The Experts below are selected from a list of 1077 Experts worldwide ranked by ideXlab platform
Hartmut Bartelt - One of the best experts on this subject based on the ideXlab platform.
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Optimisation of fibre Bragg Gratings Inscription in multicore fibres
26th International Conference on Optical Fiber Sensors, 2018Co-Authors: Ravil Idrisov, Jorg Bierlich, Martin Becker, Manfred Rothhardt, Hartmut BarteltAbstract:Fibre Bragg Gratings in multicore optical fibres are attractive sensing elements for multiplexed measurements (e.g. shape sensing). In order to achieve optimized uniformity in the Grating Inscription, a setup with control of orientation was applied.
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Fiber Bragg Grating Inscription in optical multicore fibers
24th International Conference on Optical Fibre Sensors, 2015Co-Authors: Martin Becker, Sebastian Dochow, Ines Latka, Adrian Lorenz, Kay Schuster, Tino Elsmann, Ron Spittel, Jens Kobelke, Manfred Rothhardt, Hartmut BarteltAbstract:Fiber Bragg Gratings as key components in telecommunication, fiber lasers, and sensing systems usually rely on the Bragg condition for single mode fibers. In special applications, such as in biophotonics and astrophysics, high light coupling efficiency is of great importance and therefore, multimode fibers are often preferred. The wavelength filtering effect of Bragg Gratings in multimode fibers, however is spectrally blurred over a wide modal spectrum of the fiber. With a well-designed all solid multicore microstructured fiber a good light guiding efficiency in combination with narrow spectral filtering effect by Bragg Gratings becomes possible.
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Grating Inscription with two-beam interferometry and non-homogeneous beam-splitter
Advanced Photonics, 2014Co-Authors: Martin Becker, Tino Elsmann, Manfred Rothhardt, Hartmut BarteltAbstract:We present a phase-mask interferometer for fiber Bragg Grating Inscription which uses a phase-mask as non-homogeneous beam-splitter. It allows writing continously chirped fiber Bragg Gratings while maintaining the wavelength versatility.
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160W single-mode single-frequency Yb-doped fiber laser with fiber Bragg Grating inscribed by UV femtosecond exposure and two beam interference
Photonics North 2011, 2011Co-Authors: Martin Becker, Sven Brückner, Manfred Rothhardt, Eric Lindner, Sonja Unger, Martin Leich, Hartmut BarteltAbstract:Fiber Bragg Gratings (FBGs) are attractive as reflector elements in fully integrated all-fiber laser systems. Furthermore, FBGs made with femtosecond laser technology allow to reduce splice connections in the fiber, since no special photosensitive fibers are required. Fiber Bragg Grating Inscription with deep ultraviolet femtosecond laser (267 nm) and two beam interferometry allows to target germanium-free and non-photosensitive fibers while maintaining versatility in the choice of the output wavelength of the fiber laser. This concept offers the potential of Gratings with high spatial resolution, great flexibility and good homogeneity and complements the methods of point-by-point Inscription at 800 nm or of phase-mask Inscription with 400 nm femtosecond laser exposure. We report on the application of the interferometric fiber Bragg Grating Inscription technology to build a Grating-stabilized fiber laser with high beam purity. Output powers up 160 W have been achieved.
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Towards a monolithic fiber laser with deep UV femtosecond-induced fiber Bragg Gratings
Optics Communications, 2011Co-Authors: Martin Becker, Sven Brückner, Manfred Rothhardt, Eric Lindner, Sonja Unger, Martin Leich, Sylvia Jetschke, Hartmut BarteltAbstract:Abstract Fiber Bragg Grating Inscription with a deep ultraviolet (DUV) femtosecond laser and two-beam interferometry allows Grating Inscription in germanium-free fibers without classical UV photosensitivity. Therefore such a writing technology is a promising solution for the fabrication of fiber Bragg Gratings in the active fiber material to realize a fully integrated all-fiber solution. In this paper we report on the use of the DUV femtosecond laser fiber Bragg Grating technology to build a Grating-stabilized fiber laser with high spectral purity. Output powers up to 158 W at 1083 nm and a slope efficiency of 76% have been demonstrated.
Martin Becker - One of the best experts on this subject based on the ideXlab platform.
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Fiber Bragg Grating Inscription in Multicore and Speciality Optical Fibers
Advanced Photonics 2018 (BGPP IPR NP NOMA Sensors Networks SPPCom SOF), 2018Co-Authors: Martin Becker, Tino Elsmann, Manfred RothhardtAbstract:Fiber Bragg Gratings are powerful tools for sensing and telecommunication, but applications in spectroscopy (astronomy and biophotonics) and fiber lasers require the use of fibers with increased etendue to guide an increased amount of light. On the other hand, the amount of light that can be guided in an optical fiber is linked to the supported amount of guided modes which changes filtering performance of the Bragg Gratings essentially. Additionally, special applications require fibers without Germanium doping. In this case, updated concepts of photosensitivity are required. Therefore, several aspects have to be taken into account when Bragg filters are applied where the amount of guided light is essential.
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Optimisation of fibre Bragg Gratings Inscription in multicore fibres
26th International Conference on Optical Fiber Sensors, 2018Co-Authors: Ravil Idrisov, Jorg Bierlich, Martin Becker, Manfred Rothhardt, Hartmut BarteltAbstract:Fibre Bragg Gratings in multicore optical fibres are attractive sensing elements for multiplexed measurements (e.g. shape sensing). In order to achieve optimized uniformity in the Grating Inscription, a setup with control of orientation was applied.
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Fiber Bragg Grating Inscription in optical multicore fibers
24th International Conference on Optical Fibre Sensors, 2015Co-Authors: Martin Becker, Sebastian Dochow, Ines Latka, Adrian Lorenz, Kay Schuster, Tino Elsmann, Ron Spittel, Jens Kobelke, Manfred Rothhardt, Hartmut BarteltAbstract:Fiber Bragg Gratings as key components in telecommunication, fiber lasers, and sensing systems usually rely on the Bragg condition for single mode fibers. In special applications, such as in biophotonics and astrophysics, high light coupling efficiency is of great importance and therefore, multimode fibers are often preferred. The wavelength filtering effect of Bragg Gratings in multimode fibers, however is spectrally blurred over a wide modal spectrum of the fiber. With a well-designed all solid multicore microstructured fiber a good light guiding efficiency in combination with narrow spectral filtering effect by Bragg Gratings becomes possible.
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Grating Inscription with two-beam interferometry and non-homogeneous beam-splitter
Advanced Photonics, 2014Co-Authors: Martin Becker, Tino Elsmann, Manfred Rothhardt, Hartmut BarteltAbstract:We present a phase-mask interferometer for fiber Bragg Grating Inscription which uses a phase-mask as non-homogeneous beam-splitter. It allows writing continously chirped fiber Bragg Gratings while maintaining the wavelength versatility.
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160W single-mode single-frequency Yb-doped fiber laser with fiber Bragg Grating inscribed by UV femtosecond exposure and two beam interference
Photonics North 2011, 2011Co-Authors: Martin Becker, Sven Brückner, Manfred Rothhardt, Eric Lindner, Sonja Unger, Martin Leich, Hartmut BarteltAbstract:Fiber Bragg Gratings (FBGs) are attractive as reflector elements in fully integrated all-fiber laser systems. Furthermore, FBGs made with femtosecond laser technology allow to reduce splice connections in the fiber, since no special photosensitive fibers are required. Fiber Bragg Grating Inscription with deep ultraviolet femtosecond laser (267 nm) and two beam interferometry allows to target germanium-free and non-photosensitive fibers while maintaining versatility in the choice of the output wavelength of the fiber laser. This concept offers the potential of Gratings with high spatial resolution, great flexibility and good homogeneity and complements the methods of point-by-point Inscription at 800 nm or of phase-mask Inscription with 400 nm femtosecond laser exposure. We report on the application of the interferometric fiber Bragg Grating Inscription technology to build a Grating-stabilized fiber laser with high beam purity. Output powers up 160 W have been achieved.
Manfred Rothhardt - One of the best experts on this subject based on the ideXlab platform.
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Optimisation of fibre Bragg Gratings Inscription in multicore fibres
26th International Conference on Optical Fiber Sensors, 2018Co-Authors: Ravil Idrisov, Jorg Bierlich, Martin Becker, Manfred Rothhardt, Hartmut BarteltAbstract:Fibre Bragg Gratings in multicore optical fibres are attractive sensing elements for multiplexed measurements (e.g. shape sensing). In order to achieve optimized uniformity in the Grating Inscription, a setup with control of orientation was applied.
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Fiber Bragg Grating Inscription in Multicore and Speciality Optical Fibers
Advanced Photonics 2018 (BGPP IPR NP NOMA Sensors Networks SPPCom SOF), 2018Co-Authors: Martin Becker, Tino Elsmann, Manfred RothhardtAbstract:Fiber Bragg Gratings are powerful tools for sensing and telecommunication, but applications in spectroscopy (astronomy and biophotonics) and fiber lasers require the use of fibers with increased etendue to guide an increased amount of light. On the other hand, the amount of light that can be guided in an optical fiber is linked to the supported amount of guided modes which changes filtering performance of the Bragg Gratings essentially. Additionally, special applications require fibers without Germanium doping. In this case, updated concepts of photosensitivity are required. Therefore, several aspects have to be taken into account when Bragg filters are applied where the amount of guided light is essential.
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Fiber Bragg Grating Inscription in optical multicore fibers
24th International Conference on Optical Fibre Sensors, 2015Co-Authors: Martin Becker, Sebastian Dochow, Ines Latka, Adrian Lorenz, Kay Schuster, Tino Elsmann, Ron Spittel, Jens Kobelke, Manfred Rothhardt, Hartmut BarteltAbstract:Fiber Bragg Gratings as key components in telecommunication, fiber lasers, and sensing systems usually rely on the Bragg condition for single mode fibers. In special applications, such as in biophotonics and astrophysics, high light coupling efficiency is of great importance and therefore, multimode fibers are often preferred. The wavelength filtering effect of Bragg Gratings in multimode fibers, however is spectrally blurred over a wide modal spectrum of the fiber. With a well-designed all solid multicore microstructured fiber a good light guiding efficiency in combination with narrow spectral filtering effect by Bragg Gratings becomes possible.
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high temperature sensing with fiber bragg Gratings in sapphire derived all glass optical fibers
Optics Express, 2014Co-Authors: Tino Elsmann, Adrian Lorenz, Nazila Safari Yazd, Jorg Bierlich, Kay Schuster, Tobias Habisreuther, Anka Schwuchow, Jan Dellith, Manfred Rothhardt, Ladislav KidoAbstract:A structured sapphire-derived all-glass optical fiber with an aluminum content in the core of up to 50 mol% was used for fiber Bragg Grating Inscription. The fiber provided a parabolic refractive index profile. Fiber Bragg Gratings were inscribed by means of femtosecond-laser pulses with a wavelength of 400 nm in combination with a two-beam phase mask interferometer. Heating experiments demonstrated the stability of the Gratings for temperatures up to 950°C for more than 24 h without degradation in reflectivity.
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Grating Inscription with two-beam interferometry and non-homogeneous beam-splitter
Advanced Photonics, 2014Co-Authors: Martin Becker, Tino Elsmann, Manfred Rothhardt, Hartmut BarteltAbstract:We present a phase-mask interferometer for fiber Bragg Grating Inscription which uses a phase-mask as non-homogeneous beam-splitter. It allows writing continously chirped fiber Bragg Gratings while maintaining the wavelength versatility.
Francis Berghmans - One of the best experts on this subject based on the ideXlab platform.
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Phase-shifted Bragg Grating Inscription in photonic crystal fibers by UV phase mask beam stop technique
Micro-Structured and Specialty Optical Fibres VI, 2020Co-Authors: Olga Rusyakina, Tigran Baghdasaryan, Hugo Thienpont, Francis Berghmans, Maria Konstantaki, Stavros Pissadakis, Pawel Mergo, Mariusz Makara, Thomas GeernaertAbstract:There are several techniques available for fabrication of phase-shifted Gratings in single mode fibers. Yet, very few studies have examined Inscription of such Gratings in photonic crystal fibers (PCFs). In this paper, we report what we believe to be the first demonstration of the phase-shifted Grating Inscription in PCFs using a phase mask and a beam stop. The Grating Inscription is demonstrated for three hexagonal lattice PCFs with different air-filling fractions. The transmission spectra of the fabricated Gratings reveal phase shift resonance peaks with a -3 dB bandwidth between 40 and 80 pm which is up to 4 times narrower than of the resonances of uniform Bragg Gratings inscribed in the same fibers.
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Numerical and Experimental Study on the IR Femtosecond Laser and Phase Mask-Based Grating Inscription in Photonic Crystal Fibers
2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO Europe-EQEC), 2019Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Pawel Mergo, Mariusz Makara, Adriana Morana, Emmanuel Marin, Sylvain Girard, Francis BerghmansAbstract:Femtosecond pulse laser sources enable the fabrication of fiber Bragg Gratings (FBGs) in non-photosensitive fibers, allow for through coating Grating Inscription when working at infrared (IR) wavelengths and can provide for high temperature stable Gratings. Target applications for such Gratings include, but are not limited to, optical communications, fiber lasers and fiber sensing.
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ir femtosecond pulsed laser based fiber bragg Grating Inscription in a photonic crystal fiber using a phase mask and a short focal length lens
Optics Express, 2018Co-Authors: Tigran Baghdasaryan, Hugo Thienpont, Pawel Mergo, Mariusz Makara, Adriana Morana, Emmanuel Marin, Sylvain Girard, Thomas Geernart, Francis BerghmansAbstract:Fiber Bragg Grating Inscription with infrared femtosecond pulsed lasers in photonic crystal fiber is far from being trivial due to the presence of air holes in the cladding region and the non-linear nature of the absorption process inducing the required refractive index changes. We have studied this problem numerically and experimentally for a phase mask-based writing setup equipped with short focal length cylindrical lenses, which are often used for through-coating and high temperature stable Grating writing. We have shown that for a cylindrical lens with a focal length f of 10 mm, the hexagonal lattice PCF needs to be translated away from the beam waist position by around 15 µm to efficiently deliver the energy to the core region. We have also investigated the importance of the PCF’s angular orientation and we have shown that for some optimal positions the same behavior is observed for cylindrical lenses with different focal lengths. Finally, we have succeeded in writing a 4 dB strong Grating in a photonic crystal fiber with a 1030 nm femtosecond pulsed laser in around 4 seconds, using an acylindrical lens with f = 10 mm.
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Highly birefringent photonic crystal fiber compatible with IR femtosecond Grating Inscription methods
Advanced Photonics 2018 (BGPP IPR NP NOMA Sensors Networks SPPCom SOF), 2018Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Francis BerghmansAbstract:We designed a hexagonal lattice highly birefringent photonic crystal fiber that allows for infrared femtosecond pulse laser-based fiber Bragg Grating Inscription, using both point-by-point and phase mask-based methods.
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A numerical study on the importance of non-uniform index modification during femtosecond Grating Inscription in microstructured optical fibers
Micro-Structured and Specialty Optical Fibres IV, 2016Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Francis BerghmansAbstract:Fiber Bragg Grating (FBG) Inscription methods based on femtosecond laser sources are becoming increasingly popular owing to the (usually) non-linear nature of the index modification mechanism and to the resulting advantages. They allow, for example, fabricating fiber Gratings that can survive temperatures exceeding 700°C, which can be an asset in the domain of fiber sensing. However applying femtosecond laser based Grating fabrication to microstructured optical fibers (MOFs) can be challenging due to the presence of the air holes in the fiber cladding. The microstructured cladding not only impedes light delivery to the core in most cases, but also causes a non-uniform intensity distribution in the MOF core. To deal with these challenges we present a modeling approach that allows simulating how the reflectivity of the Grating and the nature of the index modulation are affected by the Inscription conditions. We rely on transverse coupling simulations, empirical data and coupled mode analysis to model the induced index change and the resulting Grating reflectivity. For IR femtosecond Grating Inscription we show that due to the intensity redistribution in the core region, irreversible Type II index changes can be induced in a MOF at laser peak intensities below the Type II threshold for step-index fibers. The resulting non-uniform induced index change has repercussions on the reflection spectrum of the Grating as well. Our coupled mode analysis reveals, for example, that although the average index change in the core region can be high, the partial overlap of the core mode with the index change region limits the reflectivity of the Grating.
Thomas Geernaert - One of the best experts on this subject based on the ideXlab platform.
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Phase-shifted Bragg Grating Inscription in photonic crystal fibers by UV phase mask beam stop technique
Micro-Structured and Specialty Optical Fibres VI, 2020Co-Authors: Olga Rusyakina, Tigran Baghdasaryan, Hugo Thienpont, Francis Berghmans, Maria Konstantaki, Stavros Pissadakis, Pawel Mergo, Mariusz Makara, Thomas GeernaertAbstract:There are several techniques available for fabrication of phase-shifted Gratings in single mode fibers. Yet, very few studies have examined Inscription of such Gratings in photonic crystal fibers (PCFs). In this paper, we report what we believe to be the first demonstration of the phase-shifted Grating Inscription in PCFs using a phase mask and a beam stop. The Grating Inscription is demonstrated for three hexagonal lattice PCFs with different air-filling fractions. The transmission spectra of the fabricated Gratings reveal phase shift resonance peaks with a -3 dB bandwidth between 40 and 80 pm which is up to 4 times narrower than of the resonances of uniform Bragg Gratings inscribed in the same fibers.
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Numerical and Experimental Study on the IR Femtosecond Laser and Phase Mask-Based Grating Inscription in Photonic Crystal Fibers
2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO Europe-EQEC), 2019Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Pawel Mergo, Mariusz Makara, Adriana Morana, Emmanuel Marin, Sylvain Girard, Francis BerghmansAbstract:Femtosecond pulse laser sources enable the fabrication of fiber Bragg Gratings (FBGs) in non-photosensitive fibers, allow for through coating Grating Inscription when working at infrared (IR) wavelengths and can provide for high temperature stable Gratings. Target applications for such Gratings include, but are not limited to, optical communications, fiber lasers and fiber sensing.
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Highly birefringent photonic crystal fiber compatible with IR femtosecond Grating Inscription methods
Advanced Photonics 2018 (BGPP IPR NP NOMA Sensors Networks SPPCom SOF), 2018Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Francis BerghmansAbstract:We designed a hexagonal lattice highly birefringent photonic crystal fiber that allows for infrared femtosecond pulse laser-based fiber Bragg Grating Inscription, using both point-by-point and phase mask-based methods.
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A numerical study on the importance of non-uniform index modification during femtosecond Grating Inscription in microstructured optical fibers
Micro-Structured and Specialty Optical Fibres IV, 2016Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Francis BerghmansAbstract:Fiber Bragg Grating (FBG) Inscription methods based on femtosecond laser sources are becoming increasingly popular owing to the (usually) non-linear nature of the index modification mechanism and to the resulting advantages. They allow, for example, fabricating fiber Gratings that can survive temperatures exceeding 700°C, which can be an asset in the domain of fiber sensing. However applying femtosecond laser based Grating fabrication to microstructured optical fibers (MOFs) can be challenging due to the presence of the air holes in the fiber cladding. The microstructured cladding not only impedes light delivery to the core in most cases, but also causes a non-uniform intensity distribution in the MOF core. To deal with these challenges we present a modeling approach that allows simulating how the reflectivity of the Grating and the nature of the index modulation are affected by the Inscription conditions. We rely on transverse coupling simulations, empirical data and coupled mode analysis to model the induced index change and the resulting Grating reflectivity. For IR femtosecond Grating Inscription we show that due to the intensity redistribution in the core region, irreversible Type II index changes can be induced in a MOF at laser peak intensities below the Type II threshold for step-index fibers. The resulting non-uniform induced index change has repercussions on the reflection spectrum of the Grating as well. Our coupled mode analysis reveals, for example, that although the average index change in the core region can be high, the partial overlap of the core mode with the index change region limits the reflectivity of the Grating.
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Opportunities for designing microstructured optical fibers for efficient femtosecond laser Grating Inscription
Optical Components and Materials XII, 2015Co-Authors: Tigran Baghdasaryan, Thomas Geernaert, Hugo Thienpont, Francis BerghmansAbstract:Microstructured optical fibers (MOFs) are a major achievement in the field of optical fiber technology. Owing to their unprecedented design flexibility, MOFs have found numerous applications in various fields of photonics. By adapting the parameters of the holey cladding, MOFs with tailored dispersion properties, large mode area, endlessly single mode operation and high non-linear response can be designed and fabricated. This paper deals with designing MOFs with a specific microstructure that would allow increasing the efficiency with which fiber Gratings can be photo-inscribed in a MOF. The air holes are usually impeding the delivery of optical power to the core region, which results in a lower Grating writing efficiency. This problem is exacerbated when using IR femtosecond laser sources for the Inscription, as the induced refractive index changes stem from a highly non-linear multi-photon absorption process and are hence very dependent on the optical intensity that actually reaches the MOF core. In this paper we first study regular hexagonal lattice MOFs to find a range of lattice parameters that would facilitate femtosecond Grating Inscription, considering the non-linear nature of the index change. To assess the influence of the microstructured cladding on the transverse delivery of light to the core region, we introduce a figure of merit to which we refer as ‘transverse coupling efficiency’ (TCE). Second, we evaluate the index changes that would be obtained when implementing a special type of holey structure that acts as a transversely focusing microstructure – known as Mikaelian lens – in the cladding of the MOF.
