Sebastien Montant

• Dr
• Atomic Energy and Alternative Energies Commission

We propose an experimental method for the determination of the transfer function linewidth of a laser amplifier. This technique is based on a transfer function scan using frequency modulation to amplitude modulation (FM-to-AM) temporal modulation measurement as a function of wavelength. Using this method, we show that the output spectrum of a laser...

This present work outlines a parametric study of a diode side-pumped bonded laser rod. Both material combination and geometry of the samples are discussed using simulations and experiments to reduce the pump-induced thermal effects.

This work deals with the establishment of a method based on FM-to-AM conversion measurement for the regenerative amplifier transfer function determination. We applied it to study the impact of gain narrowing on transfer function linewidth.

We numerically and experimentally studied compensation of FM-to-AM conversion due to spectral gain response of a regenerative amplifier with an extra-cavity interference filter. We discuss the sensibility of this technology regarding different parameters.

We present a numerical study of a square-shape rod-like bonded laser gain medium operating at 1053 nm. The sample is composed of a 5-mm thick Nd-doped phosphate glass bonded to two α-quartz crystals. Owing to this face cooling scheme, the heat generated in the gain medium is effectively reduced, hence resulting in less optical distortions. The simu...

In this paper, we will discuss the performances of a 4-pass diode-pumped 4-active-mirrors laser amplifier. Numerical simulations along with experimental characterization paves the way to reach 1 J at 10 Hz pulse rate at 1053 nm. Both Nd :glass and Nd :Lu :CaF2 amplifier medium performances will be compared in this amplifier.

Using COMSOL Multiphysics, we simulate free convection along a pumped active mirror amplifying medium. We study the induced boundary layers and how it affects the wave front propagation. To comfort our simulations, we set up a Mach-Zehnder interferometer to characterize and measure the local variation of air refractive index and temperature.

An efficient approach to avoid Nd³⁺ clustering in CaF2:Nd³⁺ is the co-doping with non-optically active buffer (Bu) ions creating Nd-Bu emitting clusters for laser applications around 1050 nm (⁴F3/2 → ⁴I11/2) taking advantage of their unique large absorption and emission bands. A detailed spectroscopic investigation of buffer codoping with Gd³⁺, La³...

This work deals with the design and the fabrication of narrow camel-shape filters to compensate FM-to-AM conversion in the regenerative cavity of high power lasers. The feasibility of filters meeting tight specifications has been demonstrated.

In the present work, we numerically and experimentally compare the thermally-induced wavefront aberrations and birefringence of two bonded samples. These samples are made of Nd- doped laser glass and quartz crystals using two distinct bonding methods.

In order to smooth the focal spot of high-power energetic lasers, pulses are phase-modulated. However, due to propagation impairments, phase modulation is partly converted into power modulation. This is called frequency modulation to amplitude modulation (FM-to-AM conversion). This effect may increase laser damage and thus increase operating costs....

High-power nanosecond laser pulses are usually spectrally broadened via temporal phase modulations to tackle the issue of stimulated Brillouin scattering and to achieve optical smoothing of the focal spot. While propagating along the beamline, such pulses can undergo frequency modulation to amplitude modulation (FM-to-AM) conversion. This phenomeno...

We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and ${0.5}\% {\rm Nd}:{5}\% {\rm Lu}:{\rm CaF}_2$ . We observed that depending on the material, wavefront distortions’ profile can vary from a circular lens-like distortion to...

A general method to study the birefringence induced under laser pumping is presented. The method was tested on an Nd:Phosphate glass sample that is transversally and inhomogeneously pumped by a pulsed laser diode. Measurements to resolve the spatial and temporal stress-induced birefringence distribution are compared to a numerical model simulating...

We report an effect potentially harmful occurring in regenerative amplifiers due to stimulated Brillouin scattering (SBS). Most high energy laser facilities use phase-modulated pulses to prevent the transverse SBS effect in large optical components and to smooth the focal spot on target. However, this kind of pulse format may undergo a detrimental...

This work deals with the compensation of FM-to-AM conversion induced by the spectral response of regenerative cavity. We show that it is possible to reduce amplitude modulations from 44% to 9% using an interference filter.

The incorporation of nonactive ions like Lu3+, Gd3+, Y3+, La3+, Ce3+ or Sc3+ in Nd:CaF2 significantly shapes the broadband emission around 1.053μm. This would lead to the replacement of phosphate glasses in inertial fusion facilities.

We present results on tunable few-cycle laser pulses generated in the near infrared region obtained by filamentation in a krypton cell combined with group velocity dispersion compensation in fused silica. We obtain a spectral broadening of a factor ∼2–3 over the entire spectral domain studied. The central wavelength is tuned from 1.6 μm to 2 μm via...

We report on a new scheme for ultra-broadband optical parametric amplification at 2.1 µm delivering CEP-stabilized pulses of duration down to 16 fs (2.2 cycles) and energy up to 10 µJ at 100 kHz.

We report on a new scheme for ultra-broadband optical parametric amplification at 2.1 µm delivering CEP-stabilized pulses of duration down to 16 fs (2.2 cycles) and energy up to 10 µJ at 100 kHz.

We report on an experimental investigation of the noise properties of an free-running, high-power, picosecond Nd:YVO4 oscillator pumped by a 100 W laser diode. The amplitude noise has been measured with a photodiode and an electronic spectrum analyser, and then compared with other mode-locked oscillator's noise spectrum. We show that in terms of no...

We propose a new single-shot third order correlator to measure the temporal contrast of pulses in the picosecond range of high power chain lasers. We use time-to-angular coding to transfer the temporal contrast information to a 3ω probe pulse. We determine the temporal window with the resolution obtained from this technique and predict via simulati...

We report on a high-average-power 888 nm diode-pumped passively mode-locked TEM00 Nd:YVO4 oscillator with adjustable pulse durations. From 45 to 15 W output power, we produced corresponding 32 to 12 ps long pulses without spatial hole burning.

We report on a high-power passively mode-locked TEM 00 Nd : Y V O 4 oscillator, 888 nm diode-pumped, with pulse durations adjustable between 46 ps and 12 ps . The duration tunability was obtained by varying the output coupler (OC) transmission while avoiding resorting to spatial hole burning (SHB) for pulse shortening. At a repetition rate of 91 MH...

We report on a high-power, passively mode-locked, TEM00 Nd:YVO4 oscillator with adjustable pulse duration between 46 and 12ps. The laser is end-pumped by an 888nm laser diode and mode-locking is achieved with a semiconductor saturable absorber mirror (SESAM). The laser has a repetition rate of 91MHz and the M2 beam quality factor is better than 1.2...

A high-power semiconductor saturable absorber mirror (SESAM)-passively modelocked TEM₀₀ Nd:YAG oscillator based on a diode-side-pumped single laser head is reported. This laser provides 21.4 W of average power at a repetition-rate of 82 MHz with 18 ps pulse duration. This laser could be an essential part in future high flux monochromatic...

A design for a 20 W-sub-20 ps class mode-locked Nd:YAG oscillator is proposed.It demonstrates that Nd:YAG still has the potential to produce higher average power picosecond pulses with a single oscillator laser head and might be a good candidate to be part of a high flux compact X-ray source.

In order to carry out applications with single attosecond pulses isolated by controlling the carrier-envelop-phase (CEP) of the driving field in a reasonable time, the need of CEP-stabilized laser sources, currently based on Ti:sapphire, delivering pulses with both high peak and average power will increase in the next few years. The development of...

We report on the direct seeding of a 7-fs Ti:sapphire oscillator into a fiber amplifier at 100-kHz repetition rate used for pumping a NOPA. 1-muJ pulses have been then recompressed down to 15-fs.

We report on the direct seeding of a 7-fs Ti:sapphire oscillator into a fiber amplifier at 100-kHz repetition rate used for pumping a NOPA. 1-µJ pulses have been then recompressed down to 15-fs.

A multi-Petawatt high-energy laser PETAL coupled to the Ligne d'Intégration Laser (LIL) is under construction in the Aquitaine Region in France. This Petawatt laser will be dedicated to academic experiments in the fields of high energy density physics and ultra high intensity. Nd : glass laser chain coupled with the chirped pulse amplification (CPA...

The goal of this project is to develop a compact device which can produce an intense flux of monochromatic X- rays for medical applications. It is based on Compton back-scattering resulting from collisions between laser pulses and relativistic electron bunches. Intense laser beams can be obtained with a high gain Fabry-Perot cavity coupled with eit...

Using, a time resolved optical heterodyne Kerr effect experiment along with a Raman light diffusion experiment, we have measured the nuclear (non-instantaneous) and electronic (instantaneous) contributions to the nonlinear index of refraction in tellurite niobium-doped and silicate lead-doped glasses. The experimental set-up and the procedure used...

An important issue, mosaic grating compressor, is studied to recompress pulses for multiPetawatt, high energy laser systems. Alignment of the mosaic elements is crucial to control the focal spot and thus the intensity on target. No theoretical approach analyses the influence of compressor misalignment on spatial and temporal profiles in the focal p...

A l'aide de deux techniques complémentaires, nous avons étudié sur une large gamme de température la dynamique de relaxation de composés à transition d'état de spin photo-excités. Ces composés sont particulièrement intéressants pour le stockage optique d'information. Nous avons ainsi montré qu'il était possible de stocker durablement une informatio...

We present what is to our knowledge a new method for measuring the relative piston between two independent beams separated by a physical gap, typical of petawatt facilities. The feasibility of this measurement, based on quadriwave lateral shearing interferometry, has been demonstrated experimentally: piston has been measured with accuracy and sensi...

High-energy petawatt lasers using the chirped-pulse amplification technique require meter-sized gratings to limit the beam fluence on the surface of the grating. An alternative, studied by many groups, is a mosaic grating consisting of smaller, coherently added gratings. We propose what we believe to be a new compression scheme consisting of beam p...

We present a new method based on multi-wave shearing interferometry to measure the relative phase between two independent beams separated by a physical gap. Experimental results show accuracy and sensitivity better than 50nm.

A Multi-Petawatt High-Energy laser coupled to the LIL (MPWHE-LIL) is under construction in the Aquitaine Region in France. This facility will be open to academic community. Nd:glass laser chain and Chirped Pulse Amplification (CPA) technique makes possible to deliver high energy. Optical Parametric Chirped Pulse Amplification (OPCPA) for pre-amplif...

We present a new method based on multi-wave shearing interferometry to measure the relative phase between two independent beams separated by a physical gap. Experimental results show accuracy and sensitivity better than 50 nm.

We report on a novel approach of ultra-broad bandwidth parametric amplification around degeneracy. A bandwidth of up to 400-nm centered around 800 nm is amplified in a BBO crystal by using chirped pump pulses with a bandwitdth as broad as 10 nm. A supercontinuum signal is generated in a microstructured fiber, having to first order a quadratic chirp...

Using two complementary techniques, the relaxation of a photo-induced spin state transition in a strongly cooperative compound has been studied from 10 to 170 K. Up to 150 K, the relaxation rate increases with temperature. At higher temperature, the stabilization of the high-spin state results in a decrease of the relaxation rate. Within the hyster...

The parametric amplification of supercontinuum radiation generated in a microstructured fiber is reported. Up to 400-nm bandwidth is amplified by using chirped broadband pump pulses. The approach has the potential for an octave-spanning parametric amplification.

The measurement of the coherence characteristics of the speckles generated by an optically smoothed laser source is investigated. We present a new method that can be used for every kind of smoothing technique. A modified Mach–Zehnder interferometer allows us to measure both the lifetime and the spatial transverse size of the hot spots generated by...

Within the thermal hysteresis loop of the [Fe(PM-BiA)2(NCS)2] compound, a single laser pulse of 14 mJcm−2 induces a photo-conversion from the low spin (LS, S=0) to the high spin (HS, S=2) state of the Fe2+ metallic center. The temporal dynamic of this phenomena indicates that the system is firstly photo-excited into the HS state and then slowly rel...

We present a new compact laser oscillator, which delivers incoherent smoothed beam. It yields 50ns pulse width at repetition rate of 1Hz. Its 20mJ energy pulse may be directly injected in high energy laser chain.

An important issue, segmented mosaic gratings, is studied to recompress pulses for multi-PW laser systems. Alignment of the mosaic elements is crucial. We discuss theoretical model of phase shift and tolerances on alignment are presented.

We present a new compact laser oscillator, which delivers incoherent smoothed beam. It yields 50 ns pulse width at repetition rate of 1 Hz. Its 20 mJ energy pulse may be directly injected in high energy laser chain.

A multi-Petawatt Laser facility is under studies in the Ligne d'Intégration Laser (LIL) building. This Petawatt laser can be coupled with the eight nanosecond multikilojoules beams of the LIL or be used alone. The technical issues to reach the multi-petawatt level (front end, compression stage, performances) and the experimental configurations are...

The second-order nonlinear optical (SONLO) response of a series of the highly chemically and thermally stable polychlorotriphenylmethyl monoradicals 1-8 has been studied by Hyper-Rayleigh Scattering. These radicals exhibit relatively high nonlinear optical (NLO) responses with β values ranging from 118 × 10-30 to 755 × 10-30 esu, which may result f...

The second-order nonlinear optical (SONLO) response of a series of the highly chemically and thermally stable polychlorotriphenylmethyl monoradicals 1-8 has been studied by Hyper-Rayleigh Scattering. These radicals exhibit relatively high nonlinear optical (NLO) responses with beta values ranging from 118 x 10(-30) to 755 X 10(-30) esu which may re...

Molecular quadratic hyperpolarizability (βc) of substituted polychlorinated triphenylmethyl radicals, 1–8, has been determined by using the harmonic light scattering (HLS) technique. Results showed that this opens-shell family known to possess a good chemical stability also exhibited a very large SONLO response. The presence of a permanent dipole m...

Summary form only given. We have studied and demonstrated an all-optical amplitude and phase modulation scheme able to operate at frequencies above 100 GHz. This method relies on the adapted phase method which has previously allowed one to efficiently generate narrow bandwidth second harmonic and more recently fundamental or second harmonic program...

Summary form only given. A second order susceptibility χ(2) due to the coupling of the third order glass susceptibility χ(3) with a DC built-in electric field Eind has been induced in different thermally poled glasses. Here, for the first time, using a technique based on electric field induced second harmonic (EFISH), we measure the profile of the...

Quasi phase matching was induced within a few minutes by optical means in a thermally poled glass sample. The spatial modulation of χ 2 that was induced by two-photon absorption of the sample subjected to an intense sinusoidal pump intensity pattern resulted in a χ 2 grating. The second-harmonic generation produced by a probe beam was diffracted in...

Second-order susceptibility thermally induced in poled glass samples was erased in doped borophosphate, lead silica, and fused silica glasses using an optical method. A simple law describes the temporal evolution and the spatial profile of the erased nonlinear region versus the intensity and profile of the erasure laser beam. A comparison is made b...

Noncollinear frequency conversion of two femtosecond pulses is used to characterize the nonlinear profile induced in thermally poled fused silica. This technique permits one to deduce the nonlinear profile and the charge distribution induced by the poling treatment. These data and the current that passes through the sample during the poling are con...

We demonstrate that either one or two-photon absorption allow to tailor the spatial profile of second order susceptibility induced in a thermally poled borophosphate glasses. A law describing the phenomena is proposed.

Chirped femtosecond pulses are used in a pump-probe experiment to specifically characterize the non-instantaneous chi((3)) components in different liquids and glasses. Contrary to Kleinman symmetry, the chi(XXXX)((3))/chi(XYYX)((3)) ratio depends on the studied sample.

Chirped femtosecond pulses are used in a pump-probe experiment to specifically characterize the non-instantaneous X (3) components in different liquids and glasses. Contrary to Kleinman symmetry, the X (3) XXXX /X (3) XYYX ratio depends on the studied sample.

In the Born–Oppenheimer approximation and considering a Debye nuclear motion, a theoretical computation of pump–probe two-beam coupling in liquids using femtosecond chirped pulses is proposed. This technique makes it possible to specifically evidence the non-instantaneous contribution to the third-order susceptibility χ(3). Our model, which is an e...

Summary form only given. A second order susceptibility χ_ind⁽²⁾ is induced over ~10 μm beneath the anodic surface in thermally poled fused silica. It is due to coupling with a built in electric field E_int (χ_ind⁽²⁾~χ⁽³⁾E_int). To achieve quasi-phase-matching conditions (QPMC)...

Autocorrelation is one of the most commonly used methods for ultrashort pulses (<1 ps) characterization. Many measurement devices have been made with various nonlinear materials: second-harmonic generation in nonlinear crystals and Langmuir-Blodgett films, fluorescence in fused silica, absorption in semiconductors. We propose the use of a poled fus...

Summary form only given. Thermally induced second-order susceptibility located beneath the anodic surface over a 10 μm thick layer has been measured in thermally poled fused silica glasses. For many practical applications, one need to largely control the profile and the location of χ. We propose a non destructive method that allow us to infer the p...

© 2000 Optical Society of America

We demonstrate that the induced second order nonlinearity χ⁽²⁾ generated in thermal poled doped borosilicate glasses can be erased by a prolonged exposure to near IR laser radiation. The evolution of the second harmonic signal with respect to laser time exposure, intensity and wavelength is reported. The IR laser radiation induced relaxa...

Summary form only given. Separation of the electronic and nuclear (i.e. non-instantaneous) contributions in the time domain is usually difficult using femtosecond time-resolved optical techniques. To overcome this problem, it was suggested that the dominant mechanism could be identified by studying Kleinman symmetry of the nonlinear susceptibility...

Summary form only given. The occurrence of an induced χind(2) ~1 pm/V has attracted lot of interest because it offers the prospect of monolithically integrated nonlinear optical systems. However, for frequency converters, one has to create a quasi-phase matching (QPM) condition. Recent experiments suggested this could be performed using collimated...

The electronic and nuclear contributions to the third-order nonlinearity of glasses are separated by use of 100-fs pulses in a time-resolved heterodyne optical Kerr effect technique. A direct estimate of the relative strengths of electronic and nuclear contributions was made by the comparison between the nuclear contribution deduced from the Raman...

The electronic and nuclear contributions to the third order nonlinearity of glasses are separated using 100 fs pulses with a time-resolved heterodyne optical Kerr effect technique. The time evolution of the nuclear contribution is in very good agreement with results deduced from the Raman spectra. A direct estimate of the relative strengths of elec...

Second-harmonic generation in poled glasses opens new frontiers in optical material research. Within this context new borophosphate glasses of the Ca(PO3)2–CaB4O7–Na2B4O7–Nb2O5system were synthesized and their second-harmonic generation was evaluated after poling treatment. The enhancement of the second-harmonic signal with niobium oxide content is...

The first example of a spin-crossover iron(II) compound with a large negative third-order polarizability, associated with an instantaneous electronic response, is reported; magnetic measurements show that this compound, cis-bis(thio-cyanato)bis[N-(2-pyridylmethylene)aminobip henyl]iron(II), characterized by X-ray structural data is in the high-spin...

A femtosecond time-resolved optical Kerr effect experiment was carried out to study the reorientational motion of a series of cyanobiphenyl molecules around their long axis in the smectic-A phase. The Kerr effect was found to mainly result from the reorientation of the cyanobiphenyl core of the liquid crystal molecule. Three relaxation times were o...

Analysis of the spinning motion of liquid crystal molecules is reported for the first time. A femtosecond pump probe Kerr effect experiment allowed us to evidence both individual and collective contributions to this motion.

Molecular orientational dynamics of liquid crystalline (LC) materials is a subject of many researchers and has been studied by a large variety of techniques. More recently, with ultrashort laser pulses, time resolved measurements have been used to probe directly the fast dynamics for many different LC. Most of the works focus on the isotropic phase...

Times Cited: 15