Picosecond ultrasonics with a free-running dual-comb laser

We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a high-sensitivity pump-probe setup, we apply this free-running dual-comb laser to picosecond ultrasonic measurements. The ultrasonic signatures in a semiconductor multi-quantum-well structure originating from the quantum wells and superlattice regions are revealed and discussed. We further demonstrate ultrasonic measurements on a thin-film metalized sample and compare these measurements to ones obtained with a pair of locked femtosecond lasers. Our data show that a free-running dual-comb laser is well-suited for picosecond ultrasonic measurements and thus it offers a significant reduction in complexity and cost for this widely adopted non-destructive testing techniqu

Matériaux monocristallins à forte activité piézoélectrique : élaboration, caractérisation et application

Le travail traite de l\u27élaboration par la méthode Bridgman et par Bridgman modifié des monocristaux monophasiques PZN-PT et PMN-Pt de formulation générale Pb(Zn1/3Nb2/3)1-xTixO3 et Pb(Mg1/3Nb2/3)1-xTixO3. Après avoir caractérisé le monocristal PZN-0,045PT montrant ainsi la faisabilité de la croissance de cette formulation par Bridgman modifié, une étude comparative a montré que les propriétés des cristaux dépendent peu de la méthode de synthèse utilisée. Le problème de la ségrégation de titane dans les composites PMN-xPT élaborés par la méthode Bridgman classique a été mis en évidence. Il induit de fortes variations de composition et par conséquent de propriétés structurales, diélectriques et piézoélectriques le long du lingot cristallinle comportement des matériaux élaborés sous différentes conditions d\u27excitation - contrainte uniaxiale et cycle thermique - a été étudié. Cette étude permet de déterminer leurs limites de fonctionnement. L\u27application des matériaux PMN-0,25PT a été également étudiée. Il s\u27agit d\u27une poutre vibrante avec un élément piézoélectrique (cristal et céramique de même composition) qui permet de tester et de comparer les deux inserts en terme de récupération d\u27énergie

Matériaux monocristallins à forte activité piézoélectrique (élaboration, caractérisation et application)

Le travail traite de l'élaboration par la méthode Bridgman et par Bridgman modifié des monocristaux monophasiques PZN-PT et PMN-Pt de formulation générale Pb(Zn1/3Nb2/3)1-xTixO3 et Pb(Mg1/3Nb2/3)1-xTixO3. Après avoir caractérisé le monocristal PZN-0,045PT montrant ainsi la faisabilité de la croissance de cette formulation par Bridgman modifié, une étude comparative a montré que les propriétés des cristaux dépendent peu de la méthode de synthèse utilisée. Le problème de la ségrégation de titane dans les composites PMN-xPT élaborés par la méthode Bridgman classique a été mis en évidence. Il induit de fortes variations de composition et par conséquent de propriétés structurales, diélectriques et piézoélectriques le long du lingot cristallin ; le comportement des matériaux élaborés sous différentes conditions d'excitation contrainte uniaxiale et cycle thermique a été étudié. Cette étude permet de déterminer leurs limites de fonctionnement. L'application des matériaux PMN-0,25PT a été également étudiée. Il s'agit d'une poutre vibrante avec un élément piézoélectrique (cristal et céramique de même composition) qui permet de tester et de comparer les deux inserts en terme de récupération d'énergie.The work treats synthesis by the Bridgman method and modified Bridgman of single crystals PZN-PT and PMN-PT with a general formulation Pb(Zn1/3Nb2/3)1-xTixO3 et Pb(Mg1/3Nb2/3)1-xTixO3. After the characterization of PZN-0,045PT single crystal which showing the feasibility of the growth of this formulation by modified Bridgman, a comparative study that the properties of the crystals depend little on the synthesis method used. The phenomenon of titanium segregation in the PMN-xPT compositions synthesized by the Bridgman method was studied. It induced strong variations of composition and consequently of structural, dielectric and piezoelectric properties along the ingot of crystal. The behavior of materials under various conditions (uniaxial stress and thermal cycle) was studied. In order to point out the limiting factors in term of transducers performances. The application of PMN-0,25PT was also studied. The objective of the study is to test and compare ceramic and single crystal shapes harvesting energy using a vibrating beam with a piezoelectric element.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

Efficient continuous-wave Tm,Ho:CaF2 laser at 2.1 µm

We report on the first, to the best of our knowledge, continuous-wave laser operation of a Tm 3+ ,Ho 3+ -codoped calcium fluoride crystal at ∼2.1 µm. Tm,Ho:CaF 2 crystals were grown by the Bridgman method, and their spectroscopic properties were studied. The stimulated-emission cross section for the 5 I 7 → 5 I 8 Ho 3+ transition is 0.72 × 10 −20 cm 2 at 2025 nm, and the thermal equilibrium decay time is 11.0 ms. A 3 at. % Tm, 0.3 at. % Ho:CaF 2 laser generated 737 mW at 2062–2088 nm with a slope efficiency of 28.0% and a laser threshold of 133 mW. Continuous wavelength tuning between 1985 and 2114 nm (tuning range: 129 nm) was demonstrated. The Tm,Ho:CaF 2 crystals are promising for ultrashort pulse generation at ∼2 µm

Efficient Broadly Tunable Waveguide Lasers in Yb3+:CaF2 Produced by Deep Diamond Saw Dicing

International audienc

Tm3+ codoping for mid-infrared laser applications of Dy3+ doped CaF2 crystals

International audienceWe report here on a spectroscopic study of Dy3+-doped and Tm3+-Dy3+ doped CaF2 as promising candidates to develop crystalline waveguide laser sources around 3 μm. The advantages of Tm3+ ions as sensitizers to improve the excitation of Dy3+ ions in CaF2 is demonstrated: an energy transfer efficiency from Tm3+ to Dy3+ ions of 99.6% has been reached for Dy3+ concentration as high as 2 at.%, by considering a Tm3+ ratio set at 5 at.%. Moreover, the behavior of such doped crystals in a laser waveguide configuration has been modeled and the modeling results show that it seems possible to achieve promising laser perspectives around 3 μm, with laser thresholds in the watt level for singly doped Dy3+:CaF2 and around 0.2–0.3 W for codoped Tm3+-Dy3+:CaF2, presenting both laser efficiencies in the order of 30%. Finally, the saturation of the absorption which is observed in the modeling for such codoped Tm3+-Dy3+:CaF2 waveguide at Dy3+ concentration below 1% is discussed and its origin is explained

Efficient wavelength-tunable deep-diced ridge waveguide lasers in bulk Yb3+:CaF2 crystal

International audienc

Cross-relaxation and ion clustering in Tm3+:CaF2 crystals

International audienceWe systematically study cross-relaxation (CR) and ion clustering in Tm3+:CaF2 crystals using a spectroscopic approach. For this, the luminescence from the 3H4 and 3F4 states was monitored for a broad range of Tm3+ doping concentrations, from 0.01 at.% to 7 at.%. The decay curves were fitted using a model of two ions classes, namely isolated ions showing no energy-transfer processes and ions with neighbors exhibiting both CR and energy-transfer upconversion (ETU), and accounting for energy-migration. The fraction of ions with neighbors and the microscopic concentration-independent CR and ETU parameters are deduced. The critical Tm3+ doping level for which at least half of the active ions are clustered is only 0.7 at.%. The obtained results are relevant for achieving efficient laser operation of Tm3+:CaF2 crystals at the 3F4 → 3H6 (at ~1.9 μm) and the 3H4 → 3H5 (at ~2.3 μm) transitions

Mid-infrared laser operation of Er3+ -doped BaF2 and (Sr,Ba)F2 crystals

We report on the first, to our knowledge, mid-infrared laser operation of two Er 3+ -doped barium-containing fluorite-type crystals, BaF 2 and (Sr,Ba)F 2 , featuring a low-phonon energy behavior. A continuous wave 4.9 at.% Er:(Sr,Ba)F 2 laser generated 519 mW at 2.79 µm with a slope efficiency of 25.0% and a laser threshold of 27 mW. The vibronic and spectroscopic properties of these crystals are determined. The phonon energy of (Sr,Ba)F 2 is as low as 267 cm −1 . The Er 3+ ions in this crystal feature a broadband emission owing to the 4 I 11/2 → 4 I 13/2 transition and a long luminescence lifetime of the 4 I 11/2 level (10.6 ms) making this compound promising for low-threshold, broadly tunable, and pulsed 2.8-µm lasers

Er:KY 3 F 10 laser at 2.80 µm

International audienceWe report on the mid-infrared laser operation of a cubic 15 at.% E r 3 + : K Y 3 F 10 crystal. In the quasi-continuous-wave regime, the peak power reaches 255 mW at 2.80 µm (the 4 I 11 / 2 → 4 I 13 / 2 transition) with a slope efficiency of 10.9% and a laser threshold of 58 mW. Two pumping schemes (to the 4 I 11 / 2 and 4 I 9 / 2 states) are compared. The emission properties of the E r 3 + ions in K Y 3 F 10 are studied, indicating high stimulated-emission cross-section of 0.57 × 10 − 20 c m 2 at 2.80 µm, a large gain bandwidth of 40 nm, and a long 4 I 11 / 2 state lifetime of 4.64 ms