@article{AndrewsFergusonRangaswamyetal.2017,
  author    = {Andrews, N. L. P. and Ferguson, T. and Rangaswamy, A. M. M. and Bernicky, A. R. and Henning, N. and Dudelzak, A. and Reich, Oliver and Barnes, Jack A. and Loock, Hans-Peter},
  title     = {Hadamard-Transform Fluorescence Excitation-Emission-Matrix Spectroscopy},
  series = {Analytical chemistry},
  volume    = {89},
  journal   = {Analytical chemistry},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0003-2700},
  doi       = {10.1021/acs.analchem.7b02400},
  pages     = {8554 -- 8564},
  year      = {2017},
  abstract  = {We present a fluorescence excitation-emission-matrix spectrometer with superior data acquisition rates over previous instruments. Light from a white light emitting diode (LED) source is dispersed onto a digital micromirror array (DMA) and encoded using binary n-size Walsh functions ("barcodes"). The encoded excitation light is used to irradiate the liquid sample and its fluorescence is dispersed and detected using a conventional array spectrometer. After exposure to excitation light encoded in n different ways, the 2-dimensional excitation-emission-matrix (EEM) spectrum is obtained by inverse Hadamard transformation. Using this technique we examined the kinetics of the fluorescence of rhodamine B as a function of temperature and the acid-driven demetalation of chlorophyll into pheophytin-a. For these experiments, EEM spectra with 31 excitation channels and 2048 emission channels were recorded every 15 s. In total, data from over 3000 EEM spectra were included in this report. It is shown that the increase in data acquisition rate can be as high as [{n(n + 1)}/2]-fold over conventional EEM spectrometers. Spectral acquisition rates of more than two spectra per second were demonstrated.},
  language  = {en}
}
@article{AndrewsRossMunzkeetal.2016,
  author    = {Andrews, Nicholas L. P. and Ross, Rachel and Munzke, Dorit and van Hoorn, Camiel and Brzezinski, Andrew and Barnes, Jack A. and Reich, Oliver and Loock, Hans-Peter},
  title     = {In-fiber Mach-Zehnder interferometer for gas refractive index measurements based on a hollow-core photonic crystal fiber},
  series = {Optics express : the international electronic journal of optics},
  volume    = {24},
  journal   = {Optics express : the international electronic journal of optics},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1094-4087},
  doi       = {10.1364/OE.24.014086},
  pages     = {14086 -- 14099},
  year      = {2016},
  abstract  = {We describe an in-fiber interferometer based on a gas-filled hollow-core photonic crystal fiber. Expressions for the sensitivity, figure of merit and refractive index resolution are derived, and values are experimentally measured and theoretically validated using mode field calculations. The refractive indices of nine monoatomic and molecular gases are measured with a resolution of delta(ns) < 10(-6). (C)2016 Optical Society of America},
  language  = {en}
}
@article{BeschererMunzkeReichetal.2013,
  author    = {Bescherer, Klaus and Munzke, Dorit and Reich, Oliver and Loock, Hans-Peter},
  title     = {Fabrication and modeling of multimode fiber lenses},
  series = {Applied optics},
  volume    = {52},
  journal   = {Applied optics},
  number    = {4},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1559-128X},
  doi       = {10.1364/AO.52.000B40},
  pages     = {B40 -- B45},
  year      = {2013},
  abstract  = {We report on the fabrication, modeling, and experimental verification of the emission of fiber lenses fabricated on multimode fibers in different media. Concave fiber lenses with a radius of 150 mu m were fabricated onto a multimode silica fiber (100 mu m core) by grinding and polishing against a ruby sphere template. In our theoretical model we assume that the fiber guides light from a Lambertian light source and that the emission cone is governed solely by the range of permitted emission angles. We investigate concave and convex lenses at 532 nm with different radii and in a variety of surrounding media from air (n(0) = 1.00) to sapphire (n(0) = 1.77). It was found that noticeable focusing or defocusing effects of a silica fiber lens in ethanol (n(0) = 1.36) and dimethyl sulfoxide (DMSO) (n(0) = 1.48) are only observed when the fiber lens radius was less than the fiber diameter.},
  language  = {en}
}
@article{MunzkeSaundersOmranietal.2012,
  author    = {Munzke, Dorit and Saunders, John and Omrani, Hengameh and Reich, Oliver and Loock, Hans-Peter},
  title     = {Modeling of fiber-optic fluorescence probes for strongly absorbing samples},
  series = {Applied optics},
  volume    = {51},
  journal   = {Applied optics},
  number    = {26},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1559-128X},
  doi       = {10.1364/AO.51.006343},
  pages     = {6343 -- 6351},
  year      = {2012},
  abstract  = {The dynamic range of fiber-optic fluorescent probes such as single fibers and fiber bundles is calculated for strongly absorbing samples, such as process liquids, foodstuffs, and lubricants. The model assumes an excitation beam profile based on a Lambertian light source and uses analytical forms of the collection efficiency, followed by an Abel transformation and numerical integration. It is found that the effect of primary absorption of the excitation light and secondary absorption of the fluorescence is profound. For fiber bundles and bifurcated fiber probes, the upper accessible concentration limit is roughly given by the absorption length of the primary and secondary absorption. Fluorescence detectors that are placed at right angles to the excitation beam axis or collinear to the beam axis are equally strongly affected by secondary absorption. A probe in which the same fiber is used for excitation and for collection of the fluorescence emerges as the fiber probe with the largest accessible concentration range.},
  language  = {en}
}