisa, M.
    Vallar, M.
    Veranda, M.
    Vianello, N.
    Villone, F.
    Vincenzi, P.
    Visona, N.
    White, R. B.
    Xanthopoulos, P.
    Xu, X. Y.
    Yanovskiy, V.
    Zamengo, A.
    Zanca, P.
    Zaniol, B.
    Zanotto, L.
    Zhang, Y.
    Zilli, E.
    Overview of the RFX-mod fusion science activity2017Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, nr 10, artikel-id 102012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique flexibility in terms of accessible magnetic configurations. Axisymmetric and helically shaped reversed-field pinch equilibria have been studied, along with tokamak plasmas in a wide range of q(a) regimes (spanning from 4 down to 1.2 values). The full range of magnetic configurations in between the two, the so-called ultra-low q ones, has been explored, with the aim of studying specific physical issues common to all equilibria, such as, for example, the density limit phenomenon. The powerful RFX-mod feedback control system has been exploited for MHD control, which allowed us to extend the range of experimental parameters, as well as to induce specific magnetic perturbations for the study of 3D effects. In particular, transport, edge and isotope effects in 3D equilibria have been investigated, along with runaway mitigations through induced magnetic perturbations. The first transitions to an improved confinement scenario in circular and D-shaped tokamak plasmas have been obtained thanks to an active modification of the edge electric field through a polarized electrode. The experiments are supported by intense modeling with 3D MHD, gyrokinetic, guiding center and transport codes. Proposed modifications to the RFX-mod device, which will enable further contributions to the solution of key issues in the roadmap to ITER and DEMO, are also briefly presented.

  • 16775.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    QPM Devices in KTA and RKTP2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Even though KTiOPO4 (KTP) is considered to be one of the best nonlinear materials for quasi phase matched (QPM) frequency conversion in the visible and the near-infrared spectral regions, its use is often limited by poor material homogeneity, high ionic conductivity, a considerable linear absorption and photochromatic damage. On the other hand, the improved material homogeneity and the lower ionic conductivity of bulk Rb-doped KTP (RKTP) make this material an ideal alternative for fabrication of fine-pitch QPM gratings, while the arsenate isomorph KTiOAsO4 (KTA) promises a better performance in the green spectral region and adds the advantage of a wider transparency window in the infrared. Unfortunately, the available studies on these materials are limited and unable to answer the question whether RKTP and KTA are feasible alternatives to KTP in terms of periodic poling and optical performance. The optical performance of the QPM devices depends on the periodic poling quality, therefore, a detailed comprehension of domain-grating formation in the KTP isomorphs is highly desired. The goals of this thesis were to gain a better understanding of the periodic poling process in the KTP isomorphs, in order to study the specifics of ferroelectric domain engineering in KTA and RKTP, and to evaluate the optical performance of these isomorphs. Fine-pitch periodically poled structures were engineered both in KTA and RKTP crystals. It was demonstrated that QPM gratings with excellent quality and with periods as short as 8.49 μm can be fabricated in KTA crystals. Comparative transmission studies have shown that periodically poled KTA (PPKTA) crystals can be superior to KTP for QPM second harmonic generation in the visible spectral region due to lower linear absorption. It was also demonstrated that RKTP is a superior alternative to KTP for high-quality QPM grating fabrication. A consistent room-temperature periodic poling of 5 mm thick RKTP crystals with a period of 38.86 μm has been achieved. The obtained large aperture periodically poled RKTP (PPRKTP) crystals showed an outstanding QPM grating uniformity and excellent optical performance in optical parametric oscillator (OPO) applications. Moreover, it was shown that RKTP is less susceptible to blue-induced infrared absorption than KTP. Finally, a novel and a relatively simple method for self-assembling quasi-periodic sub-μm scale ferroelectric domain structure in RKTP crystals has been presented. It was shown that, after treatment in aqueous KOH/KNO3 solution, periodic poling of RKTP with planar electrodes resulted in one-dimensional ferroelectric domain structure with an average periodicity of 650±200 nm, extending over the whole 1 mm thick crystal. Such self-assembled structures in RKTP were used to demonstrate 5th order non-collinear QPM backward second harmonic generation.

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  • 16776.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Coetzee, Riaan Stuart
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Highly-efficient sub-µm periodically poled RKTP for mirrorless OPO: Fabrication, characterization and performance2018Ingår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a highly-reliable fabrication technique for sub-µm PPRKTP demonstrating periodicities as short as 500 nm. The crystals are used for counter-propagating three-wave mixing interactions with a conversion efficiency exceeding 50% and mJ-level output energy.

  • 16777.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Liljestrand, Charlotte
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Fabrication of sub-μm ferroelectric domain gratings for counter-propagating nonlinear interactions2016Konferensbidrag (Refereegranskat)
  • 16778.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Liljestrand, Charlotte
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Progress in Fabrication of sub-µm QPM Devices in Bulk Rb-doped KTP2012Konferensbidrag (Refereegranskat)
  • 16779.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Liljestrand, Charlotte
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Viotti, Anne-Lise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Highly-Efficient Cascaded Mirrorless OPO in Sub-mu m Periodically Poled RKTP Crystals2017Ingår i: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate low threshold mirrorless optical parametric oscillation in sub-mu m periodically poled RKTP crystals reaching an efficiency of 43%. The generated signal serves as a pump in a cascaded MOPO process in the same crystal.

  • 16780.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Liljestrand, Charlotte
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Viotti, Anne-Lise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Highly-efficient cascaded mirrorless OPO in sub-μm periodically poled RKTP crystals2017Ingår i: Optics InfoBase Conference Papers, Optical Society of America, 2017, Vol. Part F41Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate low threshold mirrorless optical parametric oscillation in sub-μm periodically poled RKTP crystals reaching an efficiency of 43%. The generated signal serves as a pump in a cascaded MOPO process in the same crystal.

  • 16781.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Quasi-periodic self-assembled sub-micrometer ferroelectric bulk domain gratings in Rb-doped KTiOPO42013Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, nr 25, s. 252905-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a simple technique for fabricating quasi-periodic bulk sub-μm ferroelectric domain gratings in Rb-doped KTiOPO4 (RKTP) based on self-organized ferroelectric domain formation. One-dimensional ferroelectric domain structures, with an average periodicity of 650 ± 200 nm and extending throughout 1 mm thick crystals, are obtained by etching and subsequent electric field poling using planar electrodes. The sub-μm structures in RKTP were used to demonstrate 5th order non-collinear quasi-phase matched backward second harmonic generation.

  • 16782.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Second-harmonic generation in periodically poled bulk Rb-doped KTiOPO4 below 400 nm at high peak-intensities2013Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 21, nr 2, s. 1395-1403Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate that bulk Rb-doped KTiOPO4 (RKTP) shows improved susceptibility to gray-tracking compared to flux-grown KTiOPO4. We show high-fidelity periodic poling of 1 mm thick RKTP with a period of 3.18 mu m for second harmonic generation at 398 nm with a normalized conversion efficiency of 1.79%/Wcm. The crystal is used to frequency-double 138 fs-long pulses with an efficiency of 20% and a peak intensity of 560 MW/cm(2) without visible gray-tracking signs. We demonstrate that two-photon absorption is the predominant mechanism limiting the SHG efficiency in this spectral range at high peak powers and high repetition rates.

  • 16783.
    Zukauskas, Andrius
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Fan-out periodically poled structures in Rb-doped KTiOPO4 for continuously tunable QPM devices2019Ingår i: NONLINEAR FREQUENCY GENERATION AND CONVERSION: MATERIALS AND DEVICES XVIII / [ed] Schunemann, PG Schepler, KL, SPIE-INT SOC OPTICAL ENGINEERING , 2019, artikel-id UNSP 109020NKonferensbidrag (Refereegranskat)
    Abstract [en]

    Since the first demonstration of electric field poling in 1993, the use of quasi-phase matching (QPM) technique has gained wide adoption in a multitude of applications. The QPM field today is dominated mainly by the ferroelectric oxide materials from LiNbO3 (LN) and KTiOPO4 (KTP) families, where QPM structures are implemented by the electric field poling technique. While typical QPM devices have a fixed-period, one-dimensional domain grating design, which is the most straightforward to implement, numerous applications require the ability to continuously tune the wavelength over a wider spectral range. For applications where temperature tuning is not desired, a fan-out QPM grating design may be advantageous. The tuning here is performed by transverse translation of the structure in respect to the pump beam, while keeping the crystal temperature constant. While the implementation of fan-out gratings is reasonably well researched in LN, there is a lack of reliable data for KTP isomorphs. Taking into account the high domain growth anisotropy in KTP, an important factor becomes the angle between the domain walls and the b-axis of the crystal. This angle directly affects the quality and dimensions of the QPM device. However, its upper boundary has not been determined to date. In this work we discuss the prospects and limitations of PPKTP devices with fan-out grating designs. We present a fan-out PPRKTP device, where the transverse fan-out rate is 0.5 mu m/mm. In an OPO configuration pumped by 532 nm such PPRKTP crystal is able to provide continuously tunable radiation between 0.7 -2.2 mu m.

  • 16784.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Royal Inst Technol, Dept Appl Phys, S-10691 Stockholm, Sweden..
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Grey-Track Resistant Periodically Poled Rb-doped KTiOPO(4) For Blue-Light Generation2010Ingår i: 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS), IEEE , 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present periodic poling of Rb-doped KTiOPO(4). The crystal is used to obtain blue radiation at 398 nm with an efficiency of 30% and a peak intensity of 2 MW/cm(2) without grey-tracking.

  • 16785.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Grey-Track Resistant Periodically Poled Rb-doped KTiOPO4 For Blue-Light Generation2010Ingår i: Optics InfoBase Conference Papers, 2010, s. 5500148-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present periodic poling of Rb-doped KTiOPO4. The crystal is used to obtain blue radiation at 398 nm with an efficiency of 30% and a peak intensity of 2 MW/cm2 without grey-tracking.

  • 16786.
    Zukauskas, Andrius
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Periodically poled KTiOAsO4 for second harmonic generation in the green region2013Ingår i: 2013 Conference on Lasers and Electro-Optics, CLEO 2013, IEEE Computer Society, 2013, s. 6833702-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present high-quality room temperature periodic poling of KTiOAsO4 with a period of 8.49 μm. The crystals are evaluated for SHG at 533 nm, and show deff = 10.5 pm/V and ηnorm = 1.19%/Wcm. OCIS codes: 190.4400 (Nonlinear optics, materials); 160.2260 (Ferroelectrics).

  • 16787.
    Zukauskas, Andrius
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Self-assembled ferroelectric nano-domain gratings in bulk RKTP2012Ingår i: 2012 Conference on Lasers and Electro-Optics, CLEO 2012, Institute of Electrical and Electronics Engineers (IEEE), 2012, s. 6325938-Konferensbidrag (Refereegranskat)
    Abstract [en]

     We present the fabrication of self-assembled bulk domain gratings of sub-μm periodicity in Rb-doped KTiOPO4 crystals. The structures are used to demonstrate QPM backwards propagating non-collinear second harmonic generation.

  • 16788.
    Zukauskas, Andrius
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Safinas, Maratas
    Ekspla Ltd..
    Michailovas, Andrejus
    Ekspla Ltd..
    High-Performance Periodically Poled Rb-doped KTP For Frequency Conversion In Blue/Green Region2010Ingår i: Conference digest, 2010Konferensbidrag (Refereegranskat)
  • 16789.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Strömqvist, Gustav
    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.
    Fokine, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Fabrication of submicrometer quasi-phase-matched devices in KTP and RKTP [Invited]2011Ingår i: Optical Materials Express, E-ISSN 2159-3930, Vol. 1, nr 7, s. 1319-1325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We review the techniques used for fabrication of bulk submicrometer ferroelectric domain gratings in KTiOPO4 (KTP) and demonstrate that bulk Rb-doped KTiOPO4 (RKTP) is an excellent candidate for implementation of dense domain gratings. Compared to KTP, RKTP presents predominant domain propagation along the polar c-direction, substantially reduced lateral domain broadening, and higher poling yield. As a result we obtain homogeneous sub-μm periodic poling of RKTP with a period of 690 nm in 1 mm thick samples.

  • 16790.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    5 mm Thick periodically poled rb: KTiOPO4 for high power optical frequency conversion2011Ingår i: Optics InfoBase Conference Papers, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    A periodically poled bulk Rb-doped KTiOPO4 crystal with 5 mm aperture was fabricated at room temperature. The ferroelectric domain structure is shown to be homogeneous across the whole aperture with a deff of 11 pm/V.

  • 16791.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    5 mm thick periodically poled Rb-doped KTP for high energy optical parametric frequency conversion2011Ingår i: Optical Materials Express, E-ISSN 2159-3930, Vol. 1, nr 2, s. 201-206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 5 mm thick periodically poled bulk Rb-doped KTiOPO4 (KTP) crystal with a period of 38.86 μm was fabricated by electric field poling. Chemical etching and optical evaluation show a high quality of the periodic ferroelectric domain structure through the whole crystal aperture. The fabricated quasi-phase matching (QPM) device was used in an optical parametric oscillator pumped at 1064 nm with 12 ns pulses at 100 Hz repetition rate to generate 60 mJ parametric radiation with a conversion efficiency of 50%.

  • 16792.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    5 mm Thick Periodically Poled Rb:KTiOPO4 for High Power Optical Frequency Conversion2011Ingår i: Advanced Solid State Photonics 2011, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    A periodically poled bulk Rb-doped KTiOPO 4crystal with 5 mm aperture was fabricated at room temperature. The ferroelectric domain structure is shown to be homogeneous across the whole aperture with a deffof 11 pm/V.

  • 16793.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    High fidelity large aperture periodically poled Rb:KTiOPO4 for high energy frequency conversion2011Ingår i: Optics InfoBase Conference Papers, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate periodic poling of 5 mm thick Rb-doped KTiOPO4 crystals at room temperature. The ferroelectric domain grating is shown to be uniform and homogeneous across the whole crystal aperture.

  • 16794.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    High Fidelity Large Aperture Periodically Poled Rb:KTiOPO(4) for High Energy Frequency Conversion2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate periodic poling of 5 mm thick Rb-doped KTiOPO(4) crystals at room temperature. The ferroelectric domain grating is shown to be uniform and homogeneous across the whole crystal aperture.

  • 16795.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Periodically poled KTiOAsO4 for highly efficient midinfrared optical parametric devices2009Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, nr 19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate high pattern-fidelity periodic poling of KTiOAsO4 at room temperature. The periodically poled crystal shows a d(eff) of 10.1 pm/V and is used in an optical parametric oscillator pumped at 1064 nm to generate parametric radiation at 1538 and 3452 nm with a conversion efficiency of 45%.

  • 16796.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    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.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Periodically Poled KTiOAsO4 For Mid-Infrared Light Generation2010Ingår i: Advanced Solid-State Photonics 2010, The Optical Society , 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    A periodically poled KTiOAsO4crystal was fabricated at room temperature. The poled crystal shows a deffof 10.1 pm/V and gives a parametric conversion efficiency of 45%.

  • 16797.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Viotti, Anne-Lise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Coetzee, Riaan Stuart
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Liljestrand, Charlotte
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Recent advances in sub-mu m PPKTP for non-linear interactions with counter-propagating photons2019Ingår i: NONLINEAR FREQUENCY GENERATION AND CONVERSION: MATERIALS AND DEVICES XVIII / [ed] Schunemann, PG Schepler, KL, SPIE-INT SOC OPTICAL ENGINEERING , 2019, artikel-id UNSP 109020GKonferensbidrag (Refereegranskat)
    Abstract [en]

    Mirrorless optical parametric oscillators (MOPO) represent a special class of parametric devices based on three-wave nonlinear interaction in which the generated photons counter-propagate. Owing to the phase-matching condition of the counter-propagating waves, MOPOs can sustain oscillation without mirrors and present unique and useful tuning and spectral properties. In this paper, we will review our recent advances in structuring technology to achieve quasi-phase matching periodicities as short as 500 nm in Rb-doped KTiOPO4, which are necessary to compensate for the large phase mismatch. We will also review the performance of MOPOs both in the ps- and ns- pumping regime. In the latter, our crystals reach single-pass conversion efficiencies exceeding 50%, with mJ-level output energies.

  • 16798.
    Zukauskas, Andrius
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Viotti, Anne-Lise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Liljestrand, Charlotte
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Cascaded counter-propagating nonlinear interactions inhighly-efficient sub-μm periodically poled crystals2017Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 8, artikel-id 8037Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mirrorless optical parametric oscillators (MOPOs) are very attractive parametric devices that rely on the nonlinear interaction of counter-propagating photons to inherently establish distributed feedback, without the use of external mirrors or surface coatings. These devices offer unique spectral and coherence properties that will benefit a large variety of applications ranging from spectroscopy to quantum communications. The major obstacle in exploiting their full potential is ascribed to the difficulty in engineering a nonlinear material in which the generation of counter-propagating waves can be phase matched. Here we present a reliable and consistent technique for fabrication of highly-efficient sub-micrometer periodically poled Rb-doped KTiOPO4. We experimentally demonstrate the first cascaded counter-propagating interactions in which the generated forward signal serves as a pump for a secondary MOPO process, reaching pump depletion larger than 60%. The cascaded process exemplifies the high efficiency of our nonlinear photonic structures. Our domain-engineering technique paves the way to realize counter-propagating schemes and devices that have been deemed unfeasible until now.

  • 16799.
    Zuleta, Marcelo
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Yu, Shun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Hagfeldt, Anders
    Monitoring N719 Dye Configurations on (1 x n)-Reconstructed Anatase (100) by Means of STM: Reversible Configurational Changes upon Illumination2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 16, s. 13236-13244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report experimental results concerning the STM imaging of cis-bis (isothiocyanate)-bis-(2,2'-bipyridyl-4,4'dicarboxylate)ruthenium(II)bis( tetrabutylammonium) dye (known as N719) adsorbed on a single crystal of anatase TiO2(100). The cleaning pretreatment, by sputtering and annealing, of TiO2(100) yields a reproducible (1 x n) surface reconstruction. Previous to dye deposition, TiO2 was covered with one monolayer of 4-tert-butylpyridine (4-TBP) in ultrahigh vacuum (UHV) in order to protect the surface against air contamination. N719 was subsequently deposited by dipping the crystal into the dye solution. 4-TBP was removed partially in the solution and totally by heating the sample to around 285-300 degrees C in UHV. The images of the deposited 4-TBP on TiO2(100) revealed a complete surface coverage showing three modes of adsorption on TiO2. The relatively uncomplicated desorption of 4-TBP enables the accommodation and chemisorption of most N719 molecules directly onto the TiO2 surface. The STM imaging of N719 was affected, in a reversible way, by illumination, because the quality of the image changed after a few hours in the dark or under illumination conditions. The results presented herein are discussed in terms of changes in molecular configurations and in open circuit potentials.

  • 16800.
    Zumalacarregui, Miguel
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Bellini, Emilio
    Sawicki, Ignacy
    Lesgourgues, Julien
    Ferreira, Pedro G.
    hi_class: Horndeski in the Cosmic Linear Anisotropy Solving System2017Ingår i: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, nr 8, artikel-id 019Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the public version of hi cl a ss (www . hiclass-code . net), an extension of the Boltzmann code CLASS to a broad ensemble of modifications to general relativity. In particular, hi cl a ss can calculate predictions for models based on Horndeski's theory, which is the most general scalar-tensor theory described by second-order equations of motion and encompasses any perfect-fluid dark energy, quintessence, Brans-Dicke, f( R) and covariant Galileon models. hi-class has been thoroughly tested and can be readily used to understand the impact of alternative theories of gravity on linear structure formation as well as for cosmological parameter extraction.

333334335336337338 16751 - 16800 av 16885
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