As the world's leading manufacturer of supercontinuum sources over the last 15 years, NKT Photonics will present the applications that have driven the supercontinuum technology forward: From the earliest introduction in commercial microscopes to the most recent industrial applications in highly demanding industries like semiconductor metrology. Over the years, the supercontinuum technology has made the development of several state-of-the-art applications possible, e.g. confocal microscopy, FLIM, STED, OCT, etc.. The supercontinuum technology started in research lab applications but is now mature and reliable and can be used in a wide variety of industrial process monitoring applications.
Sidsel Papior, Johannes Weirich, Mette Johansen, Christian Jakobsen, Mattia Michieletto, Marco Triches, Torben Kristensen, Anders Olesen, Christian Petersen, Thomas Andersen, Martin Maack, Thomas Alkeskjold
Photonic crystal fiber (PCF) technology for ultrafast fiber amplifiers traditionally uses air holes as key elements for large mode area (LMA) fiber designs. These air holes are crucial for the performance of high-end LMA PCFs, but makes splicing and interfacing more complex. To reduce this complexity in mid-range amplifiers, we present single-mode polarization-maintaining Yb-doped LMA PCFs without air holes for easier splicing into monolithic all-fiber amplifier designs.
A 30 μm core all-solid spliceable PCF is presented, and amplification of 1064 nm light above 50 W with an optical to optical efficiency of 80 % is demonstrated.
Furthermore, to demonstrate the excellent reliability of PCF based monolithic amplifiers, we demonstrate ultra-longterm performance data of > 35 khrs on a 14 μm core step-index type PCF amplifier with low long-term power degradation slope of < 1.5 % / 10,000 h.
Degenerate spontaneous four wave mixing is studied for the rst time in a large mode area hybrid photonic crystal ber, where light con nement is achieved by combined index- and bandgap guiding. Four wave mixing products are generated on the edges of the bandgaps, which is veri ed by numerical and experimental results. Since the core mode is in resonance with cladding modes near the bandedges an unconventional measurement technique is used, in this work named nonlinear spatial mode imaging.
We report on the generation of 830 W compressed average power at 78 MHz pulse repetition frequency and 640 fs pulse
duration. We discuss further power scaling including the issue of transversal spatial hole burning. Therefore, we
describe a low-nonlinearity fiber design capable of producing fundamental mode radiation at ultra high average powers
from short length (range of 1m) and large mode field diameter (>50μm) fibers. In conventional large mode area fiber
most of the core is typically uniformly doped. As a consequence gain factors for the fundamental mode and the next
higher order modes are comparable. Furthermore, the fundamental mode extracts inversion only in the central part of the
core according to its intensity profile, leading at high pump and signal power levels to high and unused inversion density
with a strong overlap with higher order transversal modes. In experiments this leads to a threshold-like onset of mode
instability, originating from mode competition. Finally, this effect avoids further power scaling. The presented fiber
features an optimized doping profile to prefer the amplification of the fundamental mode. In addition non-extracted
inversion is minimized avoiding the issue of transversal spatial hole burning. As a consequence ultrafast fiber laser
systems with novel performance are in reach, i.e. systems delivering simultaneously >1GW peak power and >1kW
average power. In a first iteration a ROD-type fiber with 60μm MFD and 1.7m length was used in a CPA system to
produce pump power limited 355 W of average power at 1 MHz.
In this contribution, we report on spectral combination of four sub-5ns pulsed fiber amplifier systems with an average
output power of 200W at 200kHz repetition rate resulting in 1mJ of pulse energy. A dielectric reflection grating is used
to combine four individual beams to one output possessing a measured M2 value of 1.3 and 1.8, respectively,
independent of power level. Extraction of higher pulse energies and peak powers will be discussed.
We present an effective solution for an all-polarization-maintaining modelocked femtosecond fiber laser operating
at the central wavelength of 1028 nm. The laser is based on an
Yb-doped active fiber. Modelocking is enabled
by a semiconductor saturable absorber mirror, and the central wavelength is enforced by a fiber Bragg grating.
The laser is self-starting and demonstrates excellent stability against Q-switching. Pulse energies reach 13 nJ at
34 MHz repetition rate. External compression leads to near
transform-limited pulses of 140 fs.
In this contribution we report a high repetition rate optical parametric amplifier (OPA) pumped by a chirped pulse fiber amplifier system. Fiber CPA systems have demonstrated power scaling and open the route to OPAs at repetition rates in the 100 kHz-10MHz range. The OPA stage is seeded by a continuum generated in a Sapphire plate and more than 50 nm bandwidth is efficiently amplified, resulting in 3 &mgr;J, 29 fs pulses.
We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser radiation.
Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad bandwidth signal
generation is a promising alternative to white light generation in bulky glass or sapphire plates. As pump source we
propose the use of a high repetition rate ytterbium-doped fiber chirped pulse amplification system.
The recent development of photonic bandgap fibers with solid cores enables the construction of dispersion
compensated all-fiber ultrashort mode-locked fiber lasers. Solid-core photonic bandgap fibers (SC-PBG) can
be spliced to standard fibers with relative low loss and negligible Fresnel reflection due to the matching indexes
of the cores. The fibers can provide significant anomalous dispersion with low nonlinearity and are therefore
ideal for dispersion compensation in ultrafast fiber lasers. We demonstrate the use of a SC-PBG fiber for intra
cavity dispersion compensation in an ytterbium based mode-locked fiber laser. The limitations on pulse duration
due to the relative high third order dispersion of the SC-PBG fiber are discussed.
We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser
radiation. Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad
bandwidth signal generation is a promising alternative to white light generation in bulky glass or sapphire plates.
We demonstrate a novel and successful signal engineering implemented in a setup for parametric amplification
and subsequent recompression of resonant linear waves resulting from soliton fission in a highly nonlinear
photonic crystal fiber. The applied pump source is a high repetition rate ytterbium-doped fiber chirped pulse
amplification system. The presented approach results in the generation of ~50 fs pulses at MHz repetition rate.
The potential of generating even shorter pulse duration and higher pulse energies will be discussed.
The generation of high energy femtosecond pulses in Optical Parametric Amplifier (OPA) pumped by fiber laser at a repetition rate of 1MHz is reported. Highly nonlinear fibers are used to create an intrinsically synchronized signal for the parametric amplifier. Seeding the OPA by a supercontinuum generated in a photonic crystal fiber, large tunability extending from 700 nm to 1500 nm of femtosecond pulses is demonstrated, with pulse energies as high as 1.2 μJ. Generating the seed using only SPM in a standard fiber, broadband amplification over more than 85 nm and subsequent compression down to 46 fs in a prism sequence are achieved. Pulse peak powers pulses above 10 MW together with 0.5 W of average power is achieved. This system appears to be very interesting due to scalability of pulse energy and average power of both involved concepts: fiber laser and parametric amplifier.
We investigate supercontinuum generation with a femtosecond dual-pumping scheme. A 10 MHz oscillator delivering 300 femtosecond pulses at 1028 nm is frequency doubled and both the fundamental and second harmonic are coupled into a micro structured fiber. When the two pulses are temporally overlapped in the fiber a broad supercontinuum appears. By tuning the temporal delay between the two pulses, different regions of the spectrum can be enhanced which allows either improved flatness of the spectrum or selective amplification of regions of interest. The interesting result is shown to arise from cross phase modulation imposed on the visible pulse by fundamental solitons. Results from similar experiments with picosecond and nanosecond dual-wavelength pumping show the same qualitative behaviour and demonstrate that the governing mechanism in all cases is soliton fission and subsequent cross phase modulation of the co-propagating visible pulse.
Osteons are longitudinally arranged cylindrical structures, which form the structural units of cortical bone. Cortical bone remodeling is closely related to the osteonal organization as newly formed osteons continuously replace older ones. The degree of mineralization in these new osteons is initially lower than in the existing bone as it takes time before osteons mature. Synchrotron radiation-based computed microtomography (μCT) and scanning acoustic microscopy (SAM) are two techniques, which have both sufficient spatial resolution and sensitivity to detect local variations in bone
density. The aim of this study was therefore to compare both techniques for the analysis of osteonal mineralization. Eight human cortical bone samples were scanned with both techniques and the corresponding images were matched. Synchrotron-based μCT is not affected by beam hardening and the gray values in the reconstructed images are directly related to the local mineral density. For cortical bone this means that immature osteons appear darker than their surrounding. In SAM-images the gray values are a measure of the acoustic impedance, which is a function of the local stiffness and the density. Comparison of the μCT and the SAM images of the cortical samples shows a good correspondence in the gray values of the individual osteons.
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