HAL Portal IOGS (nstitut d'Optique Graduate School)
Not a member yet
12589 research outputs found
Sort by
Characterisation of barium hexaferrite thin films in microwave frequency band
No full textInternational audienceThe characterization of barium hexaferrite thin-films at microwave frequencies is important for determining their electromagnetic properties by measuring the elements of the permeability tensor. Layers of 15 µm were deposited by RF sputtering on a coplanar line. As a result of this deposition and annealing technique, the magnetic moments are mainly oriented in the plane of the layer. By measuring the S parameters under magnetic field conditions, the µ and κ elements of the permeability tensor were extracted and their variations as a function of the applied field were highlighted. Possible applications to absorbent layers are being considered
Unveiling mechanical interactions between cell division and extracellular matrix in human colonic epithelium organoids: A 4D study using DVC
No full textInternational audienceAbstract Cell division is a major event in tissue homeostasis, enabling renewal and regeneration. Stem cells, in particular, play an important role in this homeostasis, thanks to their ability to perform symmetric or asymmetric cell divisions. To study cell division, the human colon epithelium represents a model of choice due to its rapid renewal and therefore high proliferative potential. Currently, studying the live mechanical interactions between the epithelium and its matrix in vivo is challenging due to the lack of suitable methods. 3D human colon organoids seeded in Matrigel® are good models for this purpose as, from isolated stem cells, they recapitulate the tissue architecture organization and properties. This culture set-up also allows to study the matrix displacements around the organoid. Here, we studied the impact of cell division within the colonic epithelium on the extracellular matrix. We performed and validated an original experimental and analytical process with a 3D time-lapse confocal microscopy to follow cell mitosis and matrix movements on which we performed Digital Volume Correlation. We showed that these two different types of cell division impact the matrix differently with the asymmetric divisions causing a mainly uniaxial displacement, whereas symmetric ones involved a multiaxial and more important one
Rapid and non-destructive nanofiber diameter measurement using Spontaneous Four Wave Mixing
No full textInternational audienceWe will present a rapid and non-destructive technique for the measurement of the mean diameter of a silica nanofiber using the wavelength position of the signal peak in a spontaneous four wave mixing experiment. The nanofiber diameter can be characterized in a range going at least from 650 to 1250nm. Several nanofibers were characterized, and the measured diameter show a good accordance with the one obtained using a Scanning Electron Microscope. The technique is simple to use and has even the potential to be implemented in situ in order to realize a diameter measurement during the pulling of the nanofiber for a better control of the final diameter of the nanofiber
Making Light Matter
No full textInternational audienceLasers permeate our daily lives in many ways and specifically materials processing with lasers is key for numerous applications in science, technology, medicine, and industry. During the last years, different trends have been observed in the field of laser materials processing, i.e., (1) the pursuit of reaching extremely small scales and ultimate resolution in laser nanostructuring [1], and (2) an up-scaling of the processing rates for meeting industrial demands [2]. Both trends are driven by the rapid advancements in ultrafast laser technologies in terms of throughput, complexity, and interoperabilitycurrently manifesting in a Moorelaw-like scaling law of the average output powers with timeand, at the same time, benefiting from the latest developments in data-driven processes. Most applications of laser processing do manifest between these two extremes and are critically impacted by latest developments in material sciences.Europe plays a major role in each of these fields, as it successfully combines an excellent scientific environment with advanced technological capabilities and, thus, provided the ground for developing a successful industry in laser technologies. Long lasting scientific conferences, such as the Spring Meeting of the European Materials Research Society (E-MRS) [3] represent an important platform to exchange the latest developments among those fields
First on-sky tests of LQG control for a 10m-class telescope: prelude on the Gran Telescopio Canarias adaptive optics system
No full textInternational audienceThe Gran Telescopio Canarias (GTC) is being equipped with an Adaptive Optics (AO) system, 1 developed by the Instituto de Astrofísica de Canarias (IAC). 2 The Institut d'Optique Graduate School-Laboratoire Charles Fabry (IOGS-LCF), through a collaboration with the IAC, integrated some high performance control solutions. 3 In this proceeding, we present the first and promising on-sky results on a 10-meter class telescope for such a controller, namely a full Linear Quadratic Gaussian regulator (LQG). We start with a brief description of the GTCAO system, including the data-driven LQG regulator construction. Performance results are then presented with a full LQG regulator in line with the previous on-bench experiments, 3 implemented in DARC, 4 the GTCAO RTC. A comparison is performed with the integrator, the baseline controller, through the comparison of point spread functions acquired on the scientific camera and residual slopes recorded by the wavefront sensor
Probing the Local Rapidity Distribution of a One-Dimensional Bose Gas
No full textInternational audienceOne-dimensional Bose gases with contact repulsive interactions are characterized by the presence of infinite-lifetime quasiparticles whose momenta are called the “rapidities.” Here, we develop a probe of the local rapidity distribution, based on the fact that rapidities are the asymptotic momenta of the particles after a long one-dimensional expansion. This is done by performing an expansion of a selected slice of the gas. We first apply this idea to a cloud in the quasicondensate regime at equilibrium in a trap. We obtain an experimental picture of the position-dependent rapidity distribution which is in fair agreement with the theory prediction. The asymptotic regime is barely reached, but we show that finite expansion time can be taken into account using the generalized hydrodynamics theory. We then apply this local probe to an out-of-equilibrium situation where the local rapidity distribution is expected to be doubly peaked—a hallmark of a nonthermal state—even though the global rapidity distribution would possess no such distinctive feature. We observe the doubly peaked local rapidity distribution
High-power 2.3 µm Tm:YLF laser with intracavity upconversion pumping by a Nd:ASL laser at 1051 nm
No full textInternational audienceA Tm:LiYF 4 laser operating on the 3 H 4 → 3 H 5 transition is embedded in a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 µm. This leads to a record-high output power at 2.3 µm for any bulk thulium laser pumped by an upconversion process. The continuous-wave Tm:LiYF 4 laser delivers 1.81 W at 2.3 µm for 32 W of laser-diode pump power, making this kind of pumping competitive with direct diode pumping. The intracavity pumping process allows for counteracting the low absorption inherent to upconversion pumping and to dispatch the thermal loads on two separate laser crystals. The proposed laser architecture also features a relatively weak heating of the Tm:LiYF 4 crystal and an increased tolerance to Tm 3+ absorption. This laser design opens a new paradigm that holds great promise for high-power 2.3-µm solid-state lasers based on thulium ions
