TY  - JOUR
A1  - Andrews, N. L. P.
A1  - Ferguson, T.
A1  - Rangaswamy, A. M. M.
A1  - Bernicky, A. R.
A1  - Henning, N.
A1  - Dudelzak, A.
A1  - Reich, Oliver
A1  - Barnes, Jack A.
A1  - Loock, Hans-Peter
T1  - Hadamard-Transform Fluorescence Excitation-Emission-Matrix Spectroscopy
JF  - Analytical chemistry
N2  - 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.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.analchem.7b02400
SN  - 0003-2700
SN  - 1520-6882
VL  - 89
SP  - 8554
EP  - 8564
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Andrews, Nicholas L. P.
A1  - Ross, Rachel
A1  - Munzke, Dorit
A1  - van Hoorn, Camiel
A1  - Brzezinski, Andrew
A1  - Barnes, Jack A.
A1  - Reich, Oliver
A1  - Loock, Hans-Peter
T1  - In-fiber Mach-Zehnder interferometer for gas refractive index measurements based on a hollow-core photonic crystal fiber
JF  - Optics express : the international electronic journal of optics
N2  - 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
Y1  - 2016
U6  - https://doi.org/10.1364/OE.24.014086
SN  - 1094-4087
VL  - 24
SP  - 14086
EP  - 14099
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bescherer, Klaus
A1  - Munzke, Dorit
A1  - Reich, Oliver
A1  - Loock, Hans-Peter
T1  - Fabrication and modeling of multimode fiber lenses
JF  - Applied optics
N2  - 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.
Y1  - 2013
U6  - https://doi.org/10.1364/AO.52.000B40
SN  - 1559-128X
SN  - 2155-3165
VL  - 52
IS  - 4
SP  - B40
EP  - B45
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Munzke, Dorit
A1  - Saunders, John
A1  - Omrani, Hengameh
A1  - Reich, Oliver
A1  - Loock, Hans-Peter
T1  - Modeling of fiber-optic fluorescence probes for strongly absorbing samples
JF  - Applied optics
N2  - 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.
Y1  - 2012
U6  - https://doi.org/10.1364/AO.51.006343
SN  - 1559-128X
SN  - 2155-3165
VL  - 51
IS  - 26
SP  - 6343
EP  - 6351
PB  - Optical Society of America
CY  - Washington
ER  -