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- Gierl, Christian, et al.
(författare)
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Tuneable VCSEL aiming for the application in interconnects and short haul systems
- 2011
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819484963 ; 7959
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Widely tunable vertical cavity surface emitting lasers (VCSEL) are of high interest for optical communications, gas spectroscopy and fiber-Bragg-grating measurements. In this paper we present tunable VCSEL operating at wavelength around 850 nm and 1550 nm with tuning ranges up to 20 nm and 76 nm respectively. The first versions of VCSEL operating at 1550 nm with 76 nm tuning range and an output power of 1.3mW were not designed for high speed modulation, but for applications where only stable continious tuning is essential (e.g. gas sensing). The next step was the design of non tunable VCSEL showing high speed modulation frequencies of 10 GHz with side mode supression ratios beyond 50 dB. The latest version of these devices show record output powers of 6.7mW at 20 °C and 3mW at 80 °C. The emphasis of our present and future work lies on the combination of both technologies. The tunable VCSEL operating in the 850 nm-region reaches a modulation bandwidth of 5.5GHz with an output power of 0.8mW.
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- Gustavsson, Johan, 1974, et al.
(författare)
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High-speed 850-nm VCSELs for 40 Gb/s transmission
- 2010
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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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- Gustavsson, Johan, 1974
(författare)
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Modal Dynamics of Vertical-Cavity Surface-Emitting Lasers
- 2003
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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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- Gustavsson, Johan, 1974
(författare)
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VCSEL Arrays for Multicore Fiber Interconnects
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Space-division-multiplexing using multicore optical fibers (MCFs) opens up the possibility to massively increase the data traffic capacity of optical interconnects used in data centers and high performance computing systems. One challenge with this solution is the fabrication of a dense vertical-cavity surface-emitting laser (VCSEL) array that matches the cores of the MCF, without degrading the performance of the individual VCSELs via electrical, thermal, or optical crosstalk. Here we present the development of a hexagonal VCSEL array, with 39 µm center-to-center spacing to match the geometry of a MCF from OFS, and capable of 40 Gb/s/channel providing an aggregate capacity of 240 Gb/s.
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- Haglund, Erik, 1985, et al.
(författare)
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High-contrast gratings for WDM VCSEL arrays
- 2014
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Ingår i: Optics & Photonics in Sweden, 11-12 Nov. 2014, Göteborg.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Vertical-cavity surface-emitting lasers (VCSELs) have become the workhorse of short-reach optical interconnects in datacenters and supercomputers. The last few years have seen an impressive increase in VCSEL modulation bandwidth, enabling record-high single-channel data rates exceeding 60 Gbit/s [1]. In addition to higher single-channel rates, interconnect capacity may be enhanced by employing multiplexing techniques such coarse wavelength division multiplexing (WDM). WDM VCSEL arrays can be designed using a high-contrast grating (HCG) as top mirror instead of a distributed Bragg reflector (DBR) [2]. The HCG consists of a subwavelength grating of high refractive index material (GaAs) surrounded by low refractive index material (air), see figure 1. The result is a thin, broad-band and highly reflective mirror. The reflection from the HCG has a varying phase depending on grating geometry. This can be used to set the HCG-VCSEL wavelength in a post-growth process by fabricating gratings with different period and duty-cycle. A first proof of concept has been realized and HCG-VCSELs showing resonances covering a span exceeding 20 nm have been demonstrated. Figure 1: Top: schematic figure of HCG-VCSEL array. Left: Top and cross-sectional SEM image of HCG. Right: Simulated and experimental HCG-VCSEL resonance wavelength for different duty cycles and periods (p) measured by electroluminescence. References[1] D. Kuchta et al., “64Gb/s Transmission over 57m MMF using an NRZ Modulated 850nm VCSEL,” OFC 2014[2] V. Karagodsky et al., “Monolithically integrated multi-wavelength VCSEL arrays using high-contrast gratings,” Opt. Express, 18(2), 2010
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