1. Articles from christoph m. eigenwillig

    1-21 of 21
    1. Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers

      Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers

      Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored ...

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    2. Extended coherence length megahertz FDML and its application for anterior segment imaging

      Extended coherence length megahertz FDML and its application for anterior segment imaging
      We present a 1300 nm Fourier domain mode locked (FDML) laser for optical coherence tomography (OCT) that combines both, a high 1.6 MHz wavelength sweep rate and an ultra-long instantaneous coherence length for rapid volumetric deep field imaging. By reducing the dispersion in the fiber delay line of the FDML laser, the instantaneous coherence length and hence the available imaging range is approximately quadrupled compared to previously published MHz-FDML setups, the imaging speed is increased by a factor of 16 compared to previous extended coherence length results. We present a detailed characterization of the FDML laser performance. We demonstrate ...
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    3. New rapidly wavelength-swept light sources for optical coherence tomography and picosecond pulse generation. (Thesis)

      New rapidly wavelength-swept light sources for optical coherence tomography and picosecond pulse generation. (Thesis)

      This thesis deals with research on novel, semiconductor-based, ultrafast and widely tunable wavelength-swept light sources with respect to different applications. The main focus was on the young technology of Fourier domain mode locked (FDML) lasers, where the insertion of a kilometer-long fiber delay line enables to tune a narrowband spectral filter synchronously to the roundtrip time of light in the resonator. In this way, very high sweep speeds become feasible. A very successful application in the field of biomedical imaging is optical coherence tomography (OCT), where FDML lasers allow for very large image acquisition rates. One important part of the ...

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    4. Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools

      Chromatic polarization effects of swept waveforms in FDML lasers and fiber spools

      We present detailed investigations of chromatic polarization effects, caused by fiber spools used in FDML lasers and buffering spools for rapidly wavelength swept lasers. We introduce a novel wavelength swept FDML laser source, specially tailored for polarization sensitive optical coherence tomography (OCT) which switches between two different linear polarization states separated by 45°, i.e. 90° on the Poincaré sphere. The polarization maintaining laser cavity itself generates a stable linear polarization state and uses an external buffering technique in order to provide alternating polarization states for successive wavelength sweeps. The design of the setup is based on a comprehensive analysis ...

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    5. Multi-MHz FDML OCT: snapshot retinal imaging at 6.7 million axial-scans per second

      Multi-MHz FDML OCT: snapshot retinal imaging at 6.7 million axial-scans per second

      We demonstrate the acquisition of densely sampled wide-field 3D OCT datasets of the human retina in 0.3s. This performance is achieved with a multi-MHz Fourier domain mode-locked (FDML) laser source operating at 1050nm. A two-beam setup doubles the 3.35MHz laser sweep rate to 6.7MHz, which is 16x faster than results achieved with any non-FDML source used for retinal OCT. We discuss two main benefits of these high line rates: First, large datasets over an ultra-wide field of view can be acquired with a low probability of distortions. Second, even if eye movements occur, now the scan rate ...

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    6. Feature Of The Week 9/4/11: Researchers at Ludwig-Maximilians University Continue to Blaze Trails Developing High Performance Swept Source OCT Technology and Its Application in Medical Imaging

      Feature Of The Week 9/4/11: Researchers at Ludwig-Maximilians University Continue to Blaze Trails Developing High Performance Swept Source OCT Technology and Its Application in Medical Imaging
      Researchers at Ludwig-Maximilians University continue to blaze trails in their work developing high performance swept source optical coherence tomography technology and the application of high speed frequency tuned sources in medical imaging. The Fourier-domain mode locked laser (FDML) together with tapped-delay line sweep-rate multipliers, light delivery and calibration optics, novel frame averaging and sampling techniques, wide FOV scanning technology, and high speed signal processing and visualization technology are impressive and will clearly have a significant impact on future medical imaging systems and ultimately patient care. Below is a presentation on some of their work entitled “(Multi-) MHz FDML OCT: Retinal ...
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    7. Extended focus high-speed swept source OCT with self-reconstructive illumination

      Extended focus high-speed swept source OCT with self-reconstructive illumination

      We present a Bessel beam illumination FDOCT setup using a FDML Swept Source at 1300nm with up to 440kHz A-scan rate, and discuss its advantages for structural and functional imaging of highly scattering samples. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Decoupling the illumination from the Gaussian detection increases the global sensitivity and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the sample ...

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    8. High-speed functional OCT with self-reconstructive Bessel illumination at 1300nm

      High-speed functional OCT with self-reconstructive Bessel illumination at 1300nm

      Cedric Blatter, Branislav Grajciar, and Christoph M. Eigenwillig et al. We present a Bessel beam illumination FDOCT setup with FDML buffered swept source at 1300nm. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Decoupling the illumination from the Gaussian detection improves the sensitivity as compared t ... [Proc. SPIE 8091, 809104 (2011)] published Thu Jun 09, 2011.

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    9. Megahertz OCT for ultrawide-field retinal imaging with a 1050nm Fourier domain mode-locked laser

      Megahertz OCT for ultrawide-field retinal imaging with a 1050nm Fourier domain mode-locked laser
      We demonstrate ultrahigh speed swept source retinal OCT imaging using a Fourier domain mode locked (FDML) laser. The laser uses a combination of a semiconductor optical amplifier and an ytterbium doped fiber amplifier to provide more than 50mW output power. The 1050nm FDML laser uses standard telecom fiber for the km long delay line instead of two orders of magnitude more expensive real single mode fiber. We investigate the influence of this “oligo-mode” fiber on the FDML laser performance. Two design configurations with 684,400 and 1,368,700 axial scans per second are investigated, 25x and 50x faster than ...
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    10. Wavelength swept amplified spontaneous emission source for high speed retinal optical coherence tomography at 1060 nm

      Wavelength swept amplified spontaneous emission source for high speed retinal optical coherence tomography at 1060 nm
      The wavelength swept amplified spontaneous emission (ASE) source presented in this paper is an alternative approach to realize a light source for high speed swept source optical coherence tomography (OCT). ASE alternately passes a cascade of different optical gain elements and tunable optical bandpass filters. In this work we show for the first time a wavelength swept ASE source in the 1060 nm wavelength range, enabling high speed retinal OCT imaging. We demonstrate ultra-rapid retinal OCT at a line rate of 170 kHz, a record sweep rate at 1060 nm of 340 kHz with 70 nm full sweep width, enabling ...
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    11. Direct measurement of the instantaneous linewidth of rapidly wavelength-swept lasers

      Direct measurement of the instantaneous linewidth of rapidly wavelength-swept lasers
      The instantaneous linewidth of rapidly wavelength-swept laser sources as used for optical coherence tomography (OCT) is of crucial interest for a deeper understanding of physical effects involved in their operation. Swept lasers for OCT, typically sweeping over ~15 THz in ~10μs, have linewidths of several gigahertz. The high optical-frequency sweep speed makes it impossible to measure the instantaneous spectrum with standard methods. Hence, up to now, experimental access to the instantaneous linewidth was rather indirect by the inverse Fourier transform of the coherence decay. In this Letter, we present a method by fast synchronous time gating and extraction of a ...
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    12. Feature Of The Week 9/5/10: Record Breaking OCT Volumetric Image Acquisition Rates by Researchers at Ludwig Maximilians University

      Feature Of The Week 9/5/10: Record Breaking OCT Volumetric Image Acquisition Rates by Researchers at Ludwig Maximilians University
      Feature Of The Week 9/5/10: As the 2010 academic years begins OCT News will resume its “Feature Of The Week” section. This year starts with an exciting submission by Dr. Robert Huber’s research group at Ludwig-Maximilians-Universität in Munich on record breaking OCT volumetric data set acquisition rates that were hard to imaging just a few years ago.Currently there is an ongoing debate about the optimum imaging speed of Optical Coherence Tomography (OCT) systems, considering the tradeoff between speed and image quality. Huge efforts have been made to push the imaging speed of OCT. This includes the ...
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    13. Multi-Megahertz OCT: High quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second

      Multi-Megahertz OCT: High quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second
      We present ultra high speed optical coherence tomography (OCT) with multi-megahertz line rates and investigate the achievable image quality. The presented system is a swept source OCT setup using a Fourier domain mode locked (FDML) laser. Three different FDML-based swept laser sources with sweep rates of 1, 2.6 and 5.2MHz are compared. Imaging with 4 spots in parallel quadruples the effective speed, enabling depth scan rates as high as 20.8 million lines per second. Each setup provides at least 98dB sensitivity and ~10µm resolution in tissue. High quality 2D and 3D imaging of biological samples is demonstrated ...
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    14. Feature Of The Week 12/6/09: Cascaded Wavelength Swept Amplified Spontaneous Emission Source for Optical Coherence Tomography

      Feature Of The Week 12/6/09: Cascaded Wavelength Swept Amplified Spontaneous Emission Source for Optical Coherence Tomography
      Feature Of The Week 12/6/09: Due to increasing interest in Optical Coherence Tomography (OCT) using wavelength swept lasers (SS-OCT), huge efforts have been made by both research and commercial organizations around the world to push the performance of such sources and with it OCT system capabilities. This includes sweep repetition rate, power, new wavelengths, coherence length, and more. One of the drawbacks of standard wavelength-swept lasers is the fact that lasing has to build up from amplified spontaneous emission repetitively within several roundtrips of the light, limiting the maximum achievable sweep speed. Dr. Robert Huber and other researchers ...
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    15. Wavelength swept amplified spontaneous emission source

      Wavelength swept amplified spontaneous emission source
      We present a new, alternative approach to realize a wavelength swept light source with no fundamental limit to sweep speed. Amplified spontaneous emission (ASE) light alternately passes a cascade of optical gain elements and tunable optical bandpass filters. We show that for high sweep speeds, the control signal for the different filters has to be applied with a defined, precise phase delay on the order of nanoseconds, to compensate for the light propagation time between the filters and ensure optimum operation. At a center wavelength of 1300 nm sweep rates of 10 kHz, 100 kHz and 340 kHz over a ...
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    16. Recent developments in Fourier Domain Mode Locked lasers for optical coherence tomography: Imaging at 1310 nm vs. 1550 nm wavelength

      We report on recent progress in Fourier domain mode-locking (FDML) technology. The paper focuses on developments beyond pushing the speed of these laser sources. After an overview of improvements to FDML over the last three years, a brief analysis of OCT imaging using FDML lasers with different wavelengths is presented. For the first time, high speed, high quality FDML imaging at 1550 nm is presented and compared to a system at 1310 nm. The imaging results of human skin for both wavelengths are compared and analyzed. Sample arm optics, power on the sample, heterodyne gain, detection bandwidth, colour cut levels ...
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    17. Dispersion, coherence and noise of Fourier domain mode locked lasers

      Dispersion, coherence and noise of Fourier domain mode locked lasers
      We report on the effect of chromatic dispersion on coherence length and noise of Fourier Domain Mode Locked (FDML) lasers. An FDML laser with a sweep range of 100nm around 1550nm has been investigated. Cavity configurations with and without dispersion compensation have been analyzed using different widths of the intra-cavity optical band-pass filter. The measurements are compared to non-FDML wavelength swept laser sources. Based on these observations, a simple model is developed providing a connection between timing, photon cavity lifetime and characteristic time constant of the filter. In an optimized configuration, an instantaneous laser linewidth of 20pm is observed, corresponding ...
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    18. Subharmonic Fourier domain mode locking

      Subharmonic Fourier domain mode locking
      We demonstrate a subharmonically Fourier domain mode-locked wavelength-swept laser source with a substantially reduced cavity fiber length. In contrast to a standard Fourier domain mode-locked configuration, light is recirculated repetitively in the delay line with the optical bandpass filter used as switch. The laser has a fundamental optical round trip frequency of 285 kHz and can be operated at integer fractions thereof (subharmonics). Sweep ranges up to 95 nm full width centred at 1317 nm are achieved at the 1/5th subharmonic. A maximum sensitivity of 116 dB and an axial resolution of 12 um in air are measured at ...
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    19. Raman-pumped Fourier-domain mode-locked laser: analysis of operation and application for optical coherence tomography

      We demonstrate a Raman-pumped Fourier-domain mode-locked (FDML) fiber laser and optical coherence tomography imaging with this source. The wavelength sweep range of only 30 nm centered around 1550 nm results in limited axial resolution, hence a nonbiological sample is imaged. An output power of 1.9 ... [Opt. Lett. 33, 2815-2817 (2008)]
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    20. Real time en face Fourier-domain optical coherence tomography with direct hardware frequency demodulation

      We demonstrate en face swept source optical coherence tomography (ss-OCT) without requiring a Fourier transformation step. The electronic optical coherence tomography (OCT) interference signal from a k-space linear Fourier domain mode-locked laser is mixed with an adjustable local oscillator, ... [Opt. Lett. 33, 2556-2558 (2008)]
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    21. K-space linear Fourier domain mode locked laser and applications for optical coherence tomography

      We report on a Fourier Domain Mode Locked (FDML) wavelength swept laser source with a highly linear time-frequency sweep characteristic and demonstrate OCT imaging without k-space resampling prior to Fourier transformation. A detailed theoretical framework is provided and different strategies ... [Opt. Express 16, 8916-8937 (2008)]
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    1-21 of 21
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  2. Topics in the News

    1. (21 articles) Christoph M. Eigenwillig
    2. (20 articles) Ludwig Maximilian University of Munich
    3. (20 articles) Robert A. Huber
    4. (19 articles) Wolfgang Wieser
    5. (18 articles) Benjamin R. Biedermann
    6. (11 articles) Thomas Klein
    7. (2 articles) Desmond C. Adler
    8. (2 articles) Raphael André
    9. (2 articles) Rainer A. Leitgeb
    10. (2 articles) Branislav Grajciar
    11. (1 articles) Institute of Applied Physics
    12. (1 articles) Medical University of Vienna
    13. (1 articles) Kyungpook National University
    14. (1 articles) Singapore Eye Research Institute
    15. (1 articles) University of Western Australia
    16. (1 articles) Stefan G. Sacu
    17. (1 articles) Brendan F. Kennedy
    18. (1 articles) Yongyang Huang
    19. (1 articles) Jeehyun Kim
    20. (1 articles) Ursula Schmidt-Erfurth
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    Feature Of The Week 12/6/09: Cascaded Wavelength Swept Amplified Spontaneous Emission Source for Optical Coherence Tomography Multi-Megahertz OCT: High quality 3D imaging at 20 million A-scans and 4.5 GVoxels per second Feature Of The Week 9/5/10: Record Breaking OCT Volumetric Image Acquisition Rates by Researchers at Ludwig Maximilians University Megahertz OCT for ultrawide-field retinal imaging with a 1050nm Fourier domain mode-locked laser High-speed functional OCT with self-reconstructive Bessel illumination at 1300nm Extended focus high-speed swept source OCT with self-reconstructive illumination Feature Of The Week 9/4/11: Researchers at Ludwig-Maximilians University Continue to Blaze Trails Developing High Performance Swept Source OCT Technology and Its Application in Medical Imaging Full-range space-division multiplexing optical coherence tomography angiography Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis) Optical coherence tomography for characterization of nanocomposite materials (Thesis) In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis Non-invasive optical screening of Streptococcus Pneumonia based inflammatory changes of the tympanic membrane and mastoid mucosa in guinea pig otitis media using optical coherence tomography