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Träfflista för sökning "WFRF:(Haglund Åsa 1976 ) srt2:(2013)"

Sökning: WFRF:(Haglund Åsa 1976 ) > (2013)

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1.
  • Haglund, Erik, 1985, et al. (författare)
  • 850 nm datacom VCSELs for higher-speed and longer-reach transmission
  • 2013
  • Ingår i: European VCSEL Day 2013.
  • Konferensbidrag (refereegranskat)abstract
    • The 850 nm GaAs-based VCSEL is already the dominating technology for transmitters in optical interconnects up to 100 m in datacenters, thanks to low-cost fabrication, excellent high-speed properties at low currents and the existence of high-speed OM4 multimode fiber optimized for this particular wavelength. Future datacenters will require faster and more energy-efficient VCSELs to increase the overall bandwidth and reduce the power consumption of the datacenter network. In addition, longer-reach interconnects exceeding 1 km will also be required as datacenters grow into large multi-building complexes.By optimizing the doping profiles of the DBRs to reduce resistance, using a short (½-λ) cavity to improve longitudinal optical confinement and optimizing the photon lifetime for optimal damping, we obtained a record-high small-signal modulation bandwidth of 28 GHz for a ~4 µm oxide aperture VCSEL. A 7 µm oxide aperture VCSEL (~27 GHz bandwidth) enabled error-free transmission (bit-error-rate 300 m), the large spectral width of VCSELs leads to severe signal degradation by fiber dispersion. We have investigated two methods of fabricating low-spectral width quasi-single mode VCSELs to mitigate this problem. By using a small oxide aperture of ~3 µm, error-free transmission was achieved at 22 Gbit/s over 1.1 km of OM4 fiber. An alternative approach is to use an integrated mode filter in the form of a shallow surface relief to reduce the spectral width of the VCSEL. The mode filter allows for the use of a larger oxide aperture and thereby enables a lower resistance and operation at a lower current density. A 5 µm oxide aperture VCSEL with a mode filter enabled error-free transmission at 25 Gbit/s over 500 m of OM4 fiber.
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2.
  • 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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3.
  • 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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4.
  • Hashemi, Seyed Ehsan, 1986, et al. (författare)
  • Engineering the Lateral Optical Guiding in Gallium Nitride (GaN)-based Vertical-Cavity Surface-Emitting Laser (VCSEL) Cavities to Reach the Lowest Threshold Gain
  • 2013
  • Ingår i: Japanese Journal of Applied Physics. - 1347-4065 .- 0021-4922. ; 52:8 PART 2, s. 08JG04 -
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to improve the current injection in GaN-based blue vertical-cavity surface-emitting lasers (VCSELs) a dielectric aperture is generally used in combination with an indium–tin-oxide (ITO) layer on the top intracavity p-contact layer. The most straightforward way to realize this introduces a depression of the structure near the optical axis and we show, by using a two-dimensional (2D) effective index method and a three-dimensional (3D) coupled-cavity beam propagation method, that this typically results in optically anti-guided structures with associated high optical losses and thus very high threshold gains. Remarkably, the threshold gain reduces with increased negative guiding, which is due to improved lateral confinement and reduction of lateral leakage. Still, moderately positively guided designs should be preferred to avoid the detrimental effect of lateral leakage and high diffraction loss. To ensure positive index guiding, we propose to planarize the structure or introduce an elevation near the optical axis by additional processing, with an associated reduction in threshold material gain from 6000 to 2000 cm-1 for the studied structures.
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5.
  • Stattin, Martin, 1983, et al. (författare)
  • Metal-Free Graphene as Transparent Electrode for GaN-Based Light-Emitters
  • 2013
  • Ingår i: Japanese Journal of Applied Physics. - 1347-4065 .- 0021-4922. ; 52:8 PART 2, s. 08JG05-
  • Tidskriftsartikel (refereegranskat)abstract
    • Graphene contacts to p-GaN are considered as an alternative to indium–tin-oxide transparent electrodes in GaN based vertical-cavity surface-emitting lasers (VCSELs). Contact properties were investigated on light-emitting diode and p-GaN test structures, where dielectric apertures were used to eliminate the influence of the metal pads used to bias the contacts. Using single layer graphene we were able to operate light emitting diodes with current densities of 300 A/cm2. Addition of a second layer of graphene increased the maximum bias current to 1 kA/cm2. However, the contacts are non-linear and cannot withstand high current densities for a long time. The results are promising but further investigation and improvement is needed for graphene to be a viable alternative to indium–tin-oxide for blue VCSELs.
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