NKT Photonics

Birkerød, Denmark

NKT Photonics

Birkerød, Denmark
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Dupont S.,University of Aarhus | Moselund P.M.,NKT Photonics | Leick L.,NKT Photonics | Ramsay J.,University of Aarhus | Keiding S.R.,University of Aarhus
Journal of the Optical Society of America B: Optical Physics | Year: 2013

We present an cross-correlation frequency-resolved optical gating (XFROG) measurement of a megahertz IR supercontinuum generated in a step-index ZBLAN fiber. The resulting spectrogram gives the dispersion characteristics of the fiber and reveals that it has three zero-dispersion wavelengths. A comparison of the measured spectrogram with numerical simulations shows that this dispersion profile allows a notable dispersive-wave generation toward long wavelengths. Furthermore, the sum-frequency generation process in the XFROG measurement gives the possibility of measuring the IR light with fast Si-based detectors, such as CCD arrays. © 2013 Optical Society of America.

Ramsay J.,University of Aarhus | Dupont S.,University of Aarhus | Johansen M.,University of Aarhus | Rishoj L.,Technology University of Denmark | And 3 more authors.
Optics Express | Year: 2013

Using femtosecond upconversion we investigate the time and wavelength structure of infrared supercontinuum generation. It is shown that radiation is scattered into higher order spatial modes (HOMs) when generating a supercontinuum using fibers that are not single-moded, such as a step-index ZBLAN fiber. As a consequence of intermodal scattering and the difference in group velocity for the modes, the supercontinuum splits up spatially and temporally. Experimental results indicate that a significant part of the radiation propagates in HOMs. Conventional simulations of super-continuum generation do not include scattering into HOMs, and including this provides an extra degree of freedom for tailoring supercontinuum sources. © 2013 Optical Society of America.

Eidam T.,Friedrich - Schiller University of Jena | Hanf S.,Friedrich - Schiller University of Jena | Seise E.,Friedrich - Schiller University of Jena | Andersen T.V.,NKT Photonics | And 6 more authors.
Optics Letters | Year: 2010

In this Letter we report on the generation of 830 W compressed average power from a femtosecond fiber chirped pulse amplification (CPA) system. In the high-power operation we achieved a compressor throughput of about 90% by using high-efficiency dielectric gratings. The output pulse duration of 640 fs at 78 MHz repetition rate results in a peak power of 12 MW. Additionally, we discuss further a scaling potential toward and beyond the kilowatt level by overcoming the current scaling limitations imposed by the transversal spatial hole burning. © 2010 Optical Society of America.

Laurila M.,Technical University of Denmark | Saby J.,EOlite Systems Inc. | Alkeskjold T.T.,NKT Photonics | Scolari L.,NKT Photonics | And 4 more authors.
Optics Express | Year: 2011

We demonstrate a Single-Mode (SM) Large-Mode-Area (LMA) ytterbium-doped PCF rod fiber laser with stable and close to diffraction limited beam quality with 110W output power. Distributed-Mode-Filtering (DMF) elements integrated in the cladding of the rod fiber provide a robust spatial mode with a Mode-Field-Diameter (MFD) of 59μm. We further demonstrate high pulse energy Second-Harmonic-Generation (SHG) and Third Harmonic Generation (THG) using a simple Q-switched single-stage rod fiber laser cavity architecture reaching pulse energies up to 1mJ at 515nm and 0.5mJ at 343nm. © 2011 Optical Society of America.

Alkeskjold T.T.,NKT Photonics | Laurila M.,Technical University of Denmark | Scolari L.,NKT Photonics | Broeng J.,NKT Photonics
Optics Express | Year: 2011

Enabling Single-Mode (SM) operation in Large-Mode-Area (LMA) fiber amplifiers and lasers is critical, since a SM output ensures high beam quality and excellent pointing stability. In this paper, we demonstrate and test a new design approach for achieving SM LMA rod fibers by using a photonic bandgap structure. The structure allows resonant coupling of higher-order modes from the core and acts as a spatially Distributed Mode Filter (DMF). With this approach, we demonstrate passive SM performance in an only ~50cm long and straight ytterbium-doped rod fiber. The amplifier has a mode field diameter of ∼59Lim at 1064nm and exhibits a pump absorption of 27dB/m at 976nm. © 2011 Optical Society of America.

Laurila M.,Technical University of Denmark | Jorgensen M.M.,NKT Photonics | Hansen K.R.,Technical University of Denmark | Alkeskjold T.T.,NKT Photonics | And 2 more authors.
Optics Express | Year: 2012

We demonstrate a high power fiber (85μm core) amplifier delivering up to 292Watts of average output power using a mode-locked 30ps source at 1032nm. Utilizing a single mode distributed mode filter bandgap rod fiber, we demonstrate 44% power improvement before the threshold-like onset of mode instabilities by operating the rod fiber in a leaky waveguide regime. We investigate the guiding dynamics of the rod fiber and report a distinct bandgap blue-shifting as function of increased signal power level. Furthermore, we theoretically analyze the guiding dynamics of the DMF rod fiber and explain the bandgap blue-shifting with thermally induced refractive index change of the refractive index profile. © 2012 Optical Society of America.

Jorgensen M.M.,Technical University of Denmark | Petersen S.R.,Technical University of Denmark | Laurila M.,Technical University of Denmark | Laegsgaard J.,Technical University of Denmark | Alkeskjold T.T.,NKT Photonics
Optics Express | Year: 2012

High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. Photonic crystal fibers allow realization of short LMA fiber amplifiers having high pump absorption through a pump cladding that is decoupled from the outer fiber diameter. However, achieving ultra low NA for single mode (SM) guidance is challenging, thus different design strategies must be applied. The distributed modal filtering (DMF) design enables SM guidance in ultra low NA fibers with very large cores, where large preform tolerances can be compensated during the fiber draw. Design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to previous results, achieved by utilizing the first band of cladding modes, which can cover a large fraction of the Yb emission band including wavelengths of 1030 nm and 1064 nm. Design parameters tolerating refractive index fabrication uncertainties of ± 10?4 are targeted to yield stable SM bandwidths. © 2012 Optical Society of America.

Moselund P.M.,NKT Photonics
Fiber Lasers and Applications, FILAS 2012 | Year: 2012

In this talk, we will present results on Mid-infrared supercontinuum generation using modelocked lasers. We will also discuss the challenges and potential applications of supercontinuum generation beyond the silica transmission window. © 2012 OSA.

Lovgreen S.,NKT Photonics
Laser Focus World | Year: 2014

NKT Photonics has been manufacturing low-noise, single-frequency, distributed-feedback (DFB) design fiber lasers that is essentially a short and robust laser cavity. The high Q value and the relatively long length of the DFB cavity, combined with long radiative lifetimes of rare earth ions in silica, provide for fundamentally low values of phase noise and spectral linewidth. Careful packaging design and use of low-noise pump sources reduce effects of vibrations and acoustic noise, and technical noise. Low-noise fiber lasers also play an important role in a new generation of wind-sensing light-detection-and- ranging (lidar) systems for meteorology, where the Doppler shift of light scattered by aerosols (Mie scattering) is used to indirectly measure wind velocity and turbulence by coherent homodyne detection. The NKT Photonics low-noise fiber lasers are designed to match the helium transition line at 1083 nm; the laser light pumps helium in the magnetometer, amplifying electronic magnetic resonance effects in the instrument.

Alkeskjold T.T.,NKT Photonics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

A Large-Mode Area (LMA) single-mode Ytterbium-doped fiber amplifier with distributed narrow passband filtering is demonstrated. The fiber passband is ~ 40nm wide and centered at 1070nm for efficient filtering of both short- and longwavelength Amplified Spontaneous Emission (ASE) as well as Stimulated Raman Scattering (SRS). The fiber design provides Higher-Order Mode (HOM) suppression and is polarization maintaining. It has a mode field diameter of 27μm and exhibits a slope efficiency of >60%. © 2010 Copyright SPIE - The International Society for Optical Engineering.

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