| 1. |
- Baveja, Prashant, 1985, et al.
(author)
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Impact of device parameters on thermal performance of high speed oxide confined 850 nm VCSELs
- 2012
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In: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 48:1, s. 17-26
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Journal article (peer-reviewed)abstract
- We study the impact of device parameters, such asinner-aperture diameter and cavity photon lifetime, on thermal rollover mechanisms in 850-nm, oxide-confined, vertical-cavity surface-emitting lasers (VCSELs) designed for high-speed operation. We perform measurements on four different VCSELs of different designs and use our empirical thermal model for calculating the power dissipated with increasing bias currents through various physical processes such as absorption within the cavity, carrier thermalization, carrier leakage, spontaneous carrier recombination, and Joule heating. When reducing the topmirror reflectivity to reduce internal optical absorption loss we find an increase of power dissipation due to carrier leakage. There is therefore a trade-ff between the powers dissipated owing to optical absorption and carrier leakage in the sense that overcompensating for optical absorption enhances carrier leakage (and vice versa). We further find that carrier leakage places the ultimate limit on the thermal performance for this entire class ofdevices. Our analysis yields useful design optimization strategies for mitigating the impact of carrier leakage and should thereby prove useful for the performance enhancement of 850-nm, highspeed, oxide-confined VCSELs.
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| 2. |
- Baveja, P. P., et al.
(author)
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Assessment of VCSEL thermal rollover mechanisms from measurements and empirical modeling
- 2011
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In: Optics Express. - 1094-4087 .- 1094-4087. ; 19:16, s. 15490-15505
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Journal article (peer-reviewed)abstract
- We use an empirical model together with experimental measurements for studying mechanisms contributing to thermal rollover in vertical-cavity surface-emitting lasers (VCSELs). The model is based on extraction of the temperature dependence of threshold current, internal quantum efficiency, internal optical loss, series resistance and thermal impedance from measurements of output power, voltage and lasing wavelength as a function of bias current over an ambient temperature range of 15-100 degrees C. We apply the model to an oxide-confined, 850-nm VCSEL, fabricated with a 9-mu m inner-aperture diameter and optimized for highspeed operation, and show for this specific device that power dissipation due to linear power dissipation (sum total of optical absorption, carrier thermalization, carrier leakage and spontaneous carrier recombination) exceeds power dissipation across the series resistance (quadratic power dissipation) at any ambient temperature and bias current. We further show that the dominant contributors to self-heating for this particular VCSEL are quadratic power dissipation, internal optical loss, and carrier leakage. A rapid reduction of the internal quantum efficiency at high bias currents (resulting in high temperatures) is identified as being the major cause of thermal rollover. Our method is applicable to any VCSEL and is useful for identifying the mechanisms limiting the thermal performance of the device and to formulate design strategies to ameliorate them.
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| 3. |
- Haglund, Erik, 1985, et al.
(author)
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25 Gbit/s transmission over 500 m multimode fibre using 850 nm VCSEL with integrated mode filter
- 2012
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In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 48:9, s. 517-518
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Journal article (peer-reviewed)abstract
- An integrated mode filter in the form of a shallow surface relief was used to reduce the spectral width of a high-speed 850 nm vertical-cavity surface-emitting laser (VCSEL). The mode filter reduced the RMS spectral width from 0.9 to 0.3 nm for a VCSEL with an oxide aperture as large as 5 mu m. Because of reduced effects of chromatic and modal fibre dispersion, the mode filter significantly increases the maximum error-free (bit error rate
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| 4. |
- Haglund, Erik, 1985, et al.
(author)
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Mode-filtered semiconductor lasers enable longer-reach optical interconnects
- 2012
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In: SPIE Newsroom. - : SPIE-Intl Soc Optical Eng. - 1818-2259.
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Journal article (other academic/artistic)abstract
- An integrated mode filter significantly decreases the spectral width of conventional short-wavelength vertical-cavity surface-emitting lasers, promising longer optical interconnects for future data centers.
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| 5. |
- Kögel, Benjamin, 1979, et al.
(author)
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Integrated MEMS-Tunable VCSELs Using a Self-Aligned Reflow Process
- 2012
-
In: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 48:2, s. 144-152
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Journal article (peer-reviewed)abstract
- A simple microelectromechanical systems technology for wafer-scale integration of tunable vertical-cavity surface-emitting lasers (VCSELs) is presented. The key element is a self-aligned reflow process to form photoresist droplets, which serve as sacrificial layer and preform for a curved micromirror. Using a 3-D electromagnetic model, the half-symmetric cavity is optimized for singlemode emission. The technology is demonstrated for electrically pumped, short-wavelength (850 nm) tunable VCSELs, but is transferable to other wavelengths and material systems. Fabricated devices with 10 mu m large current aperture are singlemode and tunable over 24 nm. An improved high-speed design with reduced parasitic capacitance enables direct modulation with 3dB-bandwidths up to 6 GHz and data transmission at 5Gbit/s. Small signal analysis shows that the intrinsic parameters (resonance frequency and damping) are wavelength dependent through the differential gain.
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| 6. |
- Kögel, Benjamin, 1979, et al.
(author)
-
Integrated MEMS-tunable VCSELs with high modulation bandwidth
- 2011
-
In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 47:13, s. 764-756
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Journal article (peer-reviewed)abstract
- The modulation bandwidth of micromachined tunable VCSELs is typically limited by the parasitic capacitance associated with the large mesa platform for the movable mirror. Presented is a simple technology for wafer-scale integration of tunable VCSELs with low mesa capacitance and high modulation bandwidth. Small signal measurements show a 3dB bandwidth of up to 6 GHz over a tuning range of 18 nm. Digital modulation is demonstrated with error-free data transmission at 5 Gbit/s and eye diagrams at 10 Gbit/s.
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| 7. |
- Larsson, Anders, 1957, et al.
(author)
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High speed VCSELs for short reach communication
- 2011
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In: Semiconductor Science and Technology. - 1361-6641 .- 0268-1242. ; 26:1, s. 014017-1-5-
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Journal article (peer-reviewed)abstract
- We present the design of a high-speed 850 nm multimode vertical cavity surface-emitting laser (VCSEL) and demonstrate record performance in terms of small signal modulation bandwidth (23 GHz) and error-free operation at high bit rates (40 Gb s−1). The large bandwidth was enabled by an active region design for large differential gain and small gain compression, a low reflectivity top mirror for photon lifetime reduction and multiple oxide layers for a reduction of the capacitance. Error-free operation at 40 Gb s−1 was achieved in a back-to-back configuration with less than 0 dBm of received optical power.
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| 8. |
- Safaisini, Rashid, 1981, et al.
(author)
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High-Speed 850 nm Quasi-Single Mode VCSELs for Extended Reach Optical Interconnects
- 2013
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In: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 5:7, s. 686-695
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Journal article (peer-reviewed)abstract
- This paper presents recent results on high-speed, quasi-single-mode, 850 nm vertical-cavity surface-emitting lasers (VCSELs) with a narrow spectral width for extended-reach optical interconnects. The top mirror reflectivity is adjusted for high output power, slope efficiency, and small signal modulation bandwidth. An oxide confined VCSEL with an ∼3 μm aperture diameter delivers 2 mW of output power and reaches a resonance frequency as high as 25 GHz and a modulation bandwidth exceeding 20 GHz. A small K-factor of 0.17 ns and a large D-factor of 17.3 GHz/mA1/2, extracted from the VCSEL modulation response, along with the improved DC and modal properties enable energy-efficient data transmission at high bit rates over long-distance multimode fiber. Error-free transmission at bit rates exceeding 20 Gbits/s over 1.1 km of OM4 fiber is demonstrated and shown to be limited mainly by the photoreceiver bandwidth. A theoretical investigation of the dependence of link performance on photoreceiver bandwidth is also presented.
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| 9. |
- Westbergh, Petter, 1981, et al.
(author)
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40 Gbit/s error-free operation of oxide-confined 850 nm VCSEL
- 2010
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In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 46:14, s. 1014-1015
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Journal article (peer-reviewed)abstract
- Error-free transmission is demonstrated at bit rates up to 40 Gbit/s in a back-to-back configuration and up to 35 Gbit/s over 100 m multimode fibre using a directly modulated oxide confined 850 nm vertical cavity surface emitting laser.
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| 10. |
- Westbergh, Petter, 1981, et al.
(author)
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High-speed 850 nm VCSELs with 28 GHz modulation bandwidth operating error-free up to 44 Gbit/s
- 2012
-
In: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 48:18, s. 1145-U178
-
Journal article (peer-reviewed)abstract
- A new generation of high-speed oxide confined 850 nm vertical cavity surface-emitting lasers is presented. A record high modulation bandwidth of 28 GHz is achieved and error-free data transmission at bit-rates up to 44 Gbit/s is demonstrated.
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