jean-paul yehouessi - Academia.edu (original) (raw)

Papers by jean-paul yehouessi

Research paper thumbnail of Sub-150 fs all-fiber polarization maintaining tunable laser in the mid-infrared

Fiber Lasers XVII: Technology and Systems

Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously gr... more Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously growing for many applications. Mode-locked Holmium- or Thulium-doped fiber lasers based on Saturable Absorber Mirror (SAM) are typically the first approach to generate pulses in this spectral range but this technique suffers from a lack of tunability. Indeed, the operating wavelength is fixed by the SAM and the gain fiber. Another way to reach the 2 μm-spectral range consists to exploit the nonlinear phenomena appearing in optical fibers and in particular the Soliton-Self Frequency Shift (SSFS) effect from an Erbium-fiber laser. Several systems based on this phenomenon allowed the generation of ultrashort pulses at different wavelengths and in different type of fibers (step-index, PCF, …). In this paper, we report on the design of a compact and robust all-Polarization-Maintaining (PM) fiber system entirely based on commercial PM components. This system allows to generate a single femtosecond pulse continuously tunable from 1700 nm to 2050 nm. We also demonstrate that the sub-150 fs pulses are transform-limited over all the spectral range and thanks to an optimized rate conversion close to 50 %, the pulse energy and the peak power can reach the nJclass and the kW-class respectively, which represents a gain of a factor 2 compared to the previous works.

Research paper thumbnail of Synchronized all-PM-fiber Yb-doped amplifiers for high power fs- and ps-pulse generation

Research paper thumbnail of Sub-50 fs 3.5 nJ pulses at 792 nm generated by frequency doubling of an all-PM fiber laser for Ti:sapphire injection

Fiber Lasers XVI: Technology and Systems

Frequency doubled sub 50 fs Erbium-fiber lasers are ideal tool used to seed Ti:sapphire amplifier... more Frequency doubled sub 50 fs Erbium-fiber lasers are ideal tool used to seed Ti:sapphire amplifier. Therefore, over last decade large number of all-fiber laser architecture has been reported for such application. Nevertheless, the emitted pulses are usually too long due to the gain bandwidth of Erbium or the laser architecture is not made with Polarization Maintaining (PM) fibers which will be a limitation for frequency doubling. We demonstrate a new design of an all-PM erbium doped fiber laser emitting sub 50 fs pulses with high pulse energy and we study its frequency doubling. Our architecture is based on a concatenation of three amplifiers having different group velocity dispersion. These amplifiers provide numerous degrees of freedom allowing to control the output pulse duration. Thanks to this new design, the laser produces 14 nJ pulse with a duration of 48 fs and an average power of 560 mW. This is to the best of our knowledge the shortest pulse duration with an energy higher than 10 nJ emitted by an all-fiber laser around 1.5-1.6 μm. The pulses are further converted by Second Harmonic Generation to 796 nm with an efficiency of 25 %. The average power of the doubled signal is 140 mW with 3.5 nJ pulse energy. The nonlinear crystal has been carefully chosen in order to cover all the spectral bandwidth of the pump and to ensure a sub 50 fs pulse at 796 nm.

Research paper thumbnail of 200-W single frequency laser based on short active double clad tapered fiber

Fiber Lasers XV: Technology and Systems

High power single frequency lasers are very attractive for a wide range of applications such as n... more High power single frequency lasers are very attractive for a wide range of applications such as nonlinear conversion, gravitational wave sensing or atom trapping. Power scaling in single frequency regime is a challenging domain of research. In fact, nonlinear effect as stimulated Brillouin scattering (SBS) is the primary power limitation in single frequency amplifiers. To mitigate SBS, different well-known techniques has been improved. These techniques allow generation of several hundred of watts [1]. Large mode area (LMA) fibers, transverse acoustically tailored fibers [2], coherent beam combining and also tapered fiber [3] seem to be serious candidates to continue the power scaling. We have demonstrated the generation of stable 200W output power with nearly diffraction limited output, and narrow linewidth (Δν<30kHz) by using a tapered Yb-doped fiber which allow an adiabatic transition from a small purely single mode input to a large core output.

Research paper thumbnail of nJ-class all-PM fiber tunable femtosecond laser from 1800 nm to 2050 nm via a highly efficient SSFS

Fiber Lasers and Glass Photonics: Materials through Applications II

Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously gr... more Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously growing for many applications. Mode-locked Holmium- or Thulium-doped fiber lasers based on Saturable Absorber Mirror (SAM) are typically the first approach to generate pulses in this spectral range but this technique suffers from a lack of tunability. Indeed, the operating wavelength is fixed by the SAM and the gain fiber. Another way to reach the 2 μm-spectral range consists to exploit the nonlinear phenomena appearing in optical fibers and in particular the Soliton-Self Frequency Shift (SSFS) effect from an Erbium-fiber laser. Several systems based on this phenomenon allowed the generation of ultrashort pulses at different wavelengths and in different type of fibers (step-index, PCF, …). In this paper, we report on the design of a compact and robust all-Polarization-Maintaining (PM) fiber system entirely based on commercial PM components. This system allows to generate a single femtosecond pulse continuously tunable from 1700 nm to 2050 nm. We also demonstrate that the sub-150 fs pulses are transform-limited over all the spectral range and thanks to an optimized rate conversion close to 50 %, the pulse energy and the peak power can reach the nJclass and the kW-class respectively, which represents a gain a of factor 2 compared to the previous works.

Research paper thumbnail of Modeling and characterization of pixelated bragg fibers for intense lasers application

Ces travaux portent sur la réalisation de fibres optiques à très grandes aires effectives pour ap... more Ces travaux portent sur la réalisation de fibres optiques à très grandes aires effectives pour applications aux lasers intenses. Les applications possibles de ces fibres sont le transport ou la génération de puissants faisceaux lasers. En se basant sur la famille de fibre optique appelée : "fibre de Bragg pixélisée", nous avons introduit le concept de double conditions demi-onde appliquée au mode d’ordre supérieur afin d’augmenter les pertes des modes LP11, LP21, LP02. Le principe d’hétérostructuration quant à lui a permis d’accentuer les pertes des modes d’ordre supérieur grâce à un effet de fuite. Ainsi donc, nous avons réalisé une fibre ayant un diamètre de cœur de 48 µm qui a permis l’obtention d’un diamètre de mode de 40 µm à la longueur d’onde 1050 nm. Dans un second temps, une géométrie de gaine plus simplifiée est proposée. Cette nouvelle géométrie de gaine nous a permis d’accéder à des diamètres de modes allant de 47 µm à 69 µm dans le cas de fibre à bande interdi...

Research paper thumbnail of Polarizing Large Mode Area Photonic BandGap Fiber

Conference on Lasers and Electro-Optics, Jun 21, 2015

Research paper thumbnail of 1.1 W all-PM fiber laser at 1600 nm delivering 35 fs pulses with 30 nJ energy

Laser Congress 2019 (ASSL, LAC, LS&C), 2019

We report an all-PM fiber laser based on a mode-locked seeder and only two amplification stages d... more We report an all-PM fiber laser based on a mode-locked seeder and only two amplification stages delivering 35 fs pulses with an energy of 30nJ and an average power of 1.13 W at telecom wavelength.

Research paper thumbnail of 3 W Mid-IR supercontinuum extended up to 4.6 µm based on an all-PM thulium doped fiber gain-switch laser seeding an InF3 fiber

Nonlinear Frequency Generation and Conversion: Materials and Devices XVIII, 2019

We report on a 3 W Mid-IR supercontinuum extended up to 4.6 μm based on an all-PM thulium doped f... more We report on a 3 W Mid-IR supercontinuum extended up to 4.6 μm based on an all-PM thulium doped fiber gainswitched laser seeding an InF3 fiber. This innovative fiber presents a specific design that increases non-linear effects and shows very weak background losses. Thanks to the versatility of our gain-switched laser, all the pulse parameters have been widely optimized to generate a supercontinuum emission with the highest average power and the largest spectrum.

Research paper thumbnail of Modélisation et caractérisation de fibres de Bragg pixélisées pour application aux lasers intenses

Ces travaux portent sur la realisation de fibres optiques a tres grandes aires effectives pour ap... more Ces travaux portent sur la realisation de fibres optiques a tres grandes aires effectives pour applications aux lasers intenses. Les applications possibles de ces fibres sont le transport ou la generation de puissants faisceaux lasers. En se basant sur la famille de fibre optique appelee : "fibre de Bragg pixelisee", nous avons introduit le concept de double conditions demi-onde appliquee au mode d’ordre superieur afin d’augmenter les pertes des modes LP11, LP21, LP02. Le principe d’heterostructuration quant a lui a permis d’accentuer les pertes des modes d’ordre superieur grâce a un effet de fuite. Ainsi donc, nous avons realise une fibre ayant un diametre de cœur de 48 µm qui a permis l’obtention d’un diametre de mode de 40 µm a la longueur d’onde 1050 nm. Dans un second temps, une geometrie de gaine plus simplifiee est proposee. Cette nouvelle geometrie de gaine nous a permis d’acceder a des diametres de modes allant de 47 µm a 69 µm dans le cas de fibre a bande interdi...

Research paper thumbnail of Benefit of large-mode area fiber for photonic nanojet sub-micron laser processing (Conference Presentation)

Research paper thumbnail of 30  TW and 33  fs pulses delivered by a Ti:Sa amplifier system seeded with a frequency-doubled fiber laser

Applied Optics, 2020

We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifi... more We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifier chain with a standard 15 fs Ti:Sa oscillator and 35 fs frequency-doubled fiber oscillator. The study highlights that the Ti:Sa oscillator, with high performance in terms of pulse duration and spectral width, can be replaced by the frequency-doubled fiber oscillator to seed Ti:Sa amplifier chains almost without any compromise on the output pulse duration and picosecond contrast. Finally, we demonstrate for the first time to our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.

Research paper thumbnail of Large-mode-area optical fiber for photonic nanojet generation

Optics Letters, 2019

The photonic nanojet (PNJ) generated by a shaped optical fiber tip is an attractive technology fo... more The photonic nanojet (PNJ) generated by a shaped optical fiber tip is an attractive technology for laser micro-machining. The working distance has the same order of size as the fiber core diameter; therefore, multimode (MM) fibers are generally preferred. However, the PNJ is due to the fundamental mode and, therefore, the energy coupled on the high-order modes does not contribute to the process. We demonstrate the benefit of a large-mode-area (LMA) optical fiber in the generation of the PNJ. A homemade 40 μm mode field diameter LMA fiber is compared with a 100/140 MM-shaped fiber tip. Similar micro-peaks are obtained, and an energy gain is demonstrated. The coupled energy required was eight times less intense with the LMA fiber, which may open new possibilities for laser micro- and nano-processing.

Research paper thumbnail of Pixelated Bragg fibers: bandgap guiding, generalized half-wave stack condition, and application to large mode area fibers

Journal of the Optical Society of America B, 2015

Bandgap formation in pixelated Bragg fibers is explained by using the plane wave expansion method... more Bandgap formation in pixelated Bragg fibers is explained by using the plane wave expansion method. A generalization of the half-wave stack condition is proposed and exploited by using a pixelated ring heterostructuration. Such fibers open up the way to designing new single-mode large mode area (LMA) fibers. A single-mode LMA fiber with a core diameter of 50 μm that is composed of only two rings of high-index rods is used as an example.

Research paper thumbnail of Extreme large mode area in single-mode pixelated Bragg fiber

Optics Express, 2016

This paper reports the design and the fabrication of an all-solid photonic bandgap fiber with cor... more This paper reports the design and the fabrication of an all-solid photonic bandgap fiber with core diameter larger than 100 µm, a record effective mode area of about 3700 µm 2 at 1035 nm and robust single-mode behavior on propagation length as short as 90 cm. These properties are obtained by using a pixelated Bragg fiber geometry together with an heterostructuration of the cladding and the appropriated generalized half wave stack condition applied to the first three higher order modes. We detail the numerical study that permitted to select the most efficient cladding geometry and present the experimental results that validate our approach.

Research paper thumbnail of Ultra large mode area pixelated Bragg fiber

SPIE Proceedings, 2016

We report on the design and the fabrication of a new design of an all-solid Bragg fiber based on ... more We report on the design and the fabrication of a new design of an all-solid Bragg fiber based on the pixelization and heterostructuration of a cladding made of only two high index rings. The thickness of the low index ring as well as the geometry of the heterostructuration (its symmetry and the number of removed pixels) have been chosen to maximize the confinement losses of the Higher Order Modes (HOM) (above 10 dB/m) while keeping the Fundamental Mode (FM) losses low (below 0.1 dB/m). The proposed geometry allows having access to different Mode Field Diameter (MFD) from 54 μm to 60 μm at 1 μm wavelength by drawing the same stack to different fiber (and hence, core) diameters. As a result, a record MFD of 60 μm is reported for a Solid Core Photonic Bandgap Fiber (SC-PBGF) and single-mode behavior is obtained experimentally even for a short fiber length (few tens centimeters) maintained straight.

Research paper thumbnail of Very Large Mode Area Pixelated Bragg Fibers

Workshop on Specialty Optical Fibers and Their Applications, 2015

Generalized half-wave-stack condition combined with well-chosen hetero-structured cladding is use... more Generalized half-wave-stack condition combined with well-chosen hetero-structured cladding is used to design and realize scalable single-mode pixelated Bragg fibers with mode field diameter as large as 60 μm.

Research paper thumbnail of Design and realization of flexible very large mode area pixelated Bragg fibers

Optics Letters, 2015

A new Pixelated Bragg Fiber design showing improved optical performances in terms of single-mode ... more A new Pixelated Bragg Fiber design showing improved optical performances in terms of single-mode behavior and effective area is presented. The cladding is made of 3 rings of cylindrical high refractive index rods (pixels) in which some pixels are removed to act as a modal sieve for an improved rejection of Higher Order Modes (HOMs). Two half-wave-stack conditions are used to increase the confinement losses of the 3 first HOMs: LP 11 and LP 02-LP 21 guided core modes. The realized fiber exhibits a core diameter of 48.5 μm with an effective single-mode behavior observed from 1000 nm to beyond 1700 nm even for a 1-m-long straight fiber. Losses prove to be low with a minimum value of 25 dB∕km between 1200 and 1500 nm. Bending radius of 22.5 cm is reported for this structure without any significant extra-losses above a wavelength of 1350 nm.

Research paper thumbnail of Sub-150 fs all-fiber polarization maintaining tunable laser in the mid-infrared

Fiber Lasers XVII: Technology and Systems

Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously gr... more Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously growing for many applications. Mode-locked Holmium- or Thulium-doped fiber lasers based on Saturable Absorber Mirror (SAM) are typically the first approach to generate pulses in this spectral range but this technique suffers from a lack of tunability. Indeed, the operating wavelength is fixed by the SAM and the gain fiber. Another way to reach the 2 μm-spectral range consists to exploit the nonlinear phenomena appearing in optical fibers and in particular the Soliton-Self Frequency Shift (SSFS) effect from an Erbium-fiber laser. Several systems based on this phenomenon allowed the generation of ultrashort pulses at different wavelengths and in different type of fibers (step-index, PCF, …). In this paper, we report on the design of a compact and robust all-Polarization-Maintaining (PM) fiber system entirely based on commercial PM components. This system allows to generate a single femtosecond pulse continuously tunable from 1700 nm to 2050 nm. We also demonstrate that the sub-150 fs pulses are transform-limited over all the spectral range and thanks to an optimized rate conversion close to 50 %, the pulse energy and the peak power can reach the nJclass and the kW-class respectively, which represents a gain of a factor 2 compared to the previous works.

Research paper thumbnail of Synchronized all-PM-fiber Yb-doped amplifiers for high power fs- and ps-pulse generation

Research paper thumbnail of Sub-50 fs 3.5 nJ pulses at 792 nm generated by frequency doubling of an all-PM fiber laser for Ti:sapphire injection

Fiber Lasers XVI: Technology and Systems

Frequency doubled sub 50 fs Erbium-fiber lasers are ideal tool used to seed Ti:sapphire amplifier... more Frequency doubled sub 50 fs Erbium-fiber lasers are ideal tool used to seed Ti:sapphire amplifier. Therefore, over last decade large number of all-fiber laser architecture has been reported for such application. Nevertheless, the emitted pulses are usually too long due to the gain bandwidth of Erbium or the laser architecture is not made with Polarization Maintaining (PM) fibers which will be a limitation for frequency doubling. We demonstrate a new design of an all-PM erbium doped fiber laser emitting sub 50 fs pulses with high pulse energy and we study its frequency doubling. Our architecture is based on a concatenation of three amplifiers having different group velocity dispersion. These amplifiers provide numerous degrees of freedom allowing to control the output pulse duration. Thanks to this new design, the laser produces 14 nJ pulse with a duration of 48 fs and an average power of 560 mW. This is to the best of our knowledge the shortest pulse duration with an energy higher than 10 nJ emitted by an all-fiber laser around 1.5-1.6 μm. The pulses are further converted by Second Harmonic Generation to 796 nm with an efficiency of 25 %. The average power of the doubled signal is 140 mW with 3.5 nJ pulse energy. The nonlinear crystal has been carefully chosen in order to cover all the spectral bandwidth of the pump and to ensure a sub 50 fs pulse at 796 nm.

Research paper thumbnail of 200-W single frequency laser based on short active double clad tapered fiber

Fiber Lasers XV: Technology and Systems

High power single frequency lasers are very attractive for a wide range of applications such as n... more High power single frequency lasers are very attractive for a wide range of applications such as nonlinear conversion, gravitational wave sensing or atom trapping. Power scaling in single frequency regime is a challenging domain of research. In fact, nonlinear effect as stimulated Brillouin scattering (SBS) is the primary power limitation in single frequency amplifiers. To mitigate SBS, different well-known techniques has been improved. These techniques allow generation of several hundred of watts [1]. Large mode area (LMA) fibers, transverse acoustically tailored fibers [2], coherent beam combining and also tapered fiber [3] seem to be serious candidates to continue the power scaling. We have demonstrated the generation of stable 200W output power with nearly diffraction limited output, and narrow linewidth (Δν<30kHz) by using a tapered Yb-doped fiber which allow an adiabatic transition from a small purely single mode input to a large core output.

Research paper thumbnail of nJ-class all-PM fiber tunable femtosecond laser from 1800 nm to 2050 nm via a highly efficient SSFS

Fiber Lasers and Glass Photonics: Materials through Applications II

Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously gr... more Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously growing for many applications. Mode-locked Holmium- or Thulium-doped fiber lasers based on Saturable Absorber Mirror (SAM) are typically the first approach to generate pulses in this spectral range but this technique suffers from a lack of tunability. Indeed, the operating wavelength is fixed by the SAM and the gain fiber. Another way to reach the 2 μm-spectral range consists to exploit the nonlinear phenomena appearing in optical fibers and in particular the Soliton-Self Frequency Shift (SSFS) effect from an Erbium-fiber laser. Several systems based on this phenomenon allowed the generation of ultrashort pulses at different wavelengths and in different type of fibers (step-index, PCF, …). In this paper, we report on the design of a compact and robust all-Polarization-Maintaining (PM) fiber system entirely based on commercial PM components. This system allows to generate a single femtosecond pulse continuously tunable from 1700 nm to 2050 nm. We also demonstrate that the sub-150 fs pulses are transform-limited over all the spectral range and thanks to an optimized rate conversion close to 50 %, the pulse energy and the peak power can reach the nJclass and the kW-class respectively, which represents a gain a of factor 2 compared to the previous works.

Research paper thumbnail of Modeling and characterization of pixelated bragg fibers for intense lasers application

Ces travaux portent sur la réalisation de fibres optiques à très grandes aires effectives pour ap... more Ces travaux portent sur la réalisation de fibres optiques à très grandes aires effectives pour applications aux lasers intenses. Les applications possibles de ces fibres sont le transport ou la génération de puissants faisceaux lasers. En se basant sur la famille de fibre optique appelée : "fibre de Bragg pixélisée", nous avons introduit le concept de double conditions demi-onde appliquée au mode d’ordre supérieur afin d’augmenter les pertes des modes LP11, LP21, LP02. Le principe d’hétérostructuration quant à lui a permis d’accentuer les pertes des modes d’ordre supérieur grâce à un effet de fuite. Ainsi donc, nous avons réalisé une fibre ayant un diamètre de cœur de 48 µm qui a permis l’obtention d’un diamètre de mode de 40 µm à la longueur d’onde 1050 nm. Dans un second temps, une géométrie de gaine plus simplifiée est proposée. Cette nouvelle géométrie de gaine nous a permis d’accéder à des diamètres de modes allant de 47 µm à 69 µm dans le cas de fibre à bande interdi...

Research paper thumbnail of Polarizing Large Mode Area Photonic BandGap Fiber

Conference on Lasers and Electro-Optics, Jun 21, 2015

Research paper thumbnail of 1.1 W all-PM fiber laser at 1600 nm delivering 35 fs pulses with 30 nJ energy

Laser Congress 2019 (ASSL, LAC, LS&C), 2019

We report an all-PM fiber laser based on a mode-locked seeder and only two amplification stages d... more We report an all-PM fiber laser based on a mode-locked seeder and only two amplification stages delivering 35 fs pulses with an energy of 30nJ and an average power of 1.13 W at telecom wavelength.

Research paper thumbnail of 3 W Mid-IR supercontinuum extended up to 4.6 µm based on an all-PM thulium doped fiber gain-switch laser seeding an InF3 fiber

Nonlinear Frequency Generation and Conversion: Materials and Devices XVIII, 2019

We report on a 3 W Mid-IR supercontinuum extended up to 4.6 μm based on an all-PM thulium doped f... more We report on a 3 W Mid-IR supercontinuum extended up to 4.6 μm based on an all-PM thulium doped fiber gainswitched laser seeding an InF3 fiber. This innovative fiber presents a specific design that increases non-linear effects and shows very weak background losses. Thanks to the versatility of our gain-switched laser, all the pulse parameters have been widely optimized to generate a supercontinuum emission with the highest average power and the largest spectrum.

Research paper thumbnail of Modélisation et caractérisation de fibres de Bragg pixélisées pour application aux lasers intenses

Ces travaux portent sur la realisation de fibres optiques a tres grandes aires effectives pour ap... more Ces travaux portent sur la realisation de fibres optiques a tres grandes aires effectives pour applications aux lasers intenses. Les applications possibles de ces fibres sont le transport ou la generation de puissants faisceaux lasers. En se basant sur la famille de fibre optique appelee : "fibre de Bragg pixelisee", nous avons introduit le concept de double conditions demi-onde appliquee au mode d’ordre superieur afin d’augmenter les pertes des modes LP11, LP21, LP02. Le principe d’heterostructuration quant a lui a permis d’accentuer les pertes des modes d’ordre superieur grâce a un effet de fuite. Ainsi donc, nous avons realise une fibre ayant un diametre de cœur de 48 µm qui a permis l’obtention d’un diametre de mode de 40 µm a la longueur d’onde 1050 nm. Dans un second temps, une geometrie de gaine plus simplifiee est proposee. Cette nouvelle geometrie de gaine nous a permis d’acceder a des diametres de modes allant de 47 µm a 69 µm dans le cas de fibre a bande interdi...

Research paper thumbnail of Benefit of large-mode area fiber for photonic nanojet sub-micron laser processing (Conference Presentation)

Research paper thumbnail of 30  TW and 33  fs pulses delivered by a Ti:Sa amplifier system seeded with a frequency-doubled fiber laser

Applied Optics, 2020

We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifi... more We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifier chain with a standard 15 fs Ti:Sa oscillator and 35 fs frequency-doubled fiber oscillator. The study highlights that the Ti:Sa oscillator, with high performance in terms of pulse duration and spectral width, can be replaced by the frequency-doubled fiber oscillator to seed Ti:Sa amplifier chains almost without any compromise on the output pulse duration and picosecond contrast. Finally, we demonstrate for the first time to our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.

Research paper thumbnail of Large-mode-area optical fiber for photonic nanojet generation

Optics Letters, 2019

The photonic nanojet (PNJ) generated by a shaped optical fiber tip is an attractive technology fo... more The photonic nanojet (PNJ) generated by a shaped optical fiber tip is an attractive technology for laser micro-machining. The working distance has the same order of size as the fiber core diameter; therefore, multimode (MM) fibers are generally preferred. However, the PNJ is due to the fundamental mode and, therefore, the energy coupled on the high-order modes does not contribute to the process. We demonstrate the benefit of a large-mode-area (LMA) optical fiber in the generation of the PNJ. A homemade 40 μm mode field diameter LMA fiber is compared with a 100/140 MM-shaped fiber tip. Similar micro-peaks are obtained, and an energy gain is demonstrated. The coupled energy required was eight times less intense with the LMA fiber, which may open new possibilities for laser micro- and nano-processing.

Research paper thumbnail of Pixelated Bragg fibers: bandgap guiding, generalized half-wave stack condition, and application to large mode area fibers

Journal of the Optical Society of America B, 2015

Bandgap formation in pixelated Bragg fibers is explained by using the plane wave expansion method... more Bandgap formation in pixelated Bragg fibers is explained by using the plane wave expansion method. A generalization of the half-wave stack condition is proposed and exploited by using a pixelated ring heterostructuration. Such fibers open up the way to designing new single-mode large mode area (LMA) fibers. A single-mode LMA fiber with a core diameter of 50 μm that is composed of only two rings of high-index rods is used as an example.

Research paper thumbnail of Extreme large mode area in single-mode pixelated Bragg fiber

Optics Express, 2016

This paper reports the design and the fabrication of an all-solid photonic bandgap fiber with cor... more This paper reports the design and the fabrication of an all-solid photonic bandgap fiber with core diameter larger than 100 µm, a record effective mode area of about 3700 µm 2 at 1035 nm and robust single-mode behavior on propagation length as short as 90 cm. These properties are obtained by using a pixelated Bragg fiber geometry together with an heterostructuration of the cladding and the appropriated generalized half wave stack condition applied to the first three higher order modes. We detail the numerical study that permitted to select the most efficient cladding geometry and present the experimental results that validate our approach.

Research paper thumbnail of Ultra large mode area pixelated Bragg fiber

SPIE Proceedings, 2016

We report on the design and the fabrication of a new design of an all-solid Bragg fiber based on ... more We report on the design and the fabrication of a new design of an all-solid Bragg fiber based on the pixelization and heterostructuration of a cladding made of only two high index rings. The thickness of the low index ring as well as the geometry of the heterostructuration (its symmetry and the number of removed pixels) have been chosen to maximize the confinement losses of the Higher Order Modes (HOM) (above 10 dB/m) while keeping the Fundamental Mode (FM) losses low (below 0.1 dB/m). The proposed geometry allows having access to different Mode Field Diameter (MFD) from 54 μm to 60 μm at 1 μm wavelength by drawing the same stack to different fiber (and hence, core) diameters. As a result, a record MFD of 60 μm is reported for a Solid Core Photonic Bandgap Fiber (SC-PBGF) and single-mode behavior is obtained experimentally even for a short fiber length (few tens centimeters) maintained straight.

Research paper thumbnail of Very Large Mode Area Pixelated Bragg Fibers

Workshop on Specialty Optical Fibers and Their Applications, 2015

Generalized half-wave-stack condition combined with well-chosen hetero-structured cladding is use... more Generalized half-wave-stack condition combined with well-chosen hetero-structured cladding is used to design and realize scalable single-mode pixelated Bragg fibers with mode field diameter as large as 60 μm.

Research paper thumbnail of Design and realization of flexible very large mode area pixelated Bragg fibers

Optics Letters, 2015

A new Pixelated Bragg Fiber design showing improved optical performances in terms of single-mode ... more A new Pixelated Bragg Fiber design showing improved optical performances in terms of single-mode behavior and effective area is presented. The cladding is made of 3 rings of cylindrical high refractive index rods (pixels) in which some pixels are removed to act as a modal sieve for an improved rejection of Higher Order Modes (HOMs). Two half-wave-stack conditions are used to increase the confinement losses of the 3 first HOMs: LP 11 and LP 02-LP 21 guided core modes. The realized fiber exhibits a core diameter of 48.5 μm with an effective single-mode behavior observed from 1000 nm to beyond 1700 nm even for a 1-m-long straight fiber. Losses prove to be low with a minimum value of 25 dB∕km between 1200 and 1500 nm. Bending radius of 22.5 cm is reported for this structure without any significant extra-losses above a wavelength of 1350 nm.