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Sökning: WFRF:(Gustavsson Johan 1974 )

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41.
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42.
  • Gustavsson, Johan, 1974, et al. (författare)
  • High-speed 850-nm VCSELs for 40 Gb/s transmission
  • 2010
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • We have explored the possibility to extend the data transmission rate for standard 850-nm GaAs-based VCSELs beyond the 10 Gbit/s limit of today's commercially available directly-modulated devices. By sophisticated tailoring of the design for high-speed performance we demonstrate that 10 Gb/s is far from the upper limit. For example, the thermal conductivity of the bottom mirror is improved by the use of binary compounds, and the electrical parasitics are kept at a minimum by incorporating a large diameter double layered oxide aperture in the design. We also show that the intrinsic high speed performance is significantly improved by replacing the traditional GaAs QWs with strained InGaAs QWs in the active region. The best overall performance is achieved for a device with a 9 μm diameter oxide aperture, having in a threshold current of 0.6 mA, a maximum output power of 9 mW, a thermal resistance of 1.9 °C/mW, and a differential resistance of 80 Ω. The measured 3dB bandwidth exceeds 20 GHz, and we experimentally demonstrate that the device is capable of error-free transmission (BER
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43.
  • Gustavsson, Johan, 1974, et al. (författare)
  • High speed 850nm VCSELs for >40Gb/s transmission
  • 2013
  • Ingår i: 2013 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2013. - 9781479904570 ; , s. OTh4H.4-
  • Konferensbidrag (refereegranskat)abstract
    • VCSELs capable of direct modulation exceeding 40Gb/s are needed in next generation optical interconnect standards. Using a refined high-speed design we demonstrate GaAs-based VCSELs having record-high 28GHz modulation bandwidth, and that operate error-free at 47Gb/s.
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44.
  • Gustavsson, Johan, 1974, et al. (författare)
  • High-speed, high-temperature VCSELs for optical interconnects
  • 2013
  • Ingår i: 2013 IEEE Photonics Society Summer Topical Meeting Series, PSSTMS 2013. - 9781467350600 ; , s. 7-8
  • Konferensbidrag (refereegranskat)abstract
    • Directly modulated VCSELs operating at 40Gb/s are required for next generation optical interconnect standards. Using a refined high-speed design we demonstrate GaAs-based VCSELs that operate error-free at 47Gb/s at 25°C, and 40Gb/s at 85°C.
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45.
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46.
  • Gustavsson, Johan, 1974 (författare)
  • Modal Dynamics of Vertical-Cavity Surface-Emitting Lasers
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this work, a comprehensive dynamic model has been developed for simulating a novel semiconductor laser type, referred to as the Vertical-Cavity Surface-Emitting Laser (VCSEL). The high-speed behavior was simulated and compared to experiments, where excellent agreement was found. The model was also applied in the development of high-power single mode VCSELs, using a novel surface relief technique. The VCSEL is a small volume laser, which makes it suitable for high-speed communication. The epitaxial structure of the laser is complex, but once it is fabricated, the remaining fabrication steps are relatively simple. Surface emission enables on-wafer testing and therefore the unit cost of a VCSEL can be considerably reduced compared with other semiconductor lasers. Further, the low power consumption, low threshold current and the low-divergent circular output beam are additional advantages. This has made the VCSEL an established transmitter in optical communication systems, especially in short to medium distance networks with a large number of end-users, where many reliable, high-speed, low-cost components must be used. However, a drawback of the VCSEL is the tendency to lase in multiple modes, which degrades the beam quality and affects the dynamics. Further, at 10 Gbit/s modulation, which is the next generation standard for Ethernet communication, even the VCSEL is slow in some respects. The developed model takes the 3D geometry of the laser into account, and it can follow relevant physical properties (temperature, optical fields, carrier density) in time. Also considered are the random fluctuations in the processes that supply or consume and generate or annihiliate carriers and photons, adding noise to the output. The work includes a study of the digital and analog modulation characteristics of single and multimode VCSELs, including eye diagrams, bit-error rates, and harmonic and intermodulation distortion. The noise behaviour was also investigated, including relative intensity noise, frequency noise, and linewidth. Finally, record-high fundamental mode output power from a VCSEL, using a shallow surface relief, was demonstrated.
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47.
  • Gustavsson, Johan, 1974, et al. (författare)
  • Mode and polarization control in VCSELs using shallow surface structures
  • 2007
  • Ingår i: IET Optoelectronics. ; 1:5, s. 197-205
  • Tidskriftsartikel (refereegranskat)abstract
    • Monolithic techniques for mode and polarisation control in vertical-cavity surface emitting lasers (VCSELs) using shallow surface structures are summarized and put in the context with other techniques in terms of performance and manufacturability. The method of using circular-symmetric surface structures for mode control and their combination with a sub-wavelength surface grating for simultaneous mode and polarisation control is described in detail, and adherent experimental results for both 850-nm and 1.3-µm oxide-confined VCSELs are presented.
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48.
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49.
  • Gustavsson, Johan, 1974, et al. (författare)
  • Optimized active region design for high speed 850 nm VCSELs
  • 2009
  • Ingår i: CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference; Munich; Germany; 14 June 2009 through 19 June 2009. - 9781424440801 ; , s. Art. no. 5192928-
  • Konferensbidrag (refereegranskat)abstract
    • Short wavelength (850 nm) VCSELs operating at speeds of 25 Gb/s and above are needed for future highcapacity, short reach data communication links. The modulation bandwidth is intrinsically limited by thedifferential gain of the QWs used in the active region of the VCSEL. In this work we explore the use of strainedInGaAs/AlGaAs QWs and benchmark the performance against conventional GaAs/AlGaAs QWs.An 8-band k⋅p model [1] was used to calculate the energy band dispersions, using band offsets from modelsolid theory [2]. In all cases, the QW and barrier compositions and QW thickness were chosen for a gain peak at845 nm, enabling emission at 850 nm with a small detuning between the gain peak and the cavity resonance.With increasing In-concentration the QW thickness is reduced and the Al-concentration in the barrier isincreased to maintain the gain peak at 845 nm and the number of QWs is increased to maintain opticalconfinement and enable operation at a low carrier density for high differential gain. It was found that theincorporation of up to 10% In leads to a significant reduction in threshold carrier density and increase indifferential gain. This is due to an increased separation and reduced mixing between the highest heavy-hole andlight-hole valence bands (Fig.1). A further increase of In concentration leads to a less marked improvement.With an optimum active region design (5 x 4 nm In0.10Ga0.90As/Al0.37Ga0.63As QWs) a differential gain twice ashigh as that of a conventional design with 3 x 8 nm GaAs/Al0.30Ga0.70As QWs was predicted (Table 1).The improvement of differential gain was experimentally confirmed by extracting the resonance frequencyand its dependence on current from the modulation response of VCSELs with optimized InGaAs/AlGaAs QWand conventional GaAs/AlGaAs QW active regions. The differential gain was calculated from the correspondingD-factors (Fig.2) [3]. Excellent agreement was obtained between theory and experiments (Table 1).VCSELs with an optimized InGaAs/AlGaAs QW active region have a modulation bandwidth of 20 GHz at25° and 15 GHz at 85°C [4] and have enabled error-free transmission over 50 (100) m multimode fiber up to 32(25) Gb/s at a bias current density as low as 11 kA/cm2 under direct current modulation.
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50.
  • Gustavsson, Johan, 1974, et al. (författare)
  • Silicon integrated 850-nm hybrid vertical-cavity laser for life science applications
  • 2017
  • Ingår i: VCSEL Day 2017.
  • Konferensbidrag (refereegranskat)abstract
    • The integration of efficient laser sources on silicon would enable fully integrated silicon photonic circuits with a high degree of functionality and performance complexity for many applications [1]. Different integration concepts have therefore been suggested, where one such technique is the heterogeneous integration of a vertical-cavity laser (VCL), referred to as a hybrid VCL. It is promising as it has potential to offer low drive currents, high modulation bandwidths, and small footprint [2-4]. In-plane emission with waveguide-coupling can be achieved by an intra-cavity waveguide embossed with a weak diffraction grating, as an example [5]. Integration of such short-wavelength laser sources on a silicon-nitride (SiN) waveguide platform on silicon may enable fully integrated silicon photonic circuits for applications not only in short-reach optical interconnects but also in life science and bio-photonics. As a first step in realizing short-wavelength hybrid VCLs with in-plane emission coupled to a SiN waveguide, we have developed a technique to produce high performance 850-nm hybrid VCLs with out-of-plane emission. It is based on adhesive bonding of epitaxial AlGaAs-material onto a dielectric distributed Bragg reflector (DBR) on silicon [6-8]. We have fabricated devices with surface emission having sub-mA threshold current, >2 mW output power, and 25 Gbit/s modulation speed [8]. To be able to demonstrate in-plane emission with SiN waveguide coupling from our hybrid 850-nm VCLs, our next step is to add a SiN waveguide structure with embossed grating on top of the dielectric DBR, before adhesively bonding the AlGaAs-material. So far, based on numerical simulations, we have designed a device that is predicted to yield a slope efficiency of ~0.3 W/A at 25 °C for the light coupled to a single-mode waveguide, while maintaining a sub-mA threshold current for the lasing [9]. This work is supported by the European Union’s Horizon 2020 research and innovation program under grant agreement no. 688519 (PIX4life), the Swedish Foundation for Strategic Research (SSF), and the European FP7-ERC-InSpectra Advanced Grant. References [1]  Z. Zhou et al., Light Sci. Appl., vol. 4, no. 11, p. e358, 2015. [2]  Y. Tsunemi et al., Opt. Express, vol. 21, no. 23, p. 28685, 2013. [3]  J. Ferrara et al., Opt. Express, vol. 23, no. 3, p. 2512, 2015. [4]  G.C. Park et al., Laser Photon. Rev., vol. 9, no. 3, p. L11, 2015. [5]  D. A. Louderback et al., Electron. Lett., vol. 40, no. 17, p. 1064, 2004. [6]  E.P. Haglund et al., Opt. Express, vol. 23, no. 26, p. 33634, 2015. [7]  E.P. Haglund et al., IEEE Photon. Technol. Lett., vol. 28, no. 8, p. 856, 2016. [8]  E.P. Haglund et al., IEEE J. Sel. Top. Quantum Electron., vol. 23, no. 6, p. 1700109, 2017. [9]  S. Kumari et al., Submitted to IEEE Photon. J.,2017.
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  • Resultat 41-50 av 258
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konferensbidrag (156)
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Gustavsson, Johan, 1 ... (254)
Larsson, Anders, 195 ... (199)
Haglund, Åsa, 1976 (117)
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