Search

Dieses Poster ist ein Begleitmaterial zum Beitrag "Die Entdeckung des Higgs-Bosons". This poster is supporting material for an article on the discovery of the Higgs boson.

This article illustrates different information visualization techniques applied to a database of classical composers and visualizes both the macrocosm of the Common Practice Period and the microcosms of twentieth century classical music. It uses data on personal (composer-to-composer) musical influences to generate and analyze network graphs. Data on style influences and composers ‘ecological’ data are then combined to composer-to-composer musical influences to build a similarity/distance matrix, and a multidimensional scaling analysis is used to locate the relative position of composers on a map while preserving the pairwise distances. Finally, a support-vector machines algorithm is used to generate classification maps. This article falls into the realm of an experiment in music education, not musicology. The ultimate objective is to explore parts of the classical music heritage and stimulate interest in discovering composers. In an age offering either inculcation through lists of prescribed composers and compositions to explore, or music recommendation algorithms that automatically propose works to listen to next, the analysis illustrates an alternative path that might promote the active rather than passive discovery of composers and their music in a less restrictive way than inculcation through prescription.

Upconversion pumping of thulium lasers emitting around 2.3 µm (the 3H4 → 3H5 transition) has recently attracted a lot of attention as it is compatible with the mature Yb-laser technology. To explore this possibility, we built a mid-infrared Tm:LiYF4 laser pumped by an Yb:CaF2 laser at 1.05 µm delivering an output power of 110 mW at 2.31 µm for a maximum incident pump power of 2.0 W. A strong absorption issue appeared in the Tm laser: the slope efficiency vs. the incident pump power was 7.6% while that vs. the absorbed pump power reached 29%. To overcome this issue, a dual-wavelength pumping at 0.78 µm and 1.05 µm was explored (combining both the direct and upconversion pumping schemes). The reciprocal interplay between the two pumps was studied to evaluate their benefits in terms of the pump absorption and laser efficiency. We observed an interesting decrease of the laser threshold for upconversion pumping when adding a small fraction of the direct pump revealing a seeding effect for the excited-state absorption from the metastable 3F4 level. A recycling process of this manifold by excited-state absorption in the 3F4 → 3F2,3 loop was also observed. The pump absorption seeding is a viable route for the development of low-threshold upconversion pumped thulium lasers.

The LED-pumping technology is used for the first time, to the best of our knowledge, to develop a complete master oscillator power amplifier (MOPA) system including a multipass amplifier. A pumping head using an original slab architecture is developed integrating a Cr:LiSAF slab pumped by 2112 blue LEDs via a Ce:YAG luminescent concentrator. The slab configuration enables the reaching of a large number of passes—up to 22—together with access to efficient cooling, allowing for a repetition rate scale up. For 22 passes, the amplifier delivers pulses with energy up to 2.4 mJ at 10-Hz repetition rate with a gain of 4.36 at 825 nm. A complete study of the MOPA is described, concluding in nearly constant performances versus the repetition rate, up to 100 Hz.

The discovery of the Higgs boson by the ATLAS and CMS collaborations in 2012 concluded the longest search for a particle in the history of particle physics and was based on the largest and most complex physics experiments ever conducted, involving thousands of scientists and engineers from around the world. It provided crucial evidence for a theory developed in the 1960s that describes the existence of the invisible Brout-Englert-Higgs field and the effects of this field on the mass of elementary particles. After the discovery, the work on the theoretical prediction was awarded the Nobel Prize in Physics 2013. This discovery provides a prime example of modern science in the making and a fantastic opportunity to discuss important aspects of Nature of Science (NoS) in the classroom. In this article, we draw connections between a) milestones in the discovery of the Higgs boson, b) important aspects of NoS, and c) hands-on activities with mystery boxes, which are an effective tool to enable students to experience elements of scientific discovery and explicitly reflect on NoS. We hope that this supports educators in bringing lively discussions about modern physics research into their classrooms., 18 pages, 6 figures

We report on the first laser operation of a disordered Tm:CaGdAlO4 crystal on the 3H4 → 3H5 transition. Under direct pumping at 0.79 µm, it generates 264 mW at 2.32 µm with a slope efficiency of 13.9% and 22.5% vs. incident and absorbed pump power, respectively, and a linear polarization (σ). Two strategies to overcome the bottleneck effect of the metastable 3F4 Tm3+ state leading to the ground-state bleaching are exploited: cascade lasing on the 3H4 → 3H5 and 3F4 → 3H6 transitions and dual-wavelength pumping at 0.79 and 1.05 µm combining the direct and upconversion pumping schemes. The cascade Tm-laser generates a maximum output power of 585 mW at 1.77 µm (3F4 → 3H6) and 2.32 µm (3H4 → 3H5) with a higher slope efficiency of 28.3% and a lower laser threshold of 1.43 W, out of which 332 mW are achieved at 2.32 µm. Under dual-wavelength pumping, further power scaling to 357 mW at at 2.32 µm is observed at the expense of increased laser threshold. To support the upconversion pumping experiment, excited-state absorption spectra of Tm3+ ions for the 3F4 → 3F2,3 and 3F4 → 3H4 transitions are measured for polarized light. Tm3+ ions in CaGdAlO4 exhibit broadband emission at 2.3 - 2.5 µm making this crystal promising for ultrashort pulse generation.

We report on a bulk thulium laser operating on the 3H4 → 3H5 transition with pure upconversion pumping at 1064 nm by an ytterbium fiber laser (addressing the 3F4 → 3F2,3 excited-state absorption (ESA) transition of Tm3+ ions) generating 433 mW at 2291 nm with a slope efficiency of 7.4% / 33.2% vs. the incident / absorbed pump power, respectively, and linear laser polarization representing the highest output power ever extracted from any bulk 2.3 µm thulium laser with upconversion pumping. As a gain material, a Tm3+-doped potassium lutetium double tungstate crystal is employed. The polarized ESA spectra of this material in the near-infrared are measured by the pump-probe method. The possible benefits of dual-wavelength pumping at 0.79 and 1.06 µm are also explored, indicating a positive effect of co-pumping at 0.79 µm on reducing the threshold pump power for upconversion pumping.

We study a second harmonic generation interaction geometry in the case where both group velocity mismatch and walk-off have significant impacts. This results in a frequency-converted beam exhibiting a pulse front tilt. Using the global response function of the crystal, we provide an analytical model that allows to predict the spatiotemporal structure of the second harmonic wave packet and verify its validity using numerical simulations and a simple experiment. Distinctive features of this geometry are the suppression of back-conversion and the ability to conserve the fundamental bandwidth in space and time domains. Subsequent compensation of the pulse front tilt should allow efficient generation of ultrashort pulses in the deep ultraviolet.

Cavity-free, precision-tunable source of a nanosecond, mJ-level, pulses consisting of backward optical parametric oscillator pumped by diode-seeded laser amplifier shows a record threshold of 19 MW/cm2 and an optical-to-optical efficiency exceeding 70%.

We report on an ultra-broadband mid-infrared source based on intrapulse difference-frequency-generation with time-delay and chirp optimizations of the pump and signal pulses, delivering 600 nJ, 50 fs pulses at 8.6 µm and 250 kHz repetition-rate.

Excited-state absorption of Tm3+ ions (3F4→3F2,3 and 3H4) in the KLu(WO4)2 crystal is studied. Mid-infrared laser operation (3H4→3H5) is achieved with this crystal under upconversion pumping at 1.06 μm yielding 433 mW at 2291 nm. © 2022 The Author(s)

We present studies about upconversion pumping at 1.05 µm for Tm:YLF lasers emitting at 2.3 μm. To improve the performance of this pump, we explore the possibility dual pumping with 780 nm.

Cascade lasing in a Tm:CALGO crystal at 1.8 µm (3F4→3H6) and 2.3 μm (3H4→3H5) is demonstrated with the originality of lacking a competition between the two laser channels, owing to dual-wavelength (direct and upconversion) pumping.

Precision-tunable mJ, nanosecond pulses at 1981.1 nm and 2145.6 nm are generated at 5kHz repetition with an efficiency of 70% in a cavity-free arrangement using a PPRKTP BWOPO pumped by a narrowband DPSSL at 1030nm.

We report on the design of a compact master oscillator power amplifier (MOPA) diode laser architecture at 828 nm suitable for direct-detection LIDARs, specifically applied to water vapor differential absorption LIDARs. Coherent beam combination of two pulsed high-brightness tapered amplifiers (1 μs, 10 kHz), seeded by a DBR laser diode, is demonstrated. The phase dynamics during the pulses have been thoroughly investigated. The main limitation to the CBC efficiency is quantified. The maximum combined pulse energy reaches 10.3 μJ with combining efficiency above 82% ± 5%.

This work was conducted with the aim of studying the biodiversity of benthic macroinvertebrates in the Dja River and determining the effect of the Mekin hydroelectric dam on their population in relation to the physico-chemical quality of the water. The study ran from May to October 2020 and samplings were carried out on a monthly basis in four different sampling stations located upstream and downstream of the dam. The physico-chemical analyses were done according to standard methods, while the benthic macrofauna was collected using a turbid net of 400 µm mesh size over a total area of about 6 m2per station. Physico-chemical analyses revealed a decreasing evolution from upstream to downstream of the dam of nitrogen forms (NO3-(1.67mg/L-0.41mg/L); NH4+(0.31 mg/L-0.21 mg/L) with p>0.05); Electrical Conductivity (21.45µS/Cm-17.1µS/Cm with pTrithemis dorsalis(96.05%); while downstream, Heteroptera was largely abundant and highly represented byPoissoniasp1. (79.78%). These results revealed that restoration of the upstream of the dam impacted by organic pollution and physical degradation of the environment is recommended.

We report the development of a high-brightness, high-power Ce:YAG luminescent concentrator pumped by 2240 blue LEDs in quasi-continuous wave operation (10 µs, 10 Hz). Using light confinement and recycling in the three space dimensions, the parallelepiped (1mm×14×mm×200mm) Ce:YAG emits a power of 145 W from a square output surface (1 × 1mm2) corresponding to a brightness of 4.6 kW/cm2/sr. This broadband yellow source has a unique combination of luminous flux (7.6 104 lm) and brightness (2.4 104 cd/mm2) and overcomes many other visible incoherent sources by one order of magnitude. This paper also proposes a deep understanding of the performance drop compared to a linear behavior when the pump power increases. Despite excited state absorption was unexpected for this low doped Ce:YAG pumped at a low irradiance level, we demonstrated that it affects the performance by tripling the losses in the concentrator. This effect is particularly important for small output surfaces corresponding to strong light recycling in the concentrator and to average travel distances inside the medium reaching meters.

A highly productive ablation process of 100 nm thick platinum films with a processed area rate of up to 378 cm

International audience; We report about a setup for carrier-envelope phase (CEP) control and stabilization in passive systems based on difference frequency generation (DFG). The principle of this approach relies on the amplitude to phase modulation transfer in the white-light generation process. A small modulation of the pump laser intensity is used to obtain a DFG output modulated in CEP. This technique is demonstrated in a CEP-stable system pumped by an Yb-doped fiber amplifier. It is first characterized by measuring CEP modulations produced by applying arbitrary waveforms. The CEP actuator is then used for slow drifts correction in a feedback loop. The results show the capability of this simple approach for OPA/OPCPA CEP-stabilized setups.

Transition metal-doped gain media such as Ti:sapphire, Cr:LiSAF and Alexandrite are the most appropriated crystals for femtosecond laser chains with pulse duration below 100 fs. However, because of a low gain and an absorption band in the green/red region, these materials are difficult to pump directly with diodes. Hence, the main issue for a femtosecond laser chain is the complexity and the high cost of the pump sources for the amplifiers. One innovative solution is to take advantage of the compactness, robustness, and low price of the light-emitting diodes (LED) to pump transition metal-doped gain media. In this work, we report, to our best knowledge, the first femtosecond amplifier pumped by LED. For this demonstration, we choose the Cr:LiSAF crystal for its combination of high absorption, large emission cross section and relatively long radiative lifetime. We then present a LED-pumped Cr:LiSAF regenerative amplifier in a femtosecond laser chain.

This paper applies clustering techniques and multi-dimensional scaling (MDS) analysis to a 500 × 500 composers’ similarity/distance matrix. The objective is to visualize or translate the similarity matrix into dendrograms and maps of classical (European art) music composers. We construct dendrograms and maps for the Baroque, Classical, and Romantic periods, and a map that represents seven centuries of European art music in one single graph. Finally, we also use linear and non-linear canonical correlation analyses to identify variables underlying the dimensions generated by the MDS methodology.

International audience; High-order harmonic generation (HHG) from crystals is emerging as a new ultrashort source of coherent extreme ultraviolet (XUV) light. Doping the crystal structure can offer a new way to control the source properties. Here, we present a study of HHG enhancement in the XUV spectral region from an ionic crystal, using dopant-induced vacancy defects, driven by a laser centered at a wavelength of 1.55 lm. Our numerical simulations based on solutions of the semiconductor Bloch equations and density-functional theory are supported by our experimental observations and demonstrate an increase in the XUV high harmonic yield from doped bulk magnesium oxide (MgO) compared to undoped MgO, even at a low defect concentration. The anisotropy of the harmonic emission as a function of the laser polarization shows that the pristine crystal's symmetry is preserved. Our study paves the way toward the control of HHG in solids with complex defects caused by transition-metal doping.

We present progress in high power GaAs-based single-pass semiconductor tapered optical amplifiers and modules tailored for coherent beam combining (CBC) in master-oscillator power-amplifier configuration. Amplifier design is first studied, by varying device geometry and epitaxial structure in 976nm devices. Epitaxial structures with large vertical near field and low wave-guiding from the active region enable higher CBC efficiency. However, changes to in-plane geometry did not improve performance. Overall, CBC of tapered amplifiers is stable, reproducible and robust, motivating next the development of 1064nm CBC-ready stand-alone sub-modules. Design, construction and test results from the pilot-series fabrication of these amplifier modules are presented.

International audience; Gas-filled multipass cells are an appealing alternative to capillaries to implement nonlinear temporal compression of high energy femtosecond lasers. Here, we provide an analytic expression for stationary beam coupling to multipass cells that takes into account nonlinear propagation. This allows a constant beam size on the mirrors and at the cell waist, thereby making the optical design more accurate, for example to avoid optical damage or significant ionization. The analysis is validated using spatio-temporal numerical simulations of the propagation in a near-concentric configuration. This is particularly important for multipass cells that are operated in a highly nonlinear regime, which is the current trend since it allows a lower number of roundtrips, relaxing the constraint on mirror coatings performance.

Blue-LED-pumped Ce: YAG luminescent concentrators are counting among the brightest incoherent light sources. This work shows that light recycling allows to enhance their brightness by one order of magnitude reaching 4.6 kW/cm²/sr.

In recent years, multi-petawatt laser installations have achieved unprecedented peak powers, opening new horizons to laser–matter interaction studies. Ultra-broadband and extreme temporal contrast pulse requirements make optical parametric chirped pulse amplification (OPCPA) in the few-picosecond regime the key technology in these systems. To guarantee high fidelity output, however, OPCPA requires excellent synchronization between pump and signal pulses. Here, we propose a new highly versatile architecture for the generation of optically synchronized pump–signal pairs based on the Kerr shutter effect. We obtained > 550 µ J pump pulses of 12 ps duration at 532 nm optically synchronized with a typical ultrashort CPA source at 800 nm. As a proof-of-principle demonstration, our system was also used for amplification of ∼ 20 µ J ultra-broadband pulses based on an OPCPA setup.

Diamond nanoparticles (nanodiamonds) can transport active drugs in cultured cells as well as in vivo. However, in the latter case, methods allowing to determine their bioavailability accurately are still lacking. Nanodiamond can be made fluorescent with a perfectly stable emission and a lifetime ten times longer than the one of tissue autofluorescence. Taking advantage of these properties, we present an automated quantification method of fluorescent nanodiamonds (FND) in histological sections of mouse organs and tumor, after systemic injection. We use a home-made time-delayed fluorescence microscope comprising a custom pulsed laser source synchronized on the master clock of a gated intensified array detector. This setup allows to obtain ultra-high-resolution images 120 Mpixels of whole mouse organs sections, with subcellular resolution and single-particle sensitivity. As a proof-of-principle experiment, we quantified the biodistribution and aggregation state of new cationic FNDs able to transport small interfering RNA inhibiting the oncogene responsible for Ewing sarcoma. Image analysis showed a low yield of nanodiamonds in the tumor after intravenous injection. Thus, for the in vivo efficacy assay we injected the nanomedicine into the tumor. We achieved a 28-fold inhibition of the oncogene. This method can readily be applied to other nanoemitters with $\approx$100 ns lifetime., Comment: Nanoscale, Royal Society of Chemistry, 2021

Resume Au-dela du patient, une erreur medicale peut affecter la vie personnelle et professionnelle du ou des medecins concernes. Toutes les enquetes montrent que les soignants sont plus ou moins durablement et gravement affectes a la suite d’une erreur medicale ayant eu des consequences serieuses. A l’occasion d’un evenement adverse grave, une assistance doit etre portee aux medecins concernes. Cette assistance porte a a fois sur la tracabilite et l’analyse des faits, mais aussi sur la communication avec les familles et concerne la prise en charge psychologique des praticiens. L’institution et les membres de l’equipe soignante ont un role immediat a jouer dans ce processus.

Yb-doped materials, due to their high saturation fluence and consequently their low gain, represent a challenging choice for high-energy amplifiers. In this Letter, we study two original amplifier designs adapted to a large number of passes capable of operating in the 100 mJ energy range at repetition rates up to 100 Hz using

We demonstrate that the combination of Ytterbium doped-fiber and bulk crystals amplifiers, in a Master Oscillator Power Amplifier configuration (MOPA) allows obtaining 3.6 mJ, 15 ns, single-frequency pulses and 5 kHz repetition rate.

International audience

We report on the CEP-stabilization of an ultrashort pulses Yb-doped source delivering 75 microjoules, 60 fs at 100 kHz with a measured every shot CEP noise lower than 320 mrad over 1s.

We present a technique to optimize the intrapulse difference frequency generation efficiency for mid-infrared generation. The approach employs a multi-order wave plate that is designed to selectively rotate the polarization state of the incoming spectral components on the relevant orthogonal axes for subsequent nonlinear interaction. We demonstrate a significant increase of the mid-infrared average power generated, of a factor ≥2.5 compared with the conventional scheme, owing to an optimally distributed number of photons enrolled in the difference frequency generation process.