Jean-Christophe Delagnes - Academia.edu (original) (raw)

Papers by Jean-Christophe Delagnes

High-Brightness Sources and Light-driven Interactions, 2018

International audienc

2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2017

Optical parametric generation in nonlinear crystals across the atmosphere transmission band II (3... more Optical parametric generation in nonlinear crystals across the atmosphere transmission band II (3–5 μm) is of interest for various applications such as infrared spectroscopy or countermeasures. For an efficient parametric generation in this spectral range with well-developed ultrashort laser sources, we identified Langatate La<inf>3</inf>Ga<inf>5.5</inf>Ta<inf>0.5</inf>O<inf>14</inf> (LGT) [1]. LGT is transparent from 0.25 up to 6.5 μm and can be grown in large sizes using the Czochralski method. Its unique nonlinear coefficient d<inf>11</inf>=2.4 ± 0.4 pm/V at λ=0.67 μm as well as the refinement of the Sellmeier equations are reported in ref [1]. The study highlights the potential for LGT to generate broadband spectrum between 1.5 and 5 μm if pumped around 0.97 μm available from a Ti:Sapphire (Ti:Sa) laser.

Laser & Photonics Reviews, 2017

Optics Letters, 2017

We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal La... more We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal La3Ga5.5Ta0.5O14 (LGT). Continuously tunable wavelengths between 1.4 and 4.7 µm are generated by using femtosecond sources. We also report on measurements of optical damage threshold in the femtosecond regime and on the nonlinear refractive index .

Optics Letters, 2017

We report on a laser source operating at 100 kHz repetition rate and delivering 8 µJ few cycles m... more We report on a laser source operating at 100 kHz repetition rate and delivering 8 µJ few cycles midIR pulses at 3 µm. The system is based on Optical Parametric Amplification (OPA) pumped by high repetition rate Yb-doped femtosecond fiber chirped amplifier (FCPA). This high-intensity ultrafast system is a promising tool for strong-field experiments (up to 50 GV/m and 186 T) in low ionization potential atomic and molecular systems, or solid state physics with coincidence measurements. As a proof of principle, up to the 6 th harmonic have been generated in 1 mm zinc selenide (ZnSe) sample.

Http Www Theses Fr, 2005

Je remercie tout d'abord sincèrement Bertrand Girard et Aziz Bouchene qui m'ont permis d'effectue... more Je remercie tout d'abord sincèrement Bertrand Girard et Aziz Bouchene qui m'ont permis d'effectuer ma thèse à Toulouse au sein du Laboratoire Collision Agrégats Réactivité. Aziz, nous nous connaissions bien avant ma thèse et tu as été plus qu'un directeur de thèse ... Merci pour ces merveilleuses années. Un gros merci collectif-mais non moins sincère-à l'ensemble des nombreux membres du LCAR. Merci aux membres, passés et présents, de l'équipe FEMTO : S. Zamith et J. Degert, A. Monmayrant (Bomber X), B. Chatel, et V. Blanchet-à qui j'adresse un remerciement tout particulier. Ceux sans qui, ça marcherait moins bien tout les jours :

Journal of Atomic and Molecular Sciences, 2011

We consider a double two-level system in which each single two-level system is driven by a strong... more We consider a double two-level system in which each single two-level system is driven by a strong linearly polarized pulse. The system is probed by a weak pulse orthogonally polarized. We study the distortion experienced by the probe temporal envelope when the relative phase between the pump and the probe is varied. We show that pulse behavior oscillates between two regimes that corresponds to transparency and amplification respectively. Interpretation of this effect is given within adiabatic representation.

Optics Express, 2012

In this paper, a model of the beam propagation is developed according to the physical properties ... more In this paper, a model of the beam propagation is developed according to the physical properties of THz waves used in THz computed tomography (CT) scan imaging. This model is first included in an acquisition simulator to observe and estimate the impact of the Gaussian beam intensity profile on the projection sets. Second, the model is introduced in several inversion methods as a convolution filter to perform efficient tomographic reconstructions of simulated and real acquired objects. Results obtained with three reconstruction methods (BFP, SART and OSEM) are compared to the techniques proposed in this paper. We focus our discussion on the efficiency of optimized algorithms to increase the overall quality and accuracy of the reconstructions.

2012 37th International Conference on Infrared, Millimeter, and Terahertz Waves, 2012

Sigillography is the science that studies the manifold aspects of the seals. A seal can be define... more Sigillography is the science that studies the manifold aspects of the seals. A seal can be defined as an imprint obtained on a malleable medium by imprinting an incised matrix, which transfers on it the characteristic signs of a person or an institution. We use THz spectroscopy and imaging for non-destructive evaluation of natural materials within old seals. Using a time domain THz spectroscopy and imaging system, THz transmission images are generated in the 0.1-3 THz range and demonstrate that the spectral properties of these materials allow to see across and under a thick layer of old materials.

Physical Review A, 2007

A weak resonant femtosecond pulse propagates through an optically thick atomic medium whose prope... more A weak resonant femtosecond pulse propagates through an optically thick atomic medium whose properties have been modified by a strong nonresonant ultrashort pulse. We study the energy redistribution between the spectral components of the weak resonant pulse using both experimental and theoretical methods. The transmitted spectrum exhibits an asymmetric feature that reveals an important gain-dispersion coupling. For light shifts that perturb slightly the propagation of the weak resonant pulse, this asymmetry maps out the asymptotic part of the linear susceptibility.

Physical Review B, 2008

Ultrafast dynamics of charge carriers in Br +-bombarded InP were studied using time-resolved tera... more Ultrafast dynamics of charge carriers in Br +-bombarded InP were studied using time-resolved terahertz spectroscopy. Carrier lifetimes and mobilities in various samples prepared with irradiation doses spanning from 10 9 up to 10 12 cm −2 were determined. The lifetime of photoexcited carriers appears to be determined primarily by the density of defects resulting from host-atom displacements while it is not significantly influenced by the Br-atom implantation. In the most irradiated sample, a carrier lifetime as short as 300 fs was found. All samples exhibit a high mobility ͑3000− 900 cm 2 V −1 s −1 ͒; the lower values correspond to a smaller irradiation dose. In selected samples, the density of traps along with electron and hole lifetimes was determined.

Physical Review A, 2007

We consider a duplicated two-level system where each two-level subsystem is driven by a strong re... more We consider a duplicated two-level system where each two-level subsystem is driven by a strong resonant femtosecond pulse and a weak resonant femtosecond pulse connects cross transitions. Strong interference effects are induced in such a configuration leading to a modulation of the medium gain as a function of the relative phase between the pulses ͓J. C. Delagnes and M. A. Bouchene, Phys. Rev. Lett. 98, 053602 ͑2007͔͒. We study here the influence of the temporal overlap between the pulses on the dynamics of the system and the medium gain. We show that the dynamics is dominated by two competing phenomena: Light shifts ͑LS͒ induced by the driving pulse that prevails for small delays and free induction decay ͑FID͒ that prevails for large delays. LS enhance the medium gain for = / 2 and reduce it for = 0, whereas FID always leads to a decrease of the medium gain.

Optics Communications, 2009

Far infrared transmission spectra of several graphite pencil leads on paper have been measured up... more Far infrared transmission spectra of several graphite pencil leads on paper have been measured up to 2 THz using time-domain spectroscopy. The observation of the gradual absorption depending on the graphite proportion has been assessed for different pencils from hard to soft black-marking graphite leads. The resulting graphite transmittance is used to perform two-dimensional transmission terahertz imaging of written documents.

Optics Communications, 2008

We present here some fundamental but yet underlooked features of the propagation of weak ultrasho... more We present here some fundamental but yet underlooked features of the propagation of weak ultrashort pulses (with D d s << 1, where D d is the Doppler width and s is the pulse duration) in resonant atomic media. We show that the pulse area behaviour and the pulse spectrum at resonance are governed by the usual optical depth (a 0 L, where a 0 is the absorption coefficient at resonance and L the length of the medium), whereas the pertinent parameter that governs the severity of the dispersion effects and the distortion of the pulse is the dispersion parameter e disp = (a 0 L)D d s that we introduce. Paradoxical effect such as distortionless propagation (e.g. e disp << 1) with vanishing pulse area (when a 0 L >> 1) can then explained within this formalism.

Optical Engineering, 2012

Three-dimensional (3-D) terahertz computed tomography has already been performed with three diffe... more Three-dimensional (3-D) terahertz computed tomography has already been performed with three different reconstruction methods (standard back-projection algorithm and two iterative analyses) to reconstruct 3-D objects. A Gaussian beam model is developed according to the physical properties of terahertz waves such as the energy distribution within the propagation path. This model is included as a new convolution filter into the tomographic reconstruction methods in order to analyze the impact of a such effect and then to enhance quality and accuracy of the resulting images. We demonstrate the improvements of the optimized reconstructions for applied 3-D terahertz tomography.

Nature Communications, 2013

In a bulk solid, optical control of atomic motion provides a better understanding of its physical... more In a bulk solid, optical control of atomic motion provides a better understanding of its physical properties and functionalities. Such studies would benefit from active control and visualization of atomic motions in arbitrary directions, yet, so far, mostly only one-dimensional control has been shown. Here we demonstrate a novel method to optically control and visualize two-dimensional atomic motions in a bulk solid. We use a femtosecond laser pulse to coherently superpose two orthogonal atomic motions in crystalline bismuth. The relative amplitudes of those two motions are manipulated by modulating the intensity profile of the laser pulse, and these controlled motions are quantitatively visualized by density functional theory calculations. Our control-visualization scheme is based on the simple, robust and universal concept that in any physical system, two-dimensional particle motion is decomposed into two orthogonal one-dimensional motions, and thus it is applicable to a variety o...

Journal of Physics B: Atomic, Molecular and Optical Physics, 2002

ABSTRACT We investigate in this paper the properties of electron wavepackets created in the conti... more ABSTRACT We investigate in this paper the properties of electron wavepackets created in the continuum by ultrashort pulses, linearly chirped. We consider alkali atoms, where complete quantum calculations can be carried out. The spreading of the wavepacket is radial and mainly due to free propagation, except for very low kinetic energy where Coulomb interaction has to be considered. We show that the wavepacket can be focused into a position located at macroscopic distances far from the ion core. Distances as large as several centimetres are obtained for standard values of laser parameters. Moreover, we derive the conditions where the wavepacket is temporally optimally focused. Finally, we study several characteristics of the wavepacket, such as the temporal divergence (in ps cm-1) and the temporal profile, when the focusing is not maximum.

Journal of Applied Physics, 2012

We present results of infrared pump—terahertz probe experiments applied to a set of In0.53Ga0.47A... more We present results of infrared pump—terahertz probe experiments applied to a set of In0.53Ga0.47As films irradiated with heavy ions (Br+) at doses from 109 to 1012 cm−2. Photoexcitation at 1400 nm (0.89 eV) allowed us to characterize the response close to telecommunications’ wavelengths whilst avoiding the intervalley carrier scattering observed when a shorter wavelength excitation is used. The excitation fluence was varied in our experiments in order to characterize the dynamics in detail: the lifetimes and mobilities of both electrons and holes were retrieved, and the trap filling and carrier diffusion were clearly observed. The In0.53Ga0.47As film irradiated by the dose of 1012 cm−2 exhibits simultaneously ultrashort electron lifetime (∼300 fs) and very high electron mobility (2800 cm2V−1s−1). These findings are particularly important for the design of terahertz emitters controlled by lasers operating at standard telecommunication wavelengths.

Applied Physics B, 2007

An ultrashort pulse propagating in a resonant dense atomic medium experiences an important distor... more An ultrashort pulse propagating in a resonant dense atomic medium experiences an important distortion due to a strong modification of its spectral phase. This distortion cannot be corrected using the usual simple dispersive devices (a pair of prisms, gratings, etc). We present here an experimental demonstration of the compensation of this effect using a dual 640-pixel high resolution pulse-shaper device. A cross-correlation intensity measurement combined with the XFROG (Cross-correlated Frequency Resolved Optical Gating) spectral phase measurement of the compensated pulse are performed; efficient correction of the resonant dispersive phase is shown. A spectacular temporal compression of the propagating pulse is then obtained.

High-Brightness Sources and Light-driven Interactions, 2018

International audienc

2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2017

Optical parametric generation in nonlinear crystals across the atmosphere transmission band II (3... more Optical parametric generation in nonlinear crystals across the atmosphere transmission band II (3–5 μm) is of interest for various applications such as infrared spectroscopy or countermeasures. For an efficient parametric generation in this spectral range with well-developed ultrashort laser sources, we identified Langatate La<inf>3</inf>Ga<inf>5.5</inf>Ta<inf>0.5</inf>O<inf>14</inf> (LGT) [1]. LGT is transparent from 0.25 up to 6.5 μm and can be grown in large sizes using the Czochralski method. Its unique nonlinear coefficient d<inf>11</inf>=2.4 ± 0.4 pm/V at λ=0.67 μm as well as the refinement of the Sellmeier equations are reported in ref [1]. The study highlights the potential for LGT to generate broadband spectrum between 1.5 and 5 μm if pumped around 0.97 μm available from a Ti:Sapphire (Ti:Sa) laser.

Laser & Photonics Reviews, 2017

Optics Letters, 2017

We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal La... more We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal La3Ga5.5Ta0.5O14 (LGT). Continuously tunable wavelengths between 1.4 and 4.7 µm are generated by using femtosecond sources. We also report on measurements of optical damage threshold in the femtosecond regime and on the nonlinear refractive index .

Optics Letters, 2017

We report on a laser source operating at 100 kHz repetition rate and delivering 8 µJ few cycles m... more We report on a laser source operating at 100 kHz repetition rate and delivering 8 µJ few cycles midIR pulses at 3 µm. The system is based on Optical Parametric Amplification (OPA) pumped by high repetition rate Yb-doped femtosecond fiber chirped amplifier (FCPA). This high-intensity ultrafast system is a promising tool for strong-field experiments (up to 50 GV/m and 186 T) in low ionization potential atomic and molecular systems, or solid state physics with coincidence measurements. As a proof of principle, up to the 6 th harmonic have been generated in 1 mm zinc selenide (ZnSe) sample.

Http Www Theses Fr, 2005

Je remercie tout d'abord sincèrement Bertrand Girard et Aziz Bouchene qui m'ont permis d'effectue... more Je remercie tout d'abord sincèrement Bertrand Girard et Aziz Bouchene qui m'ont permis d'effectuer ma thèse à Toulouse au sein du Laboratoire Collision Agrégats Réactivité. Aziz, nous nous connaissions bien avant ma thèse et tu as été plus qu'un directeur de thèse ... Merci pour ces merveilleuses années. Un gros merci collectif-mais non moins sincère-à l'ensemble des nombreux membres du LCAR. Merci aux membres, passés et présents, de l'équipe FEMTO : S. Zamith et J. Degert, A. Monmayrant (Bomber X), B. Chatel, et V. Blanchet-à qui j'adresse un remerciement tout particulier. Ceux sans qui, ça marcherait moins bien tout les jours :

Journal of Atomic and Molecular Sciences, 2011

We consider a double two-level system in which each single two-level system is driven by a strong... more We consider a double two-level system in which each single two-level system is driven by a strong linearly polarized pulse. The system is probed by a weak pulse orthogonally polarized. We study the distortion experienced by the probe temporal envelope when the relative phase between the pump and the probe is varied. We show that pulse behavior oscillates between two regimes that corresponds to transparency and amplification respectively. Interpretation of this effect is given within adiabatic representation.

Optics Express, 2012

In this paper, a model of the beam propagation is developed according to the physical properties ... more In this paper, a model of the beam propagation is developed according to the physical properties of THz waves used in THz computed tomography (CT) scan imaging. This model is first included in an acquisition simulator to observe and estimate the impact of the Gaussian beam intensity profile on the projection sets. Second, the model is introduced in several inversion methods as a convolution filter to perform efficient tomographic reconstructions of simulated and real acquired objects. Results obtained with three reconstruction methods (BFP, SART and OSEM) are compared to the techniques proposed in this paper. We focus our discussion on the efficiency of optimized algorithms to increase the overall quality and accuracy of the reconstructions.

2012 37th International Conference on Infrared, Millimeter, and Terahertz Waves, 2012

Sigillography is the science that studies the manifold aspects of the seals. A seal can be define... more Sigillography is the science that studies the manifold aspects of the seals. A seal can be defined as an imprint obtained on a malleable medium by imprinting an incised matrix, which transfers on it the characteristic signs of a person or an institution. We use THz spectroscopy and imaging for non-destructive evaluation of natural materials within old seals. Using a time domain THz spectroscopy and imaging system, THz transmission images are generated in the 0.1-3 THz range and demonstrate that the spectral properties of these materials allow to see across and under a thick layer of old materials.

Physical Review A, 2007

A weak resonant femtosecond pulse propagates through an optically thick atomic medium whose prope... more A weak resonant femtosecond pulse propagates through an optically thick atomic medium whose properties have been modified by a strong nonresonant ultrashort pulse. We study the energy redistribution between the spectral components of the weak resonant pulse using both experimental and theoretical methods. The transmitted spectrum exhibits an asymmetric feature that reveals an important gain-dispersion coupling. For light shifts that perturb slightly the propagation of the weak resonant pulse, this asymmetry maps out the asymptotic part of the linear susceptibility.

Physical Review B, 2008

Ultrafast dynamics of charge carriers in Br +-bombarded InP were studied using time-resolved tera... more Ultrafast dynamics of charge carriers in Br +-bombarded InP were studied using time-resolved terahertz spectroscopy. Carrier lifetimes and mobilities in various samples prepared with irradiation doses spanning from 10 9 up to 10 12 cm −2 were determined. The lifetime of photoexcited carriers appears to be determined primarily by the density of defects resulting from host-atom displacements while it is not significantly influenced by the Br-atom implantation. In the most irradiated sample, a carrier lifetime as short as 300 fs was found. All samples exhibit a high mobility ͑3000− 900 cm 2 V −1 s −1 ͒; the lower values correspond to a smaller irradiation dose. In selected samples, the density of traps along with electron and hole lifetimes was determined.

Physical Review A, 2007

We consider a duplicated two-level system where each two-level subsystem is driven by a strong re... more We consider a duplicated two-level system where each two-level subsystem is driven by a strong resonant femtosecond pulse and a weak resonant femtosecond pulse connects cross transitions. Strong interference effects are induced in such a configuration leading to a modulation of the medium gain as a function of the relative phase between the pulses ͓J. C. Delagnes and M. A. Bouchene, Phys. Rev. Lett. 98, 053602 ͑2007͔͒. We study here the influence of the temporal overlap between the pulses on the dynamics of the system and the medium gain. We show that the dynamics is dominated by two competing phenomena: Light shifts ͑LS͒ induced by the driving pulse that prevails for small delays and free induction decay ͑FID͒ that prevails for large delays. LS enhance the medium gain for = / 2 and reduce it for = 0, whereas FID always leads to a decrease of the medium gain.

Optics Communications, 2009

Far infrared transmission spectra of several graphite pencil leads on paper have been measured up... more Far infrared transmission spectra of several graphite pencil leads on paper have been measured up to 2 THz using time-domain spectroscopy. The observation of the gradual absorption depending on the graphite proportion has been assessed for different pencils from hard to soft black-marking graphite leads. The resulting graphite transmittance is used to perform two-dimensional transmission terahertz imaging of written documents.

Optics Communications, 2008

We present here some fundamental but yet underlooked features of the propagation of weak ultrasho... more We present here some fundamental but yet underlooked features of the propagation of weak ultrashort pulses (with D d s << 1, where D d is the Doppler width and s is the pulse duration) in resonant atomic media. We show that the pulse area behaviour and the pulse spectrum at resonance are governed by the usual optical depth (a 0 L, where a 0 is the absorption coefficient at resonance and L the length of the medium), whereas the pertinent parameter that governs the severity of the dispersion effects and the distortion of the pulse is the dispersion parameter e disp = (a 0 L)D d s that we introduce. Paradoxical effect such as distortionless propagation (e.g. e disp << 1) with vanishing pulse area (when a 0 L >> 1) can then explained within this formalism.

Optical Engineering, 2012

Three-dimensional (3-D) terahertz computed tomography has already been performed with three diffe... more Three-dimensional (3-D) terahertz computed tomography has already been performed with three different reconstruction methods (standard back-projection algorithm and two iterative analyses) to reconstruct 3-D objects. A Gaussian beam model is developed according to the physical properties of terahertz waves such as the energy distribution within the propagation path. This model is included as a new convolution filter into the tomographic reconstruction methods in order to analyze the impact of a such effect and then to enhance quality and accuracy of the resulting images. We demonstrate the improvements of the optimized reconstructions for applied 3-D terahertz tomography.

Nature Communications, 2013

In a bulk solid, optical control of atomic motion provides a better understanding of its physical... more In a bulk solid, optical control of atomic motion provides a better understanding of its physical properties and functionalities. Such studies would benefit from active control and visualization of atomic motions in arbitrary directions, yet, so far, mostly only one-dimensional control has been shown. Here we demonstrate a novel method to optically control and visualize two-dimensional atomic motions in a bulk solid. We use a femtosecond laser pulse to coherently superpose two orthogonal atomic motions in crystalline bismuth. The relative amplitudes of those two motions are manipulated by modulating the intensity profile of the laser pulse, and these controlled motions are quantitatively visualized by density functional theory calculations. Our control-visualization scheme is based on the simple, robust and universal concept that in any physical system, two-dimensional particle motion is decomposed into two orthogonal one-dimensional motions, and thus it is applicable to a variety o...

Journal of Physics B: Atomic, Molecular and Optical Physics, 2002

ABSTRACT We investigate in this paper the properties of electron wavepackets created in the conti... more ABSTRACT We investigate in this paper the properties of electron wavepackets created in the continuum by ultrashort pulses, linearly chirped. We consider alkali atoms, where complete quantum calculations can be carried out. The spreading of the wavepacket is radial and mainly due to free propagation, except for very low kinetic energy where Coulomb interaction has to be considered. We show that the wavepacket can be focused into a position located at macroscopic distances far from the ion core. Distances as large as several centimetres are obtained for standard values of laser parameters. Moreover, we derive the conditions where the wavepacket is temporally optimally focused. Finally, we study several characteristics of the wavepacket, such as the temporal divergence (in ps cm-1) and the temporal profile, when the focusing is not maximum.

Journal of Applied Physics, 2012

We present results of infrared pump—terahertz probe experiments applied to a set of In0.53Ga0.47A... more We present results of infrared pump—terahertz probe experiments applied to a set of In0.53Ga0.47As films irradiated with heavy ions (Br+) at doses from 109 to 1012 cm−2. Photoexcitation at 1400 nm (0.89 eV) allowed us to characterize the response close to telecommunications’ wavelengths whilst avoiding the intervalley carrier scattering observed when a shorter wavelength excitation is used. The excitation fluence was varied in our experiments in order to characterize the dynamics in detail: the lifetimes and mobilities of both electrons and holes were retrieved, and the trap filling and carrier diffusion were clearly observed. The In0.53Ga0.47As film irradiated by the dose of 1012 cm−2 exhibits simultaneously ultrashort electron lifetime (∼300 fs) and very high electron mobility (2800 cm2V−1s−1). These findings are particularly important for the design of terahertz emitters controlled by lasers operating at standard telecommunication wavelengths.

Applied Physics B, 2007

An ultrashort pulse propagating in a resonant dense atomic medium experiences an important distor... more An ultrashort pulse propagating in a resonant dense atomic medium experiences an important distortion due to a strong modification of its spectral phase. This distortion cannot be corrected using the usual simple dispersive devices (a pair of prisms, gratings, etc). We present here an experimental demonstration of the compensation of this effect using a dual 640-pixel high resolution pulse-shaper device. A cross-correlation intensity measurement combined with the XFROG (Cross-correlated Frequency Resolved Optical Gating) spectral phase measurement of the compensated pulse are performed; efficient correction of the resonant dispersive phase is shown. A spectacular temporal compression of the propagating pulse is then obtained.