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  • 101.
    Fu, Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Zeng, Yong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Berglind, Eilert
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Nanoscale excitonic-plasmonic optical waveguiding by metal-coated quantum dots2006In: Proceedings of International Symposium on Biophotonics, Nanophotonics and Metamaterials, 2006, p. 426-431Conference paper (Refereed)
    Abstract [en]

    A three-dimensional metal-coated semiconductor-quantum-dot (QD) nanoscale lattice structure is designed for optical waveguiding. It is based on three notions: i) Excitons are first photogenerated in the QDs by the incident electromagnetic field which is the optical wave to be guided: ii) The exciton-polariton effect in the QD structure induces an extra optical dispersion in the QDs: iii) The high contrast ratio between the optical dispersions of the QDs and the background material creates clear photonic bandgaps. By carefully designing the QD size and the QD lattice structure, perfect electromagnetic field reflection can be obtained for the incident wave in the lossless case, thus providing the fundamental basis of QDs for optical waveguide applications. Metal coating at the QD surface generates a surface plasmon spatially confined in the QD so that the exciton generation becomes enhanced for a better dielectric modulation.

  • 102.
    Fu, Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Andersson, J. Y.
    Asplund, C.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Optical reflection from excitonic quantum-dot multilayer structures2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 18, p. 183117-Article in journal (Refereed)
    Abstract [en]

    We study theoretically and experimentally the optical reflection from excitonic quantum-dot (QD) multilayer structures composed of InAs QDs in a GaAs substrate. Quantum mechanical and finite-difference time-domain numerical calculations indicate that the incident radiation in the optical reflectance measurement photoexcites the InAs QDs which then form excitonic dipoles. The excitonic dipole modifies significantly the dielectric constant of the QD, which results in a reflectance peak in the vicinity of the excitonic energy, as observed experimentally.

  • 103.
    Fu, Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Kowalewski, Jacob
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Wu, J.
    Yue, Y.
    Dai, N.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Radiative and nonradiative recombination of photoexcited excitons in multi-shell-coated CdSe/CdS/ZnS quantum dots2009In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 86, no 3, p. 37003-Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dots (QDs) have been widely studied for nanophotonics and bioimaging applications for which the lifetime of their fluorescence is of critical importance. We report experimental and theoretical characterizations of dynamic optical properties of multi-shell-coated CdSe/CdS/ZnS QDs. Quantum-mechanical studies of fundamental optical excitations and Monte Carlo simulations of energy relaxation mechanisms indicate that the excitonic states are densely compacted in the QDs and are easily photoexcited by the laser pulse in the presence of nonradiative electron-phonon interactions. For spherical QDs, the decay time of spontaneous radiative emission of individual photoexcited excitonic states with zero angular momenta is found to be only tens of picoseconds. In our multi-shell QDs, high-energy excitonic states of nonzero angular momenta have to go through a number of nonradiative electron-phonon interaction steps in order to relax to zero-angular-momentum excitonic states for radiative emission, resulting in an effective fluorescence peak at about 2 ns in the photoncount-time relationship. This explains the measured long average fluorescence lifetime of 3.6 ns. Such a long lifetime facilitates the applications of colloidal QDs in areas such as QD-based solar cells, bioimaging and metamaterials.

  • 104. Furdek, Marija
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Skorin-Kapov, Nina
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Compound attack-aware routing and wavelength assignment against power jamming2011In: Asia Communication and Photonics Conference and Exhibition (ACP 2011), 2011Conference paper (Refereed)
    Abstract [en]

    Transparent optical networks (TONs) are susceptible to deliberate physical-layer attacks, such as high-power jamming, which can take advantage of certain vulnerabilities of the network fundamental physical components. Combined with the high data rates employed in TONs and the difficulties of monitoring in the optical domain, these attacks can cause significant damage to the functioning of the network before reaction mechanisms are triggered, and call for new methods of increasing network security through careful network planning. In our previous work, we have considered adding attack-awareness as an objective in individual phases of the Routing and Wavelength Assignment (RWA) process. Here, we propose a new compound objective criterion for RWA, called the Maximum Attack Radius (maxAR), which is being minimized through both phases of RWA. We compare our algorithm with existing RWA approaches with different degrees of attack-awareness and show that it significantly decreases network vulnerability to high-power jamming attacks.

  • 105. Genty, Goery
    et al.
    Surakka, Minna
    Turunen, Jari
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Complete characterization of supercontinuum coherence2011In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 28, no 9, p. 2301-2309Article in journal (Refereed)
    Abstract [en]

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

  • 106. Gerschutz, F.
    et al.
    Fischer, M.
    Koeth, J.
    Chacinski, M.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Kovsh, A.
    Krestnikov, I.
    Forchel, A.
    Temperature insensitive 1.3 mu m InGaAs/GaAs quantum dot distributed feedback lasers for 10 Gbit/s transmission over 21 km2006In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 42, no 25, p. 1457-1458Article in journal (Refereed)
    Abstract [en]

    Long wavelength monomode InGaAs/GaAs quantum dot (QD) distributed feedback (DFB) lasers with emission wavelength around 1325 ran are presented. Threshold currents below 19 mA for operating temperatures up to 70 degrees C and Output powers of 10 mW at 25 degrees C (6 mW at 70 degrees C) are observed. Error-free 10 Gbit/s transmission over 21 kin fibre with an extinction ratio of 8.5 dB at room temperature (5.1 dB at 70 degrees C) is demonstrated. The low threshold, low temperature sensitivity and high modulation speed were realised using complex coupled DFB lasers with ten stacks of self-organised MBE-grown QD layers and p-type modulation doping.

  • 107. Ghiu, I.
    et al.
    Karlsson, Anders
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Broadcasting of entanglement at a distance using linear optics and telecloning of entanglement2005In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 72, no 3Article in journal (Refereed)
    Abstract [en]

    We propose a scheme for broadcasting entanglement at a distance based on linear optics. We show that an initial polarization entangled state can be simultaneously split and transmitted to a pair of observers situated at different locations with the help of two conditional Bell-state analyzers based on two beam splitters characterized by the same reflectivity R. In particular for R=1/3 the final states coincide with the output states obtained by the broadcasting protocol proposed by Buzek [Phys. Rev. A 55, 3327 (1997)]. Further we present a different protocol called telecloning of entanglement, which combines the many-to-many teleportation and nonlocal optimal asymmetric cloning of an arbitrary entangled state. This scheme allows the optimal transmission of the two nonlocal optimal clones of an entangled state to two pairs of spatially separated receivers.

  • 108. Ghiu, Iulia
    et al.
    Bjoerk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Marian, Paulina
    Marian, Tudor A.
    Probing light polarization with the quantum Chernoff bound2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 82, no 2, p. 023803-Article in journal (Refereed)
    Abstract [en]

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

  • 109. Grover, W. D.
    et al.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Fumagalli, A.
    High availability in optical networks: Introduction to the feature issue2007In: Journal of Optical Networking, ISSN 1536-5379, Vol. 6, no 3, p. 319-321Article in journal (Refereed)
    Abstract [en]

    The Journal of Optical Networking's (JON) feature issue, focuses on architectures, technologies, and theory for achieving high service availability in optical transport networks. The feature accepted 14 submissions for publication, these works reflect some important directions and objectives in optical networking research. These papers can be categorized under three themes, cost considerations in survivable optical networks, optimization in survivability design including resource sharing schemes, availability guarantees, and capacity efficiency, protection in IP/MPLS over WDM. J. Farkas, A. Paradisi, and C. Antal, in their paper, proposes and experimentally validates a low-cost, robust, and scalable Ethernet-over-fiber network architecture with fast recovery from both node and link failures. The paper submitted by M. Scheffel proposes an interesting sort of template or building-block approach to constructing the end-to-end topology of a service path.

  • 110. Grover, Wayne
    et al.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Fumagalli, Andrea
    Call for Papers: High Availability in Optical Networks2006In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 5, no 1, p. 75-76Article in journal (Other academic)
    Abstract [en]

    The Journal of Optical Networking (JON) is soliciting papers for a feature Issue pertaining to all aspects of reliable components and systems for optical networks and concepts, techniques, and experience leading to high availability of services provided by optical networks. Most nations now recognize that telecommunications in all its forms -- including voice, Internet, video, and so on -- are "critical infrastructure" for the society, commerce, government, and education. Yet all these services and applications are almost completely dependent on optical networks for their realization. "Always on" or apparently unbreakable communications connectivity is the expectation from most users and for some services is the actual requirement as well. Achieving the desired level of availability of services, and doing so with some elegance and efficiency, is a meritorious goal for current researchers. This requires development and use of high-reliability components and subsystems, but also concepts for active reconfiguration and capacity planning leading to high availability of service through unseen fast-acting survivability mechanisms. The feature issue is also intended to reflect some of the most important current directions and objectives in optical networking research, which include the aspects of integrated design and operation of multilevel survivability and realization of multiple Quality-of-Protection service classes. Dynamic survivable service provisioning, or batch re-provisioning is an important current theme, as well as methods that achieve high availability at far less investment in spare capacity than required by brute force service path duplication or 100% redundant rings, which is still the surprisingly prevalent practice. Papers of several types are envisioned in the feature issue, including outlook and forecasting types of treatments, optimization and analysis, new concepts for survivability, or papers on availability analysis methods or results. Customer, vendor, and researcher viewpoints and priorities will all be given consideration. Especially valuable to the community would be papers that include or provide measured data on actual reliability and availability performance of optical networking components or systems.Scope of SubmissionThe scope of the papers includes, but is not limited to, the following topics:

    • Reliability and availability measurement techniques specific to optical network devices or services.
    • Data on SRLG statistics and frequency of different actual failure causes.
    • Real-life accounts or data on failure and repair rates or projected values for use in availability analysis.
    • Availability analysis methods, especially for survivable networks with reconfigurable or adaptive failure-specific responses.
    • Availability analysis and comparisons of basic schemes for survivability.
    • Differentiated availability schemes.
    • Design for Multiple Quality of Protection.
    • Different schemes for on-demand survivable service provisioning.
    • Basic comparisons or proposals of new survivability mechanisms and architectures.
    • Concepts yielding higher than 1+1 protection switching availability at less than 100% redundancy.
    • Survivable service provisioning in domains of optical transparency: dealing with signal impairments.

    Manuscript Submission To submit to this special issue, follow the normal procedure for submission to JON, indicating "Feature Issue: Optical Network Availability" in the "Comments" field of the online submission form. For all other questions relating to this feature issue, please send an e-mail to jon@osa.org, subject line "Feature Issue: Optical Network Availability." Additional information can be found on the JON website: http://www.osa-jon.org/submission/.

  • 111. Grover, Wayne
    et al.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Fumagalli, Andrea
    Call for Papers: High Availability in Optical Networks2005In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 4, no 12, p. 874-875Article in journal (Other academic)
    Abstract [en]

    The Journal of Optical Networking (JON) is soliciting papers for a feature Issue pertaining to all aspects of reliable components and systems for optical networks and concepts, techniques, and experience leading to high availability of services provided by optical networks. Most nations now recognize that telecommunications in all its forms -- including voice, Internet, video, and so on -- are "critical infrastructure" for the society, commerce, government, and education. Yet all these services and applications are almost completely dependent on optical networks for their realization. "Always on" or apparently unbreakable communications connectivity is the expectation from most users and for some services is the actual requirement as well. Achieving the desired level of availability of services, and doing so with some elegance and efficiency, is a meritorious goal for current researchers. This requires development and use of high-reliability components and subsystems, but also concepts for active reconfiguration and capacity planning leading to high availability of service through unseen fast-acting survivability mechanisms. The feature issue is also intended to reflect some of the most important current directions and objectives in optical networking research, which include the aspects of integrated design and operation of multilevel survivability and realization of multiple Quality-of-Protection service classes. Dynamic survivable service provisioning, or batch re-provisioning is an important current theme, as well as methods that achieve high availability at far less investment in spare capacity than required by brute force service path duplication or 100% redundant rings, which is still the surprisingly prevalent practice. Papers of several types are envisioned in the feature issue, including outlook and forecasting types of treatments, optimization and analysis, new concepts for survivability, or papers on availability analysis methods or results. Customer, vendor, and researcher viewpoints and priorities will all be given consideration. Especially valuable to the community would be papers that include or provide measured data on actual reliability and availability performance of optical networking components or systems.Scope of SubmissionThe scope of the papers includes, but is not limited to, the following topics:

    • Reliability and availability measurement techniques specific to optical network devices or services.
    • Data on SRLG statistics and frequency of different actual failure causes.
    • Real-life accounts or data on failure and repair rates or projected values for use in availability analysis.
    • Availability analysis methods, especially for survivable networks with reconfigurable or adaptive failure-specific responses.
    • Availability analysis and comparisons of basic schemes for survivability.
    • Differentiated availability schemes.
    • Design for Multiple Quality of Protection.
    • Different schemes for on-demand survivable service provisioning.
    • Basic comparisons or proposals of new survivability mechanisms and architectures.
    • Concepts yielding higher than 1+1 protection switching availability at less than 100% redundancy.
    • Survivable service provisioning in domains of optical transparency: dealing with signal impairments.

    Manuscript Submission To submit to this special issue, follow the normal procedure for submission to JON, indicating "Feature Issue: Optical Network Availability" in the "Comments" field of the online submission form. For all other questions relating to this feature issue, please send an e-mail to jon@osa.org, subject line "Feature Issue: Optical Network Availability." Additional information can be found on the JON website: http://www.osa-jon.org/submission/.

  • 112. Gu, Feng
    et al.
    Xie, Chongyang
    Peng, Min
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Khan, Samee
    Ghani, Nasir
    Virtual Overlay Network Scheduling2011In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, no 8, p. 893-895Article in journal (Refereed)
    Abstract [en]

    As applications continue to expand, there is a growing need to provide advance reservation scheduling for higher-end virtual overlay network services. Hence this work presents an optimization formulation for this problem and studies several heuristic solutions using network simulation.

  • 113. Guina, Mircea
    et al.
    Suomalainen, Soile
    Hakulinen, Tommi
    Okhotnikov, Oleg
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Semiconductor saturable absorbers with recovery time controlled by lattice mismatch2007In: Optical Components and Materials IV / [ed] Shibin Jiang, Michel J. F. Digonnet, 2007, p. 64690P-1-64690P-7Conference paper (Refereed)
    Abstract [en]

    We propose and demonstrate a new method to reduce the absorption recovery time of semiconductor saturable absorber mirrors operating at the 1060-nm wavelength range. The method is based on controlling the amount of nonradiative recombination centers within the absorbing region by incorporating an InGaP epitaxial layer with a relative large lattice mismatch to GaAs (~2.2 %). The defect density within the absorbing region can be controlled by the thickness of a GaAs buffer layer grown between the InGaP lattice mismatched layer and the InGaAs/GaAs quantum-wells. For thickness of the GaAs buffer of ∼110 nm and∼570 nm the absorption recovery time was∼5 ps and ∼10 ps, respectively. It is important to note that the fast recovery time was achieved without degrading the nonlinear optical properties of the saturable absorber mirror. The practicality of the structures was proved by demonstrating a reliable self-starting operation of a mode-locked Yb-doped fiber laser.

  • 114. Guina, Mircea
    et al.
    Tuomisto, Pietari
    Okhotnikov, Oleg
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Mizohata, Kenichiro
    Keinonen, Juhani
    Semiconductor saturable absorbers with recovery time controlled through growth conditions2007In: Solid State Lasers XVI: Technology and Devices / [ed] Hanna J. Hoffman, Ramesh K. Shori, Norman Hodgson, 2007, p. 645113-1-645113-7Conference paper (Refereed)
    Abstract [en]

    We discuss a new method to shape the temporal response of saturable absorption in semiconductors. In particular, we investigate the possibility to control independently the absorption recovery time of each quantum-well forming the semiconductor absorber. The recovery time is tailored by irradiation with nitrogen ions produced by an RF-plasma source. The irradiation is performed in-situ as one step of the epitaxial growth process; the quantum-wells are individually exposed to a flux of N-ions after they are grown. The amount of non-radiative recombination centers within the quantum-wells is strongly related to the time interval during which the N-ions flux is active and to the thickness of the semiconductor layer grown on top of each quantum-well before the irradiation is performed. We apply this method to fabricate fast semiconductor saturable absorbers operating in the 1-μm wavelength range. The absorption recovery time could be changed from 300 ps to 10 ps without degradation of the nonlinear optical response. The practicality of the design is finally proved by using the semiconductor saturable absorbers for mode-locking Yb-doped fiber lasers.

  • 115. Guo, Changjian
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wang, Dawei
    Jiang, Meng
    Chen, Biao
    Experimental Demonstration of a Hybrid 1/2-dimentional En/Decoding Optical Code Division Multiple Access System2008In: Optical Transmission, Switching, and Subsystems VI, 2008, p. 713611-Conference paper (Refereed)
  • 116. Guo, Xin
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Bao, Jiming
    Wiley, Benjamin J.
    Yang, Qing
    Zhang, Xining
    Ma, Yaoguang
    Yu, Huakang
    Tong, Limin
    Direct Coupling of Plasmonic and Photonic Nanowires for Hybrid Nanophotonic Components and Circuits2009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 12, p. 4515-4519Article in journal (Refereed)
    Abstract [en]

    We report direct coupling of plasmonic and photonic nanowires using ultracompact near-field interaction. Photon-plasmon coupling efficiency up to 80% with coupling length down to the 200 nm level is achieved between individual Ag and ZnO nanowires. Hybrid nanophotonic components, including polarization splitters, Mach-Zehnder interferometers, and microring cavities, are fabricated out of coupled Ag and ZnO nanowires. These components offer relatively low loss with subwavelength confinement; a hybrid nanowire microcavity exhibits a Q-factor of 520.

  • 117.
    Gustafsson, Oscar
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Höglund, L.
    Karim, A.
    Noharet, B.
    Wang, Q.
    Gromov, A.
    Almqvist, S.
    Zhang, A.
    Acreo, Sweden.
    Junique, S.
    Andersson, J. Y.
    Asplund, C.
    von Würtemberg, R. Marcks
    Malm, H.
    Martijn, H.
    Long-wavelength infrared quantum-dot based interband photodetectors2011In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 54, no 3, p. 287-291Article in journal (Refereed)
    Abstract [en]

    We report on the design and fabrication of (Al)GaAs(Sb)/InAs tensile strained quantum-dot (QD) based detector material for thermal infrared imaging applications in the long-wavelength infrared (LWIR) regime. The detection is based on transitions between confined dot states and continuum states in a type-II band lineup, and we therefore refer to it as a dot-to-bulk (D2B) infrared photodetector with expected benefits including long carrier lifetime due to the type-II band alignment, suppressed Shockley-Read-Hall generation-recombination due to the relatively large-bandgap matrix material, inhibited Auger recombination processes due to the tensile strain and epitaxial simplicity. Metal-organic vapor-phase epitaxy was used to grow multiple (Al)GaAs(Sb) QD layers on InAs substrates at different QD nominal thicknesses, compositions, doping conditions and multilayer periods, and the material was characterized using atomic force and transmission electron microscopy, and Fourier-transform infrared absorption spectroscopy. Dot densities up to 1 x 10(11) cm(-2), 1 x 10(12) cm(-2) and 3 x 10(10) cm(-2) were measured for GaAs, AlGaAs and GaAsSb QDs, respectively. Strong absorption in GaAs, AlGaAs and GaAsSb multilayer QD samples was observed in the wavelength range 6-12 mu m. From the wavelength shift in the spectral absorption for samples with varying QD thickness and composition it is believed that the absorption is due to an intra- valance band transition. From this it is possible to estimate the type-II inter-band transition wavelength, thereby suggesting that (Al)GaAs(Sb) QD/InAs heterostructures are suitable candidates for LWIR detection and imaging.

  • 118.
    Gustafsson, Oscar
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Karim, Amir
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wang, Qin
    Reuterskiöld-Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Ernerheim-Jokumsen, Christopher
    KTH.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Persson, Sirpa
    Almqvist, Susanne
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Noharet, Bertrand
    Asplund, Carl
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Andersson, Jan Y.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Photoluminescence and photoresponse from InSb/InAs-based quantum dot structures2012In: Optics Express, E-ISSN 1094-4087, Vol. 20, no 19, p. 21264-21271Article in journal (Refereed)
    Abstract [en]

    InSb-based quantum dots grown by metal-organic vapor-phase epitaxy (MOVPE) on InAs substrates are studied for use as the active material in interband photon detectors. Long-wavelength infrared (LWIR) photoluminescence is demonstrated with peak emission at 8.5 mu m and photoresponse, interpreted to originate from type-II interband transitions in a p-i-n photodiode, was measured up to 6 mu m, both at 80 K. The possibilities and benefits of operation in the LWIR range (8-12 mu m) are discussed and the results suggest that InSb-based quantum dot structures can be suitable candidates for photon detection in the LWIR regime.

  • 119. Gvozdic, D. M.
    et al.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Comparison of performance of n- and p-type spin transistors with conventional transistors2005In: Journal of Superconductivity, ISSN 0896-1107, E-ISSN 1572-9605, Vol. 18, no 3, p. 349-356Article in journal (Refereed)
    Abstract [en]

    A spintronic device that has stimulated much research interest is the Datta-Das spin transistor. The mechanism behind it called the Rashba effect is that an applied voltage gives rise to a spin splitting. We propose ways to optimize this effect. The relevant spin splitting in k-space is predicted to increase with electric field at a rate that is more than two orders of magnitude larger for holes than for electrons. Furthermore, the almost negligible lattice-mismatch between GaAs and AlGaAs can be used to further enhance the advantage of hole-based spin transistors. Compared to present transistors we conclude that electron-based spin transistors will have problems to become competitive but hole-based ones are much more promising.

  • 120.
    Gvozdic, D M
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Schlachetzki, A
    Modulation response of V-groove quantum-wire lasers (vol 41, pg 842, 2005)2005In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 41, no 7, p. 1044-1044Article in journal (Refereed)
  • 121.
    Gvozdic, Dejan
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Dynamic response of V-groove quantum wire laser2005In: Physics and Simulation of Optoelectronic Devices XIII / [ed] Osinski, M; Henneberger, F; Amano, H, BELLINGHAM, WA: SPIE-INT SOC OPTICAL ENGINEERING , 2005, Vol. 5722, p. 80-89Conference paper (Refereed)
    Abstract [en]

    The dynamic characteristics of an InGaAs/InP lattice-matched V-groove quantum wire laser are theoretically considered. The differential gain of the laser is derived from the k-p theory, taking into account nonparabolicity of both bands, the conduction and the valence band. We investigate the bandwidth of the laser versus its optical confinement, driving current and roll-off time, including nonlinear gain suppression. In spite of solid differential gain and the D-factor comparable with the best-performance QW laser, the maximum bandwidth of the laser is limited to about 20GHz due to insufficient optical confinement.

  • 122.
    Gvozdic, Dejan M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Beyond the Rashba model2006In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 32, no 02-jan, p. 458-461Article in journal (Refereed)
    Abstract [en]

    We analyze some common approximations made in connection with the Rashba effect, where a macroscopic electric field gives rise to a spin splitting. We demonstrate that the size of the Rashba splitting is not given by the expectation value of the electric field or some other average electric field, as is commonly assumed. Instead we find that the local electric field near an interface of a wide asymmetric modulation-doped quantum well can give rise to a Rashba splitting that is an order of magnitude larger than expected from the average electric field. The localization of the wave functions of the spin subbands can be quite sensitive to the parallel wave vector. Clear deviations from an energy-independent wave vector splitting occur when nonparabolicity is taken into account.

  • 123.
    Gvozdić, Dejan M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. University of Belgrade, Serbia.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Novel mechanism for order-of-magnitude enhancement of rashba effect in wide modulation-doped quantum wells2007In: Physics of Semiconductors: 28th International Conference on the Physics of Semiconductors - ICPS 2006, American Institute of Physics (AIP), 2007, p. 1371-1372Conference paper (Refereed)
    Abstract [en]

    The Rashba effect leading to subband splitting in quantum wells is frequently taken to be proportional to some average electric field. We here show that taking the spatial variation of the electric field into account gives important effects. In particular we demonstrate that one can apply a moderate electric field to a wide modulation-doped quantum well and get an order-of-magnitude enhancement of the Rashba splitting characteristic of the built-in interface field. For small asymmetry the wave function localization and spin projection of a subband can be rapid functions of the in-plane wave vector.

  • 124. Hakkarainen, Timo
    et al.
    Setala, Tero
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Subwavelength electromagnetic near-field imaging of point dipole with metamaterial nanoslab2009Article in journal (Refereed)
    Abstract [en]

    We investigate near-field imaging of a point dipole by a lossy, nanoscale metamaterial slab. Making use of the electromagnetic angular-spectrum representation, we derive the Green tensor for the field transmission through the metamaterial slab, duly considering multiple reflections, polarizations, and wave-vector signs. With this general formalism, we calculate the point-spread function of the imaging system, which enables us to assess, for instance, resolution and image brightness. Our results demonstrate that with the metamaterial-slab lens one achieves resolution beyond the conventional diffraction limit of half the wavelength. In general, the resolution and image brightness are degraded when the slab thickness and absorption increase, but we show that in some cases the resolution is rather insensitive to the magnitude of the losses in the metamaterial.

  • 125. Hao, Jiaming
    et al.
    Qiu, Cheng-Wei
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Zouhdi, Said
    Design of an ultrathin broadband transparent and high-conductive screen using plasmonic nanostructures2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 23, p. 4955-4957Article in journal (Refereed)
    Abstract [en]

    In this Letter, we present a new type of ultrathin antireflection transparent and high-conductive screen based on plasmonic nanostructures that does not suffer from high loss and thickness coating and also can be used as good conductive material due to super electrical conductivity of the component (noble metal). Low reflection and greatly enhanced transmissions over a broad spectral range are observed at optical telecommunication frequencies in arbitrary polarizations. The performance is almost insensitive of the angle of incidence.

  • 126.
    Hao, Jiaming
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Zhou, Lei
    Manipulate light polarizations with metamaterials: From microwave to visible2010In: Frontiers of Physics in China, ISSN 1673-3487, Vol. 5, no 3, p. 291-307Article in journal (Refereed)
    Abstract [en]

    Polarization is an important characteristic of electromagnetic (EM) waves, and efficient manipulations over EM wave polarizations are always desirable in practical applications. Here, we review the recent efforts in controlling light polarizations with metamaterials, at frequencies ranged from microwave to visible. We first presented a 4 x 4 version transfer matrix method (TMM) to study the scatterings by an anisotropic metamaterial of EM waves with arbitrary propagating directions and polarizations. With the 4 x 4 TMM, we discovered several amazing polarization manipulation phenomena based on the reflection geometry and proposed corresponding model metamaterial systems to realize such effects. Metamaterial samples were fabricated with the help of finite-difference-time-domain (FDTD) simulations, and experiments were performed to successfully realize these ideas at both microwave and visible frequencies. Efforts in employing metamaterials to manipulate light polarizations based on the transmission geometry are also reviewed.

  • 127.
    Hao, Jiaming
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Zhou, Lei
    Manipulate light polarizations with metamaterials: From microwave to visible (vol 5, pg 291, 2010)2010In: Frontiers of Physics in China, ISSN 1673-3487, Vol. 5, no 4, p. 422-422Article in journal (Refereed)
  • 128.
    Hao, Jiaming
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Liu, Xianliang
    Padilla, Willie J.
    Zhou, Lei
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    High performance optical absorber based on a plasmonic metamaterial2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 25, p. 251104-Article in journal (Refereed)
    Abstract [en]

    High absorption efficiency is particularly desirable at present for various microtechnological applications including microbolometers, photodectors, coherent thermal emitters, and solar cells. Here we report the design, characterization, and experimental demonstration of an ultrathin, wide-angle, subwavelength high performance metamaterial absorber for optical frequencies. Experimental results show that an absorption peak of 88% is achieved at the wavelength of similar to 1.58 mu m, though theoretical results give near perfect absorption. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3442904]

  • 129.
    Hao, Jiaming
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ultrathin wide-angle optical metamaterial absorber2010In: Optical Nanostructures for Photovoltaics (PV) 2010, 2010Conference paper (Refereed)
    Abstract [en]

    We present design, analysis, and experimental demonstration of an ultra-thin, wide-angle perfect metamaterial absorber at optical frequency. The absorption is tunable by adjusting the nanostructure dimensions and is almost independent of the incidence angle.

  • 130.
    Hao, Jiaming
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Yan, Wei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Super-reflection and cloaking based on zero index metamaterial2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 10Article in journal (Refereed)
    Abstract [en]

    A zero index metamaterial (ZIM) can be utilized to block wave (super-reflection) or conceal objects completely (cloaking). The "super-reflection" device can be realized by a Mu zero (Epsilon zero) metamaterial with a perfect electric (magnetic) conductor inclusion of arbitrary shape and size for a transverse electric (magnetic) incident wave. In contrast, a Mu zero (Epsilon zero) metamaterial with a perfect magnetic (electric) conductor inclusion for a transverse electric (magnetic) incident wave can be used to conceal objects of arbitrary shape. The underlying physics here is determined by the intrinsic properties of the ZIM.

  • 131.
    Hao, Jiaming
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Zhou, Lei
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Nearly total absorption of light and heat generation by plasmonic metamaterials2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 16, p. 165107-Article in journal (Refereed)
    Abstract [en]

    We theoretically and numerically study the absorption effect and the heat generation in plasmonic metamaterials under light radiation at their plasmonic resonance. Three different types of structures, all possessing high-performance absorption for visible lights, are investigated. The main aim of this work is to present an intuitive and original understanding of the high-performance absorption effects. From the macroscopic electromagnetic point of view, the effective-medium approach is used to describe the absorption effects of the plasmonic metamaterials. On the other hand, the field distributions and heat generation effects in such plasmonic nanostructures are investigated, which also provides a satisfactory qualitative description of such absorption behavior based upon the microscopic perspective.

  • 132. Hassinen, T.
    et al.
    Tervo, J.
    Setala, T.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Hanbury Brown-Twiss effect with electromagnetic waves2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 16, p. 15188-15195Article in journal (Refereed)
    Abstract [en]

    The classic Hanbury Brown-Twiss experiment is analyzed in the space-frequency domain by taking into account the vectorial nature of the radiation. We show that as in scalar theory, the degree of electromagnetic coherence fully characterizes the fluctuations of the photoelectron currents when a random vector field with Gaussian statistics is incident onto the detectors. Interpretation of this result in terms of the modulations of optical intensity and polarization state in two-beam interference is discussed. We demonstrate that the degree of cross-polarization may generally diverge. We also evaluate the effects of the state of polarization on the correlations of intensity fluctuations in various circumstances.

  • 133. Hassinen, Timo
    et al.
    Tervo, Jani
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Cross-spectral purity of electromagnetic fields2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 24, p. 3866-3868Article in journal (Refereed)
    Abstract [en]

    We extend Mandel's scalar-wave concept of cross-spectral purity to electromagnetic fields. We show that in the electromagnetic case, assumptions similar to the scalar cross-spectral purity lead to a reduction formula, analogous with the one introduced by Mandel. We also derive a condition that shows that the absolute value of the normalized zeroth two-point Stokes parameter of two cross-spectrally pure electromagnetic fields is the same for every frequency component of the field. In analogy with the scalar theory we further introduce a measure of the cross-spectral purity of two electromagnetic fields, namely, the degree of electromagnetic cross-spectral purity.

  • 134.
    Hellström, Staffan
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Chen, Zhihui
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Soltanmoradi, R.
    Wang, Q.
    Andersson, J. Y.
    Increased photocurrent in quantum dot infrared photodetector by subwavelength hole array in metal thin film2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 23, p. 231110-Article in journal (Refereed)
    Abstract [en]

    Photocurrent enhancement in quantum dot (QD) infrared photodetector (QDIP) with an optical grating of subwavelength hole array in a thin metal film has been studied by calculating the transmission and diffraction of the infrared optical field through the grating and the light-matter interaction between the transmitted optical field and electrons confined in the QD. It is shown that due to the small aspect ratio of realistic QDs in QDIPs, the light diffraction due to the surface plasmon effect at the metal-semiconductor surface and the photonic subwavelength hole array structure is dominant in increasing the photocurrent.

  • 135.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Intersubband Electroabsorption Modulator2007In: Nitride Semiconductor Devices: Principles and Simulation / [ed] J. Piprek, Berlin: Wiley-VCH Verlagsgesellschaft, 2007, p. 253-277Chapter in book (Refereed)
  • 136.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Infrared modulator at 6 um with 1-V applied voltage swing using  intersubband transitions in step quantum wells grown by MOVPE2007Conference paper (Refereed)
  • 137.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Matsui, Satoshi
    Sophia University.
    Uchida, Hiroyuki
    Sophia University.
    Nakazato, Takuya
    Sophia University.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Aggerstam, Tomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Kikuchi, Akihiko
    Sophia University.
    Kishino, Katsumi
    Sophia University.
    Electroabsorption modulator based on intersubband transitions in (Al)(Ga)N step quantum wells considering intermixing2005Conference paper (Refereed)
  • 138.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylen, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Bratkovsky, Alexander
    METAL-NANOSHELL/QUANTUM-DOT ARRAY WAVEGUIDES WITH COMPENSATED LOSS2010In: Journal of nonlinear optical physics and materials, ISSN 0218-8635, Vol. 19, no 4, p. 595-601Article in journal (Refereed)
    Abstract [en]

    Dispersion properties of nanoarray waveguides composed of near-field-coupled arrays of metal-clad quantum dots (QDs) are calculated. The high loss due to operation of the metal shells close to resonance is mitigated by using optical gain in the QDs. The conditions for achieving loss compensated operation are given, with realistic material parameters and neglecting inhomogeneous broadening.

  • 139.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Bratkovsky, A.
    Dielectric function of quantum dots in the strong confinement regime2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, no 6Article in journal (Refereed)
    Abstract [en]

    The complex dielectric function of quantum dots (QDs) with a core-shell structure is modeled in the strong confinement regime. These results should be useful for the design of negative epsilon optical metamaterials, where the gain due to QDs could be an essential ingredient. Using the dielectric function it is also shown that conventional expressions for the gain substantially overestimate it for narrow linewidths.

  • 140.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yuan, Jun
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Bratkovsky, Alexander M.
    Hewlett-Packard Laboratories.
    Application of metal nanoparticle arrays as a metamaterial for nanooptical directional couplers2010Conference paper (Refereed)
  • 141.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yuan, Jun
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Bratkovsky, Alexander M.
    Hewlett-Packard Laboratories.
    Passive and active plasmonic nanoarray devices2011In: Metamaterials VI / [ed] Kuzmiak, Markos, Szoplik, SPIE - International Society for Optical Engineering, 2011, p. 80700T-1-80700T-6Conference paper (Refereed)
    Abstract [en]

    Metal nanoparticle arrays offer the possibility to considerably surpass the optical field confinement of silicon waveguides. The properties of directional couplers composed of such plasmonic nanoarrays are analyzed theoretically, while neglecting material losses. It is found that it is possible to generate very compact, submicron length, high fieldconfinement and functionality devices with very low switch energies. We further perform a study of spatial losses in Ag nanoparticle arrays by obtaining the group velocity and the lifetime of the surface plasmon polaritons. The losses are determined for different host permittivities, polarizations, and for spherical and spheroidal particles, with a minimum loss of 12 dB/μm. The possibilities to compensate the losses using gain materials, and the added noise associated with that, is briefly discussed.

  • 142.
    Holmström, Petter
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yuan, Jun
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. Xidian University, China.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. Hewlett-Packard Laboratories, United States.
    Bratkovsky, Alexander M.
    Hewlett-Packard Laboratories, United States.
    Theoretical study of nanophotonic directional couplers comprising near-field-coupled metal nanoparticles2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 8, p. 7885-7893Article in journal (Refereed)
    Abstract [en]

    The properties of integrated-photonics directional couplers composed of near-field- coupled arrays of metal nanoparticles are analyzed theoretically. It is found that it is possible to generate very compact, submicron length, high field-confinement and functionality devices with very low switch energies. The analysis is carried out for a hypothetical lossless silver to demonstrate the potential of this type of circuits for applications in telecom and interconnects. Employing losses of real silver, standalone devices with the above properties are still feasible in optimized metal nanoparticle structures.

  • 143.
    Iyer, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Effects of surface plasmons in subwavelength metallic structures2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The study of optical phenomena related to the strong electromagnetic response of noble metals (silver (Ag) and gold (Au) being most popular) over the last couple of decades has led to the emergence of a fast growing research area called plasmonics named after 'surface plasmons' which are electron density waves that propagate along the interface of a metal and a dielectric medium. Surface plasmons are formed by the coupling of light to the electrons on the metal surface subject to the fulfillment of certain physical conditions and they are bound to the metal surface. Depending on whether the metallic medium is a continuous film or a structure having dimensions less than or comparable to the wavelength of the exciting light, propagating or localized surface plasmons can be excited. The structure can be either a hole or an arbitrary pattern in a metal film, or a metallic particle. An array of subwavelength structures can behave as an effective homogeneous medium to incident light and this is the basis of a new class of media known as metamaterials. Metallic metamaterials enable one to engineer the electromagnetic response to  incident light and provide unconventional optical properties like negative refractive index as one prominent example. Metamaterials exhibiting negative index (also called negative index materials (NIMs)) open the door for super resolution imaging  and development of invisibility cloaks. However, the only problem affecting the utilization of plasmonic media to their fullest potential is the intrinsic loss of the metal, and it becomes a major issue especially at visible-near infrared (NIR) frequencies.

    The frequency of the surface plasmon is the same as that of the exciting light but its wavelength could be as short as that of X-rays. This property allows light of a given optical frequency to be conned into very small volumes via subwave lengthmetallic structures, that can be used to develop ecient sensors, solar cells, antennas and ultrasensitive molecular detectors to name a few applications. Also, interaction of surface plasmons excited in two or more metallic subwavelength structures in close proximity inuences the far-eld optical properties of the overall coupled system. Some eects of plasmonic interaction in certain coupled particles include polarization conversion, optical activity and transmission spectra mimicking electromagnetically-induced transparency (EIT) as observed in gas based atomicsy stems.

    In this thesis, we mainly focus on the optical properties of square arrays of certain plasmonic structures popularly researched in the last decade. The structures considered are as follows: (1) subwavelength holes of a composite hole-shape providing superior near-eld enhancement such as two intersecting circles (called' double hole') in an optically thick Au/Ag lm, (2) double layer shnets, (3) subwavelength U-shaped particles and (4) rectangular bars. The entire work is based on electromagnetic simulations using time and frequency domain methods.

    Au/Ag lms with periodic subwavelength holes provide extraordinarily high transmission of light at certain wavelengths much larger than the dimension of the perforations or holes. The spectral positions of the maxima depend on the shape of the hole and the intra-hole medium, thereby making such lms function as a refractive index sensor in the transmission mode. The sensing performance of the double-hole geometry is analyzed in detail and compared to rectangular holes.

    Fishnet metamaterials are highly preferred when it comes to constructing a NIM at optical frequencies. A shnet design that theoretically oers a negative refractive index with least losses at telecommunication wavelengths (1.4 1.5 microns) is presented.

    U-shaped subwavelength metallic particles, in particular single-slit split-ring resonators (SSRRs), provide a large negative response to the magnetic eld of light at a specic resonance frequency. The spectral positions of the structural resonances of the U-shaped particle can be found from its array far field transmission spectrum at normal incidence. An effort is made to clarify our understanding of these resonances with the help of localized surface plasmon modes excited in the overall particle. From an application point of view, it is found that a planar square array of SSRRs eectively functions as an optical half-wave waveplate at the main resonance frequency by creating a polarization in transmission that is orthogonal to that of incident light. A similar waveplate eect can be obtained purely by exploiting the near-eld interaction of dierently oriented neighbouring SSRRs. The physical reasons behind polarization conversion in dierent SSRR-array systems are discussed.

    A rectangular metallic bar having its dipolar resonance in the visible-NIR is called a nanoantenna, owing to its physical length in the order of nanometers. The excitation of localized surface plasmons, metal dispersion and the geometry of the rectangular nanoantenna make an analytical estimation of the physical length of the antenna from the desired dipolar resonance dicult. A practical map of simulated resonance values corresponding to a variation in geometrical parameters of Au bar is presented. A square array of a coupled plasmonic system comprising of three nanoantennas provides a net transmission response that mimicks the EIT effect. The high transmission spectral window possesses a peculiar dispersion profile that enables light with frequencies in that region to be slowed down. Two popular designs of such plasmonic EIT systems are numerically characterized and compared.

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  • 144.
    Iyer, Srinivasan
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Impact of apexes on the resonance shift in double hole nanocavities2010In: Optics Express, E-ISSN 1094-4087, Vol. 18, no 1, p. 193-203Article in journal (Refereed)
    Abstract [en]

    The transmission of light through metallic films with periodic double nanoholes is studied using vectorial three-dimensional finite element method. Special emphasis is given on understanding different transmission resonances arising in gold and silver films with periodic sub-wavelength holes of different shapes. The spectral shift of the hole-shape resonance resulting from a variation of the hole refractive index is analyzed for a double nanohole geometry in the transmission mode using numerical simulations. Specifically, the role of field enhancement at the apexes of the double nanohole in the sensing of medium within the hole cavity is pointed out and discussed. The presence of sharp apexes within the double nanoholes significantly improves the resonance sensitivity as compared to rectangular holes of comparable area. Impact of possible manufacturing errors on the overall sensitivity is also characterized. Robustness and a relatively simple fabrication procedure make these kinds of refractive index sensors practically attractive.

  • 145.
    Iyer, Srinivasan
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari. T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Interpreting the dipolar plasmon resonance of rectangular metallic nanoantennasIn: Plasmonics, ISSN 1557-1955, E-ISSN 1557-1963Article in journal (Other academic)
  • 146.
    Iyer, Srinivasan
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari. T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Linear birefringence in split-ring resonators2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 11, p. 2043-2045Article in journal (Refereed)
    Abstract [en]

    We study polarization-dependent transmission of light through arrays of single-slit split-ring resonator (SSRR) based systems at normal incidence using finite integration time domain (FITD) and finite element methods (FEM). It is found that a conventional planar array of SSRRs acts as an effective optical wave plate at certain polarizations of incident light. The effect is attributed to the intrinsic linear birefringence of individual SSRRs. A comparison is made with other split-ring resonator-based systems exhibiting wave-plate-like properties due to inter-SSRR coupling.

  • 147.
    Iyer, Srinivasan Shankararaman
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Loss optimization in double fishnet metamaterials at telecommunication wavelengths2011In: Journal of the European Optical Society-Rapid Publications, E-ISSN 1990-2573, Vol. 6, p. 11008-Article in journal (Refereed)
    Abstract [en]

    A hole shape optimization study was made for a double fishnet metamaterial producing a negative index of refraction within 1.4 - 1.5 mu m. It is found that within these wavelengths, elliptical holes offer lower losses as compared to rectangular ones and theoretically produce the best figure of merit (FOM) of approximately 6.

  • 148. Jacobsen, G.
    et al.
    Xu, Tianhua
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Li, J.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Zhang, Y.
    Phase noise influence in coherent optical OFDM systems with RF pilot tone: Digital IFFT multiplexing and FFT demodulation2012In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 33, no 3, p. 217-226Article in journal (Refereed)
    Abstract [en]

    We present a comparative study of the influence of dispersion induced phase noise for CO-OFDM systems using Tx channel multiplexing and Rx matched filter (analogue hardware based); and digital FFT multiplexing/ IFFT demultiplexing techniques (software based). An RF carrier pilot tone is used to mitigate the phase noise influence. From the analysis, it appears that the phase noise influence for the two OFDM implementations is very similar. The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) and this, in turns, leads to a BER specification. Numerical results focus on a CO-OFDM system with 1 GS/s QPSK channel modulation. Worst case BER results are evaluated and compared to the BER of a QPSK system with the same capacity as the OFDM implementation. Results are evaluated as a function of transmission distance, and for the QPSK system the influence of equalization enhanced phase noise (EEPN) is included. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. An important and novel observation is that the two types of systems have very closely the same BER as a function of transmission distance for the same capacity. For the high capacity QPSK implementation, the increase in BER is due to EEPN, whereas for the OFDM approach it is due to the dispersion caused walk-off of the RF pilot tone relative to the OFDM signal channels. For a total capacity of 400 Gbit/s, the transmission distance to have the BER < 10-4 is less than 277 km. For an RF pilot located in the center of the OFDM band in a CO-OFDM implementation with n-level PSK channel modulation the current results suggest that the walk-off effect is equivalent to the EEPN impact in a single channel n-level PSK system with the same capacity. This observation is important for future design of coherent long-range systems since it shows that there is a free choice between CO-OFDM and a high capacity nPSK implementation at least as long as the phase noise influence is concerned.

  • 149. Jacobsen, G.
    et al.
    Xu, Tianhua
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Sergeyev, S.
    Zhang, Y.
    Phase noise influence in long-range coherent optical OFDM systems with delay detection, IFFT multiplexing and FFT demodulation2012In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 33, no 4, p. 289-295Article in journal (Refereed)
    Abstract [en]

    We present a study of the influence of dispersion induced phase noise for CO-OFDM systems using FFT multiplexing/IFFT demultiplexing techniques (software based). The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) including - for the first time to our knowledge - in explicit form the effect of equalization enhanced phase noise (EEPN). This, in turns, leads to an analytic BER specification. Numerical results focus on a CO-OFDM system with 10-25 GS/s QPSK channel modulation. A worst case constellation configuration is identified for the phase noise influence and the resulting BER is compared to the BER of a conventional single channel QPSK system with the same capacity as the CO-OFDM implementation. Results are evaluated as a function of transmission distance. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. For a total capacity of 400 (1000) Gbit/s, the transmission distance to have the BER < 10-2 for the worst case CO-OFDM design is less than 800 and 460 km, respectively, whereas for a single channel QPSK system it is less than 1400 and 560 km.

  • 150.
    Jacobsen, Gunnar
    et al.
    Acreo AB, Electrum 236, Kista, Sweden.
    Kazovsky, L. G.
    Stanford University, USA.
    Xu, Tianhua
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Li, Jie
    Acreo AB, Electrum 236, Kista, Sweden.
    Zhang, Y.
    Tianjin University, China.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Phase noise influence in optical OFDM systems employing RF pilot tone for noise cancellation2011In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 32, no 2Article in journal (Refereed)
    Abstract [en]

    For coherent and direct-detection Orthogonal Frequency Division Multiplexed (OFDM) systems employing radio frequency (RF) pilot tone phase noise cancellation the influence of laser phase noise is evaluated. Novel analytical results for the common phase error and for the (modulation dependent) inter carrier interference are evaluated based upon Gaussian statistics for the laser phase noise. In the evaluation it is accounted for that the laser phase noise is filtered in the correlation signal detection. Numerical results are presented for OFDM systems with 4 and 16 PSK modulation, 200 OFDM bins and baud rate of 1 GS/s. It is found that about 225 km transmission is feasible for the coherent 4PSKOFDM system over normal (G.652) fiber.

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