2020

• Strauch, Matthias and Kolb, Jan Philip and Weng, Daniel and Wacker, Melanie and Draxinger, Wolfgang and Merg, Nadine and Hundt, Jennifer and Karpf, Sebastian and Huber, Robert: Two-photon microscopy for sectioning-free virtual H&E imaging. in 104. Jahrestagung der Deutschen Gesellschaft fuer Pathologie, 2020
  

  @InProceedings{Strauch2020,
    author    = {Strauch, Matthias and Kolb, Jan Philip and Weng, Daniel and Wacker, Melanie and Draxinger, Wolfgang and Merg, Nadine and Hundt, Jennifer and Karpf, Sebastian and Huber, Robert},
    booktitle = {104. Jahrestagung der Deutschen Gesellschaft fuer Pathologie},
    title     = {Two-photon microscopy for sectioning-free virtual {H&E} imaging},
    year      = {2020},
    keywords  = {AG-Huber_NL},
  }

• Strauch, M: Tunable Optics: Spectral Imaging and Surface Manipulation on Liquid Lenses. Delft University of Technology, Delft, 2020
  

  @PhdThesis{Strauch2020,
    author      = {Strauch, M},
    title       = {Tunable Optics: Spectral Imaging and Surface Manipulation on Liquid Lenses},
    institution = {Delft University of Technology},
    year        = {2020},
    date        = {2020-03-30},
    type        = {phdthesis},
    subtitle    = {Spectral Imaging and Surface Manipulation on Liquid Lenses},
    language    = {English},
    isbn        = {978-94-028-1994-6},
    pagetotal   = {151},
    doi         = {10.4233/uuid:b61aa64e-cba4-44c0-8d16-93440e028611},
    
    abstract    = {This thesis focusses on two aspects of tunable optics: Fabry-P{\'e}rot interferometers with a variable distance between their mirrors and electrowetting liquid lenses. The need for a device to detect child abuse has motivated us to design and build a camera that can detect the chemical composition of the upper skin layers of a bruise using a self-made Fabry-P{\'e}rot interferometer. The research described in the first part of this thesis has shown that wide-angle spectral imaging can be achieved with compact and cost-effective cameras using Fabry-P{\'e}rot interferometers. Designs with a full field of 90° in which the Fabry-P{\'e}rot interferometer is mounted either in front of an imaging system or behind a telecentric lens system are presented and analysed. The dependency of the spectral resolution on the numerical aperture of the lens system is derived and its value as a design criterion is shown. It is shown that the telecentric camera design is preferable over the collimated design for bruise imaging with a Fabry-P{\'e}rot interferometer.The idea to use a liquid lens for spectral imaging has directed the research towards a new concept of controlling surface waves on the surface of a liquid lens. We investigate and model surface waves because they decrease the imaging quality during fast focal switching. We propose a model that describes the surface modes appearing on a liquid lens and that predicts the resonance frequencies. The effects of those surface modes on a laser beam are simulated using geometrical optics and Fresnel propagation, and the model is verified experimentally. The model of the surface oscillations is used to develop a technique to create aspheric surface shapes on commercially available electrowetting liquid lenses. The surface waves on the liquid lens are described by Bessel functions of which a linear combination can be used to create any circularly symmetrical aspheric lens shape at an instant of time. With these surface profiles, one can realise a large set of circularly symmetrical wavefronts and hence intensity distributions of beams transmitted by the lens. The necessary liquid lens actuation to achieve a desired shape is calculated via a Hankel transform and confirmed experimentally. The voltage signal can be repeated at video rate. Measurements taken with a Mach-Zehnder interferometer confirm the model of the surface waves. The capabilities and limitations of the proposed method are demonstrated using the examples of a Bessel surface, spherical aberration, an axicon, and a top hat structure.},
  keywords = {AG-Huber},
    address     = {Delft},
    publisher   = {Delft University of Technology},
    school      = {Delft University of Technology},
  }

• Strauch, Matthias and Kolb, Jan Philip and Merg, Nadine and Hundt, Jennifer and Karpf, Sebastian and Huber, Robert: Evaluation of two-photon fluorescence microscopy for sectioning-free H&E imaging of different tissues. in 32nd Congress of the ESP and XXXIII International Congress of the IAP, 2020
  

  @InProceedings{Strauch2020a,
    author    = {Strauch, Matthias and Kolb, Jan Philip and Merg, Nadine and Hundt, Jennifer and Karpf, Sebastian and Huber, Robert},
    booktitle = {32nd Congress of the ESP and XXXIII International Congress of the IAP},
    title     = {Evaluation of two-photon fluorescence microscopy for sectioning-free {H&E} imaging of different tissues},
    year      = {2020},
    keywords  = {AG-Huber_NL},
  }

2019

• Weng, Daniel and Hakert, Hubertus and Bloemker, Torben and Kolb, Jan Philip and Strauch, Matthias and Eibl, Matthias and Lamminger, Philipp and Karpf, Sebastian and Huber, Robert: Sub-Nanosecond Pulsed Fiber Laser for 532nm Two-Photon Excitation Fluorescence (TPEF) Microscopy of UV Transitions. in 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2019
  

  @InProceedings{Weng2019,
    author    = {Weng, Daniel and Hakert, Hubertus and Bloemker, Torben and Kolb, Jan Philip and Strauch, Matthias and Eibl, Matthias and Lamminger, Philipp and Karpf, Sebastian and Huber, Robert},
    booktitle = {2019 Conference on Lasers and Electro-Optics Europe {\&} European Quantum Electronics Conference ({CLEO}/Europe-{EQEC})},
    title     = {Sub-Nanosecond Pulsed Fiber Laser for 532nm Two-Photon Excitation Fluorescence ({TPEF}) Microscopy of {UV} Transitions},
    year      = {2019},
    publisher = {{IEEE}},
    abstract  = {Summary form only given. Two-photon microscopy is a powerful technique for in vivo imaging, due to its high penetration depth and axial sectioning. Usually excitation wavelengths in the near infrared are used. However, most fluorescence techniques for live cell imaging require labeling with exogenous fluorophores. It has been shown that shorter wavelengths can be used to excite the autofluorescence of endogenous proteins, e.g. tryptophan. Recently we demonstrated a fully fiber-based laser source built around a directly modulated, ytterbium amplified 1064 nm laser diode with sub-nanosecond pulses for two-photon imaging [2]. The overall system enables to capture high-speed fluorescence lifetime imaging (FLIM) with single pulse excitation. Here, we extend the spectral range of this laser source by frequency doubling it to 532nm to achieve two-photon excited fluorescence microscopy (TPM) in the ultraviolett (UV) range to harness endogenous autofluorescence. In this presentation we explore first TPM results of tryptophan to investigate signal levels and fi delity before transitioning to biological tissues. It has been shown that TPM of endogenous tryptophan can be used to visualize immune system activity in vivo. Our laser source could be a cheap, flexible and fiber-based alternative to the OPO-based Ti:Sa Lasers currently employed. The basic concept of our design is to shift the wavelength of the pulsed fiber-based master oscillator power amplifier (MOPA) by second-harmonic generation (SHG) using phase-matching in a KTP crystal. This generates a coherent output at 532nm at a maximal peak power of 500W. We achieved a maximum conversion efficiency of about 17%. After the SHG module, the 532nm light is coupled into a single-mode fiber and delivered to a home built microscope. A 40x microscope objective is used to excite the sample and epi-collect the fluorescence. The fluorescence is recorded on a UV-enhanced photomultiplier tube (PMT). For a proof of concept measurement, crystalized tryptophan was imaged. Here we show signals of pure tryptophan, with laser parameters of 1MHz repetition rate and 100ps pulse duration. We used spectral bandpass fi lters in order to detect only fluorescence signal, however, from crystalized tryptophan we observed an unexpected short lifetime. We have recently shown that we can shift our laser output from 1064nm to longer wavelengths. By shifting to 1180nm and frequency doubling to 590nm a more efficient fluorescence excitation of tryptophan can be achieved. In the future we aim at in vivo imaging with our setup.},
    doi       = {10.1109/CLEOE-EQEC.2019.8872571},
    keywords  = {AG-Huber_NL;amplifiers;biological tissues;biomedical optical imaging;cellular biophysics;fluorescence;laser applications in medicine;medical image processing;molecular biophysics;optical microscopy;proteins;two-photon processes;ultraviolet spectra;two-photon excitation fluorescence microscopy;UV transitions;excitation wavelengths;fluorescence techniques;live cell imaging;subnanosecond pulsed fiber laser;TPEF microscopy;exogenous fluorophores;autofluorescence;endogenous proteins;fiber-based laser source;laser diode;two-photon imaging;high-speed fluorescence lifetime imaging;FLIM;single pulse excitation;tryptophan;biological tissues;immune system activity;OPO-based Ti:Sa lasers;pulsed fiber-based master oscillator power amplifier;MOPA;second-harmonic generation;SHG;phase-matching;KTP crystal;UV-enhanced photomultiplier tube;laser parameters;spectral bandpass filters;fluorescence excitation;Fluorescence;Laser excitation;Fiber lasers;Microscopy;Laser transitions;In vivo},
  }

• Strauch, Matthias and Kolb, Jan Philip and Weng, Daniel and Wacker, Melanie and Draxinger, Wolfgang and Karpf, Sebastian and Huber, Robert: Sectioning-Free Virtual H&E Imaging of Tissue Samples with Two-Photon Microscopy. in 31st Congress of the ESP, 2019
  

  @InProceedings{Strauch2019,
    author    = {Strauch, Matthias and Kolb, Jan Philip and Weng, Daniel and Wacker, Melanie and Draxinger, Wolfgang and Karpf, Sebastian and Huber, Robert},
    booktitle = {31st Congress of the ESP},
    title     = {Sectioning-Free Virtual H&E Imaging of Tissue Samples with Two-Photon Microscopy},
    year      = {2019},
    keywords  = {AG-Huber_NL},
  }

• Kolb, Jan Philip and Strauch, Matthias and Weng, Daniel and Hakert, Hubertus and Draxinger, Wolfgang and Merg, Nadine and Brinkmann, Ralf and Birngruber, Reginald and Hundt, Jennifer and Karpf, Sebastian and Huber, Robert: Fiber-Based Sub-Nanosecond Two-Photon Microscopy for Virtual H&E Histology. in European Conference on Biomedical Optics (ECBO), 2019
  

  @InProceedings{Kolb2019,
    author    = {Kolb, Jan Philip and Strauch, Matthias and Weng, Daniel and Hakert, Hubertus and Draxinger, Wolfgang and Merg, Nadine and Brinkmann, Ralf and Birngruber, Reginald and Hundt, Jennifer and Karpf, Sebastian and Huber, Robert},
    booktitle = {European Conference on Biomedical Optics (ECBO)},
    title     = {Fiber-Based Sub-Nanosecond Two-Photon Microscopy for Virtual H&E Histology},
    year      = {2019},
    keywords  = {AG-Huber_NL},
  }

2018

• Strauch, M;Somers, P A. A. M.;Bociort, F and Urbach, H. P: Creation of aspheric interfaces on an electrowetting liquid lens using surface oscillations. AIP Advances 8(11), 2018
  

  @article{Strauch2018,
     author = {Strauch, M;Somers, P A. A. M.;Bociort, F and Urbach, H. P},
     title = {Creation of aspheric interfaces on an electrowetting liquid lens using surface oscillations},
     journal = {AIP Advances} {8(11)},
     
     ISSN = {2158-3226},
     DOI = {10.1063/1.5063994},
     year = {2018},
     type = {Journal Article}
  }
  

2017

• Strauch, M;Konijnenberg, S;Shao, Y and Urbach, H P: Wavefront shaping with an electrowetting liquid lens using surface harmonics (Conference Presentation). no. 10073, SPIE, 2017
  

  @book{Strauch2017-3,
     author = {Strauch, M;Konijnenberg, S;Shao, Y and Urbach, H P},
     title = {Wavefront shaping with an electrowetting liquid lens using surface harmonics (Conference Presentation)},
     publisher = {SPIE},
     volume = {10073},
     series = {SPIE BiOS},
     url = {https://doi.org/10.1117/12.2252854},
     year = { 2017 },
     type = {Book}
  }
  

• Strauch, M;Shao, Y;Bociort, F and Urbach, H. P: Study of surface modes on a vibrating electrowetting liquid lens. Applied physics Letters111 (17), pp. 171106, 2017
  

  @article{Strauch2017,
     author = {Strauch, M;Shao, Y;Bociort, F and Urbach, H. P},
     title = {Study of surface modes on a vibrating electrowetting liquid lens},
  journal = {Applied physics Letters}{111 (17)},
  
    
     pages = {171106},
     DOI = {10.1063/1.4999562},
  keywords = {lenses,surface waves(fluid),vibrations,wetting},
  abstract = {The increased usage of liquid lenses motivates us to investigate surface waves on the liquid's surface. During fast focal switching, the surface waves decrease the imaging quality. We propose a model that describes the surface modes appearing on a liquid lens and predicts the resonance frequencies. The effects of those surface modes on a laser beam are simulated using Fresnel propagation, and the model is verified experimentally.
  We acknowledge the use of an educational licence of CODE V and LightTools. This work was funded through the Spectr@phone project (IPD 12017) of the IOP Photonic Devices program of RVO.},
  
     url = {https://aip.scitation.org/doi/abs/10.1063/1.4999562},
     year = {2017},
     type = {Journal Article}
  

2016

• Strauch, M and Urbach, H P: Surface harmonics on liquid lenses. in 2016 IEEE Photonics Conference (IPC), pp. 248-249, Oct, 2016
  

  @INPROCEEDINGS{Strauch2017,
  author={Strauch, M and Urbach, H P},
  booktitle={2016 IEEE Photonics Conference (IPC)},
  title={Surface harmonics on liquid lenses},
  year={2016},
  
  pages={248-249},
  keywords={lenses;optical harmonic generation;optical tuning;oscillations;surface harmonics;liquid lenses;tunability;nonspherical surfaces;surface oscillations;Lenses;Liquids;Surface waves;Optical surface waves;Harmonic analysis;Shape;Optical switches},
  doi={10.1109/IPCon.2016.7831063},
  ISSN={},
  month={Oct},}

2015

• Strauch, M;Livshits, I L;Bociort, F and Urbach, H P: Wide-angle spectral imaging using a Fabry-Pérot interferometer. no. 10, 2015
  

  @book{Strauch2015,
     author = {Strauch, M;Livshits, I L;Bociort, F and Urbach, H P},
     title = {Wide-angle spectral imaging using a Fabry-Pérot interferometer},
     volume = {10},
     series = {2015},
     ISBN = {1990-2573|escape}},
     url = {https://www.jeos.org/index.php/jeos_rp/article/view/15037%J Journal of the European Optical Society - Rapid publications},
     year = {2015},
     type = {Book}
  }