| 11. |
- Haglund, Erik, 1985, et al.
(author)
-
Multi-wavelength VCSEL arrays using high-contrast gratings
- 2017
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781510606678 ; 10113
-
Conference paper (peer-reviewed)abstract
- The use of a high-contrast grating (HCG) as the top mirror in a vertical-cavity surface-emitting laser (VCSEL) allows for setting the resonance wavelength by the grating parameters in a post-epitaxial growth fabrication process. Using this technique, we demonstrate electrically driven multi-wavelength VCSEL arrays at ∼980 nm wavelength. The VCSELs are GaAs-based and the suspended GaAs HCGs were fabricated using electron-beam lithography, dry etching and selective removal of an InGaP sacrificial layer. The air-coupled cavity design enabled 4-channel arrays with 5 nm wavelength spacing and sub-mA threshold currents thanks to the high HCG reflectance.
|
|
| 12. |
|
|
| 13. |
- Haglund, Åsa, 1976, et al.
(author)
-
Progress and challenges in electrically pumped GaN-based VCSELs
- 2016
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 9892
-
Conference paper (peer-reviewed)abstract
- The Vertical-Cavity Surface-Emitting Laser (VCSEL) is an established optical source in short-distance optical communication links, computer mice and tailored infrared power heating systems. Its low power consumption, easy integration into two-dimensional arrays, and low-cost manufacturing also make this type of semiconductor laser suitable for application in areas such as high-resolution printing, medical applications, and general lighting. However, these applications require emission wavelengths in the blue-UV instead of the established infrared regime, which can be achieved by using GaN-based instead of GaAs-based materials. The development of GaN-based VCSELs is challenging, but during recent years several groups have managed to demonstrate electrically pumped GaN-based VCSELs with close to 1 mW of optical output power and threshold current densities between 3-16 kA/cm2. The performance is limited by challenges such as achieving high-reflectivity mirrors, vertical and lateral carrier confinement, efficient lateral current spreading, accurate cavity length control and lateral optical mode confinement. This paper summarizes different strategies to solve these issues in electrically pumped GaN-VCSELs together with state-of-the-art results. We will highlight our work on combined transverse current and optical mode confinement, where we show that many structures used for current confinement result in unintentionally optically anti-guided resonators. Such resonators can have a very high optical loss, which easily doubles the threshold gain for lasing. We will also present an alternative to the use of distributed Bragg reflectors as high-reflectivity mirrors, namely TiO2/air high contrast gratings (HCGs). Fabricated HCGs of this type show a high reflectivity (>95%) over a 25 nm wavelength span.
|
|
| 14. |
- Larsson, Anders, 1957, et al.
(author)
-
1060 nm VCSELs for long-reach optical interconnects
- 2018
-
In: Optical Fiber Technology. - : Elsevier BV. - 1095-9912 .- 1068-5200. ; 44, s. 36-42
-
Journal article (peer-reviewed)abstract
- Reach extension of high capacity optical interconnects based on vertical-cavity surface-emitting lasers (VCSELs) and multimode fibers (MMFs), as needed for large-scale data centers, would benefit from high-speed GaAs-based VCSELs at 1060 nm. At this wavelength, the chromatic dispersion and attenuation of the optical fiber are much reduced in comparison with 850 nm. We present single and multimode 1060 nm VCSELs based on designs derived partly from our high-speed 850 nm VCSEL designs. The single-mode VCSEL, with a modulation bandwidth exceeding 22 GHz, supports back-to-back data rates up to 50 Gbps at 25 °C and 40 Gbps at 85 °C under binary NRZ (OOK) modulation. Using mode-selective launch, we demonstrate error-free 25 Gbps transmission over 1000 m of 1060 nm optimized MMF. Higher data rates and/or longer distances will be possible with equalization, forward-error-correction, and/or multilevel modulation.
|
|
| 15. |
- Lin, YB, et al.
(author)
-
Telomerase promoter mutations and copy number alterations in solitary fibrous tumours
- 2018
-
In: Journal of clinical pathology. - : BMJ. - 1472-4146 .- 0021-9746. ; 71:9, s. 832-839
-
Journal article (peer-reviewed)abstract
- Solitary fibrous tumour (SFT) is an infrequently metastasising mesenchymal tumour defined by the NAB2–STAT6 fusion gene. Activating mutations in the telomerase reverse transcriptase (hTERT) gene promoter has been reported to associate with adverse patient outcome in SFTs.MethodsWe analysed the hTERT gene for promoter mutations and copy number alterations in 43 primary extrameningeal SFTs (9 malignant and 34 benign tumours according to WHO 2013 criteria), six local recurrences and three metastatic lesions.ResultsActivating −124 C>T (n=12) or −148 C>T (n=2) mutations were found in 33% of the tumours and associated with older age (P=0.006), necrosis (P=0.009), higher mitotic rate (P=0.003), nuclear atypia (P=0.002), malignant histological diagnosis (P=0.04) and worse progression-free survival (P=0.023). We also observed frequent (24%) hTERT promoter mutations in histologically benign tumours without metastasis (mean follow-up >9 years), and in 14%–18% of low-risk SFTs as determined by three risk-stratification models. Mutations were seen in 2/6 metastatic tumours and metastatic lesions. hTERT copy number gain was seen in 11/28 hTERT promoter wild-type cases.ConclusionsActivating hTERT promoter mutations associate with aggressive histopathological features, indicating a role in tumour progression. Given the comparatively high prevalence of hTERT promoter mutations in low-risk and non-metastasising lesions, further studies are required to clarify the prognostic value of hTERT promoter analysis before implementing the analysis in clinical diagnostics.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Rodríguez, Juanjo, et al.
(author)
-
Effects of Organic Pollutants on Bacterial Communities Under Future Climate Change Scenarios
- 2018
-
In: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 9
-
Journal article (peer-reviewed)abstract
- Coastal ecosystems are highly dynamic and can be strongly influenced by climate change, anthropogenic activities (e.g. pollution) and a combination of the two pressures. As a result of climate change, the northern hemisphere is predicted to undergo an increased precipitation regime, leading in turn to higher terrestrial runoff and increased river inflow. This increased runoff will transfer terrestrial dissolved organic matter (tDOM) and anthropogenic contaminants to coastal waters. Such changes can directly influence the resident biology, particularly at the base of the food web, and can influence the partitioning of contaminants and thus their potential impact on the food web. Bacteria have been shown to respond to high tDOM concentration and organic pollutants loads, and could represent the entry of some pollutants into coastal food webs. We carried out a mesocosm experiment to determine the effects of: 1) increased tDOM concentration, 2) organic pollutant exposure, and 3) the combined effect of these two factors, on pelagic bacterial communities. This study showed significant responses in bacterial community composition under the three environmental perturbations tested. The addition of tDOM increased bacterial activity and diversity, while the addition of organic pollutants led to an overall reduction of these parameters, particularly under concurrent elevated tDOM concentration. Furthermore, we identified 33 bacterial taxa contributing to the significant differences observed in community composition, as well as 35 bacterial taxa which responded differently to extended exposure to organic pollutants. These findings point to the potential impact of organic pollutants under future climate change conditions on the basal coastal ecosystem, as well as to the potential utility of natural bacterial communities as efficient indicators of environmental disturbance.
|
|
| 19. |
- Roth, D., et al.
(author)
-
Electronic Stopping of Slow Protons in Oxides : Scaling Properties
- 2017
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 119:16
-
Journal article (peer-reviewed)abstract
- Electronic stopping of slow protons in ZnO, VO2 (metal and semiconductor phases), HfO2, and Ta2O5 was investigated experimentally. As a comparison of the resulting stopping cross sections (SCS) to data for Al2O3 and SiO2 reveals, electronic stopping of slow protons does not correlate with electronic properties of the specific material such as band gap energies. Instead, the oxygen 2p states are decisive, as corroborated by density functional theory calculations of the electronic densities of states. Hence, at low ion velocities the SCS of an oxide primarily scales with its oxygen density.
|
|
| 20. |
|
|
