@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{HassMunzkeRuizetal.2015, author = {Hass, Roland and Munzke, Dorit and Ruiz, Salome Vargas and Tippmann, Johannes and Reich, Oliver}, title = {Optical monitoring of chemical processes in turbid biogenic liquid dispersions by Photon Density Wave spectroscopy}, series = {Analytical \& bioanalytical chemistry}, volume = {407}, journal = {Analytical \& bioanalytical chemistry}, number = {10}, publisher = {Springer}, address = {Heidelberg}, issn = {1618-2642}, doi = {10.1007/s00216-015-8513-9}, pages = {2791 -- 2802}, year = {2015}, abstract = {In turbid biogenic liquid material, like blood or milk, quantitative optical analysis is often strongly hindered by multiple light scattering resulting from cells, particles, or droplets. Here, optical attenuation is caused by losses due to absorption as well as scattering of light. Fiber-based Photon Density Wave (PDW) spectroscopy is a very promising method for the precise measurement of the optical properties of such materials. They are expressed as absorption and reduced scattering coefficients (mu (a) and mu (s)', respectively) and are linked to the chemical composition and physical properties of the sample. As a process analytical technology, PDW spectroscopy can sense chemical and/or physical processes within such turbid biogenic liquids, providing new scientific insight and process understanding. Here, for the first time, several bioprocesses are analyzed by PDW spectroscopy and the resulting optical coefficients are discussed with respect to established mechanistic models of the chosen processes. As model systems, enzymatic casein coagulation in milk, temperature-induced starch hydrolysis in beer mash, and oxy- as well as deoxygenation of human donor blood were investigated by PDW spectroscopy. The findings indicate that also for very complex biomaterials (i.e., not well-defined model materials like monodisperse polymer dispersions), obtained optical coefficients allow for the assessment of a structure/process relationship and thus for a new analytical access to biogenic liquid material. This is of special relevance as PDW spectroscopy data are obtained without any dilution or calibration, as often found in conventional spectroscopic approaches.}, language = {en} } @article{MunzkeBoehmReich2015, author = {Munzke, Dorit and B{\"o}hm, Michael and Reich, Oliver}, title = {Gaseous Oxygen Detection Using Hollow-Core Fiber-Based Linear Cavity Ring-Down Spectroscopy}, series = {Journal of lightwave technology}, volume = {33}, journal = {Journal of lightwave technology}, number = {12}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {0733-8724}, doi = {10.1109/JLT.2015.2397177}, pages = {2524 -- 2529}, year = {2015}, abstract = {We demonstrate a method for the calibration-free and quantitative analysis of small volumes of gaseous samples. A 10 m hollow-core photonic bandgap fiber is used as the sample cell (volume = 0.44 mu L) and is placed inside a linear resonator setup. The application of cavity ring-down spectroscopy and in consideration of rather small coupling losses, this leads to an increased effective optical path length of up to 70 m. This implies a volume per optical interaction path length of 6.3 nL.m(-1). We used tunable diode laser spectroscopy at 760 nm and scanned the absorption for oxygen sensing. The optical loss due to sample absorption is obtained by measuring the ring-down time of light propagating inside the cavity. The resultant absorption coefficient shows a discrepancy of only 5.1\% comparing to the HITRAN database. This approach is applicable for sensitive measurements if only submicroliter sample volumes are available.}, 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} } @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{HassMunzkeReich2010, author = {Hass, Roland and Munzke, Dorit and Reich, Oliver}, title = {Inline-Partikelgroeßenmesstechniken fuer Suspensionen und Emulsionen}, issn = {0009-286X}, doi = {10.1002/cite.200900172}, year = {2010}, abstract = {Die Inline-Bestimmung von Teilchengroeßen in Emulsionen und Suspensionen stellt besondere Anforderungen an die Messtechnik, da auch bei sehr hohen Teilchenkonzentrationen im Prozess verduennungsfreie Analytik betrieben werden soll. Neben einer Klaerung der Begriffe atline, online und in-line gibt der Beitrag eine Einfuehrung in die mathematische Beschreibung von Groeßenverteilungen. Als Inline-Techniken werden Photonendichtewellen-Spektroskopie, Focused Beam Reflectance Measurement und Ultraschallextinktion-Spektroskopie diskutiert und ihre sehr unterschiedlichen physikalischen Messprinzipien erlaeutert. Auch wird kurz erklaert, wie Teilchengroeßen aus den Messresultaten erhalten werden. Die wesentlichen Charakteristika dieser drei Methoden werden abschließend im ueberblick dargestellt.}, language = {de} } @article{HilleBergBresseletal.2008, author = {Hille, Carsten and Berg, Maik and Bressel, Lena and Munzke, Dorit and Primus, Philipp and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Dosche, Carsten}, title = {Time-domain fluorescence lifetime imaging for intracellular pH sensing in living tissues}, doi = {10.1007/s00216-008-2147-0}, year = {2008}, abstract = {pH sensing in living cells represents one of the most prominent topics in biochemistry and physiology. In this study we performed one-photon and two-photon time-domain fluorescence lifetime imaging with a laser-scanning microscope using the time-correlated single-photon counting technique for imaging intracellular pH levels. The suitability of different commercial fluorescence dyes for lifetime-based pH sensing is discussed on the basis of in vitro as well of in situ measurements. Although the tested dyes are suitable for intensity-based ratiometric measurements, for lifetime- based techniques in the time-domain so far only BCECF seems to meet the requirements of reliable intracellular pH recordings in living cells.}, language = {en} } @phdthesis{Munzke2015, author = {Munzke, Dorit}, title = {Faseroptische Spektroskopie mit hochfrequent modulierten Diodenlasern zur Analyse kleinster Volumina}, school = {Universit{\"a}t Potsdam}, pages = {XIX, 98, XXXVII}, year = {2015}, language = {de} }