| 271. |
- Shao, J, et al.
(författare)
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Evolution of Valence-Band Alignment with Nitrogen Content in GaNAs/GaAs Single Quantum Wells
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:3, s. Art. Nr. 031904-
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Tidskriftsartikel (refereegranskat)abstract
- We report on experimental evidence for the transition of valence-band alignment from type I to type II in Ga Nx As1-x GaAs single quantum wells by photoreflectance measurements. The substitutional nitrogen content covers a range of 1.4%-5.9%. The turning point of the type I-type II transition occurs at x4.7%. The experimental observations can be well interpreted by a combination of band anticrossing model and model-solid theory when nonlinear behavior of either the shear deformation potential or the average valence-band energy is taken into account. The effect of dilute nitrogen on the valence-band offset of GaNAsGaAs quantum well structure is hence clarified. © 2008 American Institute of Physics.
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| 272. |
- Simpanen, Ewa, 1987, et al.
(författare)
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1060 nm single and multimode VCSELs for up to 50 Gb/s modulation
- 2017
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Ingår i: Proceedings of IEEE Photonics Conference 2017. - : IEEE. - 9781509065776 ; 2017-January, s. 65-66
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Konferensbidrag (refereegranskat)abstract
- We present the design and performance of 1060 nm VCSELs with up to 50 Gb/s intrinsic speed and demonstrate 25 Gb/s transmission over 1000 m of 1060 nm optimized MMF using a single-mode VCSEL and mode-selective launch.
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| 273. |
- Simpanen, Ewa, 1987, et al.
(författare)
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1060 nm Single-Mode VCSEL and Single-Mode Fiber Links for Long-Reach Optical Interconnects
- 2019
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:13, s. 2963-2969
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the use of a 1060 nm single-mode vertical-cavity surface-emitting laser (VCSEL) and a 1060 nm single-mode fiber as a competitive single-mode technology for cost-and power-efficient long-reach optical interconnects. Error-free transmission (bit error rate < 10-12) over 2 km is demonstrated at bitrates up to 40 Gb/s under on-off keying non-return-to-zero (OOK-NRZ) modulation, without equalization, forward-error correction, or other forms of digital signal processing. The VCSEL is extensively characterized with respect to its static and dynamic performances, including the power-voltage-current characteristics, spectral characteristics, beam divergence, modulation response, relative intensity noise, and frequency chirp. The measured dependence of power penalty on fiber length is consistent with an analysis of chirp-induced pulse compression and broadening along the negative chromatic dispersion fiber.
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| 274. |
- Simpanen, Ewa, 1987, et al.
(författare)
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1060 nm single-mode vertical-cavity surface-emitting laser operating at 50 Gbit/s data rate
- 2017
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 53:13, s. 869-870
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Tidskriftsartikel (refereegranskat)abstract
- An energy efficient 1060 nm GaAs-based oxide-confined vertical-cavity surface-emitting laser designed for high-speed modulation and singlemode emission has been developed. A record data rate of 50 Gbit/ s at an energy dissipation of 100 fJ/ bit is demonstrated for a device with > 50 dB side-mode-suppression and 0.2 mA threshold current, making this laser a promising light source for long-reach optical interconnects.
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| 275. |
- Simpanen, Ewa, 1987, et al.
(författare)
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1060 nm VCSEL for up to 40 Gbit/s Data Transmission
- 2016
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Ingår i: Conference Digest - IEEE International Semiconductor Laser Conference. - 0899-9406. - 9784885523069 ; , s. Article no 7765757-
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Konferensbidrag (refereegranskat)abstract
- A GaAs-based 1060 nm VCSEL with strained InGaAs/GaAsP QWs, doped DBRs, a short optical cavity, and multiple oxide apertures is presented. Modulation up to 40 Gbit/s at 25°C and 30 Gbit/s at 85°C is demonstrated.
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| 276. |
- Simpanen, Ewa, 1987, et al.
(författare)
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Long-Reach 1060 nm SM VCSEL - SMF Optical Interconnects
- 2018
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Ingår i: European Conference on Optical Communication, ECOC. ; 2018-September
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Konferensbidrag (refereegranskat)abstract
- We explore the low-cost, low-power GaAs-VCSEL technology for long-reach interconnects at 1060 nm. With reduced fiber attenuation and chromatic dispersion compared to 850 nm, we demonstrate error-free 40 Gbps OOK-NRZ transmission over 2 km SMF using a SM VCSEL.
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| 277. |
- Simpanen, Ewa, 1987, et al.
(författare)
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Noise Performance of Single-Mode VCSELs: Dependence on Current Confinement and Optical Loss
- 2020
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Ingår i: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 56:5
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the intensity and phase noise properties of GaAs-based 1060 nm oxide-confined single-mode vertical-cavity surface-emitting lasers (VCSELs) and their dependence on slope efficiency and current spreading, parameters that control the achievable output power. We find strong dependence of the linewidth on slope efficiency because it affects the optical resonator loss and therefore the spontaneous emission rate and the photon density. Likewise, we find strong dependence of the relative intensity noise on the slope efficiency since the optical resonator loss controls the photon lifetime, and therefore the damping of the relaxation oscillations. There is no noticeable dependence on transverse current confinement and current spreading. We measure linewidths as small as 6 MHz which we attribute to a small linewidth enhancement factor. This assumption is supported by calculations of the linewidth enhancement factor from optical resonator and optical gain simulations. The dependencies of noise on design parameters are general and therefore valid for single-mode VCSELs at other wavelengths and in other material systems.
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| 278. |
- Sjöström, Lars, et al.
(författare)
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Effects of bariatric surgery on cancer incidence in obese patients in Sweden (Swedish Obese Subjects Study): a prospective, controlled intervention trial.
- 2009
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Ingår i: The lancet oncology. - 1474-5488. ; 10:7, s. 653-62
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Obesity is a risk factor for cancer. Intentional weight loss in the obese might protect against malignancy, but evidence is limited. To our knowledge, the Swedish Obese Subjects (SOS) study is the first intervention trial in the obese population to provide prospective, controlled cancer-incidence data. METHODS: The SOS study started in 1987 and involved 2010 obese patients (body-mass index [BMI] >or=34 kg/m(2) in men, and >or=38 kg/m(2) in women) who underwent bariatric surgery and 2037 contemporaneously matched obese controls, who received conventional treatment. While the main endpoint of SOS was overall mortality, the main outcome of this exploratory report was cancer incidence until Dec 31, 2005. Cancer follow-up rate was 99.9% and the median follow-up time was 10.9 years (range 0-18.1 years). FINDINGS: Bariatric surgery resulted in a sustained mean weight reduction of 19.9 kg (SD 15.6 kg) over 10 years, whereas the mean weight change in controls was a gain of 1.3 kg (SD 13.7 kg). The number of first-time cancers after inclusion was lower in the surgery group (n=117) than in the control group (n=169; HR 0.67, 95% CI 0.53-0.85, p=0.0009). The sex-treatment interaction p value was 0.054. In women, the number of first-time cancers after inclusion was lower in the surgery group (n=79) than in the control group (n=130; HR 0.58, 0.44-0.77; p=0.0001), whereas there was no effect of surgery in men (38 in the surgery group vs 39 in the control group; HR 0.97, 0.62-1.52; p=0.90). Similar results were obtained after exclusion of all cancer cases during the first 3 years of the intervention. INTERPRETATION: Bariatric surgery was associated with reduced cancer incidence in obese women but not in obese men. FUNDING: Swedish Research Council, Swedish Foundation for Strategic Research, Swedish Federal Government under the LUA/ALF agreement, Hoffmann La Roche, Cederoths, AstraZeneca, Sanofi-Aventis, Ethicon Endosurgery.
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| 279. |
- Sjöström, Lars, et al.
(författare)
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Effects of bariatric surgery on mortality in Swedish obese subjects.
- 2007
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Ingår i: The New England journal of medicine. - 1533-4406. ; 357:8, s. 741-52
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Obesity is associated with increased mortality. Weight loss improves cardiovascular risk factors, but no prospective interventional studies have reported whether weight loss decreases overall mortality. In fact, many observational studies suggest that weight reduction is associated with increased mortality. METHODS: The prospective, controlled Swedish Obese Subjects study involved 4047 obese subjects. Of these subjects, 2010 underwent bariatric surgery (surgery group) and 2037 received conventional treatment (matched control group). We report on overall mortality during an average of 10.9 years of follow-up. At the time of the analysis (November 1, 2005), vital status was known for all but three subjects (follow-up rate, 99.9%). RESULTS: The average weight change in control subjects was less than +/-2% during the period of up to 15 years during which weights were recorded. Maximum weight losses in the surgical subgroups were observed after 1 to 2 years: gastric bypass, 32%; vertical-banded gastroplasty, 25%; and banding, 20%. After 10 years, the weight losses from baseline were stabilized at 25%, 16%, and 14%, respectively. There were 129 deaths in the control group and 101 deaths in the surgery group. The unadjusted overall hazard ratio was 0.76 in the surgery group (P=0.04), as compared with the control group, and the hazard ratio adjusted for sex, age, and risk factors was 0.71 (P=0.01). The most common causes of death were myocardial infarction (control group, 25 subjects; surgery group, 13 subjects) and cancer (control group, 47; surgery group, 29). CONCLUSIONS: Bariatric surgery for severe obesity is associated with long-term weight loss and decreased overall mortality.
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| 280. |
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