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  • 51. Chen, Biao
    et al.
    Guo, Changjian
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Zhang, Linjian
    Jiang, Qiong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Add/drop multiplexing and TDM signal transmission in an optical CDMA ring network2007In: Journal of Optical Networking, ISSN 1536-5379, Vol. 6, no 8, p. 969-974Article in journal (Refereed)
  • 52.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Biao
    He, Sailing
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    A novel algorithm for intra-ONU bandwidth allocation in ethernet passive optical networks2005In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 9, no 9, p. 850-852Article in journal (Refereed)
    Abstract [en]

    A novel decentralized algorithm is introduced for the intra-ONU bandwidth allocation in an Ethernet Passive Optical Network (EPON). The algorithm is of low computational complexity, and can guarantee both the priority and fairness of the differentiated services. Simulation results are presented and compared with those of two existing bandwidth allocation algorithms.

  • 53.
    Chen, Jiajia
    et al.
    Centre for Optical and Electromagnetic Research, Joint Laboratory of Optical Communications of Zhejiang University, Zhejiang University.
    Chen, Biao
    Centre for Optical and Electromagnetic Research, Joint Laboratory of Optical Communications of Zhejiang University, Zhejiang University.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    A novel hierarchical algorithm for intra-ONU scheduling in an ethernet passive optical network2005In: Network Architectures, Management, and Applications III, 2005, Vol. 6022, p. W220-W220Conference paper (Refereed)
    Abstract [en]

    The quality of service (QoS) requirements of end users and services are totally different, and thus the multi-oriented (user-oriented and service-oriented) scheduling for access networks based on a remote scheduling system especially for EPONs is desired to replace the single-oriented (user-oriented or service-oriented) scheduling. In this paper we introduce a novel hierarchical algorithm of intra-ONU scheduling for multi-oriented QoS, which can guarantee both the priority of the differentiated services and the fairness of the different users. Numerical results have shown that our overall scheduling algorithm can fulfill various requirements of delay and throughput for the transmission of multimedia traffic for each end user.

  • 54.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Biao
    Centre for Optical Electromagnetic Research, Joint Laboratory of Optical Communications, Zhejiang University, Hangzhou 310027, China.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Self-protection scheme against failures of distributed fiber links in an Ethernet passive optical network2006In: Journal of Optical Networking, ISSN 1536-5379, Vol. 5, no 9, p. 662-666Article in journal (Refereed)
    Abstract [en]

    A novel self-protection scheme for an Ethernet passive optical network is introduced and studied at both the physical and the media access control layers. The scheme is simple and fast and can provide 1: 1 protection and automatic traffic restoration against the fiber link failure between a remote node ( RN) and any optical network unit (ONU). Simulation results show that fiber failure does not degrade the transmission performance, and the restoration time depends mainly on the switch time of the physical layer. Our protection scheme saves many long fibers, does not influence other normal ONUs, and requires no active device in the RN.

  • 55.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Biao
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Joint Bandwidth Scheduling to Support Differentiated Services and Multiple Service Providers in 1G and 10G EPONs2009In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, ISSN 1943-0620, Vol. 1, no 4, p. 343-351Article in journal (Refereed)
    Abstract [en]

    Dynamic bandwidth allocation (DBA) is one of the key issues for the current (1G) and next-generation (10G) Ethernet-based passive optical network (EPON) systems. We present a novel bandwidth scheduling scheme that integrates specific scheduling implementations in the optical line terminal and optical network units. This scheduling enables multiservice access with scalable quality of service support for the triple-play (video, voice, and data) services and open access. Our simulation results show that the proposed scheduling algorithm performs very well in supporting service differentiation and fair allocation of bandwidth to different service providers. A performance comparison between 1G and 10G systems is also presented. To the best of our knowledge, no detailed study of DBA in a 10G EPON can be found in the literature so far.

  • 56.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    De Andrade, M.
    Skubic, Björn
    Ericsson Research.
    Ahmed, Jawwad
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Enhancing IPACT with limited service for multi-thread DBA in long-reach EPON2010In: Communications and Photonics Conference and Exhibition (ACP), 2010 Asia, 2010, p. 629-630Conference paper (Refereed)
    Abstract [en]

    In this paper we propose an enhanced IPACT with limited service for multi-thread DBA in long-reach EPON. We evaluate our scheme by simulations in single-thread and double-thread cases and show that the DBA performance in terms of average delay and jitter can be significantly improved by the proposed algorithm.

  • 57.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Jirattigalachote, Amornrat
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    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.
    Novel Node Architectures for Wavelength-Routed WDM Networks with Wavelength Conversion Capability2008In: 34th European Conference and Exhibition on Optical Communication ECOC’08, 2008, 2008Conference paper (Other academic)
    Abstract [en]

    We present and evaluate two novel node architectures based on optical switch matrices and wavelength converters (WCs). Relatively small and cheap switches are required while WCs efficiently improve blocking probability

  • 58.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Kantor, Miroslaw
    Wajda, Krzysztof
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Network Protection2008In: Next-Generation FTTH Passive Optical Networks: Research towards unlimited bandwidth access / [ed] Josep Prat, Springer, 2008, p. 111-124Chapter in book (Refereed)
    Abstract [en]

    The significance of broadband and multimedia telecommunications is still increasing and the use of fibre-optic technology in the access network is growing very fast in order to meet customers demand. Along with the higher bandwidth demand, increasing number of subscribers, and advances in the Wavelength Division Multiplexing (WDM) device technology, the WDM Passive Optical Network (PON) and hybrid WDM/TDM (Time Division Multiplexed) PON has been considered as a next generation solution for the broadband access. Meanwhile, in order to meet Service Level Agreement (SLA) and guarantee the appropriate level of connection availability, fault management within any type of the PONs becomes more significant for the reliable service delivery and business continuance. Connection availability is an issue of deep concern to network operators since failure of any access network component, and thus interruption of their services, could result in significant losses of revenue. This chapter reviews some protection schemes in PONs and provides reliability performance evaluation for the considered architectures. A customer typically expects the end-to-end service availability at least at the same level as that provided by the traditional copper based systems. Thus, before investing in a new technology network operators need to make sure that it will not degrade the service quality perceived by the customers. To avoid misunderstanding we provide the set of definitions used in this chapter. Next, we review the protection schemes in PONs and follow with the reliability analysis and performance evaluation. Finally, we draw some conclusions.

  • 59.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Khanmohamadi, Sahar
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Abtahi, Farzad
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Xu, Zhenyu
    Cassidy, Andrew
    Tremblay, Christine
    Littlewood, Paul
    Asselin, Serge
    Belanger, Michel P.
    Passive wide area network solutions: Filterless and semi-filterless optical networks2011In: 13th International Conference on Transparent Optical Networks (ICTON) / [ed] Jaworski, M; Marciniak, M, 2011Conference paper (Refereed)
    Abstract [en]

    Advances in optical coherent transmission and electrical compensation technologies (such as coherent receiver and forward error correction FEC) have stimulated ideas for novel optical network architectures. Recently proposed passive wide area network solution, referred to as filterless optical network [1 #x2013;2] eliminates or minimizes the usage of active photonic reconfigurable network elements. In this approach, only the passive splitters and combiners for interconnecting the fiber links are utilized, which makes this network architecture more cost- and energy-effective as well as more reliable compared with networks based on active optical switching. However, the filterless optical network architecture implies some constraints on fiber interconnection design, maximum fiber-tree length and wavelength reuse due to its broadcast nature. Consequently, filterless solution always requires more resources (i.e. number of wavelengths) compared with the active switched optical networks which are allowed to utilize reconfigurable and coloured components. In order to improve the wavelength utilization while maintaining flexibility of resource allocation, this work extends the idea of filterless optical network by introducing some passive coloured components (e.g., fiber Bragg grating FBG, red/blue filters, etc) to drop local signals at some determined nodes. This approach is referred to as semi-filterless optical network. Furthermore, the semi-filterless solution maintains the passive feature, enabling high reliability and efficiency of cost and energy. Meanwhile, its non-broadcast property at some determined nodes has potential to decrease the transmission impairments and hence relax the constraints on fiber interconnection design and the maximal transparent length, which are strict in the filterless optical network. Our preliminary results confirm the advantages of semi-filterless solution.

  • 60.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Advances in Fiber Access Networks Development: Efficient Resource Allocation and Cost Effective Protection2011In: BROADBAND ACCESS COMMUNICATION TECHNOLOGIES V / [ed] Dingel, B; Jain, R; Tsukamoto, K, 2011, Vol. 7958, p. 795808-1-795808-10Conference paper (Refereed)
    Abstract [en]

    Access networks based on optical fiber can easily fulfill high bandwidth demand and cover large service areas. Fiber access networks are also scalable to meet the future capacity request. Among several alternatives, passive optical network (PON)is considered as the most promising one, because its passive point-to-multipoint architecture is characterized by relatively low deployment and operational cost. On the other hand, the passive point-to-multipoint feature in PONs also creates a number of challenges, such as efficient resource allocation and cost-effective protection. This paper provides an overview of the advances related to these two issues and points out the research topics that are still open and need to be investigated.

  • 61.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Analysis of protection schemes in PON compatible with smooth migration from TDM-PON to hybrid WDM/TDM-PON2007In: Journal of Optical Networking, ISSN 1536-5379, Vol. 6, no 5, p. 514-526Article in journal (Refereed)
    Abstract [en]

    We propose what we believe to be a novel protection scheme compatible with smooth migration from a time-division multiplexing (TDM) passive optical network (PON) to a WDM/TDM-PON. We show that our scheme is very cost effective while keeping connection availability, recovery time, and power budget at an acceptable level. We focus on the protection schemes, overview the existing methods, and introduce a link protection scheme compatible with smooth migration from TDM-PON to hybrid WDM/ TDM-PON. Furthermore, we analyze the cost, connection availability, recovery time, and optical link budget for different protection schemes in order to find the cost-effective solution both for the TDM-PON and hybrid WDM/ TDM- PON. (c) 2007 Optical Society of America.

  • 62.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Performance Analysis of Protection Schemes Compatible with Smooth Migration from TDM-PON to Hybrid WDM/TDM-PON2007In: OFC/NFOEC 2007 - Optical Fiber Communication and the National Fiber Optic Engineers Conference 2007, 2007Conference paper (Refereed)
    Abstract [en]

    We propose a novel protection scheme compatible with smooth migration from TDM-PON to WDM/TDM-PON. We show that our scheme is very cost-effective while keeping connection availability, recovery time and power budget at the acceptable level.

  • 63.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chughtai, Mohsan Niaz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Forzati, Marco
    Scalable Passive Optical Network Architecture for Reliable Service Delivery2011In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 3, no 9, p. 667-673Article in journal (Refereed)
    Abstract [en]

    A scalable and reliable architecture for both a wavelength division multiplexing passive optical network and a hybrid wavelength and time division multiplexing passive optical network with self-healing capability is presented and evaluated. Our protection scheme is compatible with a cascaded arrayed waveguide grating that can accommodate an ultra-large number of end users. A simple interconnection pattern between two adjacent optical network units (ONUs) is applied in order to provide protection for distributed fibers between a remote node and the ONUs. Therefore, the investment cost on a per-user basis can be significantly reduced. Meanwhile, the performance evaluation shows that our approach can achieve high connection availability while maintaining the support of long reach and high splitting ratio.

  • 64.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A novel protection scheme for a hybrid WDM/TDM PON2007In: NETWORK ARCHITECTURES, MANAGEMENT, AND APPLICATIONS V, 2007, Vol. 6784, p. F7840-F7840Conference paper (Refereed)
    Abstract [en]

    This paper proposes a novel protection scheme based on the cyclic property of an array waveguide grating (AWG) and neighboring connection pattern between two adjacent optical network units (ONUs) for the hybrid WDM/TDM passive optical networks (PONs). Our scheme uses 50% fewer wavelengths while offering one order of magnitude better connection availability than the existing scheme.

  • 65.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    High utilization of wavelengths and simple interconnection between users in a protection scheme for passive optical networks2008In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 20, no 5-8, p. 389-391Article in journal (Refereed)
    Abstract [en]

    A novel protection architecture for passive optical networks (PONs) is presented and evaluated. It is based on the cyclic property of arrayed waveguide gratings (AWGs) and the interconnection between two adjacent optical network units. The proposed scheme is compatible with both wavelength-division-multiplexing (WDM) PONs and hybrid WDM/time-division-multiplexing PONs. It is compared with two existing schemes and shown to have several advantages: 1) 50% less wavelengths is needed; 2) the fiber interconnections are simplified; 3) the connection availability is improved by one order of magnitude.

  • 66.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    He, Sailing
    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.
    Novel Architectures of Asynchronous Optical Packet Switch2007In: 33rd European Conference and Exhibition on Optical Communication ECOC’07, 2007, IEEE conference proceedings, 2007Conference paper (Other academic)
    Abstract [en]

    We propose two asynchronous optical packet switch architectures, with efficient contention resolution based on controllable optical buffers and tunable wavelength converters TWCs. Providing a few shared optical buffers significantly boosts the performance obtained by TWCs.

  • 67.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Kantor, M.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Comparison of hybrid WDM/TDM passive optical networks (PONs) with protection2008In: 34th European Conference on Optical Communication, 2008, ECOC 2008, 2008Conference paper (Refereed)
    Abstract [en]

    We present the evolution of PON protection and compare reliability performance related to investment and management cost for some representative cases. Our results can indicate the most cost efficient architectures.

  • 68.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Tacca, Marco
    Fumagalli, Andrea
    Dynamic routing based on information summary-LSA in WDM networks with wavelength conversion2008In: Proceedings of 2008 10th Anniversary International Conference on Transparent Optical Networks, ICTON, NEW YORK: IEEE , 2008, p. 50-54Chapter in book (Other academic)
    Abstract [en]

    This Study investigates the use of information Summary (IS) applied to the advertised available resources to reduce the amount of link state advertisement (LSA) overhead, which is necessary to achieve distributed dynamic routing in WDM networks,. As illustrated in the Study, if carefully designed, the resulting IS-LSA protocol can significantly contain the size of the advertised data set without excessively affecting the network performance, i.e., the blocking probability caused by routing decisions based on incomplete link state information.

  • 69.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yan, Min
    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.
    Cui, T.
    Photothermal direct writing of metallic microstructure for frequency selective surface at terahertz frequencies2012In: Proceedings of the 2012 International Workshop on Metamaterials, Meta 2012, IEEE , 2012, p. 6464923-Conference paper (Refereed)
    Abstract [en]

    Maskless photothermal direct writing technique was investigated to fabricate planar microscale metallic structures. In this technique, we use a tightly focused nanosecond pulsed infrared light to heat the metallic thin film on substrate. With sufficient volumic power density, the metal inside a "hot spot" could be removed from substrate. This technique benefits from not only the enhanced optical absorption, thanks to the surface plasmon resonance of metallic thin film, but also the reduced thermal conductivity, due to the frequent boundary scattering of phonons inside the thin film. To verify the performance of our direct writing technique, a cross-slot periodic array is scribed in gold thin film on silica substrate. Such a pattern can serve as a frequency selective surface at terahertz, which has many applications in terahertz radio system, e. g. rejecting thermal noise before terahertz receiver or serving as reflectors in Fabry-Perot etalon for astronomy spectroscopy.

  • 70.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Yan, Min
    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.
    Hao, Jiaming
    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.
    Photothermal phenomena in plasmonics and metamaterials2011In: ADVANCES IN OPTICAL THIN FILMS IV, 2011, p. 81681K-Conference paper (Refereed)
    Abstract [en]

    Our recent theoretical and experimental investigation of the photothermal effect in a planar metamaterial absorber is reviewed in the present paper. The observed ultrasensitive photothermal heating in such an absorber nanostructure irradiated by a pulsed white-light source is elaborated with a simple yet compelling heat transfer model, which is subsequently solved with a finite-element method. The simulation results not only agree with the experimental finding, but also provide more detailed understanding of the temperature transition in the complex system.

  • 71.
    Chen, Zhihui
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hellström, Staffan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yu, Zhong-Yuan
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Time-resolved photocurrents in quantum well/dot infrared photodetectors with different optical coupling structures2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 4, p. 043502-Article in journal (Refereed)
    Abstract [en]

    Temporal developments of photocurrents excited by an infrared radiation pulse in quantum well/dot infrared photodetectors with different optical coupling structures have been theoretically studied. It is shown that the light diffraction in a conventional reflective grating structure is a near-field effect containing severe crosstalk from neighboring pixels. A concave reflector not only eliminates the crosstalk but also strongly diffracts and focuses the incident electric field into deep active layers, which significantly increases the photocurrents in the photodetectors.

  • 72.
    Chughtai, Mohsan Niaz
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Study of physical layer impairments in high speed optical networks2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work done in this thesis focuses on the impact of transmission impairments in high speed optical networks. Specifically it focuses on the impact of nonlinear impairments in long haul fiber optic data transmission. Currently deployed fiber optic transmission networks are running on NRZ OOK modulation formats with spectral efficiency of only 1 bit/symbol. To achieve spectral efficiency beyond 1 bit/symbol, fiber optic communication systems running on advanced modulation formats such as QPSK are becoming important candidates. The practical deployment of QPSK based fiber optic communication system is severely limited by Kerr-induced nonlinear distortions such as XPM and XPolM, from the neighboring NRZ OOK channels. In this thesis we focus on the impact of nonlinear impairments (XPM and XPolM) in fiber optical transmission systems running on QPSK modulation with both differential and coherent detection. The dependence of impact of nonlinear impairments on SOP, baud rate of the neighboring NRZ OOK channels and PMD in the fiber, is analyzed in detail through numerical simulations in VPItransmission Maker®. In this thesis we also analyze digital signal processing algorithms to compensate linear and nonlinear impairments in coherent fiber optic communication systems. We propose a simplification of the existing method for joint compensation of linear and nonlinear impairments called "digital back propagation". Our method is called "weighted digital back propagation". It achieves the same performance of conventional digital back propagation with up to 80% reduction in computational complexity.In the last part of the thesis we analyze the transmission performance of a newly proposed hybrid WDM/TDM protection scheme through numerical simulation in VPItransmission Maker®. The transmission performance of the hybrid WDM/TDM PON is limited by impairments from passive optical devices and fiber optical channel.

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  • 73.
    Chughtai, Mohsan Niaz
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Forzati, Marco
    AcreoNetlab, Kista.
    Mårtensson, Jonas
    AcreoNetlab, Kista.
    Tipsuwannakul, Ekawit
    Chalmers University of Technology.
    Karlsson, Magnus
    Chalmers University of Technology.
    Analysis of Non-Linear Impairments in 40 Gbaud PM DQPSK and D8PSK Transmission2010In: ICTON 2010, IEEE Press, 2010Conference paper (Refereed)
    Abstract [en]

    In this paper, 40 Gbaud transmission of single polarization (SP) and Polarization-Multiplexed (PM), RZ-DQPSK and RZ-D8PSK signals is analyzed numerically. The impact of nonlinear crosstalk arising from the presence of neighbouring intensity-modulated channels is analyzed in terms of required OSNR for the BER of 10-3versus launch power.

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    fulltext
  • 74. Crnjanski, J. V.
    et al.
    Gvozdić, Dejan M.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Intersubband absorption in modulation-doped V-shaped quantum wires2005In: NUSOD '05 - Proceedings of the 5th International Conference on Numerical Simulation of Optoelectronic Devices, 2005, p. 15-16Conference paper (Refereed)
    Abstract [en]

    The calculation of the intersubband absorption in a modulation-doped V-shaped-quantum-wire (V-QWR) is presented. The method is based on self-consistent solving of the single band Schrödinger equation in a nonparabolic approximation. Our calculation shows that the absorption spectrum is anisotropic and has two absorption peaks at 19meV and 115 meV depending on light polarization.

  • 75.
    Dai, Daoxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Guan, Xiaowei
    Wang, Jianwei
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wang, Zhechao
    Wosinski, Lech
    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.
    Nano-scale silicon hybrid plasmonic waveguides and devices2011Conference paper (Refereed)
    Abstract [en]

    A summary for our recent work on silicon hybrid plasmonic waveguides and devices is given.

  • 76.
    Dai, Daoxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Shi, Yaocheng
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Thylen, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Silicon hybrid plasmonic submicron-donut resonator with pure dielectric access waveguides2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 24, p. 23671-23682Article in journal (Refereed)
    Abstract [en]

    Characteristic analyses are given for a bent silicon hybrid plasmonic waveguide, which has the ability of submicron bending (e.g., R = 500nm) even when operating at the infrared wavelength range (1.2 mu m similar to 2 mu m). A silicon hybrid plasmonic submicron-donut resonator is then presented by utilizing the sharp-bending ability of the hybrid plasmonic waveguide. In order to enable long-distance optical interconnects, a pure dielectric access waveguide is introduced for the present hybrid plasmonic submicron-donut resonator by utilizing the evanescent coupling between this pure dielectric waveguide and the submicron hybrid plasmonic resonator. Since the hybrid plasmonic waveguide has a relatively low intrinsic loss, the theoretical intrinsic Q-value is up to 2000 even when the bending radius is reduced to 800nm. By using a three-dimensional finite-difference time-domain (FDTD) method, the spectral response of hybrid plasmonic submicron-donut resonators with a bending radius of 800nm is simulated. The critical coupling of the resonance at around 1423nm is achieved by choosing a 80nm-wide gap between the access waveguide and the resonator. The corresponding loaded Q-value of the submicron-donut resonator is about 220.

  • 77.
    Dai, Daoxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Shi, Yaocheng
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Gain enhancement in a hybrid plasmonic nano-waveguide with a low-index or high-index gain medium2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 14, p. 12925-12936Article in journal (Refereed)
    Abstract [en]

    A theoretical investigation of a nano-scale hybrid plasmonic waveguide with a low-index as well as high-index gain medium is presented. The present hybrid plasmonic waveguide structure consists of a Si substrate, a buffer layer, a high-index dielectric rib, a low-index cladding, a low-index nano-slot, and an inverted metal rib. Due to the field enhancement in the nano-slot region, a gain enhancement is observed, i.e., the ratio partial derivative G/partial derivative g > 1, where g and G are the gains of the gain medium and the TM fundamental mode of the hybrid plasmonic waveguide, respectively. For a hybrid plasmonic waveguide with a core width of w(co) = 30nm and a slot height of h(slot) = 50nm, the intrinsic loss could be compensated when using a low-index medium with a moderate gain of 176dB/cm. When introducing the high-index gain medium for the hybrid plasmonic waveguide, a higher gain is obtained by choosing a wider core width. For the high-index gain case with h(slot) = 50nm and w(co) = 500nm, a gain of about 200dB/cm also suffices for the compensation of the intrinsic loss.

  • 78.
    Dai, Jin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ye, Fei
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Light absorber based on nano-spheres on a substrate reflector2013In: Optics Express, E-ISSN 1094-4087, Vol. 21, no 6, p. 6697-6706Article in journal (Refereed)
    Abstract [en]

    We systematically study a type of plasmonic light absorber based on a monolayer of gold nano-spheres with less than 30 nm in diameters deposited on top of a continuous gold substrate. The influences of particle size, inter-particle distance, particle-substrate spacer size etc on the resonance are studied thoroughly with a 3D finite-element method. We identified that the high-absorption resonance is mainly due to gap plasmon (coupled through particle bodies) when the separation between neighboring nano-spheres is small enough, such as close to 1 nm; at larger particle separations, the resonance is dominated by particle dipoles (coupled through the host dielectric). Experimentally, an absorber was fabricated based on chemically-synthesized gold nanoparticles coated with silica shell. The absorber shows a characteristic absorption band around 810 nm with a maximum absorbance of approximately 90%, which agrees reasonably well with our numerical calculation. The fabrication technique can be easily adapted for devising efficient light absorbers of large areas.

  • 79.
    Dainese, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Wavelength selective coupler based on Bragg Reflection Waveguide2005Conference paper (Refereed)
    Abstract [en]

    Highly wavelength selective optical filters are essential components for channel management in modern Dense Wavelength Division Multiplexed communication systems with 50GHz channel spacing and below 0.4nm channel bandwidth. We have designed, fabricated and characterized a new type of wavelength selective directional coupler, based on the high differential dispersion between a Bragg Reflection Waveguide (BRW) and a conventional buried channel silica waveguide.

    The bandwidth of the device is inversely proportional to the length of the coupler as well as to the differential effective refractive index dispersion of the coupled modal fields, at the wavelength of phase matching. The BRW is made of a high index (amorphous) silicon core layer, surrounded vertically by two periodic Bragg reflectors with alternating layers of silica and silicon. The silica waveguide with a Ge-doped core, vertically stacked with the BRW, allows fiber incoupling loss below 1dB which is essentially the insertion loss of the device. The device is operating within the optical bandgap of the Bragg reflectors. Both the bandwidth and the coupling wavelength can be tuned during the fabrication process: the fields’ overlap and the coupling coefficient between the two waveguide modes are controlled by one of the Bragg reflectors (coarse control) and a spacer layer (fine control); the position of the coupling wavelength is mainly determined by the BRW core thickness.

    The devices were fabricated by depositing SiO2 and a-Si:H films on a 4” <100> oriented Si substrate, by plasma enhanced chemical vapor deposition, at a temperature of 250ºC. The 5µm wide vertical stack of BRW and silica waveguide were defined by lithography and etched in an inductively coupled plasma reactor. The 8.8µm thick coupler structure was covered with a 16µm thick silica cladding. The device can be easily integrated in a standard silica-based planar lightwave circuit.

    The measured filter suppression is 14dB and the FWHM is 0.29nm for only a 1.73mm long device, which is close to the estimated value of 0.31nm, and one of the lowest ever reported for this type of coupler.

  • 80.
    Dainese, Matteo
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Zhang, Ziyang
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Swillo, Marcin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Experimental demonstration of a vertically coupled photonic crystal filter2005Conference paper (Refereed)
    Abstract [en]

    Design, fabrication, and characterization of an optical filter based on vertical coupling between a silicon wire waveguide and a cavity in a suspended silicon photonic crystal membrane is presented for the 1550 nm wavelength spectral region.

  • 81. De Andrade, Marilet
    et al.
    Kramer, Glen
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Sallent, Sebastia
    Mukherjee, Biswanath
    Evaluating Strategies for Evolution of Passive Optical Networks2011In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 49, no 7, p. 176-184Article in journal (Refereed)
    Abstract [en]

    Rapidly-increasing traffic demands will require the upgrade of optical access networks, namely deployed Passive Optical Networks (PONs), which may soon face capacity exhaustion. Such upgrade options must consider several technical and cost factors for evolution toward a shared multiple-channel PON using Wavelength-Division Multiplexing (WDM). WDM can facilitate the seamless upgrade of PONs, since capacity can be increased by adding new wavelength channels. We study the requirements for optimal migration toward higher bandwidth per user, and examine scenarios and cost-effective solutions for PON evolution.

  • 82.
    Dong, Lin
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Optical Properties of Nanoparticles in Composite Materials2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nanoparticles are synthetic structures with dimension from 1 to 100 nanometers and are various in types. Some favorable properties peculiar to the nanoparticles (generally owing to size effects) make them prevailing and beneficial for applications in different scientific and engineering fields. A large portion of these properties find their connection to optics and photonics. In the context of optics, the thesis is devoted to study of two specific categories of nanoparticles, gold nanoparticles and CdSe-CdS core-shell quantum dots, aiming at investigating the influence and potential of the particles in applications of lasing and medical diagnosis/treatment.

    Gold nanoparticles have been widely exploited in radiative decay engineering to achieve fluorescence enhancement or quenching of fluorophores, with the help of a localized surface plasmon resonance band in visible range. As the technique is recently introduced to lasing applications, the influence of the gold nanoparticles on the photostability of the gain medium needs more attention. In this work, the effect of size and concentration of gold nanoparticles on altering the photostability of aqueous solution of Rhodamine 6G in lasing process is demonstrated and analyzed. Energy transfer and nanoparticle induced heat are found to be responsible for the acceleration of photobleaching. It is shown that coating the gold nanoparticles with a 15 nm thick silica layer can effectively diminish the photostability degradation of the gain medium.

    Gold nanorods are popular for in vivo diagnostic and therapeutic applications due to their strong absorption of near-infrared light. A novel type of multimodal nanoparticles based on gold nanorods is synthesized here and optically characterized. The coating of silica and gadolinium oxide carbonate hydrate renders the nanoparticles superior performance as MRI/CT contrast agents than commercially available products. Meanwhile, the precise temperature control of bio-tissues using the particles under laser irradiation makes them promising for photothermal treatment of cancer cells.

    The thesis also addresses several open questions with respect to CdSe-CdS core-shell quantum dots. A numerical model is built to study the spatial separation of electrons and holes in the dots with different core/shell sizes. QDs in different geometrical shapes are investigated. It is found that the spherical core-shell QDs can be flexibly tuned between the type-I and the type-II regime by varying the dimensions of the core and the shell. The feature is confirmed by time-resolved photoluminescence measurements, in which the carrier recombinations from different spatial paths can be distinguished. A sign of amplified spontaneous emission is observed with spherical dots of an appropriate combination of core radius and shell thickness, indicating the potential of the QDs for lasing applications.

    Download full text (pdf)
    Optical Properties of Nanoparticles in Composite Materials
  • 83.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Iyer, Srinivasan
    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.
    3D fabrication of waveguide and grating coupler in SU-8 by optimized gray scale electron beam lithography2010In: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010, 2010, p. 542-543Conference paper (Refereed)
    Abstract [en]

    Gray scale electron beam lithography is optimized for simple and accurate prototyping of 3D waveguides and grating output couplers in SU-8. Gratings with complex profiles and free of lag effect can be realized with this technique.

  • 84.
    Dong, Lin
    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.
    One-step fabrication of polymer components for microphotonics by gray scale electron beam lithography2011In: Journal of the European Optical Society-Rapid Publications, E-ISSN 1990-2573, Vol. 6, p. 11010-Article in journal (Refereed)
    Abstract [en]

    We demonstrate an application of gray scale electron beam lithography (EBL) for the fabrication of polymer waveguides and grating output couplers with depth variable features, using the SU-8 resist. The technique is mainly applicable for multi-level binary profile, where groove depths of the structure are controlled by choosing a proper exposure dose. Unlike reactive ion etching which is limited by the lag effect, the gray scale EBL allows free combination of groove widths and depths. Shrinking effect which is critical in polymer couplers' writing is taken into account and can be compensated. For better fabrication feasibility, the grating couplers can be simultaneously produced with waveguides with no inter-step alignment required. Therefore, this is a promising technique in manufacturing grating output couplers for polymer based waveguides with high performance in terms of mode matching/confinement and coupling efficiency.

  • 85.
    Dong, Lin
    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.
    Sergeyev, Sergey
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Spatial light modulator as a reconfigurable intracavity dispersive element for tunable lasers2010In: Central European Journal of Physics, ISSN 1895-1082, E-ISSN 1644-3608, ISSN 1895-1082 print, Vol. 8, no 2, p. 228-234Article in journal (Refereed)
    Abstract [en]

    An improved approach for narrow-band wavelength selection in tunable lasers is described. To provide the tunability, a reconfigurable diffractive optical element (DOE) based on a programmable spatial light modulator (PSLM) is applied. With a proper choice of the phase transfer function of the PSLM, the device can be used as a dispersive intra-cavity component for precise tuning within the lasing spectral band of a solid-state dye laser. The suggested design allows avoiding the mechanical movement of any cavity components. The tunability performance and simulation are demonstrated using the Fourier optics method.

  • 86.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Sugunan, Abhilash
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Hu, Jun
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Zhou, Sicheng
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots2013In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 52, no 1, p. 105-109Article in journal (Refereed)
    Abstract [en]

    Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.

  • 87.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Ye, Fei
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Chughtai, Adnan
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Liuolia, Vytautas
    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.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Lasing From Water Solution of Rhodamine 6G/Gold Nanoparticles: Impact of SiO2-Coating on Metal Surface2012In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 48, no 9, p. 1220-1226Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticles embedded in an optical gain material, particularly in a water solution of Rhodamine 6G, used in dye lasers can both increase and damp dye flourescence, thus changing the laser output intensity. Simultaneously, such nanoparticles influence the gain material's resistance against photobleaching. In this paper, we report our study on the impact of the SiO2 coating of nanoparticles on the enhancement or quenching and photobleaching of the fluorescence. The investigation demonstrates a noticeable improvement of the gain material's photostability compared to uncoated gold nanoparticles when silicon dioxide coating is implemented.

  • 88.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Ye, Fei
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Chughtai, Adnan
    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.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Enhanced photostability of aqueous solution of Rhodamine 6G with gold nanoparticles in lasing process by silica coating2012In: 2012 Conference on Lasers and Electro-Optics, CLEO 2012, IEEE , 2012, p. 6325399-Conference paper (Refereed)
    Abstract [en]

    Gold nanoparticles are mixed in aqueous solution of Rhodamine 6G to modify the lasing output intensity. The photostability deterioration of the gain medium by gold nanoparticles is successfully compensated by silica coating on the nanoparticles.

  • 89.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Ye, Fei
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Chughtai, Adnan
    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.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Photostability of lasing process from water solution of Rhodamine 6G with gold nanoparticles2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 1, p. 34-36Article in journal (Refereed)
    Abstract [en]

    We report the lasing performance and photobleaching of gain material containing a water solution of Rhodamine 6G dye and gold nanoparticles (NPs). In comparison to a pure dye solution, the investigated material demonstrated both enhancement and quenching of the lasing output, depending on the relative concentration of the gold NPs. Although the presence of NPs with an optimized concentration looks preferable in terms of the lasing output enhancement, such additives deteriorate the operational resource of the gain material; i.e., the photobleaching rate speeds up.

  • 90.
    Dong, Lin
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Ye, Fei
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Hu, Jun
    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.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Fluorescence quenching and photobleaching in Au/Rh6G nanoassemblies: impact of competition between radiative and non-radiative decay2011In: Journal of the European Optical Society-Rapid Publications, E-ISSN 1990-2573, Vol. 6, p. 11019-Article in journal (Refereed)
    Abstract [en]

    We report the study of fluorescence quenching from nanoassemblies formed by Rhodamine 6G and gold nanoparticles (Au NPs) of 2.6 nm radius. The presence of Au NPs induces long-term degradation of the photostability (photobleaching) of Rhodamine 6G used as a gain medium in a Fabry-Perot laser cavity. We found that the degradation gets profound when the Au NPs concentration is significantly increased. Calculation of the radiative rate and direct time-resolved measurement of the fluorescence decay indicates that both the decrease of radiative decay rate and increase of non-radiative decay rate are responsible for the fluorescence quenching and photostability degradation. An energy transfer from the dye molecules to gold nanoparticles is dominating within small distance between them and suppresses the quantum efficiency of Rhodamine 6G drastically. In a long time scale, the photobleaching rate was slowing down, and the laser output intensity reached a stabilized level which depends on the gold nanoparticles concentration.

  • 91.
    Ekenberg, Ulf
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. University of Belgrade, Serbia.
    Gvozdíc, Dejan M.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. University of Belgrade, Serbia.
    Spin splitting in modulation-doped semiconductor quantum wells2009In: Quantum Wells: Theory, Fabrication and Applications, Nova Science Publishers, Inc., 2009, p. 385-425Chapter in book (Refereed)
    Abstract [en]

    We review different ways to achieve a spin splitting of two-dimensional electron and hole subbands with the combination of inversion asymmetry and spin-orbit interaction. In particular we focus on novel mechanisms to achieve a substantial spin splitting with a small applied bias across the sample. We discuss the proper inclusion of electric-field-induced spin splittings in the framework of the envelope function approximation and argue that the Rashba effect should be included in the form of a macroscopic potential as diagonal terms in a multiband approach rather than commonly used terms dependent on k and electric field. One of our findings is that the expectation values of the electric field can differ substantially and even have opposite signs for the spin-split components of a subband. Thus the frequent assignment of one expectation value to a subband is sometimes not appropriate. We also discuss symmetric quantum wells with Dresselhaus terms and the influence of the interfaces on the spin splitting. Our approach is applied to wide modulation-doped n-type InGaSb quantum wells with strong built-in electric fields in the interface regions. We demonstrate an efficient mechanism for switching on and off the Rashba splitting with an electric field being an order of magnitude smaller than the local built-in field that determines the Rashba splitting. For a slightly asymmetric quantum well we demonstrate a reversal of the spin direction in a spin subband in two steps as the in-plane wave vector is increased a little. Our most significant results pertain to the superefficient Rashba effect for holes. With a careful design of doping profile and strain we find that the wave vector splitting for hole subbands can be made several thousand times stronger than for electrons at the same electric field. The implications of our findings for spintronic devices, in particular the Datta-Das spin transistor and proposed modifications of it, are discussed.

  • 92. Eriksson, U.
    et al.
    Lewén, Robert
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Irmscher, Stefan
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Design and fabrication of electroabsorption modulators for data rates up to 100 Gb/s2004In: Proc. Int. Conf. Transparent Opt. Netw., 2004, p. 41-46Conference paper (Refereed)
    Abstract [en]

    We present segmented transmission-line (TML) electroabsorption modulators (EAM) matched to 50 Ω. The devices show excellent high frequency performance up to 50 GHz, and exhibit a maximum model-extrapolated 3 dBe bandwidth of 90 GHz. Design considerations and optimization techniques for periodic segmented TML-EAMs are discussed. Also methods used for the device fabrication are presented.

  • 93. Erkintalo, Miro
    et al.
    Surakka, Minna
    Turunen, Jari
    Friberg, Ari T.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Genty, Goery
    Coherent-mode representation of supercontinuum2012In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 2, p. 169-171Article in journal (Refereed)
    Abstract [en]

    We apply the coherent-mode expansion to correlation functions used to describe the coherence properties of supercontinuum generated in nonlinear fibers. We show that the leading term of the expansion represents the quasi-coherent part of the field while the quasi-stationary part is embedded into the higher-order modes. The evolution of the modal expansion and the number of modes needed to describe the supercontinuum field are also discussed.

  • 94. Fiammengo, Martina
    et al.
    Lindström, Alexander
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Skubic, Björn
    Experimental evaluation of cyclic sleep with adaptable sleep period length for PON2011In: European Conference on Optical Communication, ECOC, Geneva, 2011Conference paper (Refereed)
    Abstract [en]

    An experimental evaluation of cyclic sleep for PON is presented where different control algorithms for adaptable sleep length period are compared.

  • 95.
    Fokine, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Wang, Jing
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Hao, Jiaming
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Meiser, Niels
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Optical Characterization of Plasmonic Metamaterial Absorber2010Conference paper (Refereed)
    Abstract [en]

    A reflectance/transmittance experiment setup to characterize a sub-wavelength, wide-angle, ultrathin metamaterial absorber at optical frequency regime is shown, and the measured results are presented.

  • 96.
    Forchheimer, Robert
    et al.
    Linköpings Universitet.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    An optical overlay network concept for hard QoS requirements2009In: ICTON 2009: 11TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, 2009, p. 1195-1198Conference paper (Other academic)
    Abstract [en]

    It has long been argued that the best-effort strategy on which Internet is based will limit its use for real-time applications such as video or telephony. However, it has been shown that such services can indeed tolerate some jitter and rate variations through various error resilience and concealment techniques. Despite of that the Internet infrastructure is continuously upgraded with higher performance components, which further reduce the transmission problems; still there are certain classes of applications that undoubtedly will need new transmission paradigms. An example is the remote control of an industrial process that may require jitter levels down to a few microseconds. Another example is quantum cryptography where an optical transparent path between sender and receiver is to be established. In this paper we present a concept based on an optical overlay network infrastructure. This network concept can be applied in an incremental way and will enable the current network infrastructure to handle demands with such extreme QoS requirements.

  • 97.
    Friberg, Ari T.
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Lajunen, Hanna
    Torres-Company, Victor
    Spectral elementary-coherence-function representation for partially coherent light pulses2007In: Optics Express, E-ISSN 1094-4087, Vol. 15, no 8, p. 5160-5165Article in journal (Refereed)
    Abstract [en]

    A broad class of partially coherent non-stationary fields can be expressed in terms of the recently proposed independent-elementary-pulse model. In this work we first introduce a corresponding dual representation in the frequency domain and then extend this concept by considering shifted and weighted elementary spectral coherence functions. We prove that this method, which closely describes practical optical systems, leads to properly defined correlation functions. As an example, we demonstrate that our new model characterizes, in a natural way, trains of ultra-short pulses, affected by noise and timing jitter, emitted by usual modulators employed in telecom applications.

  • 98.
    Fu, Ying
    et al.
    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.
    Optical transmission and waveguiding by excitonic quantum dot lattices2006In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 23, no 11, p. 2441-2447Article in journal (Refereed)
    Abstract [en]

    Metal-dielectric-metal configurations of optical waveguides have a very high laterally packaging density at the cost of high optical loss. Photonic crystals based on refractive-index-modulation materials have been used in optics, e.g., two materials having different refractive indices form a well-defined Bragg refraction mirror. Such a waveguide has lower loss but also lower packaging density. From the outset of these two notions, we propose a photonic-crystal device based on the exciton-polariton effect in a three-dimensional array of semiconductor quantum dots (QDs) for ultradense optical planar circuit applications. Excitons are first photogenerated in the QDs by the incident electromagnetic field, the exciton-polariton effect in the QD photonic crystal then induces an extra optical dispersion in QDs. The high contrast ratio between the optical dispersions of the QDs and the background therefore creates clear photonic bandgaps. By carefully designing the QD size and the QD lattice structure, perfect electromagnetic field reflection can be obtained at a specific wavelength in the lossless case, thus providing the fundamental basis for ultradense optical waveguide applications.

  • 99.
    Fu, Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Optical properties of nanostructures2011Book (Other academic)
    Abstract [en]

    Nanotechnology has been named as one of the most important areas of forthcoming technology because it promises to form the basis of future generations of electronic and optoelectronic devices. From the point of view of technical physics, all these developments greatly reduce the geometric sizes of devices, and thus the number of active electrons in the system. Quantum mechanical considerations about electronic states, electron transports, and various scattering processes, including light-matter interaction, are thus crucial. However, the theoretical study is extremely difficult. The authors' first numerical simulation work about a three-dimensional energy band structure calculation in 1995 took more than 6 months to complete for one bias configuration of a nanoscale metal-oxide-semiconductor field-effect transistor. With today's computation workstations the CPU time is reduced to less than 24 hours. This book discusses electrons and photons in and through nanostructures by the first-principles quantum mechanical theories and fundamental concepts (a unified coverage of nanostructured electronic and optical components) behind nanoelectronics and optoelectronics, the material basis, physical phenomena, device physics, as well as designs and applications. The combination of viewpoints presented in the book can help foster further research and cross-disciplinary interaction needed to surmount the barriers facing future generations of technology design.

  • 100.
    Fu, Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    A lossless negative dielectric constant from quantum dot exciton polaritons2008In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 5, p. 1551-1555Article in journal (Refereed)
    Abstract [en]

    Prospects for a lossless negative dielectric constant material for optical devices are studied. Simulations show that with sufficient gain, a mixture of two semiconductor quantum dots (QDs) can produce an effective dielectric constant that is lossless and negative. This permits, in concept, arbitrarily small scaling of the optical mode volume, a major goal in the field of nanophotonics. The proposed implementation of a lossless negative dielectric constant material based on colloidal QDs opens a tractable path.

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