2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 2009
ABSTRACT A THz-system which can measure ultrashort THz-pulses simultaneously in transmission and ... more ABSTRACT A THz-system which can measure ultrashort THz-pulses simultaneously in transmission and in reflection under 0deg and off-axis under 15deg is presented. By combining the time resolved analysis of the three measurement directions, a high amount of information of the inner sample structure can be obtained. For first analysis concepts the main pulse amplitude and spectral information of transmittance measurements were evaluated.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
ABSTRACT We report on 790 nm diode pumped double clad Tm-fibre lasers with intracore high reflect... more ABSTRACT We report on 790 nm diode pumped double clad Tm-fibre lasers with intracore high reflective FBG. More than 40 W wavelength stabilized output power and slope efficiencies of > 40 % were achieved.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
ABSTRACT We demonstrate the optical inscription of quasi phase matching structures in x-cut lithi... more ABSTRACT We demonstrate the optical inscription of quasi phase matching structures in x-cut lithium niobate crystals. Using focussed ultrashort pulses, the nonlinear refractive index is periodically lowered, enabling frequency doubling of 1.55 micron infrared light.
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, 2013
ABSTRACT Volume Bragg gratings (VBGs) are optical divices exhibiting a periodic refractive index ... more ABSTRACT Volume Bragg gratings (VBGs) are optical divices exhibiting a periodic refractive index structure typically inside bulk glass. Due to their characteristics they can be employed for a wide range of applications such as beam combiners for e.g. fiber or solid state lasers, frequency stabilizers of semiconductor lasers or pulse compressors in case of chirped VBGs. Here we report on the measurement of the spectral Gouy shift by the help of a femtosecond written VBG. In the theory on Gaussian beams an additional phase term occurs which pays tribute to the propagation behavior of a Gaussian beam with respect to a plane wave. Thereby the beam adapts a longitudinal phase delay within the Rayleigh length. This so called Gouy phase shift can experimentally be measured when using a passive fiber and characterizing the reflection behavior of the VBG by adopting the fiber end facet to the grating. Measuring the reflected signal by the help of a circulator while changing the distance between fiber and grating end facet one is able to observe a spectral shift of the central wavelength of the reflected signal which can be attributed to the Gouy phase. To prove this assertion we carried out numerical/theoretical calculations which fit very well with our measurements.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
... Christian Voigtländer, Ria G. Becker, Jens Thomas, Daniel Richter, Andreas Tünnermann, and St... more ... Christian Voigtländer, Ria G. Becker, Jens Thomas, Daniel Richter, Andreas Tünnermann, and Stefan Nolte Friedrich-Schiller-Universität Jena: Institut für angewandte Physik, Max-Wien-Platz 1, D-07743 Jena ... Phys. A 86, 153-157 (2007). [4] VN Mahajan, “Zernike circle ...
2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 2009
For THz ultrashort pulse imaging a high scan speed in combination with a high signal/noise ratio ... more For THz ultrashort pulse imaging a high scan speed in combination with a high signal/noise ratio is required. Several methods have been presented to accelerate the classical one channel THz pulse detection. For example 2D electrooptic sampling provides a short scan time, but the signal/noise ratio is low and there is a need for an expensive low repetition fs-laser amplifier
Commercial and Biomedical Applications of Ultrafast Lasers IX, 2009
Self-imaging in integrated optical devices is interesting for many applications including image t... more Self-imaging in integrated optical devices is interesting for many applications including image transmission, optical collimation and even reshaping of ultrashort laser pulses. However, in general this relies on boundary-free light propagation, since interaction with boundaries results in a considerable distortion of the self-imaging effect. This problem can be overcome in waveguide arrays by segmentation of particular lattice sites, yielding phase shifts which result in image reconstruction in one- as well as two-dimensional configurations. Here, we demonstrate the first experimental realization of this concept. For the fabrication of the segmented waveguide arrays we used the femtosecond laser direct-writing technique. The total length of the arrays is 50mm with a waveguide spacing of 16 mum and 20mum in the one- and two-dimensional case, respectively. The length of the segmented area was 2.6mm, while the segmentation period was chosen to be 16 mum. This results in a complete inversion of the global phase of the travelling field inside the array, so that the evolution dynamics are reversed and the input field is imaged onto the sample output facet. Accordingly, segmented integrated optical devices provide a new and attractive opportunity for image transmission in finite systems.
Conference on Lasers and Electro-Optics 2010, 2010
We report on the first experimental observation of two-dimensional dynamic localization of light.... more We report on the first experimental observation of two-dimensional dynamic localization of light. We demonstrate suppression of beam diffraction in femtosecond laser-written modulated waveguide arrays of hexagonal and zig-zag geometries.
(CLEO). Conference on Lasers and Electro-Optics, 2005., 2005
We report on a novel ytterbium-doped fiber design which combines the advantages of rod and fiber ... more We report on a novel ytterbium-doped fiber design which combines the advantages of rod and fiber gain media. 120 W output power in single-mode beam quality are obtained from a 48 cm long fiber cane.
We present an experimental study on the drilling of metal targets with ultrashort laser pulses at... more We present an experimental study on the drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the drilling efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investig...
Supersymmetric (SUSY) optical structures display a number of intriguing properties that can lead ... more Supersymmetric (SUSY) optical structures display a number of intriguing properties that can lead to a variety of potential applications, ranging from perfect global phase matching to highly efficient mode conversion and novel multiplexing schemes. Here, we experimentally investigate the scattering characteristics of SUSY photonic lattices. We directly observe the light dynamics in such systems and compare the reflection/transmission properties of SUSY partner structures. In doing so, we demonstrate that discrete settings constitute a promising testbed for studying the different facets of optical supersymmetry.
We report on a 2.3 m long air-clad ytterbium-doped large-modearea photonic crystal fiber laser ge... more We report on a 2.3 m long air-clad ytterbium-doped large-modearea photonic crystal fiber laser generating up to 80 W output power with a slope efficiency of 78%. Single transverse mode operation is achieved with a mode-field area of 350 microm2. No thermo-optical limitations are observed at the extracted ~35W/m, therefore such fibers allow scaling to even higher powers.
ABSTRACT We present a compact monolithic all-phosphate fiber laser with more than 500 mW single-f... more ABSTRACT We present a compact monolithic all-phosphate fiber laser with more than 500 mW single-frequency output power. The laser cavity was formed through direct inscription of fiber Bragg gratings into highly Er:Yb doped phosphate fiber using femtosecond laser pulses.
ABSTRACT We present a VBG inscribed in fused silica by three beam interference of fs pulses. The ... more ABSTRACT We present a VBG inscribed in fused silica by three beam interference of fs pulses. The generated twodimensional grating structure exhibits a discrete diffraction pattern which can be described based on the Ewald sphere.
2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 2009
ABSTRACT A THz-system which can measure ultrashort THz-pulses simultaneously in transmission and ... more ABSTRACT A THz-system which can measure ultrashort THz-pulses simultaneously in transmission and in reflection under 0deg and off-axis under 15deg is presented. By combining the time resolved analysis of the three measurement directions, a high amount of information of the inner sample structure can be obtained. For first analysis concepts the main pulse amplitude and spectral information of transmittance measurements were evaluated.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
ABSTRACT We report on 790 nm diode pumped double clad Tm-fibre lasers with intracore high reflect... more ABSTRACT We report on 790 nm diode pumped double clad Tm-fibre lasers with intracore high reflective FBG. More than 40 W wavelength stabilized output power and slope efficiencies of > 40 % were achieved.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
ABSTRACT We demonstrate the optical inscription of quasi phase matching structures in x-cut lithi... more ABSTRACT We demonstrate the optical inscription of quasi phase matching structures in x-cut lithium niobate crystals. Using focussed ultrashort pulses, the nonlinear refractive index is periodically lowered, enabling frequency doubling of 1.55 micron infrared light.
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, 2013
ABSTRACT Volume Bragg gratings (VBGs) are optical divices exhibiting a periodic refractive index ... more ABSTRACT Volume Bragg gratings (VBGs) are optical divices exhibiting a periodic refractive index structure typically inside bulk glass. Due to their characteristics they can be employed for a wide range of applications such as beam combiners for e.g. fiber or solid state lasers, frequency stabilizers of semiconductor lasers or pulse compressors in case of chirped VBGs. Here we report on the measurement of the spectral Gouy shift by the help of a femtosecond written VBG. In the theory on Gaussian beams an additional phase term occurs which pays tribute to the propagation behavior of a Gaussian beam with respect to a plane wave. Thereby the beam adapts a longitudinal phase delay within the Rayleigh length. This so called Gouy phase shift can experimentally be measured when using a passive fiber and characterizing the reflection behavior of the VBG by adopting the fiber end facet to the grating. Measuring the reflected signal by the help of a circulator while changing the distance between fiber and grating end facet one is able to observe a spectral shift of the central wavelength of the reflected signal which can be attributed to the Gouy phase. To prove this assertion we carried out numerical/theoretical calculations which fit very well with our measurements.
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
... Christian Voigtländer, Ria G. Becker, Jens Thomas, Daniel Richter, Andreas Tünnermann, and St... more ... Christian Voigtländer, Ria G. Becker, Jens Thomas, Daniel Richter, Andreas Tünnermann, and Stefan Nolte Friedrich-Schiller-Universität Jena: Institut für angewandte Physik, Max-Wien-Platz 1, D-07743 Jena ... Phys. A 86, 153-157 (2007). [4] VN Mahajan, “Zernike circle ...
2009 34th International Conference on Infrared, Millimeter, and Terahertz Waves, 2009
For THz ultrashort pulse imaging a high scan speed in combination with a high signal/noise ratio ... more For THz ultrashort pulse imaging a high scan speed in combination with a high signal/noise ratio is required. Several methods have been presented to accelerate the classical one channel THz pulse detection. For example 2D electrooptic sampling provides a short scan time, but the signal/noise ratio is low and there is a need for an expensive low repetition fs-laser amplifier
Commercial and Biomedical Applications of Ultrafast Lasers IX, 2009
Self-imaging in integrated optical devices is interesting for many applications including image t... more Self-imaging in integrated optical devices is interesting for many applications including image transmission, optical collimation and even reshaping of ultrashort laser pulses. However, in general this relies on boundary-free light propagation, since interaction with boundaries results in a considerable distortion of the self-imaging effect. This problem can be overcome in waveguide arrays by segmentation of particular lattice sites, yielding phase shifts which result in image reconstruction in one- as well as two-dimensional configurations. Here, we demonstrate the first experimental realization of this concept. For the fabrication of the segmented waveguide arrays we used the femtosecond laser direct-writing technique. The total length of the arrays is 50mm with a waveguide spacing of 16 mum and 20mum in the one- and two-dimensional case, respectively. The length of the segmented area was 2.6mm, while the segmentation period was chosen to be 16 mum. This results in a complete inversion of the global phase of the travelling field inside the array, so that the evolution dynamics are reversed and the input field is imaged onto the sample output facet. Accordingly, segmented integrated optical devices provide a new and attractive opportunity for image transmission in finite systems.
Conference on Lasers and Electro-Optics 2010, 2010
We report on the first experimental observation of two-dimensional dynamic localization of light.... more We report on the first experimental observation of two-dimensional dynamic localization of light. We demonstrate suppression of beam diffraction in femtosecond laser-written modulated waveguide arrays of hexagonal and zig-zag geometries.
(CLEO). Conference on Lasers and Electro-Optics, 2005., 2005
We report on a novel ytterbium-doped fiber design which combines the advantages of rod and fiber ... more We report on a novel ytterbium-doped fiber design which combines the advantages of rod and fiber gain media. 120 W output power in single-mode beam quality are obtained from a 48 cm long fiber cane.
We present an experimental study on the drilling of metal targets with ultrashort laser pulses at... more We present an experimental study on the drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the drilling efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investig...
Supersymmetric (SUSY) optical structures display a number of intriguing properties that can lead ... more Supersymmetric (SUSY) optical structures display a number of intriguing properties that can lead to a variety of potential applications, ranging from perfect global phase matching to highly efficient mode conversion and novel multiplexing schemes. Here, we experimentally investigate the scattering characteristics of SUSY photonic lattices. We directly observe the light dynamics in such systems and compare the reflection/transmission properties of SUSY partner structures. In doing so, we demonstrate that discrete settings constitute a promising testbed for studying the different facets of optical supersymmetry.
We report on a 2.3 m long air-clad ytterbium-doped large-modearea photonic crystal fiber laser ge... more We report on a 2.3 m long air-clad ytterbium-doped large-modearea photonic crystal fiber laser generating up to 80 W output power with a slope efficiency of 78%. Single transverse mode operation is achieved with a mode-field area of 350 microm2. No thermo-optical limitations are observed at the extracted ~35W/m, therefore such fibers allow scaling to even higher powers.
ABSTRACT We present a compact monolithic all-phosphate fiber laser with more than 500 mW single-f... more ABSTRACT We present a compact monolithic all-phosphate fiber laser with more than 500 mW single-frequency output power. The laser cavity was formed through direct inscription of fiber Bragg gratings into highly Er:Yb doped phosphate fiber using femtosecond laser pulses.
ABSTRACT We present a VBG inscribed in fused silica by three beam interference of fs pulses. The ... more ABSTRACT We present a VBG inscribed in fused silica by three beam interference of fs pulses. The generated twodimensional grating structure exhibits a discrete diffraction pattern which can be described based on the Ewald sphere.
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Papers by Stefan Nolte