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  • 1.
    Akram, Nadeem
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lateral current injection (LCI) multiple quantum-well 1.55 mu m laser with improved gain uniformity across the active region2004In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 36, no 9, p. 827-846Article in journal (Refereed)
    Abstract [en]

    A simulation study of lateral current injection 1.55 mum laser with strain-compensated multiple quantum-well (MQW) active region (InGaAsP well, InGaAlAs barrier) is presented using self-consistent 2D numerical simulations. The effects of different mesa width and p-doping in the QWs on the carrier and gain uniformity across the active region are explored. A high p-doping in the quantum wells is found to increases the carrier and gain non-uniformity across the active region. The QW region close to the n-contact side does not provide much gain at high optical powers. An asymmetric optical waveguide design is proposed to help reduce the gain non-uniformity across the active region. By shifting the optical modal peak toward the p-side, the modal overlap between the gain region and the optical mode is improved and a more even carrier and gain distribution is obtained. However, due to reduced bandgap of the quaternary InGaAsP p-cladding, an enhanced electron leakage out of the QWs into the p-cladding degrades the laser efficiency and increases the threshold current. Transient time - domain simulations are also performed to determine the small-signal modulation response of the laser promising a simulated high modulation bandwidth suitable for direct-modulation applications.

  • 2. Cheng, C.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Optimal design for a copper vapor laser with a maximum output by using a genetic algorithm2001In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 33, no 1, p. 83-98Article in journal (Refereed)
  • 3.
    Dai, Daoxin
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    He, S L
    KTH, Superseded Departments, Alfvén Laboratory.
    Calculation of the spectral response of an arrayed-waveguide gating demultiplexer with a wide-angle beam propagation method in a cylindrical coordinate system2004In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 36, no 11, p. 967-979Article in journal (Refereed)
    Abstract [en]

    The spectral response of an arrayed-waveguide grating (AWG) demultiplexer is calculated by simulating the field propagation in the output section of an AWG with a wide-angle beam propagation method (BPM) in a cylindrical coordinate system. As in a practical design of an AWG demultiplexer, each output waveguide consists of two straight sections connected by a bending section. The spectral response obtained by the present algorithm is more accurate than those obtained with two popular approximate methods, namely, the conventional overlapped integral method and the standard BPM for radially straight and infinitely long output waveguides. With the present algorithm, the dependence of the spectral response on the parameters of the output section is analyzed. The channel crosstalk and the 3 dB passband width of the spectral response depend mainly on the length of the first straight section, the end separation and the angular separation of the output waveguides. The bending section results in an asymmetrical spectral response with remarkable sidelobes which can be reduced by increasing the bending radius.

  • 4.
    Dalarsson, Mariana
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jaksic, Zoran
    Exact analytical solution for fields in a lossy cylindrical structure with hyperbolic tangent gradient index metamaterials2016In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 48, no 3, article id 209Article in journal (Refereed)
    Abstract [en]

    The advent of metamaterials with tailorable frequency dispersion ensured the emergence of transformation optics with proposed applications that include cloaking devices, superconcentrators, superabsorbers, beam shapers and benders, field and polarization rotators, etc. A crucial property of interest for transformation optics is the possibility to custom design the spatial dependence of optical properties, i.e. to attain a gradient of effective refractive index. The cylindrical geometry has been one of the prototypal proposed forms and actually the first theoretical and experimental cloaking devices had radial symmetry. In this contribution we present an exact analytical approach to the solution of Helmholtz' equations applied to radial propagation of electromagnetic waves through a cylinder containing negative and positive refractive index parts. A hyperbolic tangent gradient of refractive index is assumed. Our approach is inspired by the correspondence between transformation optics and quantum mechanics. A remarkably simple exact analytical solution is derived that takes into account realistic losses in negative-positive refractive index material composites.

  • 5. Sheng, Z. Y.
    et al.
    He, J. J.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Reduced back reflection design for an etched diffraction grating based planar demultiplexer2003In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 35, no 12, p. 1123-1131Article in journal (Refereed)
  • 6. Shi, Wei
    et al.
    Faraji, Behnam
    Greenberg, Mark
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Xiang, Yu
    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.
    Lestrade, Michel
    Li, Zhi-Qiang
    Li, Z. M. Simon
    Chrostowski, Lukas
    Invited Paper: Design and modeling of a transistor vertical-cavity surface-emitting laser2011In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 42, no 11-13, p. 659-666Article in journal (Refereed)
    Abstract [en]

    A multiple quantum well (MQW) transistor vertical-cavity surface-emitting laser (T-VCSEL) is designed and numerically modeled. The important physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a significant effect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the analytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps.

  • 7.
    Shum, Ping
    et al.
    Nanyang Technol Univ, Singapore 639798, Singapore..
    Knight, Jonathan
    Univ Bath, Dept Phys, Bath BA2 7AY, Avon, England..
    Love, John
    Australian Natl Univ, Fac Sci, Dept Phys, Opt Sci Grp, Canberra, ACT 0200, Australia..
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Symposium on microstructured and nanostructured optical fibers in ICMAT 2007 - Preface2007In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 39, no 12-13, p. 947-948Article in journal (Other academic)
  • 8.
    Song, Jun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhu, Ning
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Analysis method of the effect of fabrication errors on a planar waveguide demultiplexer2006In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 38, no 15, p. 1203-1216Article in journal (Refereed)
    Abstract [en]

    The impact of fabrication errors on a planar waveguide demultiplexer is analyzed based on an analytical method. The explicit expression of the transfer function taking into account phase and amplitude errors is presented in order to analyze the loss and crosstalk of the demultiplexer caused by fabrication errors. A basic requirement for the demultiplexer with a certain crosstalk criterion can be easily obtained. Using an etched diffraction grating demultiplexer as an example, it is shown that the analytical results have a good agreement with results from a numerical method.

  • 9.
    Zhang, Yuan
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. Lund University, Sweden; Zhejiang University, China.
    Sun, Xianhe
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. Lund University, Sweden; Zhejiang University, China.
    Liu, Wen
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. Lund University, Sweden; Zhejiang University, China.
    Lee, El-Hang
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. Lund University, Sweden; Zhejiang University, China.
    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. Lund University, Sweden; Zhejiang University, China.
    Improved properties of gold nanorods coated with thin multilayer of small organic molecules by fast and facile method for surface enhanced Raman scattering2015In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 47, no 8, p. 2759-2766Article in journal (Refereed)
    Abstract [en]

    We introduce a thin multilayer-shell-coated gold nanorods (GNRs) that we have been able to achieve by way of coating them with two thin layers of small organic molecules in a new, efficient, effective, time-saving, and easy-to-control multilayer coating method. Compared to the thick shell, due to the small size of the coating molecules, this new type of GNR, by simply mixed with the sample solution, has shown that it can act as a highly effective and improved surface enhanced Raman scattering (SERS) enhancement agent without the need of any sample connecting or doping. This enhancement is found not only related to the off-resonance surface enhancement, but also to the increased signal-to-noise ratio brought by the low level of fluorescence emission. It showed excellent stability in strong acids, bases and some organic solvents as examined by comparing the longitudinal surface plasmon resonance peak values. A living body experiment on a tumor-bearing nude mouse injected with the Raman reporter dye loaded onto our new GNRs showed strong surface enhanced Raman scattering signal in the tumor, suggesting its high potential use in many related optical applications.

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