@article{https://doi.org/10.1002/smll.202401472,
author = {Karpf, Sebastian and Glöckner Burmeister, Nina and Dubreil, Laurence and Ghosh, Shayantani and Hollandi, Reka and Pichon, Julien and Leroux, Isabelle and Henkel, Alessandra and Lutz, Valerie and Jurkevičius, Jonas and Latshaw, Alexandra and Kilin, Vasyl and Kutscher, Tonio and Wiggert, Moritz and Saavedra-Villanueva, Oscar and Vogel, Alfred and Huber, Robert A. and Horvath, Peter and Rouger, Karl and Bonacina, Luigi},
title = {Harmonic Imaging of Stem Cells in Whole Blood at GHz Pixel Rate},
journal = {Small},
volume = {n/a},
number = {n/a},
pages = {2401472},
keywords = {fiber lasers, harmonic imaging, multiphoton microscopy, nanoparticles, regenerative medicine, SHG, SLIDE},
doi = {https://doi.org/10.1002/smll.202401472},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/smll.202401472},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/smll.202401472},
abstract = {Abstract The pre-clinical validation of cell therapies requires monitoring the biodistribution of transplanted cells in tissues of host organisms. Real-time detection of these cells in the circulatory system and identification of their aggregation state is a crucial piece of information, but necessitates deep penetration and fast imaging with high selectivity, subcellular resolution, and high throughput. In this study, multiphoton-based in-flow detection of human stem cells in whole, unfiltered blood is demonstrated in a microfluidic channel. The approach relies on a multiphoton microscope with diffractive scanning in the direction perpendicular to the flow via a rapidly wavelength-swept laser. Stem cells are labeled with metal oxide harmonic nanoparticles. Thanks to their strong and quasi-instantaneous second harmonic generation (SHG), an imaging rate in excess of 10 000 frames per second is achieved with pixel dwell times of 1 ns, a duration shorter than typical fluorescence lifetimes yet compatible with SHG. Through automated cell identification and segmentation, morphological features of each individual detected event are extracted and cell aggregates are distinguished from isolated cells. This combination of high-speed multiphoton microscopy and high-sensitivity SHG nanoparticle labeling in turbid media promises the detection of rare cells in the bloodstream for assessing novel cell-based therapies.}
}

@INPROCEEDINGS{10232141,
  author={Lamminger, Philipp and Hakert, Hubertus and Lotz, Simon and Kolb, Jan Philip and Kutscher, Tonio and Karpf, Sebastian and Huber, Robert},
  booktitle={2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)}, 
  title={Four-Wave Mixing Fast Wavelength Sweeping FDML Laser with kW Peak Power at 900 nm and 1300 nm}, 
  year={2023},
  volume={},
  number={},
  pages={1-1},
  doi={10.1109/CLEO/Europe-EQEC57999.2023.10232141}}

@article{Lamminger:23,
author = {Philipp Lamminger and Hubertus Hakert and Simon Lotz and Jan Philip Kolb and Tonio Kutscher and Sebastian Karpf and Robert Huber},
journal = {Opt. Lett.},
keywords = {Green fluorescent protein; Laser beam combining; Laser crystals; Laser imaging; Optical amplifiers; Photonic crystal lasers},
number = {14},
pages = {3713--3716},
publisher = {Optica Publishing Group},
title = {Four-wave mixing seeded by a rapid wavelength-sweeping FDML laser for nonlinear imaging at 900 nm and 1300 nm},
volume = {48},
month = {Jul},
year = {2023},
url = {https://opg.optica.org/ol/abstract.cfm?URI=ol-48-14-3713},
doi = {10.1364/OL.488181},
abstract = {Four-wave mixing (FWM) enables the generation and amplification of light in spectral regions where suitable fiber gain media are unavailable. The 1300 nm and 900 nm regions are of especially high interest for time-encoded (TICO) stimulated Raman scattering microscopy and spectro-temporal laser imaging by diffracted excitation (SLIDE) two-photon microscopy. We present a new, to the best of our knowledge, FWM setup where we shift the power of a home-built fully fiber-based master oscillator power amplifier (MOPA) at 1064 nm to the 1300-nm region of a rapidly wavelength-sweeping Fourier domain mode-locked (FDML) laser in a photonic crystal fiber (PCF) creating pulses in the 900-nm region. The resulting 900-nm light can be wavelength swept over 54 nm and has up to 2.5 kW (0.2 {\textmu}J) peak power and a narrow instantaneous spectral linewidth of 70 pm. The arbitrary pulse patterns of the MOPA and the fast wavelength tuning of the FDML laser (419 kHz) allow it to rapidly tune the FWM light enabling new and faster TICO-Raman microscopy, SLIDE imaging, and other applications.},
}

@inproceedings{10.1117/12.2649663,
author = {Philipp Lamminger and Hubertus Hakert and Simon Lotz and Jan Philip Kolb and Tonio Kutscher and Sebastian Karpf and Robert Huber},
title = {{900 nm swept source FDML laser with kW peak power}},
volume = {12400},
booktitle = {Fiber Lasers XX: Technology and Systems},
editor = {V.  R. Supradeepa},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {124001I},
abstract = {A wavelength agile 900 nm 2.5 kW peak power fiber laser is created by four-wave mixing (FWM) in a photonic crystal fiber (PCF), while amplifying a 1300 nm Fourier-domain mode-locked (FDML) laser. The FWM process is pumped by a home-built 1064 nm master oscillator power amplifier (MOPA) laser and seeded by a home-built 1300 nm FDML laser, generating high power pulses at wavelengths, where amplification by active fiber media is difficult. The 900 nm pulses have a spectral linewidth of 70 pm, are tunable over 54 nm and have electronic pulse-to-pulse tuning capability. These pulses can be used for nonlinear imaging like two-photon or coherent anti-Stokes Raman microscopy (CARS) microscopy including spectro-temporal laser imaging by diffracted excitation (SLIDE) and time-encoded (Tico) stimulated Raman microscopy.},
keywords = {Fourier domain mode locking,  FDML, Raman, two photon microscopy, SLIDE, 900 nm, fiber laser, photonic crystal fiber, swept source},
year = {2023},
doi = {10.1117/12.2649663},
URL = {https://doi.org/10.1117/12.2649663}
}

@article{STRAUCH2023e210,
title = {Accelerating intraoperative tumor histology with sectioning-free multiphoton microscopy},
journal = {European Journal of Surgical Oncology},
volume = {49},
number = {2},
pages = {e210},
year = {2023},
issn = {0748-7983},
doi = {https://doi.org/10.1016/j.ejso.2022.11.575},
url = {https://www.sciencedirect.com/science/article/pii/S0748798322013245},
author = {Matthias Strauch and Jan Philip Kolb and Christian Rose and Nadine Merg and Jennifer Hundt and Christiane Kümpers and Sven Perner and Sebastian Karpf and Robert Huber}
}

@article{Meyer:23,
author = {Stefan Meyer and Tonio F. Kutscher and Philipp Lamminger and Florian Sommer and Sebastian Karpf},
journal = {Opt. Continuum},
keywords = {Femtosecond pulses; Fluorescence lifetime imaging; Phase modulation; Picosecond pulses; Single mode lasers; Ultrashort pulses},
number = {11},
pages = {2298--2307},
publisher = {Optica Publishing Group},
title = {Leveraging the periodic interference condition in electro-optic modulators for picosecond pulse generation},
volume = {2},
month = {Nov},
year = {2023},
url = {https://opg.optica.org/optcon/abstract.cfm?URI=optcon-2-11-2298},
doi = {10.1364/OPTCON.500969},
abstract = {Ultra-short optical pulses in the femtosecond and picosecond regime are typically generated using mode-locked lasers. However, in mode-locking, the pulse repetition rate is fundamentally linked to the cavity length of the laser, making it difficult to synchronize these laser pulses to other light sources. Here, we apply a pulse-on-demand approach to picosecond pulse generation with an electro-optic intensity modulator (EOM). The high, 40 GHz bandwidth of the EOM enables low picosecond pulses, however it shifts the problem of pulse generation to the electronic pulses, requiring high bandwidth electronics. In this study, we present an electro-optic operation, leveraging the periodic interference condition of intensity EOMs by operating it with rising edges at twice its V$\pi$ voltage. Utilizing this method, pulse durations as short as 10.9 ps were achieved by employing a 35 ps edge from an arbitrary waveform generator. The pulses were measured directly on a high-speed oscilloscope as well as indirectly through the spectral broadening of the generated optical pulses. We employ this approach to show arbitrary pulse length generation by applying step functions with only one V$\pi$ voltage, thus permitting direct pulse-on-demand generation of pulses with arbitrary pulse length, shape and repetition rate for applications in spectroscopy, sensing and nonlinear imaging.},
}

@article{Kutscher:23,
author = {Tonio F. Kutscher and Philipp Lamminger and Anton Gruber and Christina Leonhardt and Annika Hunold and Robert A. Huber and Sebastian Karpf},
journal = {Opt. Lett.},
keywords = {Erbium-doped fiber amplifiers; Laser imaging; Laser sources; Lidar; Multiphoton microscopy; Picosecond pulses},
number = {23},
pages = {6096--6099},
publisher = {Optica Publishing Group},
title = {Pulsed swept-source FDML-MOPA laser with kilowatt picosecond pulses around 1550 nm},
volume = {48},
month = {Dec},
year = {2023},
url = {https://opg.optica.org/ol/abstract.cfm?URI=ol-48-23-6096},
doi = {10.1364/OL.500943},
abstract = {Swept-source lasers are versatile light sources for spectroscopy, imaging, and microscopy. Swept-source-powered multiphoton microscopy can achieve high-speed, inertia-free point scanning with MHz line-scan rates. The recently introduced spectro-temporal laser imaging by diffractive excitation (SLIDE) technique employs swept-source lasers to achieve kilohertz imaging rates by using a swept-source laser in combination with a diffraction grating for point scanning. Multiphoton microscopy at a longer wavelength, especially in the shortwave infrared (SWIR) region, can have advantages in deep tissue penetration or applications in light detection and ranging (LiDAR). Here we present a swept-source laser around 1550 nm providing high-speed wavelength agility and high peak power pulses for nonlinear excitation. The swept-source laser is a Fourier-domain mode-locked (FDML) laser operating at 326 kHz sweep rate. For high peak powers, the continuous wave (cw) output is pulse modulated to short picosecond pulses and amplified using erbium-doped fiber amplifiers (EDFAs) to peak powers of several kilowatts. This FDML-master oscillator power amplifier (FDML-MOPA) setup uses reliable, low-cost fiber components. As proof-of-principle measurement, we show third-harmonic generation (THG) using harmonic nanoparticles at the 10 MHz pulse excitation rate. This new, to the best of our knowledge, laser source provides unique performance parameters for applications in nonlinear microscopy, spectroscopy, and ranging.},
}

@inproceedings{10.1117/12.2670881,
author = {Dirk Theisen-Kunde and Florian Sommer and Veit Danicke and Lion Sch{\"u}tzeck and Stefan Meyer and Christopher Kren and Maximilian Rixius and Sebastian Karpf},
title = {{Small footprint SLIDE demonstrator for 40Hz volume rate multiphoton microscopy}},
volume = {12630},
booktitle = {Advances in Microscopic Imaging IV},
editor = {Emmanuel Beaurepaire and Adela Ben-Yakar and YongKeun Park},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {126300Q},
keywords = {multiphoton microscopy, flow cytometry, Fourier Domain Mode Locked Laser, SLIDE, kHz- Imaging},
year = {2023},
doi = {10.1117/12.2670881},
URL = {https://doi.org/10.1117/12.2670881}
}

@article{Grill2022,
  doi = {10.1038/s42005-022-00960-w},
  year = {2022},
  publisher = {Springer Science and Business Media {LLC}},
  volume = {{5}},
  number = {{1}},
  author = {C. Grill, T. Bl\"{o}mker, M. Schmidt, D. Kastner, T. Pfeiffer, J.P. Kolb, W. Draxinger, S. Karpf, C. Jirauschek and R. Huber},
  title = {Towards phase-stabilized Fourier domain mode-locked frequency combs},
  journal = {{Communications Physics}},
keywords={AG-Huber_FDML, FDML, Fourier domain mode locking, phase, frequency comb, coherence, beating}
}

@inproceedings{10.1117/12.2608773,
author = {M. Klufts and S. Lotz and M. Bashir and S. Karpf and R. Huber},
title = {{Ultra-high-accuracy chromatic dispersion measurement in optical fibers}},
volume = {11997},
booktitle = {Optical Components and Materials XIX},
editor = {Shibin Jiang and Michel J. F. Digonnet},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {119970L},
abstract = {The chromatic dispersion in optical fibers is a key property for applications where a broadband light source is used and the timing of each individual wavelength is crucial. Counteracting the timing offset introduced by the fiber is a challenge in many applications especially in mode locked lasers. The dispersion parameters need to be measured with high precision. The length of the fiber, the temperature, and the used wavelength will highly impact the amount of dispersion and the accuracy of the measurement. We developed an ultra-high-accuracy dispersion measurement setup at 1080 ± 50 nm considering all the parameters that may influence the measurement. It is based on a home-built wavelength tunable laser where the output is modulated by an electro-optical modulator connected to a 24 GSamples/s arbitrary waveform generator to a complex pattern consisting of pulses and a 4 GHz sine wave. After passing through the fiber the signal is measured with an 80 GSamples/s real time oscilloscope. The fiber’s temperature is controlled to allow for reproducible measurements over several days and we achieve timing measurement accuracies down to ~200 fs. We also present the performance of the setup at ~850 nm. We will discuss and quantify all effects which can negatively impact the system accuracy and we will report on more cost-effective options using lower performance equipment.},
keywords = {Dispersion measurement, Chromatic dispersion, fiber dispersion measurement, optical component characterization, tunable laser, FDML},
year = {2022},
doi = {10.1117/12.2608773},
URL = {https://doi.org/10.1117/12.2608773}
}

@article{Hakert2021,
   author = {H. Hakert, M. Eibl, M. Tillich, R.Pries, G. Hüttmann, R. Brinkmann, B. Wollenberg, K-L. Bruchhage, S. Karpf and R. Huber},
   title = {Time-encoded stimulated Raman scattering microscopy of tumorous human pharynx tissue in the fingerprint region from 1500–1800  cm-1},
   journal = {Optics Letters},
   volume = {46(14)},
   number = {14},
   pages = {3456-3459},
keywords = {AG-Huber_NL, Clinical applications, Master oscillator power amplifiers, Optical coherence tomography, Raman scattering, Stimulated Raman scattering, Stimulated scattering},
   DOI = {https://doi.org/10.1364/OL.424726},
   year = {2021},
   type = {Journal Article}
}

@inproceedings{Grill2021,
author = {C. Grill, T. Blömker, M. Schmidt, D. Kastner, T. Pfeiffer, J.P. Kolb, W. Draxinger, S. Karpf, C. Jirauschek and R. Huber},
title = {{A detailed analysis of the coherence and field properties of an FDML laser by time resolved beat signal measurements}},
volume = {11665},
booktitle = {Fiber Lasers XVIII: Technology and Systems},
editor = {Michalis N. Zervas},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {242 -- 247},
keywords = {AG-Huber_FDML, Fourier domain mode locking, FDML laser, laser beating , tunable laser, optical coherence tomography, OCT},
year = {2021},
URL = {hhttps://doi.org/10.1117/12.2578293}
}

@Conference{Lamminger2021,
  author    = {P. Lamminger, M. Loop, J. Klee, D. Weng, J.P. Kolb, M. Strauch, S. Karpf and R. Huber},
  booktitle = {Multimodal Biomedical Imaging XVI},
  title     = {Combination of two-photon microscopy and optical coherence tomography with fully fiber-based lasers for future endoscopic setups},
  year      = {2021},
  publisher = {SPIE},
  doi       = {10.1117/12.2578679},
  keywords  = {AG-Huber_NL, AG-Huber_OCT},
}

@inproceedings{RN5318,
   author = {Strauch, M;Kolb, J P;Draxinger, W;Popp, A-K;Wacker, M;Merg, N;Hundt, J;Karpf, S and Huber, R},
   title = {Sectioning-free virtual H&E histology with fiber-based two-photon microscopy},
   booktitle = {SPIE BiOS},
   publisher = {SPIE},
   volume = {11648},
Year = {2021},
   DOI = {https://doi.org/10.1117/12.2578334},
   url = {https://doi.org/10.1117/12.2578334},
   type = {Conference Proceedings}
}

@Conference{Strauch2021b,
  author    = {M. Strauch, J.P. Kolb, C. Rose, N. Merg, J. Hundt, C. Kümpers, S. Perner, S. Karpf and R. Hubert},
  booktitle = {Virtuelle Pathologietage},
  title     = {Comparison of Sectioning-free Multiphoton Histology to H&E FFPE imaging},
  year      = {2021},
  keywords  = {AG-Huber_NL},
}

@Conference{Strauch2021,
  author    = {M. Strauch, J.P. Kolb, C. Rose, N. Merg, J. Hundt, C. Kümpers, S. Perner, S. Karpf and R. Huber},
  booktitle = {33rd Congress of the ESP},
  title     = {Quick sectioning-free H&E imaging of bulk tissue using multiphoton microscopy},
  year      = {2021},
  keywords  = {AG-Huber_NL},
}

@article{Pfeiffer:20,
author = {T. Pfeiffer, M. G\"{o}b, W. Draxinger, S. Karpf, J.P. Kolb and R. Huber},
journal = {Biomed. Opt. Express},
keywords = {AG-Huber_OCT; High speed imaging; Image quality; Optical coherence tomography; Swept lasers; Swept sources; Systems design},
number = {11},
pages = {6799--6811},
publisher = {OSA},
title = {Flexible A-scan rate MHz-OCT: efficient computational downscaling by coherent averaging},
volume = {11},
month = {Nov},
year = {2020},
doi = {10.1364/BOE.402477},
abstract = {In order to realize adjustable A-scan rates of fast optical coherence tomography (OCT) systems, we investigate averaging of OCT image data acquired with a MHz-OCT system based on a Fourier Domain Mode Locked (FDML) laser. Increased system sensitivity and image quality can be achieved with the same system at the cost of lower imaging speed. Effectively, the A-scan rate can be reduced in software by a freely selectable factor. We demonstrate a detailed technical layout of the strategies necessary to achieve efficient coherent averaging. Since there are many new challenges specific to coherent averaging in swept source MHz-OCT, we analyze them point by point and describe the appropriate solutions. We prove that coherent averaging is possible at MHz OCT-speed without special interferometer designs or digital phase stabilization. We find, that in our system up to \&\#x223C;100x coherent averaging is possible while achieving a sensitivity increase close to the ideal values. This corresponds to a speed reduction from 3.3 MHz to 33 kHz and a sensitivity gain of 20 dB. We show an imaging comparison between coherent and magnitude averaging of a human finger knuckle joint in vivo with 121\&\#x00A0;dB sensitivity for the coherent case. Further, the benefits of computational downscaling in low sensitivity MHz-OCT systems are analyzed.},
}

@InProceedings{Strauch2020,
  author    = {M. Strauch, J.P. Kolb, D. Weng, M. Wacker, W. Draxinger, N. Merg, J. Hundt, S. Karpf and R. Huber},
  booktitle = {104. Jahrestagung der Deutschen Gesellschaft fuer Pathologie},
  title     = {Two-photon microscopy for sectioning-free virtual {H&E} imaging},
URL = {https://www.pathologie-dgp.de/media/Dgp/user_upload/Verhandlungsband_2020_final__kompr._.pdf},
  year      = {2020},
  keywords  = {AG-Huber_NL},
}

@InProceedings{Strauch2020a,
  author    = {M. Strauch, J.P. Kolb, N. Merg, J. Hundt, S. Karpf and R. Huber},
  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},
}

@INPROCEEDINGS{8872571,
  author={Weng, Daniel and Hakert, Hubertus and Blömker, 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},
  volume={},
  number={},
  pages={1-1},
  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.},
  keywords={},
  doi={10.1109/CLEOE-EQEC.2019.8872571},
  ISSN={},
  month={June}}

@inproceedings{10.1117/12.2507866,
author = {Jan Philip Kolb and Daniel Weng and Hubertus Hakert and Matthias Eibl and Wolfgang Draxinger and Tobias Meyer and Thomas Gottschall and Ralf  Brinkmann and Reginald Birngruber and J{\"u}rgen Popp and Jens Limpert and Sebastian Nino Karpf and Robert Huber},
title = {{Virtual HE histology by fiber-based picosecond two-photon microscopy}},
volume = {10882},
booktitle = {Multiphoton Microscopy in the Biomedical Sciences XIX},
editor = {Ammasi Periasamy and Peter T. C. So and Karsten K{\"o}nig},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {108822F},
abstract = {Two-Photon Microscopy (TPM) can provide three-dimensional morphological and functional contrast in vivo. Through proper staining, TPM can be utilized to create virtual, HE equivalent images and thus can improve throughput in histology-based applications. We previously reported on a new light source for TPM that employs a compact and robust fiber-amplified, directly modulated laser. This laser is pulse-to-pulse wavelength switchable between 1064 nm, 1122 nm, and 1186 nm with an adjustable pulse duration from 50ps to 5ns and arbitrary repetition rates up to 1MHz at kW-peak powers. Despite the longer pulse duration, it can achieve similar average signal levels compared to fs-setups by lowering the repetition rate to achieve similar cw and peak power levels. The longer pulses lead to a larger number of photons per pulse, which yields single shot fluorescence lifetime measurements (FLIM) by applying a fast 4 GSamples/s digitizer. In the previous setup, the wavelengths were limited to 1064 nm and longer. Here, we use four wave mixing in a non-linear photonic crystal fiber to expand the wavelength range down to 940 nm. This wavelength is highly suitable for imaging green fluorescent proteins in neurosciences and stains such as acridine orange (AO), eosin yellow (EY) and sulforhodamine 101 (SR101) used for histology applications. In a more compact setup, we also show virtual HE histological imaging using a direct 1030 nm fiber MOPA.},
keywords = {Multiphoton Microscopy, Four Wave Mixing, FWM, Histology, Laser, Non Linear Microscopy, Two Photon Microscopy, JenLab Young Investigator Award},
year = {2019},
doi = {10.1117/12.2507866},
URL = {https://doi.org/10.1117/12.2507866}
}

@article{karpf2019-2,
   author = {Karpf, S and Jalali, B},
   title = {Frequency-doubled FDML-MOPA laser in the visible},
   journal = {Opt Lett 44(24)},
   keywords = {},
   pages = {5913-5916},
   DOI = {10.1364/OL.44.005913},
   
   year = {2019},
   type = {Journal Article}
}

@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},
}

@article{Karpf2019,
   author = {Karpf, S and Jalali, B },
   title = {Fourier-domain mode-locked laser combined with a master-oscillator power amplifier architecture},
   journal = {J Opt Lett},
   URL = {https://doi.org/10.1364/OL.44.001952},
   pages = {1952-1955},
   ISSN = {1539-4794},
   year = {2019},
 keywords = {},
   type = {Journal Article}
}

@article{Eibl2018,
  doi = {10.1364/boe.9.006273},
  url = {https://doi.org/10.1364/boe.9.006273},
  year = {2018},
  month = nov,
  publisher = {The Optical Society},
  volume = {9},
  number = {12},
  pages = {6273},
  author = {Matthias Eibl and Daniel Weng and Hubertus Hakert and Jan Philip Kolb and Tom Pfeiffer and Jennifer E. Hundt and Robert Huber and Sebastian Karpf},
  title = {Wavelength agile multi-photon microscopy with a fiber amplified diode laser},
  journal = {Biomedical Optics Express}
}