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  • 1.
    Anders, Berntson
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Analysis of coherent and incoherent interactions of amplitude shifted solitons in optical fibres1995Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 52, nr 5, s. 544-553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consequtive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak. 

  • 2.
    Anders, Berntson
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Analysis of coherent and incoherent interactions of amplitude shifted solitons in optical fibres1998Rapport (Annet vitenskapelig)
    Abstract [en]

    Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consecutive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak.

  • 3.
    Anders, Berntson
    et al.
    Aston University, UK; Chalmers University of Technology, Sweden.
    Doran, N. J.
    Aston University, UK.
    Forysiak, W.
    Aston University, UK.
    Nijhof, J. H. B.
    Aston University, UK.
    Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion1998Inngår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 23, nr 12, s. 900-902Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.

  • 4.
    Anders, Berntson
    et al.
    Aston University, UK.
    Doran, N. J.
    Aston University, UK.
    Forysiak, W.
    Aston University, UK.
    Nijhof, J. H. B.
    Aston University, UK.
    Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion1998Rapport (Annet vitenskapelig)
    Abstract [en]

    We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.

  • 5.
    Anders, Berntson
    et al.
    Chalmers University of Technology, Sweden.
    Malomed, Boris A.
    Chalmers University of Technology, Sweden.
    Dispersion management with filtering1998Rapport (Annet vitenskapelig)
    Abstract [en]

    We present results of analytical and numerical consideration of the pulses in a model of a DM fiber link including the fixed-frequency filters and compensating gain, both taken in the distributed approximation. Combining the variational approximation and perturbative treatment of the filtering and gain terms, we predict stationary propagation regimes. The most important new features are the absence of the minimum DM strength necessary for the existence of the pulses in the case when the average dispersion is nil or normal, and the existence of a minimum necessary normalized power in this case. These features are well corroborated by direct simulations.

  • 6.
    Anderson, D.
    et al.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Exact Schrödinger Solitons in Optical Fibers in the Presence of Space Dependent Damping or Amplification1999Inngår i: Physica scripta. T, ISSN 0281-1847, Vol. 82, s. 42-43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is shown that the nonlinear Schrödinger equation describing pulse propagation in optical fibers in the presence of a properly space-tailored damping or amplification is exactly integrable. A simple transformation of variables is given which transforms the inhomogeneous nonlinear Schrödinger equation into the standard form with constant coefficients, thus generating new explicit bright and dark soliton solutions in the cases of anomalous and normal dispersion, respectively.

  • 7.
    Anusuyadevi, Prasaanth
    et al.
    KTH Royal Institute of Technology, Sweden.
    Shanker, Ravi
    Linköping University, Sweden.
    Cui, Yuxiao
    KTH Royal Institute of Technology, Sweden.
    Riazanova, Anastasia
    KTH Royal Institute of Technology, Sweden.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Jonsson, Magnus
    Linköping University, Sweden.
    Svagan, Anna
    KTH Royal Institute of Technology, Sweden.
    Photoresponsive and Polarization-Sensitive Structural Colors from Cellulose/Liquid Crystal Nanophotonic Structures2021Inngår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 33, nr 36, artikkel-id 2101519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanocrystals (CNCs) possess the ability to form helical periodic structures that generate structural colors. Due to the helicity, such self-assembled cellulose structures preferentially reflect left-handed circularly polarized light of certain colors, while they remain transparent to right-handed circularly polarized light. This study shows that combination with a liquid crystal enables modulation of the optical response to obtain light reflection of both handedness but with reversed spectral profiles. As a result, the nanophotonic systems provide vibrant structural colors that are tunable via the incident light polarization. The results are attributed to the liquid crystal aligning on the CNC/glucose film, to form a birefringent layer that twists the incident light polarization before interaction with the chiral cellulose nanocomposite. Using a photoresponsive liquid crystal, this effect can further be turned off by exposure to UV light, which switches the nematic liquid crystal into a nonbirefringent isotropic phase. The study highlights the potential of hybrid cellulose systems to create self-assembled yet advanced photoresponsive and polarization-tunable nanophotonics. © 2021 The Authors.

  • 8.
    Axner, Ove
    et al.
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Forssén, Clayton
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Assessment of gas molar density by gas modulation refractometry: A review of its basic operating principles and extraordinary performance2021Inngår i: Spectrochimica Acta Part B - Atomic Spectroscopy, ISSN 0584-8547, E-ISSN 1873-3565, Vol. 179, artikkel-id 106121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A technique for high-precision and high-accuracy assessment of both gas molar (and number) density and pressure, Gas Modulation Refractometry (GAMOR), is presented. The technique achieves its properties by assessing refractivity as a shift of a directly measurable beat frequency by use of Fabry-Perot cavity (FPC) based refractometry utilizing the Pound-Drever-Hall laser locking technique. Conventional FPC-based refractometry is, however, often limited by fluctuations and drifts of the FPC. GAMOR remedies this by an additional utilization of a gas modulation methodology, built upon a repeated filling and evacuation of the measurement cavity together with an interpolation of the empty cavity responses. The procedure has demonstrated an ability to reduce the influence of drifts in a non-temperature stabilized dual-FPC (DFPC)-based refractometry system, when assessing pressure, by more than three orders of magnitude. When applied to a DFPC system with active temperature stabilization, it has demonstrated, for assessment of pressure of N2 at 4304 Pa at room temperature, which corresponds to a gas molar density of 1.7 × 10−6 mol/cm3, a sub-0.1 ppm precision (i.e. a resolution of 0.34 mPa). It is claimed that the ability to assess gas molar density is at least as good as so far has been demonstrated for pressure (i.e. for the molar density addressed, a resolution of at least 1.2 × 10−13 mol/cm3). It has recently been argued that the methodology should be capable of providing an accuracy that is in the low ppm range. These levels of precision and accuracy are unprecedented among laser-based techniques for detection of atomic and molecular species. Since the molar polarizability of He can be calculated by ab initio quantum mechanical calculations with sub-ppm accuracy, it can also be used as a primary or semi-primary standard of both gas molar (and number) density and pressure. © 2021 The Author(s)

  • 9.
    Bai, Xiaohong
    et al.
    Northwest University, China; Carleton University, Canada.
    Claesson, Åsa
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Laronche, Albane
    Carleton University, Canada.
    Liu, Fu
    Carleton University, Canada.
    Hu, Manli
    Northwest University, China.
    Albert, Jaques
    Carleton University, Canada.
    Sensing applications of fiber Bragg gratings in single mode fibers with as-drawn 25 μm diameter cladding2021Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 144, artikkel-id 107451Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sensing properties of fiber Bragg gratings (FBG) inscribed in single mode fiber with a 5 μm diameter core and 25 μm diameter cladding are studied experimentally for temperature, strain, bending, and surrounding refractive index. Compared to normal single mode fiber, the diameter of this fiber is 5 times smaller and it stretches 14.5 times more at the same applied load. Therefore, it is much more flexible and stretchable, while maintaining excellent optical quality at wavelengths near 1550 nm. In addition to a core mode back reflection resonance, strong FBGs inscribed in this fiber show a relatively small number of narrow bandwidth (0.7 nm) cladding mode resonances separated in wavelength by 2.5–6 nm. This relatively coarse spectral comb can then be used to sense many different kinds of perturbations involving core and cladding modes. In particular, unlike cladding-mode based sensors made from tilted FBGs, all resonances are of the same azimuthal order as the core mode (i.e. HE1m). This feature makes these gratings particularly sensitive to bending which causes the appearance of new resonances and reduced amplitudes of the original ones, each by up to 10 dB/mm−1 of curvature. On the other hand, the temperature sensitivities of all modes are similar to that of standard fiber (around 11 pm/oC) while strain sensitivities are somewhat higher (1.6–1.7 pm/μstrain). The surrounding refractive index sensitivity is also increased (by a factor of 3) over normal fiber, mostly due to the increased modal dispersion of the modes of the thinner cladding. Furthermore, it is possible to serially multiplex different gratings at different wavelengths by interleaving their resonance combs and preserving each grating identity in the combined spectrum.

  • 10.
    Cattani, F.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Effect of self-phase modulation in chirped-pulse-amplification-like schemes1999Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 16, nr 11, s. 1874-1879Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A detailed analytical investigation is made of the effect of nonlinear self-phase modulation in chirped-pulse-amplification-like schemes. It is demonstrated that self-phase modulation in the amplifier between the stretcher and the compressor breaks the dispersive sign symmetry of the configuration. This implies that, although self-phase modulation is usually considered a deleterious effect, different situations are possible, depending on the parameter regimes considered. In particular, the influence of self-phase modulation on the low-intensity wings of the compressed pulse may be more or less deleterious, depending on the dispersive sign combination of the stretcher and the compressor; in certain parameter regimes, it may in fact even enhance the pulse compression. 

  • 11.
    Coppel, L.G.
    et al.
    RISE., Innventia.
    Andersson, M.
    Edström, P.
    Determination of quantum efficiency in fluorescing turbid media2011Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, nr 17, s. 2784-2792Artikkel i tidsskrift (Fagfellevurdert)
  • 12.
    Coppel, L.G.
    et al.
    RISE., Innventia.
    Andersson, M.
    Edström, P.
    Kinnunen, J.
    Limitations in the efficiency of fluorescent whitening agents in uncoated paper2011Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, nr 3, s. 319-328Artikkel i tidsskrift (Fagfellevurdert)
  • 13.
    Coppel, L.G.
    et al.
    RISE., Innventia.
    Neuman, M.
    Edström, P.
    Extension of the Stokes equation for layered constructions to fluorescent turbid media2012Inngår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, nr 4, s. 574-578Artikkel i tidsskrift (Fagfellevurdert)
  • 14.
    Coppel, L.G.
    et al.
    RISE., Innventia.
    Neuman, M.
    Edström, P.
    Lateral light scattering in paper: MTF simulation and measurement2011Inngår i: Optics Express, E-ISSN 1094-4087, nr 25, s. 25181-25187Artikkel i tidsskrift (Fagfellevurdert)
  • 15.
    Coppel, Ludovic Gustafsson
    et al.
    Gjøvik University College, Norway.
    Andersson, Mattias
    Mid Sweden University, Sweden.
    Norberg, Ole
    Mid Sweden University, Sweden.
    Lindberg, Siv
    RISE., Innventia.
    Impact of illumination spectral power distribution on radiance factor of fluorescing materials2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The spectral radiance factor and thereby the appearance of fluorescing material is known to depend strongly on the spectral power distribution (SPD) of the illumination in the fluorophore's excitation wavelength band. The present work demonstrates the impact of the SPD in the fluorescence emission band on the total radiance factor. The total radiance factor of a fluorescing paper is measured in three different illuminations. The presence of peaks in the SPD of fluorescent light tubes dramatically decreases the luminescent radiance factor. This effect will impact the appearance of fluorescing media under illuminations with large variation in SPD, which includes recent LED illuminations.

  • 16.
    Coronel, Edvin
    et al.
    Universidade Federal de Pernambuco, Brazil.
    Das, Avishek
    Universidade Federal de Pernambuco, Brazil.
    Gonzalez, Ivan
    RISE Research Institutes of Sweden.
    Gomes, Anderson
    KTH Royal Institute of Technology, Sweden.
    Margulis, Walter
    Pontifical Catholic University of Rio de Janeiro, Brazil.
    Von Der Weid, JP
    Universidade Federal de Pernambuco, Brazil.
    Raposo, Ernesto
    Universidade Federal de Pernambuco, Brazil.
    Evaluation of Pearson correlation coefficient and Parisi parameter of replica symmetry breaking in a hybrid electronically addressable random fiber laser2021Inngår i: Optics Express, E-ISSN 1094-4087, Vol. 29, nr 15, s. 24422-24433Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hybrid electronically addressable random (HEAR) laser is a novel type of random fiber laser that presents the remarkable property of selection of the fiber section with lasing emission. Here we present a joint analysis of the correlations between intensity fluctuations at distinct wavelengths and replica symmetry breaking (RSB) behavior of the HEAR laser. We introduce a modified Pearson coefficient that simultaneously comprises both the Parisi overlap parameter and standard Pearson correlation coefficient. Our results highlight the contrast between the correlations and presence or not of RSB phenomenon in the spontaneous emission behavior well below threshold, replica-symmetric ASE regime slightly below threshold, and RSB phase with random lasing emission above threshold. In particular, in the latter we find that the onset of RSB behavior is accompanied by a stochastic dynamics of the lasing modes, leading to competition for gain intertwined with correlation and anti-correlation between modes in this complex photonic phase. 

  • 17.
    Culleton, Lucy
    et al.
    NPL National Physical Laboratory, UK.
    Di Meane, Elena
    NPL National Physical Laboratory, UK.
    Ward, Michael
    NPL National Physical Laboratory, UK.
    Ferracci, Valerio
    NPL National Physical Laboratory, UK.
    Persijn, Stefan
    VSL, Netherlands.
    Holmqvist, Albin
    RISE Research Institutes of Sweden, Säkerhet och transport, Kontroll och kalibrering.
    Arrhenius, Karine
    RISE Research Institutes of Sweden, Material och produktion, Kemi och Tillämpad mekanik.
    Murugan, Arul
    NPL National Physical Laboratory, UK.
    Brewer, Paul
    NPL National Physical Laboratory, UK.
    Characterization of Fourier Transform Infrared, Cavity Ring-Down Spectroscopy, and Optical Feedback Cavity-Enhanced Absorption Spectroscopy Instruments for the Analysis of Ammonia in Biogas and Biomethane2022Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 94, nr 44, s. 15207-15214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Novel traceable analytical methods and reference gas standards were developed for the detection of trace-level ammonia in biogas and biomethane. This work focused on an ammonia amount fraction at an upper limit level of 10 mg m-3(corresponding to approximately 14 μmol mol-1) specified in EN 16723-1:2016. The application of spectroscopic analytical methods, such as Fourier transform infrared spectroscopy, cavity ring-down spectroscopy, and optical feedback cavity-enhanced absorption spectroscopy, was investigated. These techniques all exhibited the necessary ammonia sensitivity at the required 14 μmol mol-1amount fraction. A 29-month stability study of reference gas mixtures of 10 μmol mol-1ammonia in methane and synthetic biogas is also reported. 

  • 18.
    Dimitrevski, K.
    et al.
    Chalmers University of Technology, Sweden.
    Reimhult, E.
    Chalmers University of Technology, Sweden.
    Svensson, E.
    Chalmers University of Technology, Sweden.
    Öhgren, A.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Quiroga-Teixeiro, M. L.
    Chalmers University of Technology, Sweden.
    Analysis of stable self-trapping of laser beams in cubic-quintic nonlinear media1998Inngår i: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 248, nr 5-6, s. 369-376Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A numerical and analytical analysis of two-dimensional laser beam propagation in cubic-quintic nonlinear optical media demonstrates the existence of stable stationary radially symmetric modes. By means of a variational method, involving super-Gaussian trial functions and Ritz optimization, approximate stationary solutions are obtained, showing very good agreement with numerical results, even in the strongly non-linear, almost saturated, regime. The stability of the stationary modes are verified by analytical analysis and by direct numerical simulations. 

  • 19.
    Dominguez, Armand
    et al.
    Lund University, Sweden.
    Borggren, Jesper
    Beamonics AB, Sweden.
    Xu, Can
    Beamonics AB, Sweden.
    Otxoterena, Paul
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Försth, Michael
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. Luleå University of Technology, Sweden.
    Leffler, Tomas
    Vattenfall AB, Sweden; Chalmers University of Technology, Sweden.
    Bood, Joakim
    Lund University, Sweden.
    A compact Scheimpflug lidar imaging instrument for industrial diagnostics of flames2023Inngår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 34, nr 7, artikkel-id 075901Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scheimpflug lidar is a compact alternative to traditional lidar setups. With Scheimpflug lidar it is possible to make continuous range-resolved measurements. In this study we investigate the feasibility of a Scheimpflug lidar instrument for remote sensing in pool flames, which are characterized by strong particle scattering, large temperature gradients, and substantial fluctuations in particle distribution due to turbulence. An extinction coefficient can be extracted using the information about the transmitted laser power and the spatial extent of the flame. The transmitted laser power is manifested by the intensity of the ‘echo’ from a hard-target termination of the beam located behind the flame, while the information of the spatial extent of the flame along the laser beam is provided by the range-resolved scattering signal. Measurements were performed in heptane and diesel flames, respectively. © 2023 The Author(s). 

  • 20.
    Duvefelt, Kenneth
    et al.
    KTH Royal Institute of Technology, Sweden.
    Olofsson, Ulf
    KTH Royal Institute of Technology, Sweden.
    Johannesson, Carl Michael
    KTH Royal Institute of Technology, Sweden.
    Skedung, Lisa
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, s. 389-394Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the main parameters affecting finger friction, friction-induced vibrations in the finger, and consequently tactility is surface topography. Recently Skedung et al. performed finger friction measurements on fine controlled surfaces. These surfaces were sinusoidal with wavelengths from 0.27 to 8.8 μm and amplitudes from 0.007 to 6 μm. Building on those tests an analytical model for the contact was developed to explain the differences in friction coefficient. The contact was modelled as trapezoids in a circular pattern pressed against a sinusoidal plane. Results showed that the calculated contact area and therefore friction coefficient corresponded well with the measurements. This model can be used to see how the different surface parameters influence friction.

  • 21.
    Fallqvist, Björn
    et al.
    KTH Royal Institute of Technology, Sweden.
    Fielden, Matthew L.
    KTH Royal Institute of Technology, Sweden.
    Pettersson, Torbjörn
    KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Kroon, Martin
    KTH Royal Institute of Technology, Sweden.
    Gad, Annica K. B.
    Karolinska Institute, Sweden.
    Experimental and computational assessment of F-actin influence in regulating cellular stiffness and relaxation behaviour of fibroblasts2016Inngår i: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 59, s. 168-184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In biomechanics, a complete understanding of the structures and mechanisms that regulate cellular stiffness at a molecular level remain elusive. In this paper, we have elucidated the role of filamentous actin (F-actin) in regulating elastic and viscous properties of the cytoplasm and the nucleus. Specifically, we performed colloidal-probe atomic force microscopy (AFM) on BjhTERT fibroblast cells incubated with Latrunculin B (LatB), which results in depolymerisation of F-actin, or DMSO control. We found that the treatment with LatB not only reduced cellular stiffness, but also greatly increased the relaxation rate for the cytoplasm in the peripheral region and in the vicinity of the nucleus. We thus conclude that F-actin is a major determinant in not only providing elastic stiffness to the cell, but also in regulating its viscous behaviour. To further investigate the interdependence of different cytoskeletal networks and cell shape, we provided a computational model in a finite element framework. The computational model is based on a split strain energy function of separate cellular constituents, here assumed to be cytoskeletal components, for which a composite strain energy function was defined. We found a significant influence of cell geometry on the predicted mechanical response. Importantly, the relaxation behaviour of the cell can be characterised by a material model with two time constants that have previously been found to predict mechanical behaviour of actin and intermediate filament networks. By merely tuning two effective stiffness parameters, the model predicts experimental results in cells with a partly depolymerised actin cytoskeleton as well as in untreated control. This indicates that actin and intermediate filament networks are instrumental in providing elastic stiffness in response to applied forces, as well as governing the relaxation behaviour over shorter and longer time-scales, respectively.

  • 22.
    Forssén, Clayton
    et al.
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Silander, I.
    Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, O.
    Umeå University, Sweden.
    Fabry-Perot-cavity-based refractometry without influence of mirror penetration depth2021Inngår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 39, nr 6, artikkel-id 065001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Assessments of refractivity in a Fabry-Perot (FP) cavity by refractometry often encompass a step in which the penetration depth of the light into the mirrors is estimated to correct for the fraction of the cavity length into which no gas can penetrate. However, as it is currently carried out, this procedure is not always coherently performed. Here, we discuss a common pitfall that can be a reason for this and provide a recipe on how to perform FP-cavity-based refractometry without any influence of mirror penetration depth. © 2021 Author(s).

  • 23.
    Fu, Ying
    et al.
    Halmstad University, Sweden.
    Yager, Tom
    University of Latvia, Latvia.
    Chikvaidze, George
    University of Latvia, Latvia.
    Iyer, Srinivasan
    Senseair AB, Sweden.
    Wang, Qin
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Time-Resolved FDTD and Experimental FTIR Study of Gold Micropatch Arrays for Wavelength-Selective Mid-Infrared Optical Coupling2021Inngår i: Sensors, E-ISSN 1424-8220, Vol. 21, nr 15, artikkel-id 5203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Infrared radiation reflection and transmission of a single layer of gold micropatch two-dimensional arrays, of patch length ∼1.0μm and width ∼0.2μm, have been carefully studied by a finite-difference time-domain (FDTD) method, and Fourier-transform infrared spectroscopy (FTIR). Through precision design of the micropatch array structure geometry, we achieve a significantly enhanced reflectance (85%), a substantial diffraction (10%), and a much reduced transmittance (5%) for an array of only 15% surface metal coverage. This results in an efficient far-field optical coupling with promising practical implications for efficient mid-infrared photodetectors. Most importantly we find that the propagating electromagnetic fields are transiently concentrated around the gold micropatch array in a time duration of tens of ns, providing us with a novel efficient near-field optical coupling.

  • 24.
    Hall, B.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Boyer, G.
    Ecole Polytechnique, France.
    Karlsson, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Ericsson Telecom AB, Sweden.
    Pump-probe collision in optical fibers: Four-wave-mixing induced frequency jump2001Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 18, nr 11, s. 1652-1658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation is made of ultrafast pump-probe pulse collisions near the zero-dispersion wavelength in an optical single-mode fiber. A steplike probe frequency shift is observed when the pump power is gradually increased. The magnitude of this frequency jump is shown to depend on the phase difference between the pulses. This new effect is investigated numerically and experimentally and is attributed to four-wave mixing.

  • 25.
    Helczynski, L.
    et al.
    Chalmers University of Technology, Sweden.
    Hall, B.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Ericsson Telecom AB, Sweden.
    Desaix, M.
    Cross Phase Modulation Induced Pulse Splitting - The Optical Axe2000Inngår i: Physica scripta. T, ISSN 0281-1847, Vol. 84, s. 81-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An analytical as well as numerical analysis is made of the dynamics induced on a weak signal wave pulse by a co-propagating strong pump wave pulse in a nonlinear Kerr medium. Emphasis is given to the situation where the group velocity dispersion and the non-linearity of the signal pulse have opposite signs. In this defocusing situation, it is demonstrated that the pump splits the signal pulse into two frequency shifted pulse fragments which separate in time, asymptotically with constant separation velocity. Explicit analytical predictions for the velocity of separation are obtained and corroborated by numerical simulations.

  • 26.
    Karlsson, Stefan
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Functional cover glass materials for solar energy applications2023Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Glass materials are essential in everyone’s life by enabling daylight to reach the interior of our buildings,being the primary component for communication via optical fibers and a key component in electronic devices as protective cover and/or dielectric material. It is also an essential component in solar energy applications which comprise, e.g., photovoltaics , solar thermal collectors, greenhouses and algae reactors, by acting as a protective and light transmitting barrier. Adding functionalities to glass in an intelligent way creates opportunities to enhance the properties of the glass material for its use. There are several possibilities to add functionalities and the wider concept Transparent Intelligence will be briefly introduced and how it can aid our efforts to overcome today’s societal challenges. Glass as a cover material for solar energy applications constitutes a significant part of the costs and isan important component for efficient light capture and protection to the environment. The research and development of cover glass for solar energy applications have so far received limited attention eventhough it is an important material for our future sustainable development. Recent research efforts have provided knowledge of which properties that needs to be optimized ‐ balancing efficiency, service lifetime and cost. The challenges of cover glass for different solar energy applications differs somewhat but all have in common the efficient solar light capture and protection to the environment. Thus, theknow‐how can be used in several different industrial sectors. The fundamentals of cover glasses for solarenergy applications as well as previous and on‐going project concepts will be presented. This includes i) state‐of‐the‐art of cover materials for greenhouses, ii) results on optimization of cover glass for photovoltaics, iii) initial results on how to provide both anti‐reflective and anti‐soiling properties,iv) results on broadband antireflective coatings for solar thermal energy, and v) other promising concepts. At last will some future challenges and needs be discussed, e.g., in relation to the concept ofideal material choices for PV.

  • 27.
    Karlsson, Stefan
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Zäll, Erik
    Umeå University, Sweden.
    Antireflektiv beläggning i världsklass ger effektivare solfångare2023Inngår i: GLAS, nr 4, s. 36-37Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    I ett nyligen avslutat forskningsprojekt har Absolicon Solar Collector tillsammans med RISE Research Institutes of Sweden och Umeå universitet utvecklat en ny toppmodern antireflektiv beläggning som kan göra Absolicons solfångare än mer effektiva. Nu siktar man på ett nytt projekt för att skala upp metoden.

    Fulltekst (pdf)
    fulltext
  • 28.
    Karlsson, Stefan
    et al.
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Material- och ytdesign.
    Österlund, Lars
    Uppsala University, Sweden.
    Anand, Srinivasan
    KTH Royal Institute of Technology, Sweden.
    Multifunktionella glasytor för solceller2023Inngår i: GLAS, nr 4, s. 38-39Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    I ett forskningsprojekt som kommer avslutas vid årsskiftet har framtidens multifunktionella glasytor för solceller utvecklats. Antireflektiva, UV-skyddande, fotokatalytiska och lättrengörliga glasytor är egenskaperna som glasytorna kommer att få. Forskningsidén baseras på tidigare kunskap ifrån forskning vid RISE, Uppsala universitet och KTH och förväntas leda till effektiva solceller med längre livslängd.

    Fulltekst (pdf)
    fulltext
  • 29.
    Leyssner, Felix
    et al.
    Engionic Femto Gratings GMBH, Germany.
    Myumyun, Erray
    Somni Corporation BV, Netherlands.
    Meijer, Eric
    Somni Corporation BV, Netherlands.
    Knoppers, Rik
    Somni Corporation BV, Netherlands.
    Daugherty, Tim
    Millar, Inc, USA.
    Stoker, Anne
    Millar, Inc, USA.
    Claesson, Åsa
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Nieuwland, Remco
    Somni Corporation BV, Netherlands.
    fs-IR laser point-by-point inscription of Fiber Bragg Gratings for a new generation of miniature sensors using novel 25μm diameter optical fibers2022Inngår i: Optics InfoBase Conference Papers, Optica Publishing Group (formerly OSA) , 2022Konferansepaper (Fagfellevurdert)
    Abstract [en]

    fs-point-by-point through the coating written FBGs as a basis for novel sensor concepts using 25μm optical fiber. fs-point-by-point FBGs in novel single mode fiber with a cladding diameter of 25μm have been produced in fiber that is 5 times smaller than conventional telecommunication optical fiber. The development opens the path to new sensor types including miniature pressure sensors with a diameter of only 330μm (1Fr.). © 2022 The Author(s).

  • 30.
    Liu, Xiaoyan
    et al.
    KTH Royal Institute of Technology, Sweden.
    Yun, Sang Ho
    Sungkyunkwan University, South Korea.
    Claesson, Per M.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. KTH Royal Institute of Technology, Sweden.
    Frictional behavior of micro-patterned silicon surface2015Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 456, s. 76-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A micro-patterned silicon surface, consisting of depressions with walls having a tilt angle of 30°, was created by photolithography followed by etching. The friction forces in single asperity contact acting between such a surface and an AFM tip was measured in air. This allowed elucidation of the validity of some common friction rules for this particular situation where a small tip traces a surface having roughness features that are significantly larger than the tip itself. The rules that was compared with our data were Amontons' first rule of friction stating that the friction force should be proportional to the load; Amontons' third rule stating that the friction force should be independent of sliding speed, and Euler's rule providing a relation between slope angle and friction coefficient. We found that both nanoscale surface heterogeneities and the μm-sized depressions affect friction forces, and considerable reproducible variations were found along a particular scan line. Nevertheless Amontons' first rule described average friction forces well. Amontons' third rule and Euler's rule were found to be less applicable to our system.

  • 31.
    Lobov, Gleb S.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Zhao, Yichen
    KTH Royal Institute of Technology, Sweden.
    Marinins, Aleksandrs
    KTH Royal Institute of Technology, Sweden.
    Yan, Max
    KTH Royal Institute of Technology, Sweden.
    Li, Jiantong
    KTH Royal Institute of Technology, Sweden.
    Toprak, Muhammet Sadaka
    KTH Royal Institute of Technology, Sweden.
    Sugunan, Abhilash
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Thylen, Lars
    Hewlett-Packard Laboratories, US; KTH Royal Institute of Technology, Sweden.
    Wosinski, Lech
    KTH Royal Institute of Technology, Sweden.
    Östling, Mikael
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution2015Inngår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 5, nr 11, s. 2642-2647Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nanofiber morphology of regioregular Poly-3- hexylthiophene (P3HT) is a 1D crystalline structure organized by π - π stacking of the backbone chains. In this study, we report the impact of electric field on the orientation and optical properties of P3HT nanofibers dispersed in liquid solution. We demonstrate that alternating electric field aligns nanofibers, whereas static electric field forces them to migrate towards the cathode. The alignment of nanofibers introduces anisotropic optical properties, which can be dynamically manipulated until the solvent has evaporated. Time resolved spectroscopic measurements revealed that the electro-optical response time decreases significantly with the magnitude of applied electric field. Thus, for electric field 1.3 V ·μm-1 the response time was measured as low as 20 ms, while for 0.65 V ·μm-1 it was 110-150 ms. Observed phenomenon is the first mention of P3HT supramolecules associated with electrooptical effect. Proposed method provides real time control over the orientation of nanofibers, which is a starting point for a novel practical implementation. With further development P3HT nanofibers can be used individually as an anisotropic solution or as an active component in a guest-host system.

  • 32.
    Lobov, Gleb S.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Zhao, Yichen
    KTH Royal Institute of Technology, Sweden.
    Marinins, Aleksandrs
    KTH Royal Institute of Technology, Sweden.
    Yan, Min
    KTH Royal Institute of Technology, Sweden.
    Li, Jiantong
    KTH Royal Institute of Technology, Sweden.
    Sugunan, Abhilash
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Thylén, Lars
    Hewlett-Packard Laboratories, US; KTH Royal Institute of Technology, Sweden.
    Wosinski, Lech
    KTH Royal Institute of Technology, Sweden.
    Östling, Mikael
    KTH Royal Institute of Technology, Sweden.
    Toprak, Muhammet S.
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Size impact of ordered P3HT nanofibers on optical anisotropy2016Inngår i: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 217, nr 9, s. 1089-1095Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofibers are dispersed in nonconducting solvent, they react to external alternate electric field by aligning along the field lines. This can be used to create layers of ordered nanofibers and is referred to as alternating current poling method. P3HT nanofibers with three different size distributions are fabricated, using self-assembly mechanism in marginal solvents, and used for the alignment studies. Anisotropic absorption of oriented 2 μm long nanofibers exponentially increases with the magnitude of applied field to a certain asymptotic limit at 0.8 V μm-1, while 100-500 nm long nanofibers respond to electric field negligibly. Effective optical birefringence of oriented 2 μm long nanofibers is calculated, based on the phase shift at 633 nm and the average layer thickness, to be 0.41. These results combined with further studies on real-time control over orientation of P3HT nanofibers in liquid solution or host system are promising in terms of exploiting them in electroabsorptive and electrorefractive applications.

  • 33.
    Lobov, Gleb S.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Zhao, Yichen
    KTH Royal Institute of Technology, Sweden.
    Marinins, Alexandrs
    KTH Royal Institute of Technology, Sweden.
    Yan, Min
    KTH Royal Institute of Technology, Sweden.
    Li, Jiantong
    KTH Royal Institute of Technology, Sweden.
    Sugunan, Abhilash
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Thylén, Lars
    Hewlett-Packard Laboratories, US; KTH Royal Institute of Technology, Sweden.
    Wosinski, Lech
    KTH Royal Institute of Technology, Sweden.
    Östling, Mikael
    KTH Royal Institute of Technology, Sweden.
    Toprak, Muhammet S.
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Dynamic manipulation of optical anisotropy of suspended Poly-3-hexylthiophene nanofibers2016Inngår i: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 4, nr 10, s. 1651-1656Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications.​.

  • 34.
    Lundberg, Martin
    et al.
    Lund University, Sweden.
    Samuelsson, Olof
    Lund University, Sweden.
    Hillberg, Emil
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Local voltage control in distribution networks using PI control of active and reactive power2022Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 212, artikkel-id 108475Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Overvoltage is becoming increasingly prevalent in distribution networks with high penetration of renewable distributed energy sources (DERs). Local control of converter-based resources is a flexible and scalable method to prevent this growing issue. Reactive power is used for voltage control in many local control schemes. However, the typical range of R/X ratios for distribution power lines indicates that mitigation of overvoltage often requires excessive amounts of reactive power. Complete reliance on reactive power thus limits the effectiveness of local control strategies. In this work we instead propose a method that combines enhanced power factor voltage control with upper voltage limit tracking using PI control. We develop a modelling framework and demonstrate the stability of the proposed method. We then simulate the nonlinear operation of two parallel PI controllers in a medium voltage test system. © 2022 The Authors

  • 35. Malmberg, F.
    et al.
    Lindblad, J.
    Östlund, C.
    RISE., Innventia.
    Almgren, K.M.
    RISE., Innventia.
    Gamstedt, E.K.
    RISE., Innventia.
    Measurement of fibrefibre contact in three-dimensional images of fibrous materials obtained from X-ray synchrotron microtomography2011Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, nr 1, s. 143-148Artikkel i tidsskrift (Fagfellevurdert)
  • 36.
    Malomed, B. A.
    et al.
    Tel Aviv University, Israel.
    Anders, Berntson
    Ericsson Telecom AB, Sweden.
    Propagation of an optical pulse in a fiber link with random-dispersion management2001Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 18, nr 9, s. 1243-1251Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model of a long optical communication line consisting of alternating segments with anomalous and normal dispersion, whose lengths are picked randomly from a certain interval, is considered. As the first stage of the analysis, we calculate small changes in parameters of a quasi-Gaussian pulse passing a double-segment cell by means of the variational approximation (VA) and we approximate the evolution of the pulse passing many cells by smoothed ordinary differential equations with random coefficients, which are solved numerically. Next we perform systematic direct simulations of the model. Simulations reveal slow long-scale dynamics of the pulse, frequently in the form of long-period oscillations of its width. It is thus found that the soliton is most stable in the case of zero path-average dispersion (PAD), less stable in the case of anomalous PAD, and least stable in the case of normal PAD. The soliton's stability also strongly depends on its energy, the soliton with low energy being much more robust than its high energy counterpart. 

  • 37.
    Malomed, B. A.
    et al.
    Chalmers University of Technology, Sweden; Tel Aviv University, Israel.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Florjanczyk, M.
    Chalmers University of Technology, Sweden; Optiwave Corporation, Canada .
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Decay of parametric solitons in a lossy medium with quadratic nonlinearity1996Inngår i: Pure and Applied Optics (Print edition) (United Kingdom), ISSN 0963-9659, Vol. 5, nr 6, s. 941-946Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An investigation is made into the evolution of two-wave solitons in a second-haimonic-generation system under the action of weak dissipation. Using the balance equation for the soliton energy and a previously developed variational approximation for its shape, a general evolutional equation is derived for the soliton parameters. The equation is solved explicitly for the asymptotic stage of the evolution 

  • 38.
    Murnieks, Rihards
    et al.
    Riga Technical University, Latvia.
    Salgals, Toms
    Riga Technical University, Latvia.
    Alnis, Janis
    University of Latvia, Latvia.
    Ostrovskis, Armands
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digitala system, Industriella system. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Brice, Inga
    University of Latvia, Latvia.
    Sedulis, Arvids
    Riga Technical University, Latvia; University of Latvia, Latvia.
    Draguns, Kristians
    University of Latvia, Latvia.
    Lyashuk, Ilya
    Riga Technical University, Latvia.
    Berkis, Roberts
    University of Latvia, Latvia; University of Innsbruck, Austria.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Bi, Toby
    Max Planck Institute, Germany; Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digitala system, Industriella system. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Porins, Jurgis
    Riga Technical University, Latvia.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Del' Haye, Pascal
    Max Planck Institute, Germany; Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Silica micro-rod resonator-based Kerr frequency comb for high-speed short-reach optical interconnects.2023Inngår i: Optics Express, E-ISSN 1094-4087, Vol. 31, nr 12, s. 20306-20320Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional data center interconnects rely on power-hungry arrays of discrete wavelength laser sources. However, growing bandwidth demand severely challenges ensuring the power and spectral efficiency toward which data center interconnects tend to strive. Kerr frequency combs based on silica microresonators can replace multiple laser arrays, easing the pressure on data center interconnect infrastructure. Therefore, we experimentally demonstrate a bit rate of up to 100 Gbps/λ employing 4-level pulse amplitude modulated signal transmission over a 2 km long short-reach optical interconnect that can be considered a record using any Kerr frequency comb light source, specifically based on a silica micro-rod. In addition, data transmission using the non-return to zero on-off keying modulation format is demonstrated to achieve 60 Gbps/λ. The silica micro-rod resonator-based Kerr frequency comb light source generates an optical frequency comb in the optical C-band with 90 GHz spacing between optical carriers. Data transmission is supported by frequency domain pre-equalization techniques to compensate amplitude–frequency distortions and limited bandwidths of electrical system components. Additionally, achievable results are enhanced with offline digital signal processing, implementing post-equalization using feed-forward and feedback taps.

  • 39. Neuman, M.
    et al.
    Coppel, L.G.
    RISE., Innventia.
    Edström, P.
    Angle resolved color of bulk scattering media2011Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, nr 36, s. 6555-6563Artikkel i tidsskrift (Fagfellevurdert)
  • 40. Neuman, M.
    et al.
    Coppel, L.G.
    RISE., Innventia.
    Edström, P.
    Point spreading in turbid media with anisotropic single scattering2011Inngår i: Optics Express, E-ISSN 1094-4087, nr 3, s. 1915-1920Artikkel i tidsskrift (Fagfellevurdert)
  • 41.
    Otxoterena Af Drake, Paul
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Andersson, Sven
    Chalmers University of Technology, Sweden.
    Andersson, Mats
    Chalmers University of Technology, Sweden.
    Two Dimensional Measurements of Soot Size and Concentration in Diesel Flames by Laser Based Optical Methods2022Inngår i: SAE Technical Paper Issue 202229 March 2022, SAE International , 2022, nr 2022Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Soot particle size, particle concentration and volume fraction were measured by laser based methods in optically dense, highly turbulent combusting diesel sprays under engine-like conditions. Experiments were done in the Chalmers High Pressure, High Temperature spray rig under isobaric conditions and combusting commercial diesel fuel. Laser Induced Incandescence (LII), Elastic Scattering and Light Extinction were combined quasi-simultaneously to quantify particle characteristics spatially resolved in the middle plane of a combusting spray at two instants after the start of combustion. The influence that fuel injection pressure, gas temperature and gas pressure exert on particle size, particle concentration and volume fraction were studied. Probability density functions of particle size and two-dimensional images of particle diameter, particle concentration and volume fraction concerning instantaneous single-shot cases and average measurements are presented. High injection pressure led to a reduction in the mean particle size, total number of particles and total amount of soot compared to a low injection pressure. Higher gas pressure resulted in larger amount of soot and larger soot particle size, with higher gas temperature having similar effects. 

  • 42.
    Pereira, Joao
    et al.
    KTH Royal Institute of Technology, Sweden.
    Grüner-Nielsen, Lars
    DTU Technical University of Denmark, Denmark.
    Rottwitt, Karsten
    DTU Technical University of Denmark, Denmark.
    Town, Graham
    Macquarie University, Australia.
    Laurell, Fredrik
    KTH Royal Institute of Technology, Sweden.
    Margulis, Walter
    KTH Royal Institute of Technology, Sweden; Fiberactivity Ltda, Brazil.
    Electrooptic control of the modal distribution in a silicate fiber2022Inngår i: Optics Express, E-ISSN 1094-4087, Vol. 30, nr 8, s. 12474-12483Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate the use of the electrooptic effect to control the propagation constant of the guided modes in silicate few mode fibers with internal electrodes. The electrooptic effect induces a perturbation of the fiber's refractive index profile that controls intermodal interference. To increase the electrooptic effect the silicate fibers are poled. The response time is in the nanosecond range. 

  • 43.
    Pereira, Joao
    et al.
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara. KTH Royal Institute of Technology, Sweden.
    Tarasenko, Oleksander
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Claesson, Åsa
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Laurell, Fredrik
    KTH Royal Institute of Technology, Sweden.
    Margulis, Walter
    KTH Royal Institute of Technology, Sweden; Fiberactivity Ltda, Brazil.
    Optical poling by means of electrical corona discharge2022Inngår i: Optics Express, E-ISSN 1094-4087, Vol. 30, nr 12, s. 20605-20613Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrical corona discharge is employed in this work to deposit ions on the surface of an optical fiber, creating a strong electric field that is used for poling. Green laser light propagating in the core frees photocarriers that are displaced by the poling field. The technique presented can induce a higher optical nonlinearity than previously obtained in traditional optical poling with internal metal electrodes. To date, a maximum second order nonlinearity 0.13 pm/V has been achieved for a 15 kV corona discharge bias. 

  • 44.
    Quiroga-Teixeiro, M. L.
    et al.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Michinel, H.
    Universidade de Vigo, Spain.
    Internal dynamics of nonlinear beams in their ground states: Short- and long-lived excitation1999Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 16, nr 10, s. 1697-1704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the dynamics of optical beams in a cubic (focusing)-quintic (defocusing) nonlinear medium. In particular, we have found that strong beams can show long-lived elliptical oscillations, whereas in other cases, i.e., for weak beams or cylindrical oscillations, the dynamics decay quickly. This finding explains the observed higher efficiency in the fusion of two strong beams. We have also investigated, numerically and analytically, the robustness of the beams to an initial phase chirp. 

  • 45.
    Quiroga-Teixeiro, M. L.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Compression of optical solitons by conversion of nonlinear modes1995Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 12, nr 6, s. 1110-1116Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One can transform an optical pulse containing higher-order soliton modes and/or radiation modes into a compressed almost ideal single-soliton pulse by passing it through an initial adaptive fiber of suitably chosen length and dispersion. Analytical approximations, in good agreement with numerical simulations, are found for the optimal values of the length and the dispersion of the adaptive fiber. The technique is applied to the case of nonadiabatically amplified soliton pulses, for which the transformation is shown to result in efficiently compressed soliton pulses. 

  • 46.
    Quiroga-Teixeiro, M. L.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Compression of optical solitons by conversion of nonlinear modes1998Rapport (Annet vitenskapelig)
    Abstract [en]

    One can transform an optical pulse containing higher-order soliton modes and/or radiation modes into a compressed almost ideal single-soliton pulse by passing it through an initial adaptive fiber of suitably chosen length and dispersion. Analytical approximations, in good agreement with numerical simulations, are found for the optimal values of the length and the dispersion of the adaptive fiber. The technique is applied to the case of nonadiabatically amplified soliton pulses, for which the transformation is shown to result in efficiently compressed soliton pulses.

  • 47.
    Quiroga-Teixeiro, M. L.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, Dan
    Chalmers University of Technology, Sweden.
    Andrekson, P. A.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Efficient soliton compression by fast adiabatic amplification1996Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 13, nr 4, s. 687-692Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper shows the possibility of obtaining fast, but still adiabatic, amplification of soliton pulses by using a rapidly increasing distributed amplification with scale lengths comparable with the characteristic dispersion length. Explicit expressions for the required distribution of this gain and the variation of the pulse width are given, and theoretical predictions have been verified by numerical simulations. The practical implementation of the compression scheme should be possible by using an active fiber with a doping proportional to the required gain distribution. A study was also made of how efficient compression of solitons can be obtained.

  • 48. Rasheed, Faiza
    et al.
    Newson, William R
    Plivelic, Tomas S
    Kuktaite, Ramune
    Hedenqvist, Mikael S
    Gällstedt, Mikael
    RISE., Innventia.
    Johansson, Eva
    Structural architecture and solubility of native and modified gliadin and glutenin proteins: non-crystalline molecular and atomic organization2014Inngår i: RSC Advances, E-ISSN 2046-2069, nr 4, s. 2051-2060Artikkel i tidsskrift (Fagfellevurdert)
  • 49.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Helgason, Óskar B.
    Chalmers University of Technology, Sweden.
    Durán, Vicente
    Jaume I University, Spain.
    Girardi, Marcello
    Chalmers University of Technology, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Active feedback stabilization of super-efficient microcombs in photonic molecules2024Inngår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 49, nr 9, s. 2325-2328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dissipative Kerr soliton (DKS) frequency combs, when generated within coupled cavities, exhibit exceptional performance concerning controlled initiation and power conversion efficiency. Nevertheless, to fully exploit these enhanced capabilities, it is necessary to maintain the frequency comb in a low-noise state over an extended duration. In this study, we demonstrate the control and stabilization of super-efficient microcombs in a photonic molecule. Our findings demonstrate that there is a direct relation between effective detuning and soliton power, allowing the latter to be used as a setpoint in a feedback control loop. Employing this method, we achieve the stabilization of a highly efficient microcomb indefinitely, paving the way for its practical deployment in optical communications and dual-comb spectroscopy applications. 

  • 50.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Ye, Z.
    Chalmers University of Technology, Sweden.
    Christensen, S.
    DTU Technical University of Denmark, Denmark.
    Lei, F.
    Chalmers University of Technology, Sweden.
    Twayana, K.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Schröder, J.
    Chalmers University of Technology, Sweden.
    Torres-Company, V.
    Chalmers University of Technology, Sweden.
    Nonlinear broadening of electro-optic frequency combs in all-normal dispersion Si3N4 waveguides2021Inngår i: Optics InfoBase Conference Papers, The Optical Society , 2021Konferansepaper (Fagfellevurdert)
12 1 - 50 of 63
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