Demonstration of an erbium doped microdisk laser on a silicon chip

An erbium doped micro-laser is demonstrated utilizing $\mathrm{SiO_{2}}$ microdisk resonators on a silicon chip. Passive microdisk resonators exhibit whispering gallery type (WGM) modes with intrinsic optical quality factors of up to $6\times{10^{7}}$ and were doped with trivalent erbium ions (peak concentration $\mathrm{\sim3.8\times{10^{20}cm^{-3})}}$ using MeV ion implantation. Coupling to the fundamental WGM of the microdisk resonator was achieved by using a tapered optical fiber. Upon pumping of the $^{4}I_{15/2}\longrightarrow$ $^{4}I_{13/2}$ erbium transition at 1450 nm, a gradual transition from spontaneous to stimulated emission was observed in the 1550 nm band. Analysis of the pump-output power relation yielded a pump threshold of 43 $\mathrm{\mu}$W and allowed measuring the spontaneous emission coupling factor: $\beta\approx1\times10^{-3}$

Design and characterization of SiON integrated optics components for optical coherence tomography

Optical coherence tomography (OCT) is a technique for high resolution imaging of biological tissues with a depth range of a few millimeters. OCT is based on interferometry to enable depth ranging. Currently, optical components for OCT are rather bulky and expensive; the use of integrated optical circuits presents a great opportunity to reduce costs and enhance system functionality and performance. We present the design and characterization of SiON-based integrated optics waveguides, splitters, couplers and interferometers for OCT operating at a wavelength of 1.3 um

Spectral-domain optical coherence tomography with an arrayed waveguide grating spectrometer

We designed and fabricated an arrayed waveguide grating (AWG) with 2.1cmx2.6cm footprint. Using the AWG as spectrometer in a spectral-domain optical coherence tomography (OCT) set-up we demonstrate OCT imaging up to the maximum depth of 1 mm with 19 µm spatial resolution in air and in a multi-layered phantom

Checklist of the Odonata (Insecta) of Sundaland and Wallacea (Malaysia, Singapore, Brunei, Indonesia and Timor Leste)

A checklist, based on a database containing published data, of the Odonata (dragonflies and damselflies) occurring in Sundaland and wallacea is presented. The presence of (sub)species is indicated for eight main regions (Singapore & Peninsular Malaysia, South China Sea (islands in the South China Sea that are not sensibly treated as satellites of larger landmasses), Borneo, Sumatra, Java & Bali, Lesser Sunda, Sulawesi, Moluccas), 22 subregions and 80 smaller islands and island groups. In total 743 full species are recorded from the entire area with 549 species known from Sundaland and 270 from wallacea. Of these 482 are not found outside Sundaland and wallacea, 385 (ca. 52% of the fauna) of which are single region endemics; the majority of these are actually single island endemics. Notes are provided on taxonomic problems or indicating problematic distribution records. Prodasineura lansbergei is considered to be a nomen nudum (stat nov.). For each of the eight main regions the history of the study of odonates is briefly discussed, information is provided on the coverage of the available data and the faunal composition is described. An overview is given of genera for which no larvae have been described. A brief comparison is made between the faunas of Sundaland and wallacea showing that they only share 10% of the species between them (76 of 743)

L-infinity algebra connections and applications to String- and Chern-Simons n-transport

We give a generalization of the notion of a Cartan-Ehresmann connection from Lie algebras to L-infinity algebras and use it to study the obstruction theory of lifts through higher String-like extensions of Lie algebras. We find (generalized) Chern-Simons and BF-theory functionals this way and describe aspects of their parallel transport and quantization. It is known that over a D-brane the Kalb-Ramond background field of the string restricts to a 2-bundle with connection (a gerbe) which can be seen as the obstruction to lifting the PU(H)-bundle on the D-brane to a U(H)-bundle. We discuss how this phenomenon generalizes from the ordinary central extension U(1) -> U(H) -> PU(H) to higher categorical central extensions, like the String-extension BU(1) -> String(G) -> G. Here the obstruction to the lift is a 3-bundle with connection (a 2-gerbe): the Chern-Simons 3-bundle classified by the first Pontrjagin class. For G = Spin(n) this obstructs the existence of a String-structure. We discuss how to describe this obstruction problem in terms of Lie n-algebras and their corresponding categorified Cartan-Ehresmann connections. Generalizations even beyond String-extensions are then straightforward. For G = Spin(n) the next step is "Fivebrane structures" whose existence is obstructed by certain generalized Chern-Simons 7-bundles classified by the second Pontrjagin class.Comment: 100 pages, references and clarifications added; correction to section 5.1 and further example to 9.3.1 adde

Higgs Bundles, Gauge Theories and Quantum Groups

The appearance of the Bethe Ansatz equation for the Nonlinear Schr\"{o}dinger equation in the equivariant integration over the moduli space of Higgs bundles is revisited. We argue that the wave functions of the corresponding two-dimensional topological U(N) gauge theory reproduce quantum wave functions of the Nonlinear Schr\"{o}dinger equation in the $N$-particle sector. This implies the full equivalence between the above gauge theory and the $N$-particle sub-sector of the quantum theory of Nonlinear Schr\"{o}dinger equation. This also implies the explicit correspondence between the gauge theory and the representation theory of degenerate double affine Hecke algebra. We propose similar construction based on the $G/G$ gauged WZW model leading to the representation theory of the double affine Hecke algebra. The relation with the Nahm transform and the geometric Langlands correspondence is briefly discussed.Comment: 48 pages, typos corrected, one reference adde

Risk of perioperative thyroid storm in hyperthyroid patients: a systematic review

Background: Thyroid storm is a feared complication in patients with hyperthyroidism undergoing surgery. We assessed the risk of thyroid storm for different preoperative treatment options for patients with primary hyperthyroidism undergoing surgery. Methods: Pubmed, EMBASE, and The Cochrane Library were searched systematically for all studies reporting on adult hyperthyroid patients undergoing elective surgery under general anaesthesia. Selected studies were categorised based on preoperative treatment: no treatment, antithyroid medication (thionamides), iodine, β-blocking medication, or a combination thereof. Treatment effect, that is restoring euthyroidism, was extracted from the publications if available. Risk of bias was assessed using the Risk of Bias in Non-randomised Studies of Interventions (ROBINS-I) or the Cochrane Risk of Bias tool for randomised studies. Results: The search yielded 7009 articles, of which 26 studies published between 1975 and 2020 were selected for critical appraisal. All studies had moderate to critical risk of bias, mainly attributable to risk of confounding, classification of intervention status, and definition of the outcome. All studies reported on thyroidectomy patients. We found no randomised studies comparing the risk of thyroid storm between treated and untreated patients. Cases of thyroid storm were reported in all treatment groups with incidences described ranging from 0% to 14%. Conclusion: Evidence assessing the risk of perioperative thyroid storm is of insufficient quality. Given the seriousness of this complication and the impossibility of identifying patients at increased risk, preoperative treatment of these patients remains warranted