Optical gain in erbium-implanted Al2O3 waveguides

Al/sub 2/O/sub 3/ ridge waveguides implanted with 1.3 at.% Er, pumped with 2.5 mW 1.47 mu m light show 4.5 dB/cm enhancement of a 1.53 mu m signal beam. The maximum gain is limited by cooperative upconversion effects. Calculations for lower Er concentrations show that 1 dB/cm net optical gain is possible at 10 mW pump powe

Upconversion in Er-implanted Al2O3 waveguides

When pumped with a 1.48 mu m laser diode, Er-implanted Al/sub 2/O/sub 3/ ridge waveguides emit a broad spectrum consisting of several distinct peaks having wavelengths ranging from the midinfrared (1.53 mu m) to the visible (520 nm). In order to explain these observations, three different upconversion mechanisms are considered: cooperative upconversion, excited state absorption, and pair-induced quenching. It is found that for samples with a high Er concentration (1.4 at.%), cooperative upconversion completely dominates the deexcitation of the Er/sup 3+/ ions. For a much lower concentration (0.12 at.%), the influence of cooperative upconversion is strongly reduced, and another upconversion effect becomes apparent: excited state absorption. These conclusions are based on measurements of the luminescence emission versus pump intensity, and also on measured luminescence decay curves. The upconversion coefficient is found to be (4+or-1)*10/sup -18/ cm/sup 3//s; the excited state absorption cross section is (0.9+or-0.3)*10/sup -21/ cm/sup 2/. It is shown that in spite of these upconversion effects, a high fraction of the Er/sup 3+/ can be excited at low pump powers. For pump powers between 2 and 10 mW, the optimum Er concentration is calculated. The results show that for an Er concentration of 0.5 at.%, more than 2 dB/cm net optical gain is achievable at a pump power less than 10 m

Unravelling the evolution of Africa's drainage basins through a widespread freshwater fish, the African sharptooth catfish Clarias gariepinus

Aim The formation history of Africa's current river basins remains largely unknown. In order to date changes in landscape and climate, we studied the biogeography of the African freshwater fish with the largest natural distribution. We also validated biogeographical units. Location Continental Africa. Taxon Clarias gariepinus sl. Methods We investigated mitochondrial cytb sequences of 443 individuals from 97 localities, using a haplotype network and a genetic landscape analysis. We inferred a dated phylogeny using maximum likelihood and Bayesian inference approaches and reconstructed ancestral areas with S-DEC and S-DIVA models. Microsatellite genotyping complemented the mitochondrial approach in the Congo basin, where the latter revealed complex patterns. Results Limited differentiation is found in northern and south-western Africa, and sharp genetic differentiation in the continent's east and centre. Populations with affinities to neighbouring basins occur at the edges of the Congo province. High diversity exists in the south of the Congo basin. The Zambezi province is partitioned into eastern, central and western sectors. In the east, specimens were related to those from the Congo. In the west, they were similar to Southern representatives. Phylogenetic inference placed the origin of C. gariepinus in the East Coast, with intraspecific diversification starting around the Great Lakes. These events occurred ca. 4.8-1.65 and 2.3-0.8 MYA respectively. Main conclusions Clades of C. gariepinus sl. show a clear geographical signature. The origin of C. gariepinus in the East Coast and diversification around the Great Lakes coincided with the periods of increased aridity. Low genetic differentiation in northern and southern Africa may result from connectivity during recent periods of higher rainfall. In contrast to other widespread African freshwater fish, colonization rather than extinction seemed to mediate distribution patterns. This can be explained by a high ecological tolerance. We highlight the species' suitability to study landscape and climate evolution at various scales.Peer reviewe

Erbium ion implantation doping of opto-electronic materials operating at 1.5 mu m

Soda-lime silicate and Al/sub 2/O/sub 3/ waveguide films, LiNbO/sub 3/ single crystal, as well as crystal Si are doped with erbium by ion implantation. All materials show luminescence at 1.5 mu m, characteristic for Er, with lifetimes up to 12 m

On the equivalence of the Langevin and auxiliary field quantization methods for absorbing dielectrics

Recently two methods have been developed for the quantization of the electromagnetic field in general dispersing and absorbing linear dielectrics. The first is based upon the introduction of a quantum Langevin current in Maxwell's equations [T. Gruner and D.-G. Welsch, Phys. Rev. A 53, 1818 (1996); Ho Trung Dung, L. Kn\"{o}ll, and D.-G. Welsch, Phys. Rev. A 57, 3931 (1998); S. Scheel, L. Kn\"{o}ll, and D.-G. Welsch, Phys. Rev. A 58, 700 (1998)], whereas the second makes use of a set of auxiliary fields, followed by a canonical quantization procedure [A. Tip, Phys. Rev. A 57, 4818 (1998)]. We show that both approaches are equivalent.Comment: 7 pages, RevTeX, no figure

Development of a value-based healthcare burns core set for adult burn care

Background: Value-based healthcare (VBHC) is increasingly implemented in healthcare worldwide. Transparent measurement of the outcomes most important and relevant to patients is essential in VBHC, which is supported by a core set of most important quality indicators and outcomes. Therefore, the aim of this study was to develop a VBHC-burns core set for adult burn patients. Methods: A three-round modified national Delphi study, including 44 outcomes and 24 quality indicators, was conducted to reach consensus among Dutch patients, burn care professionals and researchers. Items were rated on a nine-point Likert scale and selected if ≥ 70% in each group considered an item ‘important’. Subsequently, instruments quantifying selected outcomes were identified based on a literature review and were chosen in a consensus meeting using recommendations from the Dutch consensus-based standard set and the Dutch Centre of Expertise on Health Disparities. Time assessment points were chosen to reflect the burn care and patient recovery process. Finally, the initial core set was evaluated in practice, leading to the adapted VBHC-burns core set. Results: Twenty-seven patients, 63 burn care professionals and 23 researchers participated. Ten outcomes and four quality indicators were selected in the Delphi study, including the outcomes pain, wound healing, physical activity, self-care, independence, return to work, depression, itching, scar flexibility and return to school. Quality indicators included shared decision-making (SDM), the number of patients receiving aftercare, determination of burn depth, and assessment of active range of motion. After evaluation of its use in clinical practice, the core set included all items except SDM, which are assessed by 9 patient-reported outcome instruments or measured in clinical care. Assessment time points included are at discharge, 2 weeks, 3 months, 12 months after discharge and annually afterwards. Conclusion: A VBHC-burns core set was developed, consisting of outcomes and quality indicators that are important to burn patients and burn care professionals. The VBHC-burns core set is now systemically monitored and analysed in Dutch burn care to improve care and patient relevant outcomes. As improving burn care and patient relevant outcomes is important worldwide, the developed VBHC-burns core set could be inspiring for other countries.</p