P. Georges - Academia.edu (original) (raw)
Papers by P. Georges
Stability of soliton regimes near bifurcation in passively modelocked high gain Yb-doped femtosecond lasers
Clinical Nutrition Supplements
ABSTRACT
Low-repetition-rate femtosecond operation in long cavity modelocked Yb:CALGO laser
2008 Conference on Lasers and Electro-Optics, 2008
ABSTRACT
Tunable dye-doped xerogel lasers
Conference on Lasers and Electro-Optics Europe
The easiest route to produce tunable optical pulses is to use a broadband fluorescent gain medium... more The easiest route to produce tunable optical pulses is to use a broadband fluorescent gain medium. For this purpose organic dye molecules are very suitable and have been widely used in solution during the past 30 years. Today, new crystals such as titanium sapphire, and nonlinear techniques such as optical parametric oscillation, may provide solid state systems. For dyes to remain competitive, it would be interesting to disperse the molecules in solid host matrices, instead of diluting them in solutions. This may be achieved by using the sol-gel process.1–3
Solid State Lasers XIV: Technology and Devices, 2005
We report on direct, absolute and spatially resolved temperature measurements in various diode-en... more We report on direct, absolute and spatially resolved temperature measurements in various diode-endpumped laser crystals, using an infrared camera. Our measurement method requires careful calibrations of the camera, to take into account the emissivity of the crystals. We tested the repeatability of the calibration process, and the linearity of calibrations curves was verified to up to 100°C. We also compared our experimental results with finite elements analysis simulations done with LASCAD. We used our setup to compare different types of thermal contacts and to measure the corresponding heat transfer coefficients using an Yb:YAG crystal. Finally we compared the thermal behaviour of Nd:YVO 4 and Nd:GdVO 4 crystals under the same pumping conditions.
Divided-pulse nonlinear compression
SPIE Proceedings, 2014
ABSTRACT Passive spatial and temporal coherent combining schemes are implemented to scale the out... more ABSTRACT Passive spatial and temporal coherent combining schemes are implemented to scale the output energy of a nonlinear temporal compression setup. By generating 32 replicas of the incident femtosecond pulses, the output of a high energy fiber chirped-pulse amplifier can be compressed using self-phase modulation in a large mode area rod-type fiber at peak power levels well beyond the self-focusing threshold of 4 MW. We demonstrate the generation of 71 fs 7.5 μJ pulses at 100 kHz repetition rate, corresponding to a peak power of 86 MW.
Optics Express, 2009
We report the use of nonlinear compression in a very large mode-area rod-type photonic crystal fi... more We report the use of nonlinear compression in a very large mode-area rod-type photonic crystal fiber. This fiber allows the use of high energy pulses in the few microjoule range. We demonstrate the compression of 4 µJ, 338 fs pulses from a fiber chirped pulse amplification (FCPA) system down to 49 fs, 41 MW peak power pulses at a repetition rate of 200 kHz with an average power of 400 mW. The nonlinear compression setup is composed of a 5-cm-long rod-type fiber and a pair of SF10 prisms. The system was optimized to obtain good temporal quality, with a temporal Strehl ration of 86 % for the compressed 49 fs pulses.
Optics Letters, 1996
We measured small-signal gain in a cw diode-pumped Cr : LiSAF and showed that upconversion and th... more We measured small-signal gain in a cw diode-pumped Cr : LiSAF and showed that upconversion and thermal quenching of f luorescence strongly limit small-signal gain. Then we optimized the gain in a Cr : LiSAF laser pumped by two 400-mW red diodes. In Q-switched operation, this laser produced tunable nanosecond pulses between 800 and 900 nm. At 850 nm, we obtained 230-ns pulses with an energy of 6.5 mJ at a repetition rate of 10 kHz.
Optics Letters, 2006
We present what we believe to be the first true three-level laser based on a Nd-doped crystal. Fr... more We present what we believe to be the first true three-level laser based on a Nd-doped crystal. From the 4 F 3/2-4 I 9/2 laser transition, the lower laser level being the ground state, emission at 879 nm in NdGdVO 4 has been obtained with diode pumping. Up to 0.8 W of power has been achieved in cw operation and 24 J per pulse ͑35 ns͒ in the Q-switched regime. Intracavity second-harmonic generation in the pulsed regime is also demonstrated with 178 mW of average output power at 439.5 nm, corresponding to an energy of 17 J per pulse.
Optics Letters, 1993
We have developed a cw krypton-ion-laser-pumped Cr 3 + :LiSrAlF 6 regenerative amplifier for femt... more We have developed a cw krypton-ion-laser-pumped Cr 3 + :LiSrAlF 6 regenerative amplifier for femtosecond pulses operating at a 5-kHz repetition rate. After recompression, we obtained 3.6-,uJ, 170-fs pulses at 825 nm. By focusing these pulses in a cell of water, we generated a white-light continuum.
Optics Letters, 1995
We describe a diode-pumped Kerr-lens mode-locked Cr 31 :LiSrAlF 6 laser that produces 50 mW of 70... more We describe a diode-pumped Kerr-lens mode-locked Cr 31 :LiSrAlF 6 laser that produces 50 mW of 70-fs pulses in the 820-890-nm range when pumped by two red diodes of 400 mW each. By using a lower-transmission output coupler we have demonstrated for the f irst time to our knowledge a self-starting regime with an output power of 10 mW and 55-fs pulses.
Optics Express, 2005
A single-mode Yb-doped fiber laser producing 2 W CW at 978 nm is demonstrated with a high slope e... more A single-mode Yb-doped fiber laser producing 2 W CW at 978 nm is demonstrated with a high slope efficiency of 72%. Thanks to its narrow bandwidth, lower than 0.02 nm, and its tunability of 6 nm, it has been efficiently frequency doubled in a periodically poled MgO:LiNbO 3 waveguide, leading to a power of 83 mW at 489 nm and an internal conversion efficiency of 26 %.
Optics Express, 2010
The generation of high contrast and ultrashort laser pulses via a compact and energy-scalable cro... more The generation of high contrast and ultrashort laser pulses via a compact and energy-scalable cross polarized wave filter is presented. The setup incorporates a waveguide spatial filter into a single crystal XPW configuration, enabling high energy and high intensity transmission, efficient contrast enhancement and pulse shortening at the multi-mJ level. Excellent XPW conversion of up to 33% (global efficiency: 20%, intensity transmission: 40%) led to an output energy of 650 µJ for an input of 3.3 mJ. Additionally, efficient conversion under specific input phase conditions, allowed pulse shortening from 25 fs to 9.6 fs, indicating the prospective application of this setup as a high energy, ultrabroad laser source.
Journal of the Optical Society of America B, 2010
A comparative study between 808 and 914 nm pumping of Nd:YVO 4 crystals for laser operation at 10... more A comparative study between 808 and 914 nm pumping of Nd:YVO 4 crystals for laser operation at 1064 nm has been carried out. Using similar setups, performances of both configurations were first studied in the continuous wave, small-signal gain, and Q-switched regimes. Thanks to a numerical model, it is shown that fluorescence quenching and upconversion processes limit the possible uses for the 914 nm pumping scheme to regimes with low population inversions.
Optical Materials, 2002
We present an efficient tunable continuous-wave diode-pumped Yb 3þ :Ca 4 GdOðBO 3 Þ 3 (Yb:GdCOB) ... more We present an efficient tunable continuous-wave diode-pumped Yb 3þ :Ca 4 GdOðBO 3 Þ 3 (Yb:GdCOB) laser producing at room temperature up to 3.2 W average power with a slope efficiency of 80% when pumped with a 10 W laser diode. A large tunability from 1017 to 1086 nm is obtained. The broad emission spectrum has been used to develop a diodepumped Yb:GdCOB femtosecond laser. The laser generated 90 fs pulses,at a center wavelength of 1045 nm. By using a semiconductor saturable absorber mirror (SESAM) for the mode locking, the average power was 40 mW and the repetition rate of 100 MHz.
IEEE Journal of Quantum Electronics, 2004
A theoretical and experimental study of thermal lensing in Yb-doped crystals is presented. This p... more A theoretical and experimental study of thermal lensing in Yb-doped crystals is presented. This papers follows the presentation of theoretical considerations and experimental wavefront measurements, which have been the subject of Part I. In this paper, we study the evolution of thermal lensing versus absorbed pump power, and we derive two parameters valuable for laser design and power scaling. The quantum efficiency and the thermo-optic coefficient, in Yb-doped YAG, GGG, GdCOB, YCOB, KGW and YSO. The clear difference between thermal lensing under lasing and nonlasing conditions is the proof that nonradiative effects occur in all the crystals under investigation. An analytical model which takes into account the laser extraction efficiency enables to explain all the experimental features and allows to infer the fluorescence quantum efficiency of the samples (in the range 0.7-0.96). Under nonlasing conditions, the thermal lens dioptric power experiences a roll-off, for which we propose an explanation based on the theory presented in Part I. These results are then used to yield the thermo-optic coefficient of the crystals. At last, we propose a simple analytical formulation useful for a rough estimation of the focal length.
Applied Physics B, 2011
We report on high power amplification of femtosecond pulses in 40-µm core diameter Yb-doped photo... more We report on high power amplification of femtosecond pulses in 40-µm core diameter Yb-doped photonic bandgap Bragg fibers. The robustness to bending and transverse spatial behavior of these fibers is analyzed through simulations. The fibers are used in both stages of a moderately stretched (150 ps) femtosecond chirped pulsed amplification (CPA) system. A compressed average power of 6.3 W is obtained using a lowindex polymer-coated Bragg fiber with excellent beam quality and high efficiency, in agreement with numerical simulations. The use of an air-clad Bragg fiber allows us to scale the output power to 47 W at a repetition rate of 35 MHz. This experiment demonstrates the great potential of Bragg fibers to increase the mode area and the power of practical bending-tolerant femtosecond fiber systems.
Applied Physics B, 2005
Lasers and Optics Applied Physics B a. major 1, * ,u j.s. aitchison 1 p.w.e. smith 1 f. druon 2 p... more Lasers and Optics Applied Physics B a. major 1, * ,u j.s. aitchison 1 p.w.e. smith 1 f. druon 2 p. georges 2 b. viana 3 g.p. aka 3 Z-scan measurements of the nonlinear refractive indices of novel Yb-doped laser crystal hosts
Applied Optics, 1997
Significant improvements have been obtained for solid-state dye lasers with doped xerogels. By us... more Significant improvements have been obtained for solid-state dye lasers with doped xerogels. By using longitudinal pumping with a frequency-doubled Q-switched Nd: YAG laser, we obtained as much as 86% slope efficiency and 5 ϫ 10 5 pulses lifetime. Furthermore, newly prepared deoxygenated samples exhibited even greater lifetimes.
Stability of soliton regimes near bifurcation in passively modelocked high gain Yb-doped femtosecond lasers
Clinical Nutrition Supplements
ABSTRACT
Low-repetition-rate femtosecond operation in long cavity modelocked Yb:CALGO laser
2008 Conference on Lasers and Electro-Optics, 2008
ABSTRACT
Tunable dye-doped xerogel lasers
Conference on Lasers and Electro-Optics Europe
The easiest route to produce tunable optical pulses is to use a broadband fluorescent gain medium... more The easiest route to produce tunable optical pulses is to use a broadband fluorescent gain medium. For this purpose organic dye molecules are very suitable and have been widely used in solution during the past 30 years. Today, new crystals such as titanium sapphire, and nonlinear techniques such as optical parametric oscillation, may provide solid state systems. For dyes to remain competitive, it would be interesting to disperse the molecules in solid host matrices, instead of diluting them in solutions. This may be achieved by using the sol-gel process.1–3
Solid State Lasers XIV: Technology and Devices, 2005
We report on direct, absolute and spatially resolved temperature measurements in various diode-en... more We report on direct, absolute and spatially resolved temperature measurements in various diode-endpumped laser crystals, using an infrared camera. Our measurement method requires careful calibrations of the camera, to take into account the emissivity of the crystals. We tested the repeatability of the calibration process, and the linearity of calibrations curves was verified to up to 100°C. We also compared our experimental results with finite elements analysis simulations done with LASCAD. We used our setup to compare different types of thermal contacts and to measure the corresponding heat transfer coefficients using an Yb:YAG crystal. Finally we compared the thermal behaviour of Nd:YVO 4 and Nd:GdVO 4 crystals under the same pumping conditions.
Divided-pulse nonlinear compression
SPIE Proceedings, 2014
ABSTRACT Passive spatial and temporal coherent combining schemes are implemented to scale the out... more ABSTRACT Passive spatial and temporal coherent combining schemes are implemented to scale the output energy of a nonlinear temporal compression setup. By generating 32 replicas of the incident femtosecond pulses, the output of a high energy fiber chirped-pulse amplifier can be compressed using self-phase modulation in a large mode area rod-type fiber at peak power levels well beyond the self-focusing threshold of 4 MW. We demonstrate the generation of 71 fs 7.5 μJ pulses at 100 kHz repetition rate, corresponding to a peak power of 86 MW.
Optics Express, 2009
We report the use of nonlinear compression in a very large mode-area rod-type photonic crystal fi... more We report the use of nonlinear compression in a very large mode-area rod-type photonic crystal fiber. This fiber allows the use of high energy pulses in the few microjoule range. We demonstrate the compression of 4 µJ, 338 fs pulses from a fiber chirped pulse amplification (FCPA) system down to 49 fs, 41 MW peak power pulses at a repetition rate of 200 kHz with an average power of 400 mW. The nonlinear compression setup is composed of a 5-cm-long rod-type fiber and a pair of SF10 prisms. The system was optimized to obtain good temporal quality, with a temporal Strehl ration of 86 % for the compressed 49 fs pulses.
Optics Letters, 1996
We measured small-signal gain in a cw diode-pumped Cr : LiSAF and showed that upconversion and th... more We measured small-signal gain in a cw diode-pumped Cr : LiSAF and showed that upconversion and thermal quenching of f luorescence strongly limit small-signal gain. Then we optimized the gain in a Cr : LiSAF laser pumped by two 400-mW red diodes. In Q-switched operation, this laser produced tunable nanosecond pulses between 800 and 900 nm. At 850 nm, we obtained 230-ns pulses with an energy of 6.5 mJ at a repetition rate of 10 kHz.
Optics Letters, 2006
We present what we believe to be the first true three-level laser based on a Nd-doped crystal. Fr... more We present what we believe to be the first true three-level laser based on a Nd-doped crystal. From the 4 F 3/2-4 I 9/2 laser transition, the lower laser level being the ground state, emission at 879 nm in NdGdVO 4 has been obtained with diode pumping. Up to 0.8 W of power has been achieved in cw operation and 24 J per pulse ͑35 ns͒ in the Q-switched regime. Intracavity second-harmonic generation in the pulsed regime is also demonstrated with 178 mW of average output power at 439.5 nm, corresponding to an energy of 17 J per pulse.
Optics Letters, 1993
We have developed a cw krypton-ion-laser-pumped Cr 3 + :LiSrAlF 6 regenerative amplifier for femt... more We have developed a cw krypton-ion-laser-pumped Cr 3 + :LiSrAlF 6 regenerative amplifier for femtosecond pulses operating at a 5-kHz repetition rate. After recompression, we obtained 3.6-,uJ, 170-fs pulses at 825 nm. By focusing these pulses in a cell of water, we generated a white-light continuum.
Optics Letters, 1995
We describe a diode-pumped Kerr-lens mode-locked Cr 31 :LiSrAlF 6 laser that produces 50 mW of 70... more We describe a diode-pumped Kerr-lens mode-locked Cr 31 :LiSrAlF 6 laser that produces 50 mW of 70-fs pulses in the 820-890-nm range when pumped by two red diodes of 400 mW each. By using a lower-transmission output coupler we have demonstrated for the f irst time to our knowledge a self-starting regime with an output power of 10 mW and 55-fs pulses.
Optics Express, 2005
A single-mode Yb-doped fiber laser producing 2 W CW at 978 nm is demonstrated with a high slope e... more A single-mode Yb-doped fiber laser producing 2 W CW at 978 nm is demonstrated with a high slope efficiency of 72%. Thanks to its narrow bandwidth, lower than 0.02 nm, and its tunability of 6 nm, it has been efficiently frequency doubled in a periodically poled MgO:LiNbO 3 waveguide, leading to a power of 83 mW at 489 nm and an internal conversion efficiency of 26 %.
Optics Express, 2010
The generation of high contrast and ultrashort laser pulses via a compact and energy-scalable cro... more The generation of high contrast and ultrashort laser pulses via a compact and energy-scalable cross polarized wave filter is presented. The setup incorporates a waveguide spatial filter into a single crystal XPW configuration, enabling high energy and high intensity transmission, efficient contrast enhancement and pulse shortening at the multi-mJ level. Excellent XPW conversion of up to 33% (global efficiency: 20%, intensity transmission: 40%) led to an output energy of 650 µJ for an input of 3.3 mJ. Additionally, efficient conversion under specific input phase conditions, allowed pulse shortening from 25 fs to 9.6 fs, indicating the prospective application of this setup as a high energy, ultrabroad laser source.
Journal of the Optical Society of America B, 2010
A comparative study between 808 and 914 nm pumping of Nd:YVO 4 crystals for laser operation at 10... more A comparative study between 808 and 914 nm pumping of Nd:YVO 4 crystals for laser operation at 1064 nm has been carried out. Using similar setups, performances of both configurations were first studied in the continuous wave, small-signal gain, and Q-switched regimes. Thanks to a numerical model, it is shown that fluorescence quenching and upconversion processes limit the possible uses for the 914 nm pumping scheme to regimes with low population inversions.
Optical Materials, 2002
We present an efficient tunable continuous-wave diode-pumped Yb 3þ :Ca 4 GdOðBO 3 Þ 3 (Yb:GdCOB) ... more We present an efficient tunable continuous-wave diode-pumped Yb 3þ :Ca 4 GdOðBO 3 Þ 3 (Yb:GdCOB) laser producing at room temperature up to 3.2 W average power with a slope efficiency of 80% when pumped with a 10 W laser diode. A large tunability from 1017 to 1086 nm is obtained. The broad emission spectrum has been used to develop a diodepumped Yb:GdCOB femtosecond laser. The laser generated 90 fs pulses,at a center wavelength of 1045 nm. By using a semiconductor saturable absorber mirror (SESAM) for the mode locking, the average power was 40 mW and the repetition rate of 100 MHz.
IEEE Journal of Quantum Electronics, 2004
A theoretical and experimental study of thermal lensing in Yb-doped crystals is presented. This p... more A theoretical and experimental study of thermal lensing in Yb-doped crystals is presented. This papers follows the presentation of theoretical considerations and experimental wavefront measurements, which have been the subject of Part I. In this paper, we study the evolution of thermal lensing versus absorbed pump power, and we derive two parameters valuable for laser design and power scaling. The quantum efficiency and the thermo-optic coefficient, in Yb-doped YAG, GGG, GdCOB, YCOB, KGW and YSO. The clear difference between thermal lensing under lasing and nonlasing conditions is the proof that nonradiative effects occur in all the crystals under investigation. An analytical model which takes into account the laser extraction efficiency enables to explain all the experimental features and allows to infer the fluorescence quantum efficiency of the samples (in the range 0.7-0.96). Under nonlasing conditions, the thermal lens dioptric power experiences a roll-off, for which we propose an explanation based on the theory presented in Part I. These results are then used to yield the thermo-optic coefficient of the crystals. At last, we propose a simple analytical formulation useful for a rough estimation of the focal length.
Applied Physics B, 2011
We report on high power amplification of femtosecond pulses in 40-µm core diameter Yb-doped photo... more We report on high power amplification of femtosecond pulses in 40-µm core diameter Yb-doped photonic bandgap Bragg fibers. The robustness to bending and transverse spatial behavior of these fibers is analyzed through simulations. The fibers are used in both stages of a moderately stretched (150 ps) femtosecond chirped pulsed amplification (CPA) system. A compressed average power of 6.3 W is obtained using a lowindex polymer-coated Bragg fiber with excellent beam quality and high efficiency, in agreement with numerical simulations. The use of an air-clad Bragg fiber allows us to scale the output power to 47 W at a repetition rate of 35 MHz. This experiment demonstrates the great potential of Bragg fibers to increase the mode area and the power of practical bending-tolerant femtosecond fiber systems.
Applied Physics B, 2005
Lasers and Optics Applied Physics B a. major 1, * ,u j.s. aitchison 1 p.w.e. smith 1 f. druon 2 p... more Lasers and Optics Applied Physics B a. major 1, * ,u j.s. aitchison 1 p.w.e. smith 1 f. druon 2 p. georges 2 b. viana 3 g.p. aka 3 Z-scan measurements of the nonlinear refractive indices of novel Yb-doped laser crystal hosts
Applied Optics, 1997
Significant improvements have been obtained for solid-state dye lasers with doped xerogels. By us... more Significant improvements have been obtained for solid-state dye lasers with doped xerogels. By using longitudinal pumping with a frequency-doubled Q-switched Nd: YAG laser, we obtained as much as 86% slope efficiency and 5 ϫ 10 5 pulses lifetime. Furthermore, newly prepared deoxygenated samples exhibited even greater lifetimes.