Change search
Refine search result
1 - 31 of 31
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Akram, Nadeem
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Marcinkevičius, Saulius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    The effect of barrier composition on the vertical carrier transport and lasing properties of 1.55-mu m multiple quantum-well structures2006In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 42, no 7, p. 713-714Article in journal (Refereed)
    Abstract [en]

    In this paper, the effect of barrier bandgap and composition on the optical performance of 1.55-mu m InGaAsP/In-GaAsP and InGaAsP/InGaAlAs multiple quantum-well structures and Fabry-Perot lasers is evaluated experimentally. Direct vertical carrier transport measurements were performed through strain-compensated multiple quantum-well (MQW) test structures using femto-second laser pulse excitation and time-resolved photoluminescence up-conversion method. MQW test structures were grown with different barrier composition (InGaAsP and InGaAlAs) and barrier bandgap (varied from lambda(g) = 1440 to 1260 nm) having different conduction band Delta E-c and valence band discontinuity Delta E-v, while keeping the same InGaAsP well composition for all the structures. The ambipolar carrier transport was found to be faster in the structures with lower valence band discontinuity Delta E-v. Regrown semi-insulating buried heterostructure Fabry-Perot (SIBH-FP) lasers were fabricated from similar QWs and their static light-current-voltage characteristics (including optical gain and chirp spectra below threshold) and thermal characteristics were measured. Lasers with InGaAlAs barrier showed improved high-temperature operation, higher optical gain, higher differential gain, and lower chirp, making them suitable candidates for high-bandwidth directly modulated uncooled laser applications.

  • 2. Benisty, H.
    et al.
    Olivier, S.
    Weisbuch, C.
    Agio, M.
    Kafesaki, M.
    Soukoulis, C. M.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jaskorzynska, Bozena
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Talneau, A.
    Moosburger, J.
    Kamp, M.
    Forchel, A.
    Ferrini, R.
    Houdre, R.
    Oesterle, U.
    Models and measurements for the transmission of submicron-width waveguide bends defined in two-dimensional photonic crystals2002In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 38, no 7, p. 770-785Article in journal (Refereed)
    Abstract [en]

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

  • 3.
    Berglind, Eilert
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Holmström, Petter
    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.
    On the Possibilities to Create a Negative Permittivity Metamaterial with Zero Imaginary Part of the Permittivity at a Specific Frequency-Electrical Network Theory Approach2012In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 48, no 4, p. 507-511Article in journal (Refereed)
    Abstract [en]

    A permittivity function suggested in the literature describing a material that exhibits negative permittivity and no loss at a specific frequency (and losses at other frequencies) is analyzed using electrical network theory. An equivalent circuit of the polarization admittance consisting of RLC components is derived. Further, a proof is given showing that if the admittance is lossless at a specific frequency, then all components with losses (resistances) in the circuit have to be short circuited or blocked or virtually disconnected at this frequency by the use of ideal lossless resonant LC circuits. However, in the literature, inductors in metamaterials are associated with inherently lossy metal nanoparticles, hence invalidating the suggested permittivity function unless a lossless inductor at optical frequencies is found or proved possible.

  • 4. Carlsson, C.
    et al.
    Barrios, C. A.
    Messmer, E. R.
    Lovqvist, A.
    Halonen, J.
    Vukusic, J.
    Ghisoni, M.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Larsson, A.
    Performance characteristics of buried heterostructure VCSELs using semi-insulating GaInP: Fe regrowth2001In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 37, no 7, p. 945-950Article in journal (Refereed)
    Abstract [en]

    We have fabricated GaAs-AlGaAs buried heterostructure vertical cavity surface emitting lasers, emitting at 850 nm, using semi-insulating GaInP:Fe regrowth and investigated their static properties. Lasers of different size (10-21 mum) have threshold currents in the range 2.8-7.0 mA, and produce a maximum output power of 1.7-6.0 mW at room temperature. The variation of threshold current with device size shows that the leakage current at the regrowth interface accounts for a significant part of the injection current. In spite of this, a differential quantum efficiency in the range 20%-30% is obtained which indicates that the regrowth interface is smooth and does not introduce any significant scattering loss. Studies of the transverse mode properties suggest that the GaInP provides weak guiding, resulting in single mode operation up to an output power of 0.7 mW and a beam divergence of only 6 degrees for lasers as large as 10 mum.

  • 5.
    Chacinski, Marek
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Impact of losses in the Bragg section on the dynamics of detuned loaded DBR lasers2010In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 46, no 9, p. 1360-1367Article in journal (Refereed)
    Abstract [en]

    The dynamics of a distributed Bragg reflector laser with optical losses in the Bragg section is studied in detail. It is found that the modulation response depends not only on the detuning of the lasing wavelength from the Bragg reflectivity peak but also on the magnitude of the waveguide losses in the Bragg section. Depending on the losses, the damping of the relaxation peak can either increase or decrease when the laser is detuned on the long wavelength flank of the Bragg peak. Hence, in order to achieve maximum modulation bandwidth of the laser, the laser needs not only to have the correct detuning but also an optimized waveguide loss in the Bragg section. The physical reason for this dependence is discussed in terms of a modified rate equation model.

  • 6.
    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.
    Theoretical Investigation for Reducing Polarization Sensitivity in Si-Nanowire-Based Arrayed-Waveguide Grating (de)Multiplexer With Polarization-Beam-Splitters and Reflectors2009In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 45, no 5-6, p. 654-660Article in journal (Refereed)
    Abstract [en]

    A novel design for reducing polarization sensitivity in silicon-on-insulator-based arrayed-waveguide grating (AWG) (de)multiplexer is presented. Each arrayed waveguide has two sections separated by a polarization beam splitter (PBS). These two sections have different core widths and length differences. With these PBSs, one polarization is reflected and the other one goes through. The through polarization enters the second section and is then reflected by a reflector at the end of the second section of the arrayed waveguide. The theoretical simulation shows that one can diminish greatly the polarization sensitivity of both the central channel wavelength and the channel spacing by optimizing the core width and length difference of the second section. The design procedure and formulas are given and an appropriate diffraction order is chosen to obtain a good fabrication tolerance. As an example, an ultrasmall (82.2 x 85.1 mu m(2)) AWG (de)multiplexer with eight channels and a channel spacing of 4 nm is designed to have minimized polarization sensitivity and Bragg-grating PBSs and photonic crystal reflectors are used.

  • 7. Davanco, M.
    et al.
    Holmstrom, P.
    Blumenthal, D. J.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Directional coupler wavelength filters based on waveguides exhibiting electromagnetically induced transparency2003In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 39, no 4, p. 608-613Article in journal (Refereed)
    Abstract [en]

    We describe the principle and analyze the operation of an integrated optics directional coupler filter based on coupling between a regular waveguide and one, that exhibits electromagnetically induced transparency. Bandwidth length products on the order of 2 pm x mm are obtainable, as an example, using this approach.

  • 8.
    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.

  • 9. Ferrini, R.
    et al.
    Leuenberger, D.
    Mulot, M.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Moosburger, J.
    Kamp, M.
    Forchel, A.
    Anand, Srinivasan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Houdre, R.
    Optical study of two-dimensional InP-based photonic crystals by internal light source technique2002In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 38, no 7, p. 786-799Article in journal (Refereed)
    Abstract [en]

    We present the first optical study of 2-D photonic crystals (PCs) deeply etched in an InP/GaInAsP step-index waveguide. Following the same internal light source approach proposed by Labilloy and coworkers for the investigation of GaAs-based 2-D PCs, transmission measurements through simple PC slabs and 1-D Fabry-Perot (FP) cavities between PC mirrors were performed. Details are given on the experimental setup which has been implemented with respect to the original scheme and adapted to InP-based systems working at 1.5-mum. 2-D plane-wave expansion and finite difference time-domain (FDTD) methods are used to fit the experimental data. Out-of-plane losses were evaluated according to a recently introduced phenomenological model. In spite of the complex hole morphology in the measured samples, preliminary results are presented which indicate the possibility of separating different loss contributions from finite etch depth and hole shape. As for 1-D cavities, both FDTD and classical theory for planar resonators are applied in order to deduce the optical properties of the PC mirrors. The origin of an anomalously high transmission observed inside the stopgap is discussed and arguments are given to demonstrate the need for further modeling efforts when working in the bandgap regime.

  • 10.
    Forsberg, Erik
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hessmo, Björn
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Limits to modulation rates of electroabsorption modulators2004In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 40, no 4, p. 400-405Article in journal (Refereed)
    Abstract [en]

    We analyze the speed limitations of optical electroabsorption modulators. We argue that modulation rate limits are closely related to quantum mechanical adiabaticity. By analyzing the breakdown of the adiabatic approximation, analytical expressions for modulation limits are found. These expressions are numerically validated. Furthermore, we discuss the constraints on the allowable modulation rate set by losses from the quantum well and transition linewidth.

  • 11.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Spatial Wave Dynamics in 2-D Periodically Poled LiNbO3 Waveguides2009In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 45, no 11, p. 1415-1420Article in journal (Refereed)
    Abstract [en]

    Recent results on parametric spatial solitary waves arising from multiple resonances in purely nonlinear 2-D lattices are presented. Theory and experiments highlight new possibilities for light self-confinement and steering via engineered planar nonlinear structures in periodically poled materials.

  • 12. Garcia-Cortes, Alberto
    et al.
    Cascales, Concepcion
    de Andres, Alicia
    Zaldo, Carlos
    Zharikov, Evgenii V.
    Subbotin, Kirill A.
    Bjurshagen, Stefan
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Rico, Mauricio
    Raman scattering and Nd3+ laser operation in NaLa(WO4)(2)2007In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 43, no 1, p. 157-167Article in journal (Refereed)
    Abstract [en]

    The continuous-wave laser operation of Nd-doped tetragonal NaLa(WO4)(2) crystal is studied at room temperature by optical pumping in the spectral region overlapping AlGaAs diode laser emission. This crystal has inhomogenously broadened optical bands. From the room-temperature spectroscopic parameters determined it is found that the optimum Nd concentration for the F-4(3/2) -> I-4(J) laser channels must be in the 3-5 at.% range. For J = 11/2 and 13/2 channels (lambda approximate to 1.06 and 1.3 mu m) the most favourable polarization configuration is parallel to the crystallographic c axis, while for J = 9/2 little polarization dependence of the laser efficiency is predicted. Laser operation was achieved with a 3.35 at.% Nd-doped sample grown by the Czochralski method. The laser operation was tested in an hemispherical optical cavity pumped by a Ti:sapphire laser. Stimulated emission at lambda = 1056 nm was achieved for a wide spectral pumping range, lambda = 790-820 nm. Stimulated Raman scattering was achieved in the picosecond regime with an efficiency similar to that of monoclinic KY(WO4)(2) reference compound.

  • 13.
    Gvozdic, Dejan M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schlachetzki, A
    Modulation response of V-groove quantum-wire lasers2005In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 41, no 6, p. 842-847Article in journal (Refereed)
    Abstract [en]

    We analyze the modulation speed of an InGaAs-InP quantum-wire laser of a V-groove-shaped structure. The bandwidth is affected by the optical confinement Gamma, exhibiting a maximum at Gamma = 0.016. The maximum bandwidth for the intrinsic device is 20 GHz as a result of a calculation based on the experimentally obtained cross section of the device and including the nonparabolicity of the conduction and valence bands. We discuss the reduction of the bandwidth of the device itself by summarily considering the influence of the roll-off time and the cavity length as well as the nonlinear gain suppression.

  • 14. He, G. S.
    et al.
    Yong, K. T.
    Qin, H. Y.
    Zheng, Q. D.
    Prasad, P. N.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Stimulated Rayleigh-Bragg Scattering From a Two-Photon Absorbing CdSe-CdS-ZnS Quantum-Rods System: Optical Power Limiting and Phase-Conjugation2008In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 44, no 9-10, p. 894-901Article in journal (Refereed)
    Abstract [en]

    This work reports the properties of stimulated Rayleigh-Bragg scattering (SRBS) from a two-photon absorbing CdSe-Cds-ZnS quantum-rods (QRs) solution in chloroform, excited by 1064-nm and similar to 13-ns laser pulses. The two-photon absorbing capability of the scattering medium, as well as the pump threshold, spectral structure, and pulse waveforms of the backward stimulated scattering were measured. Comparing to a pure solvent or an organic dye-solution, the semiconductor QR system has many advantages such as the lower pump threshold, higher energy transfer efficiency, and better photo-physical and photo-chemical stability. The measured output/input characteristic curve shows that the backward SRBS can enhance the optical power limiting performance that is based on two-photon absorption, backward stimulated scattering, and other nonlinear absorption mechanisms. In addition, the backward SRBS beam from our sample medium exhibits a fairly good optical phase-conjugation capability, so that the distortion influence from an inserted aberrator can be automatically removed.

  • 15. He, G. S.
    et al.
    Zhang, A. P.
    Zheng, Q. D.
    Qin, Haiyan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Prasad, P. N.
    He, Sailing
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Multifocus Structures of Ultrashort Self-Focusing Laser Beam Observed in a Three-Photon Fluorescent Medium2009In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 45, no 7, p. 816-824Article in journal (Refereed)
    Abstract [en]

    Self-focusing effect and multifocus structures of an ultrashort (similar to 160-fs) pulsed laser beam of similar to 1.3-mu m wavelength are investigated in several organic liquids. The intensity-dependent self-focusing formation and multifocus structures of the infrared (IR) laser beam were directly observed in a three-photon active fluorescent dye solution cell, in which a high contrast image of the spatial structure of the self-focusing beam can be obtained due to the cubic dependence of the fluorescence intensity on the local IR laser intensity. By combining this dye solution cell with another cell filled with various transparent organic liquids, the contributions of these tested liquids to the observed self-focusing effect are elucidated. The numerical simulations for this type of self-focusing behavior are presented, based on the assumption that the major contribution to the observed self-focusing is the nonlinear refractive-index change of the solvent due to electronic-cloud distortion. The simulation results are in fairly good agreement with the experimental results.

  • 16.
    Hellström, Jonas E.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Finite beams in reflective volume Bragg gratings: theory and experiments2008In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 44, no 1, p. 81-89Article in journal (Refereed)
    Abstract [en]

    We present a theoretical model to describe finite beams incident on reflective volume Bragg gratings. We also give experimental results that verify our model. From these results, we identify certain properties of reflective volume Bragg gratings, such as beam waist, incidence angle and beam profile, that have direct impact on the design of laser cavities that include such gratings. We also show how these gratings can act as spatial mode filters.

  • 17. Holmstrom, P.
    et al.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ekenberg, Ulf
    KTH, Superseded Departments, Physics.
    Proposal of an optical modulator based on resonant tunneling and intersubband transitions2001In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 37, no 2, p. 224-230Article in journal (Refereed)
    Abstract [en]

    We propose and analyze an optical modulator based on intersubband transitions. The absorption is modulated by modulating the carrier density in the ground state of a quantum well (QW). Electrons are injected resonantly into this subband from a QW reservoir subband through a single barrier. When the two states are tuned out of resonance, the electrons are rapidly evacuated by means of the optical held, A waveguide based on surface plasmons is assumed in order to have a high optical mode overlap. Calculations are performed for a cascaded structure with four periods, assuming InGaAs-InAlAs QWs, The considered modulator structure operates at lambda =6.0 mum and is RC limited to 27 GHz, An extinction ratio of it is obtained with a low applied voltage of 0.6 V, At larger applied voltages, the absorption is bistable, Absorption at shorter/longer wavelengths can be obtained by using materials with a larger/smaller conduction band offset. We also assess resonant tunneling from a 2-D electron gas reservoir into an array of quantum dots and compare it to the 2-D-2-D tunneling resonance.

  • 18.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Electroabsorption modulator using intersubband transitions in GaN-AlGaN-AlN step quantum wells2006In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 42, no 7-8, p. 810-819Article in journal (Refereed)
    Abstract [en]

    We calculate the high-speed modulation properties of an electroabsorption modulator for lambda = 1.55 mu m based on Stark shifting an intersubband resonance in GaN-AlGaN-AlN step quantum wells. In a realistic simulation assuming an absorption linewidth Gamma = 100 meV we obtain an RC-limited electrical f(3dB) similar to 60 GHz at an applied voltage swing V-pp = 2.8 V. We also show that a small negative effective chirp parameter suitable for standard single-mode fiber is obtained and that the absorption is virtually unsaturable. The waveguide is proposed to be based on the plasma effect in order to simultaneously achieve a strong confinement of the optical mode, a low series resistance, and lattice-matched cladding and core waveguide layers. Extrapolated results reflecting the decisive dependence of the high-speed performance on the intersubband absorption linewidth Gamma are also given. At the assumed linewidth the modulation speed versus signal power ratio is on a par with existing lumped interband modulators based on the quantum confined Stark effect.

  • 19.
    Jänes, Peter
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Holmström, Petter
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ekenberg, Ulf
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A high-speed intersubband modulator based on quantum interference in double quantum wells2002In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 38, no 2, p. 178-184Article in journal (Refereed)
    Abstract [en]

    Calculations on a modulator based on quantum interference in AlGaAs/GaAs asymmetric double quantum wells (QWs) are performed. The modulation of the absorption is based on the anti-crossing behavior of the two lowest states in the coupled wells. At anti-crossing, the oscillator strengths of the transitions from these two lowest states to a higher state are changed in opposite directions. The width of the barrier between the wells should be thick enough to allow a large change in oscillator strength with applied field, yet thin enough so that the absorption peaks of the transitions are resolved. The QWs are designed so that one absorption peak has only a small energy shift for the transition used for modulation while the absorption varies rapidly with the applied voltage. A complete structure including a surface plasmon waveguide is proposed enabling calculations of modal absorption. Parameters important for the performance of the modulator are then determined. An extinction ratio of 10 dB at a wavelength of 8.4 mum is predicted for a device length of 18 mum and a peak-to-peak voltage of 0.9 V. The resistance-capacitance-limited 3-dB bandwidth is 130 GHz. The predicted performance compares very favorably with present interband modulators based on the quantum-confined Stark effect.

  • 20. Khoptyar, D.
    et al.
    Sergeyev, S.
    Jaskorzynska, Bozena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Upconversion assisted decay of population inversion in Er-doped silica after delta-pulse excitation2005In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 41, no 2, p. 205-212Article in journal (Refereed)
    Abstract [en]

    We investigate homogeneous upconversion (HUC) assisted decay of the population inversion in Er-doped silica after delta-pulse excitations by means of Monte Carlo simulations. We derive an analytic expression for this decay when energy migration among Er is negligible and show that it is essentially an extension of the Forster-type donor-acceptor quenching decay for the case when donor and acceptor ions are the same species. We compare HUC during the decay to HUC while pumping CW and show that they considerably differ at the low and moderate Er concentrations. Based on Monte Carlo (MC) simulations, we construct a neuristic approximation to the HUC assisted decay, which makes our MC results readily available for the future experimental and theoretical studies and provides simple means for determination of HUC parameters by fitting to experimental data.

  • 21.
    Liu, Kexin
    et al.
    Zhejiang University, China.
    Shen, Linfang
    Zheng, Xiaodong
    He, Sailing
    Zhejiang University, China.
    Interaction Between Two One-Way Waveguides2012In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 48, no 8, p. 1059-1064Article in journal (Refereed)
    Abstract [en]

    The interaction between two (parallel) one-way waveguidesformed by photonic crystals is investigated theoretically. It is shown that when thetwo waveguides support modes propagating in opposite directions, they can effectively interact with each other only within a narrow guiding region where their propagation constants are nearly zero. In this coupling window, the waveguides are contra-directionally coupled and the efficiency grows monotonously with the coupling length, reaching 100% as the coupling length is large enough. When the one-waywaveguides support the modes propagating in the same direction, they may be efficiently coupled through the whole guiding regime, and their coupling exhibits the same behavior as the conventional uniform waveguides. The coupling between theone-way waveguides is first analyzed with the coupled-mode approximation and then verified by rigorous numerical simulation. 

  • 22.
    Mogg, Sebastian
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Chitica, Nicolae
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Christiansson, Ulf
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Asplund, Carl
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hammar, Mattias
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sundgren, Petrus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Temperature sensitivity of the threshold current of long-wavelength InGaAs/GaAs VCSELs with large gain-cavity detuning2004In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 40, no 5, p. 453-462Article in journal (Refereed)
    Abstract [en]

    Record-long emission wavelengths up to 1.3 mhaverecently been demonstrated from highly strained InGaAs–GaAsdouble-quantum-well (DQW) vertical-cavity surface-emittinglasers (VCSELs). The operation of InGaAs VCSELs at suchlong wavelengths has relied on a large detuning between thespectral positions of QW gain maximum and cavity resonance.This detuning also affects the high-temperature performance andtemperature sensitivity of such devices. In this paper, we presentand evaluate the threshold current–temperature characteristicof such lasers in relation to the gain-cavity detuning at roomtemperature (RT). For a near-zero gain peak offset from theemission wavelength at RT, the minimum threshold current isfound at the temperature where the gain peak wavelength and thecavity resonance are approximately aligned. This is well in linewith a common design rule for GaAs-based VCSELs. However,we show that this design rule fails in the case of larger gain-cavitymisalignment at RT. Instead, a minimum threshold current is obtainedconsiderably below the temperature of zero gain offset. Wepropose a conceptual model that relates the gain-cavity detuning atRT to the temperature sensitivity of the active region performance,which qualitatively describes the threshold current–temperaturecharacteristic typical of VCSELs. The results demonstrate theimportance of improving the temperature characteristic of theactive region in order to reduce the high temperature sensitivityof devices with large detuning.

  • 23. Morthier, G.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kjebon, Olle
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Extended modulation bandwidth of DBR and external cavity lasers by utilizing a cavity resonance for equalization2000In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 36, no 12, p. 1468-1475Article in journal (Refereed)
    Abstract [en]

    We have investigated the occurence of a second resonance frequency in distributed Bragg reflector laser diodes and the high modulation bandwidth resulting from it. The influence of different laser parameters has been theoretically investigated. It is also shown that a similar behavior can be obtained in laser diodes with a passive, low-loss, and gratingless external cavity, The possibilities of large-signal digital modulation are also investigated.

  • 24.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dynamics of spatial hole burning effects in DFB lasers1995In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 31, p. 1981-1993Article in journal (Refereed)
    Abstract [en]

    A lumped small-signal model for intensity and frequency modulation response of semiconductor lasers, including the effects of longitudinal spatial hole burning (SHB), is presented. It is shown that the laser dynamics including SHB-effects can be accurately described by three small-signal rate equations. The simplicity of the model gives new insight into SHB-effects on modulation response and cavity state stability. It is shown that SHB-effects have a cut-off frequency that depends on the carrier lifetime (including stimulated recombination) and the feedback of perturbations in the longitudinal intensity distribution during modulation

  • 25.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Longitudinal spatial instability in symmetric semiconductor lasers due to spatial hole burning1992In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 28, p. 1443-1449Article in journal (Refereed)
    Abstract [en]

    A novel type of longitudinal instability due to spatial hole burning in symmetric semiconductor laser structures (DFB lasers in particular) is examined analytically and numerically. It is shown that, at a certain output power, the gain and refractive index spatial distributions of the lasing mode become unstable. Above this output power, the modal gains and oscillation frequencies change drastically, which often causes multimode operation. A measure of the cavity stability is introduced and derived analytically for a Fabry-Perot and a single phase-shifted DFB laser. Results from numerical simulations of a multiple phase-shifted DFB laser are presented

  • 26. Sergeyev, Sergey
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Two-Section Fiber Optic Raman Polarizer2012In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 48, no 1, p. 56-60Article in journal (Refereed)
    Abstract [en]

    We report on a theoretical study of polarization impairments in periodically spun fiber Raman amplifiers. Based on the Stochastic Generator approach we have derived averaged equations to calculate polarization dependent gain and mean-square gain fluctuations. We show that periodically spun fiber can work as a Raman polarizer but it suffers from increased polarization dependent gain and gain fluctuations. Unlike this, application of a depolarizer can result in suppression of polarization dependent gain and gain fluctuations. We demonstrate that it is possible to design a new fiber Raman polarizer by combining a short fiber without spin and properly chosen parameters and a long periodically spun fiber. This polarizer provides almost the same polarization pulling for all input signal states of polarization and so has very small polarization dependent gain.

  • 27. Sergeyev, Sergey
    et al.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Friberg, Ari T.
    Virtually Isotropic Transmission Media With Fiber Raman Amplifier2010In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 46, no 10, p. 1492-1497Article in journal (Refereed)
    Abstract [en]

    We report a theoretical study and simulations of a novel fiber-spin tailoring technique to suppress the polarization impairments, namely polarization mode dispersion and polarization dependent gain (PDG), in fiber Raman amplifiers. Whereas use of depolarizer or multiplexing pump laser diodes with a final degree of pump polarization of 1% for periodically spun fiber results in PDG of about 0.3 dB, we demonstrate that application of just a two-section fiber (where the first part is short and has no spin, and the second one is periodically spun) can reduce the PDG to as low as below 0.1 dB.

  • 28. Sheng, Z.
    et al.
    Yang, B.
    Yang, L.
    Hu, J.
    Dai, D. X.
    He, Sailing
    Experimental Demonstration of Deeply-Etched SiO2 Ridge Optical Waveguides and Devices2010In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 46, no 1, p. 28-34Article in journal (Refereed)
    Abstract [en]

    Deeply-etched SiO2 optical ridge waveguides are fabricated and characterized. A detailed discussion of the fabrication process (especially for the deep etching process) is presented. The measured propagation losses for the fabricated waveguides with different core widths range from 0.33 similar to 0.81 dB/mm. The loss is mainly caused by the scattering due to the sidewall roughness. The losses in bending sections are also characterized, which show the possibility of realizing a small bending radius (several tens of microns). 1 x N(N = 2, 4, 8) multimode interference couplers based on the deeply-etched SiO ridge waveguide are also fabricated and show fairly good performances.

  • 29. Shi, Kezhang
    et al.
    Bao, Fanglin
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Spectral Control of Near-Field Thermal Radiation With Periodic Cross Resonance Metasurfaces2018In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 54, no 1, article id 7000107Article in journal (Refereed)
    Abstract [en]

    Near-field thermal spectra can be engineered using periodic cross resonance metasurfaces. Structures consisting of single crosses, double crosses, and multiple crosses are proposed to control the spectral heat flux from narrow band to broadband with the Fabry-Perot-cavity-like effect and the interaction between the emitter and receiver. Radiation peaks originating from the cross structures split into two adjacent peaks in the near-field, due to the separate contributions of s- and p-polariton modes. Their frequency can be manipulated by adjusting the length of the crosses. Multiple radiation peaks can be generated by double crosses, and due to the strong coupling of resonance modes, multiple crosses can yield a broadband thermal spectrum ranging from 100-180 THz, with the total heat flux two orders of magnitude above the blackbody limit. The inherent physical mechanisms are illustrated by analyzing the energy transmission coefficients of the cross structures. The features of the radiation peaks and spectra are robust to the change of the gap distance or the temperature, which is advantageous for both the experimental design and fabrication of thermal radiation devices.

  • 30. Skagerlund, J.
    et al.
    Pusa, F.
    Sahlen, O.
    Gillner, L.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Granestrand, P.
    Lundqvist, L.
    Stoltz, B.
    Terlecki, J.
    Wahlin, F.
    Morner, A. -C
    Wallin, J.
    Oberg, O.
    Evaluation of an automatic method to extract the grating coupling coefficient in different types of fabricated DFB lasers1998In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 34, p. 141-146Article in journal (Refereed)
    Abstract [en]

    Distributed feedback (DFB) laser parameters such as grating coupling coefficient, effective indices, facet reflectances, and the phases of facet reflectances have been determined using a method based on least-square fitting of theoretical spectra to measured, subthreshold DFB laser emission spectra. The only inputs needed are geometrical parameters such as length, grating period, and internal grating phase shifts. A larger number of devices have been successfully characterized, and consistent results have been obtained in both 1.3- mu;m multi-quantum-well (MQW) DFB lasers with both facets as-cleaved, and in 1.55- mu;m MQW DFB lasers with no, one, or two facets as-cleaved

  • 31.
    Thylen, Lars
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Bratkovsky, Alexander
    Li, Jingjing
    Wang, Shih-Yuan
    Limits on Integration as Determined by Power Dissipation and Signal-to-Noise Ratio in Loss-Compensated Photonic Integrated Circuits Based on Metal/Quantum-Dot Materials2010In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 46, no 4, p. 518-524Article in journal (Refereed)
    Abstract [en]

    We analyze the power dissipation that is associated with using the gain of an embedded medium (quantum dots) to overcome the losses inherent in plasmonics systems employed to produce a negative dielectric constant for nanophotonics circuits. This power dissipation is primarily due to the dissipative losses in the metal structures and Auger recombination in the quantum dots. The impact of amplifier mediated signal-to-noise ratio (SNR) degradation and its effect on integration is analyzed, and a tradeoff between low power dissipation and SNR is quantified.

1 - 31 of 31
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf