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End date: 2019 × Start date: 2019 × End date: 2019 × Start date: 2010 × Type: Text × WGL Institute: IPHT ×

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    PHONA - photonische Nanomaterialien : Schlussbericht ; Laufzeit des Vorhabens: 01.12.2009-30.11.2014
    (Hannover : Technische Informationsbibliothek (TIB), 2014) Hübner, Uwe; Popp, Jürgen
    [no abstract available]
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    Beyond endoscopic assessment in inflammatory bowel disease: real-time histology of disease activity by non-linear multimodal imaging
    (London : Nature Publishing Group, 2016) Chernavskaia, Olga; Heuke, Sandro; Vieth, Michael; Friedrich, Oliver; Schürmann, Sebastian; Atreya, Raja; Stallmach, Andreas; Neurath, Markus F.; Waldner, Maximilian; Petersen, Iver; Schmitt, Michael; Bocklitz, Thomas; Popp, Jürgen
    Assessing disease activity is a prerequisite for an adequate treatment of inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis. In addition to endoscopic mucosal healing, histologic remission poses a promising end-point of IBD therapy. However, evaluating histological remission harbors the risk for complications due to the acquisition of biopsies and results in a delay of diagnosis because of tissue processing procedures. In this regard, non-linear multimodal imaging techniques might serve as an unparalleled technique that allows the real-time evaluation of microscopic IBD activity in the endoscopy unit. In this study, tissue sections were investigated using the non-linear multimodal microscopy combination of coherent anti-Stokes Raman scattering (CARS), two-photon excited auto fluorescence (TPEF) and second-harmonic generation (SHG). After the measurement a gold-standard assessment of histological indexes was carried out based on a conventional H&E stain. Subsequently, various geometry and intensity related features were extracted from the multimodal images. An optimized feature set was utilized to predict histological index levels based on a linear classifier. Based on the automated prediction, the diagnosis time interval is decreased. Therefore, non-linear multimodal imaging may provide a real-time diagnosis of IBD activity suited to assist clinical decision making within the endoscopy unit.
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    Evaluation of shifted excitation Raman difference spectroscopy and comparison to computational background correction methods applied to biochemical Raman spectra
    (Basel : MDPI, 2017) Cordero, Eliana; Korinth, Florian; Stiebing, Clara; Krafft, Christoph; Schie, Iwan W.; Popp, Jürgen
    Raman spectroscopy provides label-free biochemical information from tissue samples without complicated sample preparation. The clinical capability of Raman spectroscopy has been demonstrated in a wide range of in vitro and in vivo applications. However, a challenge for in vivo applications is the simultaneous excitation of auto-fluorescence in the majority of tissues of interest, such as liver, bladder, brain, and others. Raman bands are then superimposed on a fluorescence background, which can be several orders of magnitude larger than the Raman signal. To eliminate the disturbing fluorescence background, several approaches are available. Among instrumentational methods shifted excitation Raman difference spectroscopy (SERDS) has been widely applied and studied. Similarly, computational techniques, for instance extended multiplicative scatter correction (EMSC), have also been employed to remove undesired background contributions. Here, we present a theoretical and experimental evaluation and comparison of fluorescence background removal approaches for Raman spectra based on SERDS and EMSC.
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    Sub-picosecond temporal resolution of anomalous Hall currents in GaAs
    (Berlin : Nature Pulishing, 2017) Schmidt, Christian B.; Priyadarshi, Shekhar; Bieler, Mark
    Peroxidase-mimicking DNAzyme was applied as a catalyst of silver deposition on gold nanoparticles. This DNAzyme is formed when hemin binds to the G-quadruplex-forming DNA sequence. Such a system is able to catalyze a redox reaction with a one- or two-electron transfer. The process of silver deposition was monitored via a localized surface plasmon resonance technique (LSPR), which allows one to record scattering spectrum of a single nanoparticle. Our study showed that DNAzyme is able to catalyze silver deposition. The AFM experiments proved that DNAzyme induced the deposition of silver shells of approximately 20 nm thickness on Au nanoparticles (AuNPs). Such an effect is not observed when hemin is absent in the system. However, we noticed non-specific binding of hemin to the capture oligonucleotides on a gold NP probe that also induced some silver deposition, even though the capture probe was unable to form G-quadruplex. Analysis of SEM images indicated that the surface morphology of the silver layer deposited by DNAzyme is different from that obtained for hemin alone. The proposed strategy of silver layer synthesis on gold nanoparticles catalyzed by DNAzyme is an innovative approach and can be applied in bioanalysis (LSPR, electrochemistry) as well as in material sciences.
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    Using machine-learning to optimize phase contrast in a low-cost cellphone microscope
    (San Francisco, CA : Public Library of Science, 2018) Diederich, Benedict; Wartmann, Rolf; Schadwinkel, Harald; Heintzmann, Rainer
    Cellphones equipped with high-quality cameras and powerful CPUs as well as GPUs are widespread. This opens new prospects to use such existing computational and imaging resources to perform medical diagnosis in developing countries at a very low cost. Many relevant samples, like biological cells or waterborn parasites, are almost fully transparent. As they do not exhibit absorption, but alter the light’s phase only, they are almost invisible in brightfield microscopy. Expensive equipment and procedures for microscopic contrasting or sample staining often are not available. Dedicated illumination approaches, tailored to the sample under investigation help to boost the contrast. This is achieved by a programmable illumination source, which also allows to measure the phase gradient using the differential phase contrast (DPC) [1, 2] or even the quantitative phase using the derived qDPC approach [3]. By applying machine-learning techniques, such as a convolutional neural network (CNN), it is possible to learn a relationship between samples to be examined and its optimal light source shapes, in order to increase e.g. phase contrast, from a given dataset to enable real-time applications. For the experimental setup, we developed a 3D-printed smartphone microscope for less than 100 $ using off-the-shelf components only such as a low-cost video projector. The fully automated system assures true Koehler illumination with an LCD as the condenser aperture and a reversed smartphone lens as the microscope objective. We show that the effect of a varied light source shape, using the pre-trained CNN, does not only improve the phase contrast, but also the impression of an improvement in optical resolution without adding any special optics, as demonstrated by measurements.
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    Comparison of hyperspectral coherent Raman scattering microscopies for biomedical applications
    (College Park : American Institute of Physics, 2018) Bocklitz, Thomas W.; Meyer, Tobias; Schmitt, Michael; Rimke, Ingo; Hoffmann, Franziska; von Eggeling, Ferdinand; Ernst, G.; Guntinas-Lichius, Orlando; Popp, Jürgen
    Raman scattering based imaging represents a very powerful optical tool for biomedical diagnostics. Different Raman signatures obtained by distinct tissue structures and disease induced changes provoke sophisticated analysis of the hyperspectral Raman datasets. While the analysis of linear Raman spectroscopic tissue data is quite established, the evaluation of hyperspectral nonlinear Raman data has not yet been evaluated in great detail. The two most common nonlinear Raman methods are CARS (coherent anti-Stokes Raman scattering) and SRS (stimulated Raman scattering) spectroscopy. Specifically the linear concentration dependence of SRS as compared to the quadratic dependence of CARS has fostered the application of SRS tissue imaging. Here, we applied spectral processing to hyperspectral SRS and CARS data for tissue characterization. We could demonstrate for the first time that similar cluster distributions can be obtained for multispectral CARS and SRS data but that clustering is based on different spectral features due to interference effects in CARS and the different concentration dependence of CARS and SRS. It is shown that a direct combination of CARS and SRS data does not improve the clustering results.
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    Germania and alumina dopant diffusion and viscous flow effects at preparation of doped optical fibers
    (Ostrava : VSB - Technical University of Ostrava and University of Zilina Faculty of Electrical Engineering, 2017) Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Unger, Sonja; Schwuchow, Anka; Elsmann, Tino; Dellith, Jan; Aichele, Claudia; Fatobene Ando, Ron; Bartelt, Hartmut
    We report on germania and alumina dopant profile shift effects at preparation of compact optical fibers using packaging methods (Stack-and-Draw method, Rod-in-Tube (RiT) technique). The sintering of package hollow volume by viscous flow results in a shift of the core-pitch ratio in all-solid microstructured fibers. The ratio is increased by about 5% in the case of a hexagonal package. The shift by diffusion effects of both dopants is simulated for typical slow speed drawing parameters. Thermodynamic approximations of surface dissociation of germania doped silica suggest the need of an adequate undoped silica barrier layer to prevent an undesired bubble formation at fiber drawing. In contrast, alumina doping does not estimate critical dissociation effects with vaporous aluminium oxide components. We report guide values of diffusion length of germania and alumina for the drawing process by kinetic approximation. The germania diffusion involves a small core enlargement, typically in the sub-micrometer scale. Though, the alumina diffusion enlarges it by a few micrometers. A drawn pure alumina preform core rod transforms to an amorphous aluminosilicate core with a molar alumina concentration of only about 50% and a non-gaussian concentration profile.
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    High-bit rate ultra-compact light routing with mode-selective on-chip nanoantennas
    (Washington D.C. : AAAS, 2017) Guo, Rui; Decker, Manuel; Setzpfandt, Frank; Gai, Xin; Choi, Duk-Yong; Kiselev, Roman; Chipouline, Arkadi; Staude, Isabelle; Pertsch, Thomas; Neshev, Dragomir N.
    Optical nanoantennas provide a promising pathway toward advanced manipulation of light waves, such as directional scattering, polarization conversion, and fluorescence enhancement. Although these functionalities were mainly studied for nanoantennas in free space or on homogeneous substrates, their integration with optical waveguides offers an important “wired” connection to other functional optical components. Taking advantage of the nanoantenna’s versatility and unrivaled compactness, their imprinting onto optical waveguides would enable a marked enhancement of design freedom and integration density for optical on-chip devices. Several examples of this concept have been demonstrated recently. However, the important question of whether nanoantennas can fulfill functionalities for high-bit rate signal transmission without degradation, which is the core purpose of many integrated optical applications, has not yet been experimentally investigated. We introduce and investigate directional, polarization-selective, and mode-selective on-chip nanoantennas integrated with a silicon rib waveguide. We demonstrate that these nanoantennas can separate optical signals with different polarizations by coupling the different polarizations of light vertically to different waveguide modes propagating into opposite directions. As the central result of this work, we show the suitability of this concept for the control of optical signals with ASK (amplitude-shift keying) NRZ (nonreturn to zero) modulation [10 Gigabit/s (Gb/s)] without significant bit error rate impairments. Our results demonstrate that waveguide-integrated nanoantennas have the potential to be used as ultra-compact polarization-demultiplexing on-chip devices for high–bit rate telecommunication applications.
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    Nanoboomerang-based inverse metasurfaces - a promising path towards ultrathin photonic devices for transmission operation
    (College Park : American Institute of Physics, 2017) Zeisberger, Matthias; Schneidewind, Henrik; Hübner, Uwe; Popp, Jürgen; Schmidt, Markus A.
    Metasurfaces have revolutionized photonics due to their ability to shape phase fronts as requested and to tune beam directionality using nanoscale metallic or dielectric scatterers. Here we reveal inverse metasurfaces showing superior properties compared to their positive counterparts if transmission mode operation is considered. The key advantage of such slot-type metasurfaces is the strong reduction of light in the parallel-polarization state, making the crossed-polarization, being essential for metasurface operation, dominant and highly visible. In the experiment, we show an up to four times improvement in polarization extinction for the individual metasurface element geometry consisting of deep subwavelength nanoboomerangs with feature sizes of the order of 100 nm. As confirmed by simulations, strong plasmonic hybridization yields two spectrally separated plasmonic resonances, ultimately allowing for the desired phase and scattering engineering in transmission. Due to the design flexibility of inverse metasurfaces, a large number of highly integrated ultra-flat photonic elements can be envisioned, examples of which include monolithic lenses for telecommunications and spectroscopy, beam shaper or generator for particle trapping or acceleration or sophisticated polarization control for microscopy.