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End date: 2019 × Start date: 2019 × End date: 2019 × Start date: 2010 × Type: Text × Publisher: Washington, DC : Optical Society of America × WGL Institute: IPHT ×

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Now showing 1 - 3 of 3
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    Identification of zero density of states domains in band gap fibers using a single binary function
    (Washington, DC : Optical Society of America, 2016) Li, Guangrui; Schmidt, Markus A.
    Here we introduce a new calculation method to find the domains of zero density of states for photonic band gap guiding fibers consisting of arrays of high refractive index strands in a low refractive index cladding. We find an analytic expression that associates any combination of geometric parameter, effective index, material and wavelength with a single binary function which allows direct determination whether the density of cladding states is zero or not. The method neither requires the typically used root finding procedure for dispersion tracking nor simulation volume discretization. We verify the validity of our approach on well-established results and reveal as example that band gap regions are mainly determined by the two lowest order Bessel function orders. Our method allows for extensive parameter scans and evaluation of photonic band gap structures against structural and material inaccuracies with substantially reduced simulation effort.
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    Motion artefact detection in structured illumination microscopy for live cell imaging
    (Washington, DC : Optical Society of America, 2016) Förster, Ronny; Wicker, Kai; Müller, Walter; Jost, Aurélie; Heintzmann, Rainer
    The reconstruction process of structured illumination microscopy (SIM) creates substantial artefacts if the specimen has moved during the acquisition. This reduces the applicability of SIM for live cell imaging, because these artefacts cannot always be recognized as such in the final image. A movement is not necessarily visible in the raw data, due to the varying excitation patterns and the photon noise. We present a method to detect motion by extracting and comparing two independent 3D wide-field images out of the standard SIM raw data without needing additional images. Their difference reveals moving objects overlaid with noise, which are distinguished by a probability theory-based analysis. Our algorithm tags motion-artefacts in the final high-resolution image for the first time, preventing the end-user from misinterpreting the data. We show and explain different types of artefacts and demonstrate our algorithm on a living cell.
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    Single mode criterion - a benchmark figure to optimize the performance of nonlinear fibers
    (Washington, DC : Optical Society of America, 2016) Chemnitz, Mario; Schmidt, Markus A.
    Optical fibers with sub-wavelength cores are promising systems for efficient nonlinear light generation. Here we reveal that the single-mode criterion represents a convenient design tool to optimize the performance of nonlinear fibers circumventing intense numerical calculations. We introduce a quasi-analytic expression for the nonlinear coefficient allowing us to investigate its behavior over a large parameter range. The study is independent of the actual value of the material nonlinearity and shows the fundamental dependencies of the nonlinear coefficient on wavelength, refractive index and core diameter, elucidated by detailed case studies of fused silica and chalcogenide tapers and hybrid fibers.