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Dive into the research topics where Marco Reuter is active.

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Featured researches published by Marco Reuter.


Optics Express | 2009

Terahertz time-domain spectroscopy as a tool to monitor the glass transition in polymers.

Steffen Wietzke; Christian Jansen; T. Jung; Marco Reuter; Benjamin Baudrit; Martin Bastian; S. Chatterjee; Martin Koch

We demonstrate the suitability of terahertz time-domain spectroscopy as a non-destructive, contact-free tool to monitor the glass transition in polymers--a core feature of the amorphous phase. Below the glass transition temperature T(g), segmental motions along the polymer chain are frozen due to the lack of free volume between neighboring macromolecules. We show that this transition also reflects in the temperature dependence of the refractive index at terahertz frequencies. Two domains can be identified, which differ in their sensitivity to temperature changes. To verify the proposed approach, we determine the glass transition temperature T(g) of semi-crystalline poly(oxymethylene) (POM) with terahertz time-domain spectroscopy and validate the results by destructive differential scanning calorimetry (DSC) measurements.


Optics Express | 2012

Ultrabroadband terahertz spectroscopy of a liquid crystal

N. Vieweg; Bernd M. Fischer; Marco Reuter; P. Kula; R. Dabrowski; Mehmet Ali Celik; Gernot Frenking; Martin Koch; Peter Uhd Jepsen

Liquid crystals (LCs) are becoming increasingly important for applications in the terahertz frequency range. A detailed understanding of the spectroscopic parameters of these materials over a broad frequency range is crucial in order to design customized LC mixtures for improved performance. We present the frequency dependent index of refraction and the absorption coefficients of the nematic liquid crystal 5CB over a frequency range from 0.3 THz to 15 THz using a dispersion-free THz time-domain spectrometer system based on two-color plasma generation and air biased coherent detection (ABCD). We show that the spectra are dominated by multiple strong spectral features mainly at frequencies above 4 THz, originating from intramolecular vibrational modes of the weakly LC molecules.


Applied Physics Letters | 2010

Thermomorphological study of the terahertz lattice modes in polyvinylidene fluoride and high-density polyethylene

Steffen Wietzke; Christian Jansen; Marco Reuter; T. Jung; Judith Hehl; Dietmar Kraft; S. Chatterjee; Andreas Greiner; Martin Koch

Semicrystalline polymers possess a complex morphology comprising both crystalline and amorphous domains. We investigate two representatives from this group, polyvinylidene fluoride and high-density polyethylene, with terahertz time-domain spectroscopy. Intriguingly, the thermal gradient of lattice modes arising from the crystalline phase changes at the glass transition. Thus, terahertz spectroscopy can identify the glass transition temperature Tg even in highly crystalline polymers, where conventional methods such as differential scanning calorimetry fail. Furthermore, these findings provide experimental evidence of the strong interactions between the amorphous and the crystalline domains, as the glass transition is an exclusive feature of the mobile amorphous fraction.


Journal of Materials Chemistry C | 2013

Terahertz and optical properties of nematic mixtures composed of liquid crystal isothiocyanates, fluorides and cyanides

Marco Reuter; Katarzyna Garbat; N. Vieweg; Bernd M. Fischer; Roman Dąbrowski; Martin Koch; Jerzy Dziaduszek; S. Urban

Several simple nematic eutectic liquid crystal mixtures composed of different two and three ring isothiocyanato compounds as well as mixtures consisting of analogous cyano and fluoro compounds were formulated. The optical properties of the thereby obtained mixtures, i.e. refractive indices, birefringence and absorption coefficients αe and αo are measured in the frequency range between 0.5 and 2.5 THz and in the visible range at 589 nm. Our results show that two mixtures can be identified, which seems particularly promising for applications in the terahertz (THz) range: those consisting only of isothiocyanates show the highest birefringence at THz frequencies while those consisting of isothiocyanates and cyanides have the smallest dichroic ratio over a broad THz range. We also found that in most cases, the absorption coefficients of the isothiocyanato compounds fulfill the relationship αe > αo while for cyano and fluoro compounds, αo > αe is observed as a dominating trend. Furthermore, we show that by carefully selecting constituents of both isothiocyanato and cyano compounds, we can achieve a mixture for which the values of αo are in the same order as for αe for THz frequencies below 2 THz.


Optics Express | 2013

Polymer stabilized liquid crystal phase shifter for terahertz waves

Kristian Altmann; Marco Reuter; Katarzyna Garbat; Martin Koch; R. Dabrowski; Ingo Dierking

We propose an electrically tunable phase shifter for terahertz frequencies. The device is based on a polymer stabilized liquid crystal which allows for a simple device geometry. The polymer stabilized liquid crystal enables continuous tuning of the introduced phase shift with only one pair of electrodes. By characterizing the device with terahertz time-domain spectroscopy we demonstrate a phase shift up to 2.5 terahertz, only slightly changed properties of the neat liquid crystal and significantly reduced response times.


Optics Letters | 2013

High-Q terahertz bandpass filters based on coherently interfering metasurface reflections

Norman Born; Marco Reuter; Martin Koch; Maik Scheller

We present compact and easy-to-realize terahertz bandpass filters with Q values in the order of 500. The filters are based on coherently interfering reflections from two parallel metasurfaces applied to the boundaries of a semiconductor disk. By changing the thickness of the semiconductor disk and the dimensions of the metasurface structures, the filter can be optimized for various terahertz frequencies. Moreover, a precise tuning of the resonance frequency is possible via the temperature of the structure or its angle with respect to the propagation direction.


ieee international conference on solid dielectrics | 2010

Terahertz spectroscopy: A powerful tool for the characterization of plastic materials

Steffen Wietzke; Christian Jansen; N. Krumbholz; Ole Peters; N. Vieweg; Christian Jördens; Maik Scheller; D. Romeike; T. Jung; Marco Reuter; S. Chatterjee; Martin Koch; Fachbereich Physik; Benjamin Baudrit; T. Zentgraf; Thomas Hochrein; Martin Bastian

Terahertz (THz) spectroscopy holds a high potential as non-destructive, contact-free testing tool for the analysis of macromolecules, the monitoring of plastic processing and the inspection of plastic components. Even molecular properties, such as the glass transition temperature of highly-crystalline polymers, can be derived from THz measurements. Furthermore, we have identified a plethora of emerging applications in the plastics industry. To appeal to these upcoming challenges, we developed the first THz time-domain spectroscopy (TDS) system for the inline monitoring of compounding processes, which was awarded the Otto von Guericke Prize 2009. It has been demonstrated that the filler content at the end of the extrusion line could be precisely determined by time-of-flight measurements. In addition, THz technology is capable of measuring the water content sensitively, THz birefringence measurements reveal the fiber orientation in reinforced plastics and the quality of plastic weld joints or adhesive bonds can be inspected by the interference evaluation of the THz data. Due to the outstanding dielectric contrast of materials at THz frequencies, even contaminations invisible to x-rays or ultrasonic measurements can be revealed by THz TDS imaging opening the door for a new generation of non-destructive, contact-free quality control systems.


IEEE Transactions on Terahertz Science and Technology | 2013

Investigating Material Characteristics and Morphology of Polymers Using Terahertz Technologies

Bernd M. Fischer; Steffen Wietzke; Marco Reuter; Ole Peters; Ralf Gente; Christian Jansen; N. Vieweg; Martin Koch

The high transmittance of polymers in the terahertz (THz) frequency range is certainly the main reason for the pronounced interest this class of materials receives from the community. Polymers are commonly applied as base material for optical components, sample carriers, or simply test samples, in most fields of THz spectroscopy and imaging. On the other hand, polymers offer an important opportunity for demonstrating the potential of THz technologies as versatile tool for analytical investigations. In this paper, we summarize some recent technical advances underlining the suitability of THz spectroscopy and imaging for material characterization and contact-free testing. The absorption coefficient and refractive index of several biodegradable polymers before and after aging in water are reported. Furthermore, the influence of additive agglomeration in elastomers complements the evaluation of this review of the analytical potential of THz technologies with respect to polymers.


Journal of Biomaterials Science-polymer Edition | 2012

A Fast Degrading Odd–Odd Aliphatic Polyester-5,7 Made by Condensation Polymerization for Biomedical Applications

Fei Chen; Jan Martin Nölle; Steffen Wietzke; Marco Reuter; S. Chatterjee; Martin Koch; Seema Agarwal

Abstract A fast enzymatic degradable aliphatic all-odd-polyester-5,7, based on 1,7-heptanedioic acid (pimelic acid) and 1,5-pentanediol, was synthesized by polycondensation. The structural characterization of the polyester was done using 1D- and 2D-NMR spectroscopic techniques. The properties of the resulting polyester-like crystallization behavior, enzymatic degradation, thermal stability, etc., were investigated using differential scanning calorimetry, wide-angle X-ray diffraction, scanning electron microscopy and gel-permeation chromatography. Terahertz time-domain spectroscopy was employed to determine the glass transition temperature, which could not be revealed reliably by conventional thermal analysis. The properties of all-odd-polyester-5,7 were compared with a well-known enzymatic degradable polyester (polycaprolactone). The results indicated that polyester-5,7 has a crystal structure similar to PCL, but a much faster degradation rate. The morphology of polyester-5,7 film during enzymatic degradation showed a fibrillar structure and degradation began by surface erosion.


Applied Physics Letters | 2016

Terahertz spectroscopy across liquid crystalline phase transitions

Marco Reuter; N. Vieweg; Martin Koch; Ingo Dierking

Using terahertz time-domain spectroscopy we investigate the far-infrared properties of liquid crystal CE8 which exhibits a plethora of phases upon variation of the temperature. Phase transitions that are correlated with structural ordering at different dimensions clearly reflect in the terahertz refractive index. On the contrary, phase transitions related to ordering phenomena within a certain group of phases do not lead to significant steps in the n(T) relation. Nevertheless, we additionally demonstrate that also 2nd order phase transitions, like the SmA*-SmC* phase change, can be resolved by THz spectroscopy.

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N. Vieweg

University of Marburg

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R. Dabrowski

Military Technical Academy

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T. Jung

University of Marburg

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