Wolfgang Draxinger

@article{Draxinger:24,
author = {Wolfgang Draxinger and Nicolas Detrez and Paul Strenge and Veit Danicke and Dirk Theisen-Kunde and Lion Sch\"{u}tzeck and Sonja Spahr-Hess and Patrick Kuppler and Jessica Kren and Wolfgang Wieser and Matteo Mario Bonsanto and Ralf Brinkmann and Robert Huber},
journal = {Biomed. Opt. Express},
keywords = {Brain imaging; Imaging systems; In vivo imaging; Magnetic resonance imaging; Speckle imaging; Spectral domain optical coherence tomography},
number = {10},
pages = {5960--5979},
publisher = {Optica Publishing Group},
title = {Microscope integrated MHz optical coherence tomography system for neurosurgery: development and clinical in-vivo imaging},
volume = {15},
month = {Oct},
year = {2024},
url = {https://opg.optica.org/boe/abstract.cfm?URI=boe-15-10-5960},
doi = {10.1364/BOE.530976},
abstract = {Neurosurgical interventions on the brain are impeded by the requirement to keep damages to healthy tissue at a minimum. A new contrast channel enhancing the visual separation of malign tissue should be created. A commercially available surgical microscope was modified with adaptation optics adapting the MHz speed optical coherence tomography (OCT) imaging system developed in our group. This required the design of a scanner optics and beam delivery system overcoming constraints posed by the mechanical and optical parameters of the microscope. High quality volumetric OCT C-scans with dense sample spacing can be acquired in-vivo as part of surgical procedures within seconds and are immediately available for post-processing.},
}

@article{RN5474,
   author = {Schulte, Berenice;Göb, Madita;Singh, Awanish Pratap;Lotz, Simon;Draxinger, Wolfgang;Heimke, Marvin;pieper, Mario;Heinze, Tillmann;Wedel, Thilo;Rahlves, Maik;Huber, Robert and Ellrichmann, Mark},
   title = {High-resolution rectoscopy using MHz optical coherence tomography: a step towards real time 3D endoscopy},
   journal = {Scientific Reports},
   volume = {14},
   number = {1},
   pages = {4672},
   ISSN = {2045-2322},
   DOI = {10.1038/s41598-024-55338-5},
   url = {https://doi.org/10.1038/s41598-024-55338-5},
   year = {2024},
   type = {Journal Article}
}

@Article{Schulte2024,
author={Schulte, B.; Burhan, S.; Singh, A. P.; Draxinger, W.; Lotz, S.; Heimke, M.; Heinze, T.; Wedel, T.; Rahlves, M.; Huber, R.; Ellrichmann, M.},
title={Hochaufl{\"o}sende Rektoskopie mittels dual-mode MHz optischer Koh{\"a}renztomographie -- ein Schritt zur real time 3D Endoskopie},
journal={Z Gastroenterol},
year={2024},
month={Sep},
day={26},
publisher={Georg Thieme Verlag KG},
volume={62},
number={09},
pages={KV 355},
issn={0044-2771},
doi={10.1055/s-0044-1790019},
url={http://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0044-1790019},
url={https://doi.org/10.1055/s-0044-1790019},
language={DE}
}

@article { Microscopeintegratedopticalcoherencetomographyforinvivohumanbraintumordetectionwithartificialintelligence,
      author = "Patrick Kuppler and Paul Strenge and Birgit Lange and Sonja Spahr-Hess and Wolfgang Draxinger and Christian Hagel and Dirk Theisen-Kunde and Ralf Brinkmann and Robert Huber and Volker Tronnier and Matteo Mario Bonsanto",
      title = "Microscope-integrated optical coherence tomography for in vivo human brain tumor detection with artificial intelligence",
      journal = "Journal of Neurosurgery",
      year = "2024",
      publisher = "American Association of Neurological Surgeons",
      doi = "10.3171/2024.1.JNS231511",
      pages=      "1 - 9",
      url = "https://thejns.org/view/journals/j-neurosurg/aop/article-10.3171-2024.1.JNS231511/article-10.3171-2024.1.JNS231511.xml"
}

@inproceedings{10.1117/12.2670907,
author = {Paul Strenge and Birgit Lange and Wolfgang Draxinger and Christian Hagel and Christin Grill and Veit Danicke and Dirk Theisen-Kunde and Sonja Spahr-Hess and Matteo M. Bonsanto and Robert Huber and Heinz Handels and Ralf Brinkmann},
title = {{Demarcation of brain and tumor tissue with optical coherence tomography using prior neural networks}},
volume = {12632},
booktitle = {Optical Coherence Imaging Techniques and Imaging in Scattering Media V},
editor = {Benjamin J. Vakoc and Maciej Wojtkowski and Yoshiaki Yasuno},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {126321P},
keywords = {Brain Tumor, OCT, Optical Coherence Tomography, Prior Network, Glioblastoma Multiforme, Neural Network, Classification},
year = {2023},
doi = {10.1117/12.2670907},
URL = {https://doi.org/10.1117/12.2670907}
}

@inproceedings{10.1117/12.2670953,
author = {Wolfgang Draxinger and Dirk Theisen-Kunde and Lion Schuetz and Nicolas Detrez and Paul Strenge and Maximilian Rixius and Veit Danicke and Wolfgang Wieser and Jessica Kren and Patrick Kuppler and Sonja Spar-Hess and Matteo Mario Bonsanto M.D. and Ralf Brinkmann and Robert Huber},
title = {{Microscope integrated realtime high density 4D MHz-OCT in neurosurgery: a depth and tissue resolving visual contrast channel and the challenge of fused presentation}},
volume = {12627},
booktitle = {Translational Biophotonics: Diagnostics and Therapeutics III},
editor = {Zhiwei Huang and Lothar D. Lilge},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {126270W},
abstract = {Microscope integrated realtime 4D MHz-OCT operating at high scanning densities are capable of capturing additional visual contrast resolving depth and tissue. Even within a plain C-scan en-face projection structures are recognizable, that are not visible in a white light camera image. With advanced post processing methods, such as absorbtion coefficient mapping, and morphological classifiers more information is extraced. Presentation to the user in an intuitive way poses practical challenges that go beyond the implementation of a mere overlay display. We present our microscope integrated high speed 4D OCT imaging system, its clinical study use for in-vivo brain tissue imaging, and user feedback on the presentation methods we developed.},
keywords = {optical coherence tomography, neurosurgery, tissue contrast, image fusion, surgical guidance, theranostics},
year = {2023},
doi = {10.1117/12.2670953},
URL = {https://doi.org/10.1117/12.2670953}
}

@INPROCEEDINGS{10231419,
  author={Lotz, Simon and Göb, Madita and Draxinger, Wolfgang and Dick, Anneli and Huber, Robert},
  booktitle={2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)}, 
  title={13.4 MHz FDML Laser for Intra-Surgical Optical Coherence Tomography}, 
  year={2023},
  volume={},
  number={},
  pages={1-1},
  doi={10.1109/CLEO/Europe-EQEC57999.2023.10231419}}

Kuppler P, Strenge P, Lange B, Spahr-Hess S, Draxinger W, Hagel C, Theisen-Kunde D, Brinkmann R, Huber R, Tronnier V and Bonsanto MM (2023) The neurosurgical benefit of contactless in vivo optical coherence tomography regarding residual tumor detection: A clinical study. Front. Oncol. 13:1151149. doi: 10.3389/fonc.2023.1151149

@inproceedings{10.1117/12.2648505,
author = {Wolfgang Draxinger and Dirk Theisen-Kunde and Lion Sch{\"u}tzeck and Nicolas Detrez and Paul Strenge and Veit Danicke and Jessica Kren and Patrick Kuppler and Sonja Spahr-Hess and Matteo Mario Bonsanto and Ralf Brinkmann and Robert Huber},
title = {{High speed 4D in-vivo OCT imaging of the human brain: creating high density datasets for machine learning toward identification of malign tissue in real time}},
volume = {12390},
booktitle = {High-Speed Biomedical Imaging and Spectroscopy VIII},
editor = {Kevin K. Tsia and Keisuke Goda},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {123900D},
abstract = {Neuro-surgery is challenged by the difficulties of determining brain tumor boundaries during excisions. Optical coherence tomography is investigated as an imaging modality for providing a viable contrast channel. Our MHz-OCT technology enables rapid volumetric imaging, suitable for surgical workflows. We present a surgical microscope integrated MHz-OCT imaging system, which is used for the collection of in-vivo images of human brains, with the purpose of being used in machine learning systems that shall be trained to identify and classify tumorous tissue.},
keywords = {optical coherence tomography, brain tumor, neurosurgery, machine learning, contrast augmentation, histology dataset, clinical study, in-vivo imaging},
year = {2023},
doi = {10.1117/12.2648505},
URL = {https://doi.org/10.1117/12.2648505}
}

@inproceedings{10.1117/12.2649963,
author = {Paul Strenge and Birgit Lange and Wolfgang Draxinger and Christian Hagel and Christin Grill and Veit Danicke and Dirk Theisen-Kunde and Sonja Spahr-Hess and Matteo M. Bonsanto and Robert Huber and Heinz Handels and Ralf Brinkmann},
title = {{Dual wavelength analysis and classification of brain tumor tissue with optical coherence tomography}},
volume = {12368},
booktitle = {Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XXI},
editor = {Caroline Boudoux and James W. Tunnell},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {1236805},
abstract = {The ill-defined tumor borders of glioblastoma multiforme pose a major challenge for the surgeon during tumor resection,  since the goal of the tumor resection is the complete removal, while saving as much healthy brain tissue as possible. In  recent years, optical coherence tomography (OCT) was successfully used to classify white matter from tumor infiltrated  white matter by several research groups. Motivated by these results, a dataset was created, which consisted of sets of  corresponding ex vivo OCT images, which were acquired by two OCT-systems with different properties (e.g. wavelength  and resolution). Each image was annotated with semantic labels. The labels differentiate between white and gray matter  and three different stages of tumor infiltration. The data from both systems not only allowed a comparison of the ability of  a system to identify the different tissue types present during the tumor resection, but also enable a multimodal tissue  analysis evaluating corresponding OCT images of the two systems simultaneously. A convolutional neural network with  dirichlet prior was trained, which allowed to capture the uncertainty of a prediction. The approach increased the sensitivity  of identifying tumor infiltration from 58 % to 78 % for data with a low prediction uncertainty compared to a previous  monomodal approach. },
keywords = {optical coherence tomography, oct, brain, classification, tumor, dual wavelength, glioblastoma multiforme, tissue analysis},
year = {2023},
doi = {10.1117/12.2649963},
URL = {https://doi.org/10.1117/12.2649963}
}

@inproceedings{10.1117/12.2670953,
author = {Wolfgang Draxinger and Dirk Theisen-Kunde and Lion Schuetz and Nicolas Detrez and Paul Strenge and Maximilian Rixius and Veit Danicke and Wolfgang Wieser and Jessica Kren and Patrick Kuppler and Sonja Spar-Hess and Matteo Mario Bonsanto M.D. and Ralf Brinkmann and Robert Huber},
title = {{Microscope integrated realtime high density 4D MHz-OCT in neurosurgery: a depth and tissue resolving visual contrast channel and the challenge of fused presentation}},
volume = {12627},
booktitle = {Translational Biophotonics: Diagnostics and Therapeutics III},
editor = {Zhiwei Huang and Lothar D. Lilge},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {126270W},
keywords = {optical coherence tomography, neurosurgery, tissue contrast, image fusion, surgical guidance, theranostics},
year = {2023},
doi = {10.1117/12.2670953},
URL = {https://doi.org/10.1117/12.2670953}
}

@article{Strenge-2022,
   author = {Strenge, P.;Lange, B.;Grill,C.;Danicke,V.;Theisen-Kunde, D.;Hagel, C.;Spahr-Hess, S.;;Bonsanto, Matteo M.;Handels, H.; and Huber, R.;Brinkmann, R.},
   title = {Differentiation of different stages of brain tumor infiltration using optical coherence tomography: Comparison of two systems and histology},
   journal = {Frontiers in Oncology},
Keywords = {AG-Huber_FDML, AG-Huber_OCT, brain, tumor, glioblastoma multiforme, OCT, neural network, attenuation (absorption)
coefficient, optical coherence tomography},
   DOI = {https://doi.org/10.3389/fonc.2022.896060},
   url = {https://www.frontiersin.org/articles/10.3389/fonc.2022.896060/full},
   year = {2022},
   type = {Journal Article}
}

@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}
}

@article{Strenge2022,
   author = {Strenge, P;Lange, B;Grill, C;Draxinger, W;Danicke, V;Theisen-Kunde, D;Hagel, C;Spahr-Hess, S;Bonsanto, Matteo M.;Huber, R;Handels, H and Brinkmann, R},
   title = {Registration of histological brain images onto optical coherence tomography images based on shape information},
keywords = {brain, glioblastoma multiforme, shape, OCT, optical coherence tomography, AG-Huber_OCT,},
   journal = {Physics in Medicine & Biology},
   ISSN = {0031-9155},
   url = {http://iopscience.iop.org/article/10.1088/1361-6560/ac6d9d},
   year = {2022},
   type = {Journal Article}
}

@article{Gob:22,
author = {Madita G\"{o}b and Tom Pfeiffer and Wolfgang Draxinger and Simon Lotz and Jan Philip Kolb and Robert Huber},
journal = {Biomed. Opt. Express},
keywords = {High speed imaging; Image processing; Image quality; In vivo imaging; Range imaging; Vertical cavity surface emitting lasers},
number = {2},
pages = {713--727},
publisher = {Optica Publishing Group},
title = {Continuous spectral zooming for in vivo live 4D-OCT with MHz A-scan rates and long coherence},
volume = {13},
month = {Feb},
year = {2022},
url = {https://opg.optica.org/boe/abstract.cfm?URI=boe-13-2-713},
doi = {10.1364/BOE.448353},
abstract = {We present continuous three-dimensional spectral zooming in live 4D-OCT using a home-built FDML based OCT system with 3.28 MHz A-scan rate. Improved coherence characteristics of the FDML laser allow for imaging ranges up to 10 cm. For the axial spectral zoom feature, we switch between high resolution and long imaging range by adjusting the sweep range of our laser. We present a new imaging setup allowing for synchronized adjustments of the imaging range and lateral field of view during live OCT imaging. For this, a novel inline recalibration algorithm was implemented that enables numerical k-linearization of the raw OCT fringes for every frame instead of every volume. This is realized by acquiring recalibration data within the dead time of the raster scan at the turning points of the fast axis scanner. We demonstrate in vivo OCT images of fingers and hands at different resolution modes and show real three-dimensional zooming during live 4D-OCT. A three-dimensional spectral zooming feature for live 4D-OCT is expected to be a useful tool for a wide range of biomedical, scientific and research applications, especially in OCT guided surgery.},
}

@inproceedings{Strenge:21,
author = {P. Strenge, B. Lange, C. Grill, W. Draxinger, V. Danicke, D. Theisen-Kunde, H. Handels, M. M. Bonsanto, C. Hagel, R. Huber and R. Brinkmann},
journal = {European Conferences on Biomedical Optics 2021 (ECBO)},
keywords = {AG-Huber_OCT; Absorption coefficient; Attenuation coefficient; Fourier domain mode locking; Multiple scattering; Optical coherence tomography; Spectral domain optical coherence tomography},
pages = {EW1C.7},
publisher = {Optical Society of America},
title = {Comparison of two optical coherence tomography systems to identify human brain tumor},
year = {2021},
url = {https://doi.org/10.1117/12.2616044},
abstract = {The identification of ex vivo brain tumor tissue was investigated with two different optical coherence tomography systems exploiting two optical parameters. The optical parameters were calculated from semantically labelled OCT B-scans.},
}

@inproceedings{Gob:21,
author = {Madita G\"{o}b and Sazgar Burhan and Wolfgang Draxinger and Jan Philip Kolb and Robert Huber},
booktitle = {European Conferences on Biomedical Optics 2021 (ECBO)},
journal = {European Conferences on Biomedical Optics 2021 (ECBO)},
keywords = {AG-Huber_OCT;Fourier domain mode locking; Image processing; Image quality; Optical coherence tomography; Temporal resolution; Three dimensional imaging},
pages = {EW3C.4},
publisher = {Optical Society of America},
title = {Towards densely sampled ultra-large area multi-MHz-OCT for in vivo skin measurements beyond 1 cm$^2$/sec},
year = {2021},
url = {http://www.osapublishing.org/abstract.cfm?URI=ECBO-2021-EW3C.4},
abstract = {We demonstrate a 3.3 MHz A-scan rate OCT for rapid scanning of large areas of human skin. The mosaicking performance and different OCT imaging modalities including intervolume speckle contrast are evaluated.},
}

@INPROCEEDINGS{9542126,
  author={Grill, Christin and Lotz, Simon and Blömker, Torben and Schmidt, Mark and Draxinger, Wolfgang and Kolb, Jan Philip and Jirauschek, Christian and Huber, Robert},
  booktitle={2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)}, 
  title={Superposition of two independent FDML lasers}, 
  year={2021},
  volume={},
  number={},
  pages={1-1},
  abstract={Fourier domain mode locking (FDML) is a laser operating regime, which was developed in 2005 [1] . The output of this laser is a train of optical wavelength sweeps, equivalent to extremely chirped pulses with an optical bandwidth of up to 25 THz and frequency tuning rates of >10 19 Hz/s. This laser type was developed for optical coherence tomography [2] , but found recently more and more applications like LiDAR [3] , Raman microscopy [4] or two-photon microscopy [5] . The laser’s coherence properties are relevant for a better understanding of the FDML laser itself and its applications. Because of the wide sweep range and high tuning rate, the laser linewidth cannot be measured with an RF spectrometer. Superposition with a narrowband continuous wave laser only yields phase information for small fractions of the sweep [6] . However, beat signal measurements between two independent FDML lasers with equal sweep range and direction can give information about the complete sweep.},
  keywords={},
  doi={10.1109/CLEO/Europe-EQEC52157.2021.9542126},
  ISSN={},
  month={June}
}

@inproceedings{Strenge2021A,
author = {P. Strenge, B. Lange, C. Grill, W. Draxinger, V. Danicke, D. Theisen-Kunde, H. Handels, M. Bonsanto, C. Hagel, R. Huber and R. Brinkmann},
title = {{Characterization of brain tumor tissue with 1310 nm optical coherence tomography}},
volume = {11630},
booktitle = {Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXV},
editor = {Joseph A. Izatt and James G. Fujimoto},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {74 -- 80},
abstract = {The separation of tumorous brain tissue and healthy brain tissue is still a big challenge in the field of neurosurgery, especially when it comes to the detection of different infiltration grades of glioblastoma multiforme at the tumor border. On the basis of a recently created labelled OCT dataset of ex vivo glioblastoma multiforme tumor samples the detection of brain tumor tissue and the identification of zones with varying degrees of infiltration of tumor cells was investigated. The identification was based on the optical properties, which were extracted by an exponential fit function. The results showed that a separation of tumorous tissue and healthy white matter based on these optical properties is possible. A support vector machine was trained on the optical properties to separate tumor from healthy white matter tissue, which achieved a sensitivity of 91% and a specificity of 76% on an independent training dataset.},
keywords = {AG-Huber_OCT, optical coherence tomography, OCT, glioblastoma multiforme, MHz-OCT, brain imaging, tumor, neurosurgery},
year = {2021},
URL = {hhttps://doi.org/10.1117/12.2578409}
}

@article{Lotz2021,
   author = {S. Lotz, C. Grill, M. Göb, W. Draxinger, J.P. Kolb and R. Huber},
   title = {Cavity length control for Fourier domain mode locked (FDML) lasers with µm precision},
   journal = {Biomedical Optics Express},
   volume = {12(5)},
   keywords={AG-Huber_FDML},
   pages = {2604-2616},
   url = {https://doi.org/10.1364/BOE.422898},
   year = {2021},
   type = {Journal Article}
}

@inproceedings{Strenge2021,
author = {P. Strenge, B. Lange, C. Grill, W. Draxinger, V. Danicke, D. Theisen-Kunde, H. Handels, C. Hagel, M. Bonsanto, R. Huber and R. Brinkmann},
title = {{Creating a depth-resolved OCT-dataset for supervised classification based on ex vivo human brain samples}},
volume = {11630},
booktitle = {Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXV},
editor = {Joseph A. Izatt and James G. Fujimoto},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {66 -- 73},
abstract = {Optical coherence tomography (OCT) has the potential to become an additional imaging modality for surgical guidance in the field of neurosurgery, especially when it comes to the detection of different infiltration grades of glioblastoma multiforme at the tumor border. Interpretation of the images, however, is still a big challenge. A method to create a labeled OCT dataset based on ex vivo brain samples is introduced. The tissue samples were embedded in an agarose mold giving them a distinctive shape before images were acquired with two OCT systems (spectral domain (SD) and swept source (SS) OCT) and histological sections were created and segmented by a neuropathologist. Based on the given shape, the corresponding OCT images for each histological image can be determined. The transfer of the labels from the histological images onto the OCT images was done with a non-affine image registration approach based on the tissue shape. It was demonstrated that finding OCT images of a tissue sample corresponding to segmented histological images without any color or laser marking is possible. It was also shown that the set labels can be transferred onto OCT images. The accuracy of method is 26 ± 11 pixel, which translates to 192 ± 75 μm for the SS-OCT and 94 ± 43 μm for the SD-OCT. The dataset consists of several hundred labeled OCT images, which can be used to train a classification algorithm.},
keywords = {AG-Huber_OCT, optical coherence tomography, OCT, image registration, glioblastoma multiforme, MHz-OCT, brain imaging, tumor, neurosurgery},
year = {2021},
URL = {https://doi.org/10.1117/12.2578391}
}

@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}
}

@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}
}

@inproceedings{LotzLASE2021,
author = {S. Lotz, C. Grill, M. Göb, W. Draxinger, J. P. Kolb and R. Huber},
title = {{Characterization of the dynamics of an FDML laser during closed-loop cavity length control}},
volume = {11665},
booktitle = {Fiber Lasers XVIII: Technology and Systems},
editor = {Michalis N. Zervas},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {236 -- 241},
abstract = {In Fourier domain mode locked (FDML) lasers, extremely precise and stable matching of the filter tuning period and light circulation time in the cavity is essential for ultra-low noise operation. During the operation of FDML lasers, the ultra-low noise mode can be lost due to temperature drifts of the already temperature stabilized cavity resulting in increased intensity noise. Until now, the filter frequency is continuously regulated to match the changing light circulation time. However, this causes the filter frequency to constantly change by a few mHz and leads to synchronization issues in cases where a fixed filter frequency is desired. We present an actively cavity length controlled FDML laser and a robust and high precision feedback loop algorithm for maintaining ultra-low noise operation. Instead of adapting the filter frequency, the cavity length is adjusted by a motorized free space beam path to match the fixed filter frequency. The closed-loop system achieves a stability of ~0.18 mHz at a sweep repetition rate of ~418 kHz which corresponds to a ratio of 4×10<sup>-10</sup>. We investigate the coherence properties during the active cavity length adjustments and observe no noise increase compared to fixed cavity length. The cavity length control is fully functional and for the first time, offers the possibility to operate an FDML laser in sweet spot mode at a fixed frequency or phase locked to an external clock. This opens new possibilities for system integration of FDML lasers.},
keywords = {AG-Huber_FDML, FDML, Fourier domain mode locking, laser beating, tunable laser, optical coherence tomography, OCT},
year = {2021},
URL = {hhttps://doi.org/10.1117/12.2578514}
}