| 1. |
- Haglund, Erik, 1985, et al.
(författare)
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850 nm datacom VCSELs for higher-speed and longer-reach transmission
- 2013
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Ingår i: European VCSEL Day 2013.
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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. |
- Haglund, Erik, 1985, et al.
(författare)
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Quasi-single mode VCSELs for longer-reach multimode fiber optical interconnects
- 2014
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Ingår i: Summers School on Optical Interconnects, 3-6 June 2014, Thessaloniki.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Longer-reach (>300 m) optical interconnects are needed asdatacenters grow ever larger. Today the reach of 850 nmVCSEL-based optical interconnects is mainly limited by fiber dispersion. By reducing the spectral width of the VCSEL, the effects of fiber dispersion may be reduced, effectively increasing the error-free transmission distance.
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| 3. |
- Kumari, Sulakshna, et al.
(författare)
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Integration of GaAs-based VCSEL array on SiN platform with HCG reflectors for WDM applications
- 2015
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781628414622 ; 9372, s. Art. no. 93720U-
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Konferensbidrag (refereegranskat)abstract
- We present a GaAs-based VCSEL structure, BCB bonded to a Si3N4 waveguide circuit, where one DBR is substituted by a free-standing Si3N4 high-contrast-grating (HCG) reflector realized in the Si3N4 waveguide layer. This design enables solutions for on-chip spectroscopic sensing, and the dense integration of 850-nm WDM data communication transmitters where individual channel wavelengths are set by varying the HCG parameters. RCWA shows that a 300nm-thick Si3N4 HCG with 800nm period and 40% duty cycle reflects strongly (
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| 4. |
- Larsson, Anders, 1957, et al.
(författare)
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VCSEL modulation capacity: Continued improvements or physical limits?
- 2017
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Ingår i: 6th IEEE Photonics Society Optical Interconnects Conference, OI 2017. - 9781509050154 ; , s. 53-54
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Konferensbidrag (refereegranskat)abstract
- The short-reach optical interconnects used in datacenters and high-performance computing systems are dominated by VCSEL and multimode fiber (MMF) links 1 . The VCSEL-MMF technology is the most cost and power efficient and offers the smallest footprint. VCSELs operating at 25-28 Gbit/s are in production 2 while research has extended the VCSEL modulation bandwidth to 30 GHz 3 (Fig.1) and enabled OOK-NRZ data transmission up to 57 Gbit/s at 25°C 4 and 50 Gbit/s at 85°C 5 , without equalization or forward-error-correction (FEC). A VCSEL energy dissipation below 100 fJ/bit has been demonstrated at 25-50 Gbit/s 3 (Fig.1). The need for higher interconnect capacity raises the question whether the speed and dynamics of VCSELs can be further improved or whether physical limits preventing this have been reached. Higher speed VCSELs would enable higher lane rates and therefore reduced number of lanes and increased bandwidth density for a given aggregate interconnect capacity.
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| 5. |
- Haglund, Erik, 1985, et al.
(författare)
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30 GHz bandwidth 850 nm VCSEL with sub-100 fJ/bit energy dissipation at 25-50 Gbit/s
- 2015
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 51:14, s. 1096-1097
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Tidskriftsartikel (refereegranskat)abstract
- A high-speed and energy-efficient oxide-confined 850 nm vertical-cavity surface-emitting laser (VCSEL) for optical interconnects is presented. A record-high modulation bandwidth of 30 GHz is reached for a 3.5 mu m oxide aperture VCSEL, with 25 GHz bandwidth already at a bias current of 1.8 mA. The high bandwidth at low currents enables energy-efficient transmission with a dissipated heat energy in the VCSEL of
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| 6. |
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| 7. |
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| 8. |
- Haglund, Erik, 1985, et al.
(författare)
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High-Speed VCSELs with Strong Confinement of Optical Fields and Carriers
- 2016
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:2, s. 269-277
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Tidskriftsartikel (refereegranskat)abstract
- We present the design, fabrication, and performance of our latest generation high-speed oxide-confined 850-nm verticalcavity surface-emitting lasers. Excellent high-speed properties are obtained by strong confinement of optical fields and carriers. Highspeed modulation is facilitated by using the shortest possible cavity length of one half wavelength and placing oxide apertures close to the active region to efficiently confine charge carriers. The resulting strong current confinement boosts internal quantum efficiency, leading to low threshold currents, high wall-plug efficiency, and state-of-the-art high-speed properties at low bias currents. The temperature dependent static and dynamic performance is analyzed by current-power-voltage and small-signal modulation measurements.
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| 9. |
- Haglund, Emanuel, 1988, et al.
(författare)
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Hybrid vertical-cavity laser integration on silicon
- 2017
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781510606852 ; 10122, s. 101220H-
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Konferensbidrag (refereegranskat)abstract
- The hybrid vertical-cavity laser is a potential low current, high-efficiency, and small footprint light source for silicon photonics integration. As part of the development of such light sources we demonstrate hybrid-cavity VCSELs (HC-VCSELs) on silicon where a GaAs-based half-VCSEL is attached to a dielectric distributed Bragg reflector on silicon by adhesive bonding. HC-VCSELs at 850 nm with sub-mA threshold current, >2 mW output power, and 25 Gbit/s modulation speed are demonstrated. Integration of short-wavelength lasers will enable fully integrated photonic circuits on a silicon-nitride waveguide platform on silicon for applications in life science, bio-photonics, and short-reach optical interconnects.
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| 10. |
- Haglund, Emanuel, 1988, et al.
(författare)
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Impact of Bonding Interface Thickness on the Performance of Silicon-Integrated Hybrid-Cavity VCSELs
- 2016
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Ingår i: Conference Digest - IEEE International Semiconductor Laser Conference. - 0899-9406. - 9784885523069 ; , s. Article no 7765752-
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Konferensbidrag (refereegranskat)abstract
- The dependence of the performance of short-wavelength silicon-integrated hybrid-cavity VCSELs on the thickness of the bonding interface used for the heterogeneous integration has been studied. Performance measures investigated include the emission wavelength, thermal impedance, and variation of threshold current and output power with temperature.
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