| 1. |
- Gustavsson, Johan, 1974, et al.
(författare)
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Optimized active region design for high speed 850 nm VCSELs
- 2009
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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-
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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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| 2. |
- Kögel, Benjamin, 1979, et al.
(författare)
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Short-wavelength tunable VCSELs
- 2009
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Ingår i: European Semiconductor Laser Workshop (ESLW).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 3. |
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| 4. |
- Larsson, Anders, 1957, et al.
(författare)
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VCSELs for broadband access and interconnects
- 2009
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Ingår i: Proc. 2009 International Nano-Optoelectronics Workshop, Stockholm-Berlin, August 2009. ; , s. 87-88
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Konferensbidrag (refereegranskat)
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| 5. |
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| 6. |
- Ou, Yiyu, et al.
(författare)
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Impedance characteristics and parasitic speed limitations of high speed 850 nm VCSELs
- 2009
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 21, s. 1840-
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Tidskriftsartikel (refereegranskat)abstract
- Abstract—The impedance characteristics of high-speed oxideconfined 850-nm vertical-cavity surface-emitting lasers have been studied with the aim of identifying the importance of device parasitics for the modulation bandwidth. Through equivalent circuit modeling, it is confirmed that device parasitics have a major impact on the bandwidth and the importance of each individual circuit element has been investigated. According to the extrapolation of the parameters derived from S11 measurements below 20 GHz towards higher frequencies and assuming that the mesa capacitance can be reduced by adding a few extra oxide layers without significantly affecting series resistance, our model predicts that the 3-dB parasitic frequency can be increased from 22 to above 30 GHz. Accounting also for bandwidth limitations due to thermal effects, we expect an increase of the modulation bandwidth of several gigahertz which may enable direct current modulation at 40 Gb/s.
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| 7. |
- Westbergh, Petter, 1981, et al.
(författare)
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32 Gb/s transmission experiments using high speed 850 nm VCSELs
- 2009
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Ingår i: Conference on Lasers and Electro-Optics (CLEO). - 2162-2701. - 9781557528698 ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- We demonstrate error free transmission at bit rates up to 32 Gb/s at room temperature and 25 Gb/s at 85degC using a 9 mum oxide aperture 850 nm VCSEL. The VCSEL design is optimized for high speed operation by minimizing parasitics, reducing self-heating, and using strained InGaAs quantum wells to improve differential gain.
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| 8. |
- Westbergh, Petter, 1981, et al.
(författare)
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32 Gbit/s multimode fibre transmission using high-speed, low current density 850 nm VCSEL
- 2009
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 45:7, s. 366 - 368
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Tidskriftsartikel (refereegranskat)abstract
- Error free transmission over multimode fibre at data rates up to 32 Gbit/s at 25C and 25 Gbit/s at 85C using an oxide confined 850 nm VCSEL biased at a current density of 11–14 kA/cm2 is demonstrated. The VCSEL is optimised for high-speed by reducing capacitance and self-heating and by using strained InGaAs quantum wells for high differential gain.
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| 9. |
- Westbergh, Petter, 1981, et al.
(författare)
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A high-speed laser for future data-communication links
- 2009
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Ingår i: SPIE Newsroom. - : SPIE-Intl Soc Optical Eng. - 1818-2259.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Optimized designs significantly improve the transmission rate of standard short-wavelength light sources.
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| 10. |
- Westbergh, Petter, 1981, et al.
(författare)
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High speed large aperture 850 nm VCSELs
- 2009
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Ingår i: International Nano-Optoelectronics Workshop (iNOW).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Error-free transmission over 50 m of OM3 fiber at 32 Gbit/s is demonstrated at a bias current density of 11 kA/cm2 using a large aperture 850 nm oxide-confined VCSEL optimized for high speed operation.
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