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  • 51.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kleimann, P.
    LENAC, Univ.́ Claude Bernard Lyon-I, Villeurbanne.
    Norlin, B.
    Department of Information Technology, Mid-Sweden University, Sundsvall.
    Koskiahde, E.
    Metorex International Oy, Espoo.
    Valpas, K.
    Metorex International Oy, Espoo.
    Nenonen, S.
    Metorex International Oy, Espoo.
    Petersson, Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fröjdh, C.
    Department of Information Technology, Mid-Sweden University, Sundsvall.
    Metallized and oxidized silicon macropore arrays filled with a scintillator for CCD-based X-ray imaging detectors2004In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 51, no 3, p. 1001-1005Article in journal (Refereed)
    Abstract [en]

    Silicon charge-coupled devices (CCDs) covered with a scintillating film are now available on the market for use in digital medical imaging. However, these devices could still be improved in terms of sensitivity and especially spatial resolution by coating the CCD with an array of scintillating waveguides. In this paper, such waveguides were fabricated by first etching pores in silicon, then performing metallization or oxidation of the pore walls and finally filling the pores with CsI(TI). The resulting structures were observed using scanning electron microscopy and tested under X-ray exposure. Theoretical efficiencies of macropore arrays filled with CsI(TI) were also calculated, indicating that the optimal pore depth for metallized macropore arrays is about 80 mum while it is around 350 mum for oxidized ones. This result, together with the roughness of the metal coating, explains why lower SNR values were measured with the metallized macropores. Indeed, the macropore arrays had depths in the range of 210-390 mum, which is favorable to oxidized structures.

  • 52.
    Bagula, Antoine B
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Online traffic engineering: a hybrid IGP/MPLS routing approach2004In: Quality of Service in the Emerging Networking Panorama, SPRINGER-VERLAG BERLIN , 2004, Vol. 3266, p. 134-143Chapter in book (Other academic)
    Abstract [en]

    The dualism of IGP and MPLS routing has raised a debate separating the IP community into divergent groups expressing different opinions concerning how the future Internet will be engineered. This paper presents an on-line traffic engineering model which uses a hybrid IGP+MPLS routing approach to achieve efficient routing of flows in IP networks. The approach referred to as Hybrid assumes a network-design process where an optimal network configuration is built around optimality, reliability and simplicity. The IGP+MPLS routing approach is applied to compute paths for the traffic offered to a 50-node network. Simulation reveals performance improvements compared to both IGP and MPLS routing in terms of several performance parameters including routing optimality, network reliability and network simplicity.

  • 53.
    Bagula, Antoine B
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Online traffic engineering: the least interference optimization algorithm2004In: Proceedings of the ICC2004 conference, 2004Conference paper (Refereed)
  • 54. Baldantoni, Luca
    et al.
    Lundqvist, Henrik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Adaptive End-to-End FEC for Improving TCP Performance over Wireless Links2004In: 2004 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, 2004, p. 4023-4027Conference paper (Refereed)
    Abstract [en]

    TCP is a reliable transport protocol that has been tuned to perform well in networks where packet losses occur mostly because of congestion. However, wireless networks are different: TCP responds both to congestion-based and error-based losses by invoking a congestion control algorithm and reducing the sending rate, resulting in degraded end-to-end performance for wireless systems. We investigate a new end-to-end approach for improving TCP performance over lossy links by using adaptive, end-to-end forward error correction (FEC) for recovering losses and consequently avoiding the TCP back-off behaviour. Of course there is a clear trade-off between the capacity consumed by FEC and the gain achieved in the overall throughput. An adaptive algorithm is needed to calculate the optimum ratio of redundancy given the state of the connection. The sender uses feedback information from the receiver to dynamically tune the FEC parameters. Through simulations we evaluate the performance of TCP with end-to-end FEC in mixed wired and wireless networks. The simulation results show in different scenarios that the throughput can be significantly improved by adding end-to-end FEC to TCP. However, compared to other improved TCP variants such as Westwood+ the performance is not improved, hence a direct modification of TCP congestion control appears to be more efficient than adding end-to-end FEC.

  • 55. Barnes, W. L.
    et al.
    Björk, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Gerard, J. M.
    Jonsson, P.
    Wasey, J. A. E.
    Worthing, P. T.
    Zwiller, V.
    Solid-state single photon sources: light collection strategies2002In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 18, no 2, p. 197-210Article in journal (Refereed)
    Abstract [en]

    We examine the problem of efficiently collecting the photons produced by solid-state single photon sources. The extent of the problem is first established with the aid of simple physical concepts. Several approaches to improving the collection efficiency are then examined and are broadly categorized into two types. First are those based on cavity quantum dynamics, in which the pathways by which the source may emit a photon are restricted, thus channeling emission into one desired mode. Second are those where we try to reshape the free space modes into a target mode in an optimal way, by means of refraction, without fundamentally altering the way in which the source emits. Respectively, we examine a variety of microcavities and solid immersion lenses. Whilst we find that the micropillar microcavities offer the highest collection efficiency (similar to70%), choosing this approach may not always be appropriate due to other constraints. Details of the different approaches, their merits and drawbacks are discussed in detail.

  • 56. Barrios, C. A.
    et al.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Martinsson, H.
    Analysis of leakage current in GaAs/AlGaAs buried-heterostructure lasers with a semi-insulating GaInP: Fe burying layer2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, no 5, p. 2506-2517Article in journal (Refereed)
    Abstract [en]

    The leakage current in recently demonstrated GaAs/AlGaAs buried heterostructure (BH) lasers with a semi-insulating (SI) GaInP:Fe burying layer has been theoretically and experimentally analyzed. Calculated current-voltage characteristics of n-GaAs/SI-GaInP/n-GaAs and p-GaAs/SI-GaInP/p-GaAs planar configurations have been studied specially to assess the behavior of SI-GaInP:Fe under electron and hole injection. Two-dimensional potential profiles have been used to explain the leakage current mechanism in the SI-GaInP-buried lasers. Simulations reveal that the total leakage current decreases as the active trap concentration in the SI-GaInP:Fe burying layer is increased as expected, but the leakage current is strongly confined in the vicinity of the active region where the local leakage current density increases significantly as the trap density increases. It is found that the insertion of a n-GaInP hole blocking layer between the p-metal and the SI-GaInP layer decreases the total leakage current. Experimental light-current and current-voltage characteristics of fabricated lasers with and without an additional n-GaInP layer, and electroluminescence (EL) emitted from the burying GaInP:Fe layers corroborate qualitatively the simulations and demonstrate the benefits of using a n-GaInP layer for reducing leakage current in these type of lasers.

  • 57. Barrios, C. A.
    et al.
    Messmer, E. R.
    Holmgren, M.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    GaAs/AlGaAs buried heterostructure laser by wet etching and semi-insulating GaInP: Fe regrowth2000In: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 3, no 9, p. 439-441Article in journal (Refereed)
    Abstract [en]

    Selective regrowth of semi-insulating Ga0.51In0.49P:Fe (SI-GaInP:Fe) by hydride vapor-phase epitaxy around Al-containing wet etched laser mesas is used for the first time to fabricate a GaAs/AlGaAs buried heterostructure laser emitting at 808 nm. The reverse and forward current-voltage characteristics measured at different temperatures up to 80 degrees C indicate no serious leakage current problems. The performance of the laser shows that the SI-GaInP: Fe burying layer fulfills its function as a current and optical confinement layer. The fabrication procedure and the laser characteristics are presented.

  • 58. Barrios, C. A.
    et al.
    Messmer, E. R.
    Holmgren, M.
    Risberg, A.
    Halonen, J.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Epitaxially regrown GaAs/AlGaAs laser mesas with semi-insulating GaInP: Fe and GaAs : Fe2001In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 30, no 8, p. 987-991Article in journal (Refereed)
    Abstract [en]

    Selective regrowth of semi-insulating iron-doped Ga0.51In0.49P (SI-GaInP:Fe) and SI-GaAs:Fe around GaAs/AlGaAs mesas by hydride vapor phase epitaxy (HVPE) has been achieved. A HCl based in-situ cleaning procedure has been used to remove aluminum oxide from the etched walls of the mesas. Regrowth conducted without proper cleaning results in an irregular interface with voids. Regrowth morphology aspects are also presented. Our cleaning and regrowth methods have been used for fabricating GaAs/AlGaAs buried heterostructure in-plane lasers and vertical-cavity surface-emitting lasers.

  • 59. Barrios, C. A.
    et al.
    Messmer, E. R.
    Risberg, A.
    Carlsson, C.
    Halonen, J.
    Ghisoni, M.
    Larsson, A.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    GaAs/AlGaAs buried-heterostructure vertical-cavity surface-emitting laser with semi-insulating GalnP: Fe regrowth2000In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 36, no 18, p. 1542-1544Article in journal (Refereed)
    Abstract [en]

    The authors report the first results of a GaAs/AlGaAs buried-heterostructure vertical-cavity surface-emitting laser (VCSEL) with semi-insulating Ga0.51In0.49P:Fe (SI-GaInP:Fe) as the burying layer. Regrowth of SI-GaInP:Fe around 15 mu m diameter and 8 mu m tall VCSEL mesas was carried out by hydride vapour phase epitaxy (HVPE). Under room temperature continuous wave (CW) operation. the device exhibited a threshold current of 3.5mA, a differential quantum efficency of 33% and a light output power of 4.2mW. CW operation at temperatures up to 97 degrees C is also demonstrated.

  • 60. Baskar, K.
    et al.
    Sundgren, P.
    Douheret, O.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Surface morphology and localised states of GaInNAs single quantum wells grown by MOVPE2003In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 248, p. 431-436Article in journal (Refereed)
    Abstract [en]

    GaInNAs/GaAs single quantum wells (QWs) have been grown by metalorganic vapour phase epitaxy (MOVPE). The surface morphology has been studied by atomic force microscopy (AFM). The density of pits observed on the surface of QW structures was found to depend on the growth temperature and dimethylhydrazine (DMHy) flow. Cross-sectional AFM image showed the presence of defects at the interface of GaInNAs/GaAs. The low temperature photoluminescence characteristics of the QWs as a function of growth temperature. DMHy flow and density of surface pits have been discussed. The origin of pit formation is addressed based on the pyrolysis products present during the growth of QWs. The results suggest that higher growth temperature maybe desirable to obtain good quality GaInNAs QWS.

  • 61. Ben Dhaou, I.
    et al.
    Parhi, K. K.
    Tenhunen, Hannu
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Energy efficient signaling in deep-submicron technology2002In: VLSI design (Print), ISSN 1065-514X, E-ISSN 1563-5171, Vol. 15, no 3, p. 563-586Article in journal (Refereed)
    Abstract [en]

    In deep-submicron technology, global interconnect capacitances have started reaching several orders of magnitude greater than the intrinsic capacitances of the CMOS gates. The dynamic power consumption of a CMOS gate driving a global wire is the sum of the power dissipated due to (dis)charging (i) the intrinsic capacitance of the gate, and (ii) the wire capacitance. The latter is referred to as on-chip signaling power consumption. In this paper, a scheme has been proposed for combating crosstalk noise and reducing power consumption while driving the global wire at an optimal delay. This scheme is based on reduced voltage-swing signaling combined with buffer-insertion and resizing. The buffers are inserted and resized to compensate for the speed degradation caused by scaling the supply voltage and eradicating the crosstalk noise. A new buffer insertion algorithm called VIJIM has been described here, along with accurate delay and crosstalk-noise estimation algorithms for distributed RLC wires. The experimental results show that the VIJIM algorithm inserts fewer buffers into non-critical nets than does the existing buffer-insertion algorithms. In a 0.25 mm CMOS process, the experimental results show that energy savings of over 60% can be achived if the supply voltage is reduced from 2.5 to 1.5 V.

  • 62.
    Ben Dhaou, Imed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Low Power Design Techniques for Deep Submicron Technology with Application to Wireless Transceiver Design2002Doctoral thesis, monograph (Other scientific)
  • 63.
    Bengtsson, Tomas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Boolean decomposition in combinational logic synthesis2003Licentiate thesis, comprehensive summary (Other scientific)
  • 64. Benisty, H.
    et al.
    Olivier, S.
    Weisbuch, C.
    Agio, M.
    Kafesaki, M.
    Soukoulis, C. M.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jaskorzynska, Bozena
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Talneau, A.
    Moosburger, J.
    Kamp, M.
    Forchel, A.
    Ferrini, R.
    Houdre, R.
    Oesterle, U.
    Models and measurements for the transmission of submicron-width waveguide bends defined in two-dimensional photonic crystals2002In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 38, no 7, p. 770-785Article in journal (Refereed)
    Abstract [en]

    One of the essential building-blocks of miniature photonic crystal (PC)-based photonic integrated circuits (PICs) is the sharp bend. Our group has focused on the 2-D photonic crystal based on a triangular lattice of holes perforating a standard heterostructure. The latter, GaAlAs-based or InP-based, is vertically a monomode waveguide. We consider essentially one or two 60 bends defined by one to five missing rows, spanning both cases of monomode and multimode channel waveguides. From intensive modeling and various experimental measurements (both on GaAs and InP), we point out the origin of the present level of bend insertion losses and discuss the merits of the many roads open for improved design.

  • 65. Benisty, H.
    et al.
    Weisbuch, C.
    Olivier, S.
    Houdré, R.
    Ferrini, R.
    Leuenberger, D.
    Wild, B.
    Lombardet, B.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Anand, Srinivasan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mulot, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jazkorzynska, B.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Agio, M.
    Kafesaki, M.
    Soukoulis, C. M.
    Talneau, A.
    Kamp, M.
    Forchel, A.
    Moosburger, J.
    Happ, T.
    Duan, G. -H
    Cuisin, C.
    Chandouineau, J. -P
    Drisse, O.
    Gaborit, F.
    Legouézigou, L.
    Legouézigou, O.
    Lelarge, F.
    Poingt, F.
    Pommereau, F.
    Thedrez, B.
    Low-loss photonic-crystal and monolithic InP integration: Bands, bends, lasers, filters2004In: Photonic Crystal Materials and Devices II, SPIE - International Society for Optical Engineering, 2004, p. 119-128Conference paper (Refereed)
    Abstract [en]

    Practical realizations of 2D (planar) photonics crystal (PhC) are either on a membrane or etched through a conventional heterostructure. While fascinating objects can emerge from the first approach, only the latter approach lends itself to a progressive integration of more compact PhC's towards monolithic PICs based on InP. We describe in this talk the various aspects from technology to functions and devices, as emerged from the European collaboration "PCIC". The main technology tour de force is deep-etching with aspect ratio of about 10 and vertical sidewall, achieved by three techniques (CAIBE, ICP-RIE, ECR-RIE). The basic functions explored are bends, splitters/combiners, mirrors, tapers, and the devices are filters and lasers. At the end of the talk, I will emphasize some positive aspects of "broad" multimode PhC waveguides, in view of compact add-drop filtering action, notably.

  • 66.
    Bentzen, Andreas
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Menon, Cyril
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Radamson, Henry H.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mechanisms of diffusion-enhanced thermal stability of Si/Si1-xGex/Si heterostructures grown by chemical vapor deposition2004In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 261, no 1, p. 22-29Article in journal (Refereed)
    Abstract [en]

    The thermal stability of doped Si/Si0.8Ge0.2/Si (n-p-n or p-n-p) structures grown by reduced pressure chemical vapor deposition has been studied in correlation with the dopant in- and out-diffusion, using high-resolution X-ray reciprocal lattice mapping and secondary ion mass spectrometry as the main characterization tools. Initially, by doping the strained Si0.8Ge0.2 layer with reasonable amounts of boron, phosphorus, or arsenic, the thermal stability of the structures is shown to be dramatically increased compared to intrinsic layers. Secondly, the results show that when the dopants are present only in the Si buffer and cap layers, intrinsic Si spacer layers are required to obtain a significant enhancement in the thermal stability. These spacers reduce the interfacial dopant concentration and act as barriers for direct injection of precipitates into the SiGe layers. Finally, p-n-p and n-p-n structures were studied showing a very good thermal stability, due to enhanced out-diffusion of dopants from the SiGe layer upon in-diffusion from the adjacent layers. By employing i-Si spacers, the boron out-diffusion in a n-p-n structure was reduced, giving rise to a degradation of the thermal stability of this structure.

  • 67. Ber, B. Y.
    et al.
    Kazantsev, D. Y.
    Kalinina, E. V.
    Kovarskii, A. P.
    Kossov, V. G.
    Hallén, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Yafaev, R. R.
    Determination of nitrogen in silicon carbide by secondary ion mass spectrometry2004In: Journal of Analytical Chemistry, ISSN 1061-9348, E-ISSN 1608-3199, Vol. 59, no 3, p. 250-254Article in journal (Refereed)
    Abstract [en]

    The emission of atomic and complex nitrogen ions, which are the main impurity determining the n type conduction of silicon carbide, is investigated. It is shown that, among all the secondary ions of the CxN and SixN kind (x = 0, 1, 2, 3), the (26)(CN)(-) fragment exhibits the highest ion yield. The use of an ion peak with a specified mass as an analytical signal provides a detection limit for nitrogen in SiC at a level of 10(16) cm(-3). This result is attained in measurements at high mass resolution (M/DeltaM = 7500, interference peak (26)(C-13(2))(-)).

  • 68.
    Berrier, Audrey
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mulot, Mikaël
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Talneau, A.
    CNRS, Lab Photon & Nanostruct.
    Anand, Srinivasan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Negative Refraction at Infrared Wavelengths in a Two-Dimensional Photonic Crystal2004In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 93, no 073902Article in journal (Refereed)
    Abstract [en]

    We report on the first experimental evidence of negative refraction at telecommunication wavelengths by a two-dimensional photonic crystal field. Samples were fabricated by chemically assisted ion beam etching in the InP-based low-index constrast system. Experiments of beam imaging and light collection show light focusing by the photonic crystal field. Finite-difference time-domain simulations confirm that the observed focusing is due to negative refraction in the photonic crystal area.

  • 69. Bertilsson, K.
    et al.
    Dubaric, E.
    Nilsson, H. E.
    Hjelm, M.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Monte Carlo simulation of vertical MESFETs in 2H, 4H and 6H-SiC2001In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 10, no 3-7, p. 1283-1286Article in journal (Refereed)
    Abstract [en]

    The 4H-SiC static induction transistor (SIT) is a very competitive device for high frequency and high power applications (3-6 GHz range). The large breakdown voltage and the high thermal conductivity of 4H-SiC allow transistors with extremely high current density at high voltages. The SIT transistor shows better output power capabilities but the unity current-gain frequency is lower compared to a MESFET device. In this work we show, using a very accurate numerical model, that a compromise between the features given by the SIT structure and the ordinary MESFET structure can be obtained using the vertical MESFET structure. The device dimension has been selected very aggressively to demonstrate the performance of an optimized technology. We also present results from drift-diffusion simulations of devices, using transport parameters obtained from the Monte Carlo simulation. The simulations indicate that 2H-SiC is superior to both 4H and 6H-SiC for vertical devices. For lateral devices, 2H-SiC is slightly faster compared to an identical 4H-SiC device.

  • 70. Bertilsson, K.
    et al.
    Dubaric, E.
    Thungstrom, G.
    Nilsson, H. E.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Simulation of a low atmospheric-noise modified four-quadrant position sensitive detector2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, no 1, p. 183-187Article in journal (Refereed)
    Abstract [en]

    A modified four-quadrant position sensitive detector (PSD) is developed. This structure is less sensitive to atmospheric turbulence that is a major drawback with the traditional four-quadrant detector. The inter-electrode resistance is as high as for the four-quadrant detector, which is an advantage compared to the lateral effect PSD. The linearity for the modified four-quadrant detector is good in the whole active range of sensing. The structures are limited to small sensing areas with well focused beams and are suitable for use in detectors up to 1 mm in size.

  • 71. Bertilsson, K.
    et al.
    Nilsson, H. E.
    Hjelm, M.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kackell, P.
    Persson, Clas
    The effect of different transport models in simulation of high frequency 4H-SiC and 6H-SiC vertical MESFETs2001In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 45, no 5, p. 645-653Article in journal (Refereed)
    Abstract [en]

    A full band Monte Carlo (MC) study of the high frequency performance of a 4H-SiC short channel vertical MESFET is presented. The MC model used is based on data from a full potential band structure calculation using the local density approximation to the density functional theory. The MC results have been compared with simulations using state of the art drift-diffusion and hydrodynamic transport models. Transport parameters such as mobility, saturation velocity and energy relaxation time are extracted from MC simulations.

  • 72.
    Bertilsson, Kent
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Simulation and Optimization of SiC Field Effect Transistors2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Silicon Carbide (SiC) is a wide band-gap semiconductor material with excel-lent material properties for high frequency, high power and high temperature elec-tronics. In this work different SiC field-effect transistors have been studied using theoretical methods, with the focus on both the devices and the methods used. The rapid miniaturization of commercial devices demands better physical models than the drift-diffusion and hydrodynamic models most commonly used at present.

    The Monte Carlo method is the most accurate physical methods available and has been used in this work to study the performance in short-channel SiC field-effect devices. The drawback of the Monte-Carlo method is the computational power required and it is thus not well suited for device design where the layout requires to be optimized for best device performance. One approach to reduce the simulation time in the Monte Carlo method is to use a time-domain drift-diffusion model in contact and bulk regions of the device. In this work, a time-domain drift-diffusion model is implemented and verified against commercial tools and would be suitable for inclusion in the Monte-Carlo device simulator framework.

    Device optimization is traditionally performed by hand, changing device pa-rameters until sufficient performance is achieved. This is very time consuming work without any guarantee of achieving an optimal layout. In this work a tool is developed, which automatically changes device layout until optimal device per-formance is achieved. Device optimization requires hundreds of device simulations and thus it is essential that computationally efficient methods are used. One impor-tant physical process for RF power devices is self heating. Self heating can be fairly accurately modeled in two dimensions but this will greatly reduce the computa-tional speed. For realistic influence self heating must be studied in three dimensions and a method is developed using a combination of 2D electrical and 3D thermal simulations. The accuracy is much improved by using the proposed method in comparison to a 2D coupled electro/thermal simulation and at the same time offers greater efficiency. Linearity is another very important issue for RF power devices for telecommunication applications. A method to predict the linearity is imple-mented using nonlinear circuit simulation of the active device and neighboring passive elements.

  • 73.
    Bertilsson, Kent
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Nilsson, Hans-Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    The power of using automatic device optimization, based on iterative device simulations, in design of high-performance devices2004In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 48, no 10-11, p. 1721-1725Article in journal (Refereed)
    Abstract [en]

    An automatic optimization tool for semiconductor devices based on iterative device simulations is developed. The tool is used for optimization of different kinds of semiconductor devices using various performance measures. High performance optimization algorithms, both local and global, are used to achieve an efficient design in shortest possible time. In this paper the effects of different optimization algorithms, performance measures, and number of variables in the optimization are studied. Both the computational efficiency and the devices achieved with different performance measures are studied. We give a demonstration of the usefulness of this method in a comparison between different device topologies, which have been optimized for best performance.

  • 74. Bhattacharjee, P S
    et al.
    Saha, D
    Mukherjee, Amitava
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An approach for location area planning in a personal communication services network (PCSN)2004In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 3, no 4, p. 1176-1187Article in journal (Refereed)
    Abstract [en]

    This paper deals with an approach for planning location areas (LAs) in a personal communication services network (PCSN) to be overlaid on an existing wired network. Given the average speed of mobile terminals, the number of mobile switching centers (MSCs), their locations, call handling capacity of each MSC, handoff cost between adjacent cells and call arrival rate, an important consideration in a PCSN is to identify the cells in every LA to be connected to the corresponding NISC in a cost effective manner. In this work, while planning a location area, we present a two-step approach, namely optimization of total system recurring cost (subproblem I) and optimization of hybrid cost (subproblem II). The planning first determines the optimum number of cells in an LA from subproblem I. Then, it finds out the exact LAs by assigning cells to the switches, while optimizing the hybrid cost which comprises the handoff cost and the cable cost, in subproblem II. This divide-and-conquer strategy provides a practical way for designing LAs. As our approach toward LA planning takes into accounts both cost and network planning factors, this unique combination will be of great interest to PCSN designers. It develops an optimum network planning method for a wide range of call-to-mobility ratios that minimizes the total system recurring cost while still ensuring a good system performance. Our study shows that acceptable results are achievable with a reasonable computational effort, which supports the engineered planning of a PCSN.

  • 75.
    Bilien, Johan
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Eliasson, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vatn, Jon-Olov
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Call establishment delay for secure VoIP2004In: Proceedings of WiOpt '04: Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, 2004Conference paper (Refereed)
    Abstract [en]

     

     

  • 76. Bjornangen, T.
    et al.
    Axnas, J.
    Eltsev, Y.
    Rapp, Östen.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    In-plane anisotropy and chain contribution from the magnetoresistivity of YBa2Cu3O7-delta2000In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 341, p. 1885-1886Article in journal (Refereed)
    Abstract [en]

    Magnetoresistivity measurements were made in untwinned YBa2Cu3O7-delta above T-c for B\\c and B\\ab, with I\\a or b. A fluctuation theory that allows for an in-plane coherence length anisotropy (gamma = xi (b)/xi (a)) was used to determine gamma. The contribution to the magnetoconductivity from the CuO-chains was also analyzed.

  • 77. Bjornangen, T.
    et al.
    Axnas, J.
    Eltsev, Y.
    Rydh, A.
    Rapp, Östen.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    In-plane anisotropy and possible chain contribution to magnetoconductivity in YBa2Cu3O7-delta2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 6322, no 22Article in journal (Refereed)
    Abstract [en]

    The magnetoresistivity of untwinned YBa2Cu3O7-delta Single crystals was measured in magnetic fields up to 12 T-c for B parallel toc and B parallel to ab. at temperatures up to T-c + 84 K and T-c + 50 K, respectively. Two issues were addressed; determination of the in-plane coherence length anisotropy gamma=xi (b)/xi (a) and discussion of the role of the CuO chains in the magnetoconductivity Delta sigma. A fluctuation conductivity theory that allows for an in-plane coherence length anisotropy (xi (a)not equal xi (b)) as well as an extension of the usual Aronov-Hikami-Larkin theory that does not, were used in analyses. The results suggest that the anisotropy gamma is close to 1. The analyses also suggest a contribution to the magnetoconductivity from the CuO chains of a sign which depends on the direction between held and current.

  • 78. Bjornangen, T.
    et al.
    Rydh, A.
    Rapp, Östen.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Multiterminal transport measurements: In-plane anisotropy and vortex liquid correlation in YBa2Cu3O7-delta2001In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 64, no 22Article in journal (Refereed)
    Abstract [en]

    Using a modified pseudoflux transformer geometry, the in-plane anisotropy and vortex-liquid correlation of an untwinned YBa2Cu3O7-delta single crystal have been studied. The square-shaped, multiterminal sample design allows comparative studies of a- and b-axis properties for arbitrarily oriented magnetic fields. We compare the in-plane resistivity in the case of intrinsic pinning with the longitudinal resistivity, i.e., with the resistivity in absence of a macroscopic Lorentz force. The relative ratio between resistivities rho (a) and rho (b) in the vortex state can be made to vary over a wide range by controlling the direction of the applied magnetic field. Evidence is found for almost isotropic fluctuations corresponding to a fluctuation anisotropy gamma (A)(ab)approximate to1.1, noted to be clearly lower than the anisotropy gamma (ab)=1.27 obtained from the vortex phase diagram.

  • 79. Bjornangen, T.
    et al.
    Rydh, A.
    Rapp, Östen.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vortex liquid and solid correlation in untwinned YBa2Cu3O7-delta2003In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 388, p. 727-728Article in journal (Refereed)
    Abstract [en]

    Longitudinal- and inter-vortex correlations in an untwinned YBa2Cu3O7-delta single crystal were studied in the liquid and driven solid state, using a modified, symmetric pseudo-flux transformer method. The response of the flowing vortex system below T-m was significantly different along the field (Hparallel toa) and perpendicular to it (Hparallel toc), with both cases probed by an in-plane current mainly parallel to b.

  • 80. Bjureus, P.
    et al.
    Jantsch, Axel
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Modeling of mixed control and dataflow systems in MASCOT2001In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, Vol. 9, no 5, p. 690-703Article in journal (Refereed)
    Abstract [en]

    The Matlab and SDL Codesign Technique (MASCOT) method integrates modeling of data flow and control dominated parts at the system level. Based on the established languages specification and description language (SDL) and Matlab, MASCOT provides a modeling and simulation technique which realizes the communication and synchronization between the two domains. Moreover, it offers modeling guidelines for a disciplined and efficient way of using the technique. Most of the tedious details of modeling synchronization and communication is handled automatically and is transparent to the user. Consequently, the user can focus on the application and on the important tradeoffs to be made at the system level.

  • 81.
    Bjuréus, Per
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    High-level modeling and evaluation of embedded real-time systems2002Doctoral thesis, monograph (Other scientific)
  • 82.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Inoue, S.
    Soderholm, J.
    Visibility is not a good measure of a well-defined relative phase2000In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 6202, no 2Article in journal (Refereed)
    Abstract [en]

    In a recent paper Marburger and Das [J. H. Marburger III and K. K. Das, Phys. Rev. A 59, 2213 (1999)] considered an interference visibility experiment involving two weakly interacting Bose-Einstein condensates. It was shown that condensate eigenstates of the Hermitian relative phase operator do not give interference fringes with unit visibility in a Young's double slit type of experiment. The authors concluded that ... these states are not especially well suited to describe weakly interacting multiply occupied coherent bosonic systems. In this work we suggest a criterion for states with a well-defined relative phase. Subsequently we show that the relative phase operator eigenstates satisfy this criterion. This suggests that the concept of interference visibility can, and should, be generalized, since it is widely believed that interference visibility is a measure of the relative phase properties. We therefore propose a broader, but still operational, definition of interference visibility, which we call generalized visibility, and prove that the relative phase operator eigenstates indeed can show unit generalized visibility. We also derive a simple, but general, criterion for states which can display a unit generalized visibility. Somewhat surprisingly, this criterion is weaker than the criterion for a well-defined relative phase. Finally, we discuss which two-mode states can display unit (ordinary) visibility.

  • 83.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jonsson, P.
    Heydari, H.
    Soderholm, J.
    Hessmo, B.
    Hilbert space factorization and partial measurements2003In: Optics and Spectroscopy, ISSN 0030-400X, E-ISSN 1562-6911, Vol. 94, no 5, p. 695-699Article in journal (Refereed)
    Abstract [en]

    A quantum system whose state vector belongs to a finite-dimensional Hilbert space is considered. If this space has a dimension that is a composite number, one can factor the space into a tensor product of subspaces. An observable that acts only in one of these subspaces is called a partial measurement. Some of the properties and the interpretation of such partial measurements are discussed.

  • 84.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jonsson, P.
    Sanchez-Soto, L. L.
    Single-particle nonlocality and entanglement with the vacuum2001In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 6404, no 4Article in journal (Refereed)
    Abstract [en]

    We propose a single-particle experiment that is equivalent to the conventional two-particle experiment used to demonstrate a violation of Bell's inequalities. Hence, we argue that quantum mechanical nonlocality can be demonstrated by single-particle states. The validity of such a claim has been discussed in the literature, but without reaching a clear consensus. We show that the disagreement can be traced to what part of the total state of the experiment one assigns to the (macroscopic) measurement apparatus. However, with a conventional and legitimate interpretation of the measurement process one is led to the conclusion that even a single particle can show nonlocal properties.

  • 85.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Porta Mana, Piero Giovanni Luca
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A size criterion for macroscopic superposition states2004In: Journal of Optics B-Quantum and Semiclassical Optics, ISSN 1464-4266, E-ISSN 1741-3575, Vol. 6, no 11, p. 429-436Article in journal (Refereed)
    Abstract [en]

    An operational measure to quantify the sizes of some 'macroscopic quantum superpositions', realized in recent experiments, is proposed. The measure is based on the fact that a superposition presents greater sensitivity in interferometric applications than its superposed constituent states. This enhanced sensitivity, or 'interference utility', may then be used as a size criterion among superpositions.

  • 86.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Porta Mana, Piero Giovanni Luca
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schrödinger-cat states: size classification based on evolution or dissipation2004In: Proceedings of SPIE - The International Society for Optical Engineering: Vol. 5468 / [ed] Heszler P; Abbott D; GeaBanacloche JR; Hemmer PR, 2004, p. 335-343Conference paper (Refereed)
    Abstract [en]

    The issue of estimating how "macroscopic" a superposition state is, can be addressed by analysing the rapidity of the state's evolution under a preferred observable, compared to that of the states forming the superposition. This fast evolution. which arises from the larger dispersion of the superposition state for the preferred operator, also represents a useful characteristic for interferometric applications. This approach can be compared to others in which a superposition's macroscopality is estimated in terms of the fragility to dissipation.

  • 87.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sanchez-Soto, L. L.
    Soderholm, J.
    Entangled-state lithography: Tailoring any pattern with a single state2001In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 86, no 20, p. 4516-4519Article in journal (Refereed)
    Abstract [en]

    We demonstrate a systematic approach to Heisenberg-Limited lithographic image formation using four-mode reciprocal binomial states. By controlling the exposure pattern with a simple bank of birefringent plates, any pixel pattern on a (N + 1) X (N + 1) grid, occupying a square with the side half a wavelength long, can be generated from a 2N-photon state.

  • 88.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sanchez-Soto, L. L.
    Soderholm, J.
    Subwavelength lithography over extended areas2001In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 6401, no 1Article in journal (Refereed)
    Abstract [en]

    We demonstrate a systematic approach to subwavelength resolution Lithographic image formation on films covering areas larger than a wavelength squared. For example, it is possible to make a lithographic pattern with a feature size resolution of lambda/[2(N+1)] by using a particular 2M-photon, multimode entangled state, where N less than or equal toM, and banks of birefringent plates. By preparing such a statistically mixed state, one can form any pixel pattern on a 2(M-N)(N+1) x 2(M-N)(N+1) pixel grid occupying a square with side L = 2(M-N-1)lambda. Hence, there is a trade off between the exposed area, the minimum lithographic feature size resolution, and the number of photons used for the exposure. We also show that the proposed method will work even under nonideal conditions, albeit with somewhat poorer performance.

  • 89.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Soderholm, J.
    Trifonov, A.
    Tsegaye, T.
    A theory of the relative phase and number difference of two quantized harmonic oscillators2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T102, p. 133-146Article in journal (Refereed)
    Abstract [en]

    We present a comprehensive and self-consistent theory of relative-phase measurements and the associated Hermitian relative-phase operator of two harmonic oscillators. We find that since Nature does not favor any particular initial condition of the two oscillators, the relative-phase operator is not unique. We show that the relative-phase eigenstates; are maximally entangled. Therefore. most relative-phase operators lack a classical correspondence, even in the high-excitation limit. Furthermore, we find that the relative phase and the excitation number difference are noncommuting, noncanonical observables and we derive a commutation relation.

  • 90.
    Björk, Gunnar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Söderholm, Jonas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sanchez-Soto, L. L.
    Two-photon imaging and quantum holography2004In: Journal of Optics B-Quantum and Semiclassical Optics, ISSN 1464-4266, E-ISSN 1741-3575, Vol. 6, no 6, p. S478-S482Article in journal (Refereed)
    Abstract [en]

    We discuss when the use of entangled photon pairs in an imaging system can be simulated with a classically correlated source. In particular, we consider two recently proposed schemes with 'bucket detection' of one of the photons. We argue that these schemes give identical results for entangled states as for appropriately prepared classically correlated states.

  • 91.
    Björnängen, Therese
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fors, Rickard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Eltsev, Yurii
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rapp, Östen
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vortex correlation parallel in underdoped and perpendicular to H vertical bar vertical bar ab YBa2Cu3O7-delta2004In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 408-10, p. 564-565Article in journal (Refereed)
    Abstract [en]

    Vortex correlation in the region of the depinning transition has been studied in twinned YBa2Cu3O7-delta single crystals with T-c approximate to 80 K. Transport properties along the e-axis were performed in magnetic fields parallel to the ab-plane, using the pseudo flux-transformer method. By rotating the sample around the c-axis, both longitudinal and transverse vortex correlation could be studied. Compared to optimally doped samples, transverse vortex velocity correlation was enhanced at high fields, while longitudinal correlation remained qualitatively the same.

  • 92. Blank, T. V.
    et al.
    Gol'dberg, Y. A.
    Kalinina, E. V.
    Konstantinov, O. V.
    Konstantinov, A. O.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Temperature dependence of the quantum efficiency of 4H-SiC-Based Schottky photodiodes2001In: Technical physics letters, ISSN 1063-7850, E-ISSN 1090-6533, Vol. 27, no 9, p. 776-778Article in journal (Refereed)
    Abstract [en]

    Using metal-semiconductor structures based on a pure epitaxial layer of n-4H-SiC (N-d - N-a = 4 x 10(15) cm(-3)), UV photodetectors were created with a maximum photosensitivity at 4.9 eV and a quantum efficiency up to 0.3 el/ph. The photosensitivity spectrum of the base structure is close to the spectrum of bactericidal action of the UV radiation. For photon energies in the 3.4 - 4.7 eV range, the quantum efficiency of the photoelectric conversion exhibits rapid growth with the temperature above 300 K, which is explained by the participation of photons in indirect interband transitions. This growth is not manifested when the photon energy is close to the threshold energy of direct optical transitions in the nondirect-bandgap semiconductor, which allows the threshold energy to be evaluated (similar to4.9 eV).

  • 93.
    Blom, Hans
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Correlation spectroscopy of single emitters: fundamental studies and applications2001Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Correlation analysis and correlation spectroscopy has eversince the first developments, to characterise light emittingprocesses and biomolecular dynamics, continued to extend itspractical applicability. Today, correlation spectroscopy can beused in life science to study dynamical processes even at thesingle molecule level. Correlation analysis can in one of itsextreme be applied to investigate single photon processes fromsolid-state emitters. This thesis is an account of my studiesof fluorescent emitter related to quantum optics and lifescience. It presents some fundamental results and discussesapplications of emitters like single quantum dots or singledyes attached to biomolecules. The studies were performed bythe means of correlation analysis and correlation spectroscopyon self-made optical setups. One task of this thesis was todevelop fluorescence correlation spectroscopy for ultravioletexcitation and emission. With ultraviolet excitation thenatural intrinsic chromophores of certain nucleotides and aminoacids can be used. No external labelling of biomolecules couldbecome a reality using ultraviolet excitation and emission. Asecond task was to apply correlation spectroscopy to performhigh spatial-resolution flow profiling and trafficking ofsingle dye-labeled biomolecules in microstructured channels.Future transports effects, flow monitoring, flow profiling andprolonged fluorescence detection in artificial microstructuresor in cells, could benefit from this application. An additionaltask was to apply correlation spectroscopy to so-calledmicroarrays for parallel acquisition of dynamical data at thesingle molecule level. Parallel excitation and detection wasachieved with the use of diffractive optical elements andintegrated semiconductor single-photon sensitive detectors. Thecurrent throughput rate in biological diagnostic or screeninganalysis could be increased dramatically with implementation ofthis parallel confocal excitation and detection technique. Yetanother task of this thesis was to investigations single-photongeneration by InAs-semiconductor quantum dots. We show that aquantum dots can be used for single-photon generation ondemand. Besides the single-photon generation in quantum dots,the possibility of two-photon generation, and generation ofentangled photon-pair, has also been investigated

  • 94.
    Blom, Hans
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Correlation spectrosopy of single eitters: fundamental studies and applications related to quantum optics and life science2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Correlation analysis and correlation spectroscopy has eversince the first developments, to characterise light emittingprocesses and biomolecular dynamics, continued to extend itspractical applicability. Today, correlation spectroscopy can beused in life science to study dynamical processes even at thesingle molecule level. Correlation analysis can in one of itsextreme be applied to investigate single photon processes fromsolid-state emitters. This thesis is an account of my studiesof fluorescent emitter related to quantum optics and lifescience. It presents some fundamental results and discussesapplicationsof emitters like single quantum dots or singledyes attached to biomolecules. The studies were performed bythe means of correlation analysis and correlation spectroscopyon self-made optical setups. One task of this thesis was todevelop fluorescence correlation spectroscopy for ultravioletexcitation and emission. With ultraviolet excitation thenatural intrinsic chromophores of certain nucleotides and aminoacids can be used. No external labelling of biomolecules couldbecome a reality using ultraviolet excitation and emission. Asecond task was to apply correlation spectroscopy to performhigh spatial-resolution flow profiling and trafficking ofsingle dye-labeled biomolecules in microstructured channels.Future transports effects, flow monitoring, flow profiling andprolonged fluorescence detection in artificial microstructuresor in cells, could benefit from this application. An additionaltask was to apply correlation spectroscopy to so-calledmicroarrays for parallel acquisition of dynamical data at thesingle molecule level. Parallel excitation and detection wasachieved with the use of diffractive optical elements andintegrated semiconductor single-photon sensitive detectors. Thecurrent throughput rate in biological diagnostic or screeninganalysis could be increased dramatically with implementation ofthis parallel confocal excitation and detection technique. Yetanother task of this thesis was to investigations single-photongeneration by InAs-semiconductor quantum dots. We show that aquantum dots can be used for single-photon generation ondemand. Besides the single-photon generation in quantum dots,the possibility of two-photon generation, and generation ofentangled photon-pair, has also been investigated.

  • 95.
    Blom, Hans
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Bark, Niklas
    Gösch, Michael
    Forsberg, Erik
    Heino, Toni
    Holm, Johan
    Björk, Gunnar
    Rigler, Rudolf
    Elliptical line focus in fluorescence spectroscopy: theory and applicationManuscript (preprint) (Other academic)
  • 96.
    Blom, Hans
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Björk, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Gösch, Michael
    Rigler, Rudolf
    Fluorescence correlation spectroscopy with Lorentzian intensity distributionManuscript (preprint) (Other academic)
  • 97.
    Blom, Hans
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Johansson, Mathias
    Gösch, Michael
    Sigmundsson, Toni
    Holm, Johan
    Hård, Sverker
    Rigler, Rudolf
    Parallel Flow Measurements in Microstructures by Use of a Multifocal 4 x 1 Diffractive Optical Fan-Out Element2002In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, no 31, p. 6614-6620Article in journal (Refereed)
    Abstract [en]

    We have developed a multifocal optical fluorescence correlation spectroscopy system for parallel flow analyses. Multifocal excitation was made possible through a 4 x 1 diffractive optical fan-out element, which produces uniform intensity in all four foci. Autocorrelation flow analyses inside a 20 μm x 20 μm square microchannel, with the 4 x 1 fan-out foci perpendicular to the flow direction, made it possible to monitor different flows in all four foci simultaneously. We were able to perform cross-correlation flow analyses by turning the microstructure, thereby having all four foci parallel to the direction of flow. Transport effects of the diffusion as a function of flow and distance could then also be studied.

  • 98.
    Blom, Hans
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Johansson, Mathias
    Hedman, Anna-Sara
    Lundberg, Liselotte
    Hanning, Anders
    Hård, Sverker
    Rigler, Rudolf
    Parallel Fluorescence Detection of Single Biomolecules in Microarrays by a Diffractive-Optical-Designed 2 x 2 Fan-Out Element2002In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, no 16, p. 3336-3342Article in journal (Refereed)
    Abstract [en]

    We have developed a multifocal diffractive-optical fluorescence correlation spectroscopy system for parallel excitation and detection of single tetramethylrhodamine biomolecules in microarrays. Multifocal excitation was made possible through the use of a 2 × 2 fan-out diffractive-optical element with uniform intensity in all foci. Characterization of the 2 × 2 fan-out diffractive-optical element shows formation of almost perfect Gaussian foci of submicrometer lateral diameter, as analyzed by thermal motion of tetramethylrhodamine dye molecules in solution. Results of parallel excitation and detection in a high-density microarray of circular wells show single-biomolecule sensitivity in all four foci simultaneously.

  • 99.
    Blomqvist, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ferroelectric Na0.5K0.5NbO3 as an electro-optic material2002Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Ferroelectrics are a group of advanced electronic materialswith a wide variety of properties useful in applications suchas memory devices, resonators and filters, infrared sensors,microelectromechanical systems, and optical waveguides andmodulators. Among the oxide perovskite-structured ferroelectricthin film materials sodium potassium niobate or Na0.5K0.5NbO3(NKN) has recently emerged as one of the most promisingmaterials in microwave applications due to high dielectrictunability and low dielectric loss. This licentiate thesispresents results on growth and structural, optical, andelectrical characterization of Na0.5K0.5NbO3 thin films. Thefilms were deposited by rf-magnetron sputtering of astoichiometric, high density, ceramic Na0.5K0.5NbO3 target ontosingle crystal LaAlO3 and Al2O3, and polycrystalline Pt80Ir20substrates. By x-ray diffractometry, NKN films on c-axisoriented LaAlO3 substrates were found to grow epitaxially,whereas films on hexagonal sapphire and polycrystallinePt80Ir20 substrates were found to be preferentially (00l)oriented. Optical and waveguiding properties of theNa0.5K0.5NbO3/Al2O3 heterostructure were characterized using aprism-coupling technique. Sharp and distinguishable transversemagnetic (TM) and electric (TE) propagation modes wereobserved. The extraordinary and ordinary refractive indiceswere calculated to ne = 2.216±0.003 and no =2.247±0.002 for a 2.0 μm thick film at λ = 632.8nm. This implies a birefringence Δn = ne - no =-0.031±0.003 in the film. The ferroelectric state inNKN/Pt80Ir20 films at room temperature was indicated by apolarization loop with polarization as high as 33.4 μC/cm2at 700 kV/cm, remnant polarization of 9.9 μC/cm2 andcoercive field of 91 kV/cm. Current-voltage characteristics ofvertical Au/NKN/Pt80Ir20 capacitive cells and planar Au/NKN/LaAlO3 interdigital capacitors (IDCs) showed very goodinsulating properties, with the leakage current density for anNKN IDC on the order of 30 nA/cm2 at 400 kV/cm. Rf dielectricspectroscopy demonstrated low loss, low frequency dispersion,and high voltage tunability. At 1 MHz NKN/LaAlO3 showed adissipation factor tan δ of 0.010 and a tunability of 16.5% at 200 kV/cm. For the same structure the frequencydispersion, Δεr, between 1 kHz and 1 MHz was 8.5%.

    Key words:ferroelectrics, sodium potassium niobates,thin films, rf-magnetron sputtering, waveguiding, refractiveindex, prism coupling, dielectric tunability

  • 100.
    Blomqvist, Mats
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Petraru, Adrian
    Institute of Thin Films and Interfaces, Section: Ion Technology, Forschungzentrum Jülich.
    Rf sputtered Na0.5K0.5NbO3 films on oxide substrates as optical waveguiding material2003In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 54, p. 631-640Article in journal (Refereed)
    Abstract [en]

    Highly crystalline Na0.5K0.5NbO3 (NKN) thin films of 1-2 mum thickness were deposited by rf-magnetron sputtering of a stoichiometric, ceramic target on single crystal LaAlO3 (001) and Al2O3 (01 (1) under bar2) substrates. X-ray diffraction measurements revealed epitaxial quality of NKN/LaAlO3 film structures, whereas NKN films on sapphire substrates were found to be preferentially c -axis oriented. A prism-coupling technique was used to characterize optical and waveguiding properties. A bright-line spectrum at lambda = 632.8 nm, revealed sharp peaks, corresponding to transverse magnetic (TM) and electric (TE) waveguide propagation modes in NKN/LaAlO3 and NKN/Al2O3 thin films. Using a least mean square fit the refractive index for the films and film thickness were calculated. The extraordinary and ordinary refractive indices were determined to n(e) = 2.207 +/- 0.002 and n(o) = 2.261 +/- 0.002, and n(e) = 2.216 +/- 0.002 and n(o) = 2.247 +/- 0.002 at lambda = 632.8 nm for 2.0 mum thick NKN films on LaAlO3 and Al2O3 , respectively. This corresponds to a birefringence Deltan = n(e) - n(o) = -0.054 +/- 0.003 and Deltan = -0.031 +/- 0.003 in the films, where the larger Deltan for the NKN/LaAlO3 structure can be explained by the superior crystalline quality compared to NKN/Al2O3 . Atomic force microscopy images of the film surfaces revealed rms roughnesses of 2.5 nm and 8.0 nm for 1.0-mum thick NKN/LaAlO3 and NKN/Al2O3 films, respectively. We believe surface scattering is one of the main sources of waveguide losses in the thin films.

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