Leon Brillouin Research Articles

100 years of Brillouin scattering: Historical and future perspectives

The Year 2022 marks 100 years since Leon Brillouin predicted and theoretically described the interaction of optical waves with acoustic waves in a medium. Accordingly, this resonant multi-wave interaction is referred to as Brillouin scattering. Today, Brillouin scattering has found a multitude of applications, ranging from microscopy of biological tissue, remote sensing over many kilometers, and signal processing in compact photonic integrated circuits smaller than the size of a thumbnail. What allows Brillouin scattering to be harnessed over such different length scales and research domains are its unique underlying properties, namely, its narrow linewidth in the MHz range, a frequency shift in the GHz range, large frequency selective gain or loss, frequency tunability, and optical reconfigurability. Brillouin scattering is also a ubiquitous effect that can be observed in many different media, such as freely propagating in gases and liquids, as well as over long lengths of low-loss optical glass fibers or short semiconductor waveguides. A recent trend of Brillouin research focuses on micro-structured waveguides and integrated photonic platforms. The reduction in the size of waveguides allows tailoring the overlap between the optical and acoustic waves and promises many novel applications in a compact footprint. In this review article, we give an overview of the evolution and development of the field of Brillouin scattering over the last one hundred years toward current lines of active research. We provide the reader with a perspective of recent trends and challenges that demand further research efforts and give an outlook toward the future of this exciting and diverse research field.

SONATE, a French CANS for materials science research

Since 2015, the Laboratoire Leon Brillouin (LLB), operated by the CEA and the CNRS in France, has been developing a project plan to build a facility using a compact accelerator driven neutron sourc...

SpinWave, a software dedicated to spin wave simulations

An easy-to-use and versatile software, SpinWave, to calculate spin waves in any arbitrary magnetic lattice, has been developed at the Laboratoire Leon Brillouin and is now freely available.Develope...

7C2, the new neutron diffractometer for liquids and disordered materials at LLB

The disordered-materials diffractometer 7C2 at the Laboratoire Leon Brillouin (LLB), Saclay, France has been upgraded through the replacement of its detector. The old one, a banana like BF3 detector, has been replaced by a new ensemble of 3He tubes arranged on a cylindrical surface concentric with the sample position, covering an angular range of 133°, with an angular step of 0.52°. At the shortest wavelength, 0.57 Å, this represents a maximum momentum transfer of 20 Å-1. The gas pressure in the 3He tubes is 30 bars, which increases the efficiency to 80% for 0.72 Å neutrons, compared to 17% for the previous detector. A larger solid angle of detection and an improved efficiency have increased the total counting rate by a factor of 22, thereby reducing random error in the diffraction measurements. The banana-like multidetector gives to 7C2 the possibility of registering a complete diffractogram over the whole angular range in one shot, which is a comparative advantage with respect to other hot-neutrons two-axis diffractometers.

On the design and experimental realization of a multislit-based very small angle neutron scattering instrument at the European Spallation Source

This article reports the design of a versatile multislit-based very small angle neutron scattering (VSANS) instrument working either as a dedicated instrument or as an add-on for any small-angle neutron scattering machine like the proposed SANS instrument, SKADI, at the future European Spallation Source. The use of multiple slits as a VSANS collimator for the time-of-flight techniques has been validated using McStas simulations. Various instrument configurations to achieve different minimum wavevector transfers in scattering experiments are proposed. The flexibility of the multislit VSANS instrument concept is demonstrated by showing the possibility of instrument length scaling for the first time, allowing access to varying minimum wavevector transfers with the same multislit setup. These options can provide smooth access to minimum wavevector transfers lower than ∼4 × 10−5 Å−1 and an overlapping of wavevector coverage with normal SANS mode, e.g. with the SKADI wavevector range of 10−3–1.1 Å−1. Such an angularly well defined and intense neutron beam will allow faster SANS studies of objects larger than 1 µm. Calculations have also been carried out for a radial collimator as an alternative to the multislit collimator setup. This extends the SANS Q range by an order of magnitude to 1 × 10−4 Å−1 with much simpler alignment. The multislit idea has been realized experimentally by building a prototype at Laboratoire Leon Brillouin, Saclay, with cross-talk-free geometry. Feasibility studies were carried out by making VSANS measurements with single- and multislit collimators, and the results are compared with multiple-pinhole geometry using classical SANS analysis tools.

EROS II: A boosted time-of-flight reflectometer for multi-purposes applications at the Laboratoire Léon Brillouin

We present the characteristics and performances of the time-of-flight EROS reflectometer, located at Laboratoire Leon Brillouin (Saclay, France), which operates on the high-flux Orphee reactor. It is a versatile spectrometer with a horizontal geometry enabling air/liquid, air/solid and solid/liquid measurements. It is mostly dedicated to soft matter projects but welcomes also studies on thin solid films. It is equipped with a multi-disc chopper providing a tunable δλ/λ resolution, a collimation system with two deviating supermirrors and slits with flexible apertures allowing any given δθ/θ higher than 0.007, a large sample area, and a detector (either single tube or positioning sensitive detector). The accessible Q min is 0.0026 A−1 and the accessible Q max is 0.36 A−1 in air/solid or solid/liquid geometries and 0.21 A−1 in air/liquid geometry. The spectrometer has been upgraded during the last decade in order to reach a gain in flux of ∼ 50 from its original version. In air/solid geometry, we reach R min = 2×10−5 in 1 hour, R min = 8×10−7 in 4 hours and R min = 4×10−7 in 12 hours on a sample of ∼ 20 cm2 with EROS II, while it was difficult to go below 10−5 with the initial version dating from 1992. In air/liquid or solid/liquid geometries, we show that the main limitation to reach very low reflectivities is the incoherent scattering of the liquid solvent (D2O) . For such geometries, we obtain R min of 5×10−6 in 4 hours after incoherent background subtraction. The rejuvenated EROS allows thus measurements of 15-20 samples of a few tens cm2 in a span of 4 days, which corresponds to the minimum time allocated to external users for a given experiment.

Optical Fiber Sensors Based on Brillouin Scattering

Optical physicists are carrying on the legacy of Leon Brillouin by developing and studying Brillouin-based optical fibers that can be used in telecommunications, nonlinear optics and the monitoring of civil structures such as bridges and dams.

Shear-Induced Desorption in Polymer Brushes

Shear-Induced Desorption in Polymer Brushes

New evanescent neutron wave diffractometer at LLB

A new surface diffraction option has been mounted on the reflectometer EROS at the Laboratoire Leon Brillouin (LLB). The originality of the design lies in the fact that we are working in a Laue-type configuration. The sample is mounted horizontally on a goniometric table. A position-sensitive detector (PSD; 200 mm × 200 mm) can be swept around the sample in the horizontal plane. The sample is illuminated by a white beam, the Bragg diffraction angle is defined by the PSD position, the dhkl is fixed by the material then according to Bragg’s law the wavelength is selected. Time-of-flight measurements can be performed to measure the diffracted wavelength. Measurements on 1-cm2 samples show that the intensity in the surface diffraction peaks at about 0.5–1 counts s-1.Measurements have been performed on non-magnetic crystals and on a magnetic Co epitaxial thin film.

Characterization of 'strong-fragile' behaviour of glass-forming aqueous solutions by neutron scattering

Neutron-scattering measurements have been performed on trehalose/H2O and sucrose/H2O mixtures by using the spectrometer MIBEMOL at the Laboratoire Leon Brillouin (LLB, Saclay) as a function of temperature and concentration. In order to characterize the different rigidities of both the disaccharide/H2O mixtures, we have evaluated the R1(Tg) parameter connected to the ‘strong–fragile’ classification of the systems according to Angell’s nomenclature.

Vibrational versus relaxational contribution for disaccharide-water glass formers: Neutron scattering evidence

Abstract The results of neutron scattering measurements performed on trehalose-H2O and sucrose-H2O mixtures are reported. Measurements have been carried out using the time-of-flight spectrometer MIBEMOL at the Laboratoire Leon Brillouin (Saclay). The investigated temperature range was 88-283 K. The study is principally addressed to the evaluation of the relative weight of vibrational over relaxational contributions of homologous disaccharide-H2O glass formers. The comparison with literature data allows us to characterize their different degrees of fragility.

Determination of steep stress gradients at surfaces or interfaces by means of neutron diffraction

Abstract A series of measurements has been performed on the neutron strain scanner of the Laboratoire Leon Brillouin in order to explore the limits of the spatial resolution achievable by neutron stress analysis. Two types of samples were investigated, i.e. sandwich structures consisting of thin sheets of copper and aluminum nitride (AIN) and shot peened steel sheets. With slits before and after the sample as small as 0.3 × 10 mm2 (AIN) or even 0.15 × 10mm2 (steel) counting times were not longer than 1–2 h/peak. Checks revealed that a spatial resolution of ≈0.3 mm (AIN) resp. 0.15 mm (steel) was indeed achieved in the direction perpendicular to the surface. Using partial immersion of the gauge volume, near-surface/interface strains could be explored with even higher spatial resolution, down to ≈30 μm in the case of steel. The stress gradients determined by neutron diffraction were checked by measurements using other techniques.

Vibrational and relaxational contributions indisaccharide/H2Oglass formers

Among oligosaccharides, trehalose seems to be unique in nature as a bioprotector in drying and freezing processes. To understand the molecular mechanisms underlying the unusual bioprotective properties of trehalose in comparison with other disaccharides, the low-frequency dynamics of aqueous $({\mathrm{H}}_{2}\mathrm{O}$ and ${\mathrm{D}}_{2}\mathrm{O})$ mixtures of homologous disaccharides, trehalose, and sucrose has been studied by neutron scattering measurements carried out using the Mibemol spectrometer at the Laboratoire Leon Brillouin (LLB, Saclay). The principal aim of this work is to compare the relaxational versus low-energy vibrational contributions of ${\mathrm{s}\mathrm{u}\mathrm{c}\mathrm{r}\mathrm{o}\mathrm{s}\mathrm{e}/\mathrm{H}}_{2}\mathrm{O}$ and ${\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}\mathrm{s}\mathrm{e}/\mathrm{H}}_{2}\mathrm{O}$ mixtures across the glass transition, in order to characterize, following a procedure first proposed by Sokolov and co-workers, the different ``fragile'' character of both the ${\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{a}\mathrm{c}\mathrm{c}\mathrm{h}\mathrm{a}\mathrm{r}\mathrm{i}\mathrm{d}\mathrm{e}/\mathrm{H}}_{2}\mathrm{O}$ mixtures.

Comparison of disaccharide solutions across glass transition

Quasi-elastic neutron scattering (QENS) measurements on trehalose/H 2O and sucrose/H 2O mixtures have been carried out using the spectrometer MIBEMOL at the Laboratoire Leon Brillouin (LLB, Saclay). The study, addressed to the comparison of the vibrational properties of the two homologous disaccharide water mixtures across the glass transition, allows to characterize the different rigidity of both the disaccharide/H 2O mixtures.

Neutron diffraction and computer simulation study of liquid CS2 and CSe2

The structure factor of liquid CS2 has been measured at ambient temperature by the 7C2 diffractometer at the Laboratoire Leon Brillouin†, Saclay, France. The result has been modelled by the reverse Monte Carlo (RMC) method. The only reported neutron diffraction measurement on liquid CSe2 has also been investigated in detail. In both cases initial configurations for the RMC runs have been obtained by molecular dynamics simulation using a simple soft sphere potential. It has been found that the main features of experimental results have been reproduced even by this choice suggesting that the structure of these systems is almost entirely described by the excluded volume. Examination of model size dependence of results has also been carried out revealing the importance of using large simulation boxes.

John Bardeen and the BCS Theory of Superconductivity

Every theory of superconductivity can be disproved! This tongue-in-cheek theorem struck a chord when Felix Bloch announced it in the early 1930s. Virtually every major physicist then working on theory—including Bloch, Niels Bohr, Wolfgang Pauli, Werner Heisenberg, Lev Landau, Leon Brillouin, W. Elsasser, Yakov Frenkel, and Ralph Kronig—had tried and failed to explain the mysterious phenomenon in which below a few degrees kelvin certain metals and alloys lose all their electrical resistance. The frequency with which Bloch's theorem was quoted suggests the frustration of the many physicists who were struggling to explain superconductivity.Neither the tools nor the evidence were yet adequate for solving the problem. These would gradually be created during the 1940s and 1950s, but bringing them to bear on superconductivity and solving the long-standing riddle required a special set of talents and abilities: a deep understanding of quantum mechanics and solid-state physics, confidence in the solubility of the problem, intuition about the phenomenon, a practical approach to problem-solving, patience, teamwork, and above all refusal to give up in the face of repeated failures. When John Bardeen took on the problem of superconductivity in the late 1930s, he held it like a bulldog holds a piece of meat, until he, his student J. Robert Schrieffer, and postdoctoral candidate Leon Cooper solved it in 1957.

Experimental investigation of the structure of nonionic microemulsions and their relation to the bending elasticity of the amphiphilic film.

Oil-in-water microemulsions of nonionic surfactants of type ${\mathrm{C}}_{n}{E}_{j}$ with various hydrocarbons have been characterized by means of small-angle-neutron-scattering (SANS) (carried out at the Laboratoire Leon Brillouin, CEA-CNRS, Saclay, France) and interfacial tension measurements. The obtained structural parameters (radius $R$ and polydispersity index $p$) of this droplet system and the interfacial tension $\ensuremath{\gamma}$ were related to the bending elasticity of the amphiphilic film that can be described by the spontaneous curvature and two elastic constants, bending modulus $\ensuremath{\kappa}$ and saddle-splay modulus $\overline{\ensuremath{\kappa}}$. The validity of our method to extract $p$ from the shape analysis of the scattering curves has been confirmed by an independent contrast variation experiment. Both $p$ and $\ensuremath{\gamma}$ lead independently for all systems to very similar values for the elastic moduli. Their sum $2\ensuremath{\kappa}+\overline{\ensuremath{\kappa}}$ is proportional to the chain length of the surfactant but independent of our employed hydrocarbons (hexane\ensuremath{\rightarrow}decane). Finally, we also performed SANS experiments for a dilution series, where from the concentration dependence of $R$ and $p$ we are able to deduce independently this sum of the elastic constants that agrees well with the values obtained before. The elastic theory of the amphiphilic film allows for a self-consistent interpretation of structural and interfacial tension data and also to reliably predict one of these quantities from the knowledge of the other ones.

Surfaces and interfaces using neutron reflectivity

During the past ten years, neutron reflectivity has proved to be a very useful tool for the investigation of surfaces and interfaces. At Laboratoire Leon Brillouin in Saclay, we have developed a vast program of research centred on four different fields. Concentration profiles of polymers in the vicinity of the surface of solvent have been studied. Interdiffusion between polymer layers has also been investigated. Metallic multilayers which are now commonly used in many neutron optics devices like neutron guides, monochromators and supermirrors have received our interest.

Supermirrors study by neutron multireflection

We present here time of flight neutron multireflection measurements. This technique has been developed at the Laboratoire Leon Brillouin (Saclay-France). Used in the investigation of supermirrors NiC/Ti, it allows us to increase the precision of the measurement of the most important part of the curve for technological applications: the extension of the total reflection plateau. The results on three systems ( 58 Ni single layer, multilayer NiC/Ti, supermirror NiC/Ti) are presented in this paper. Beyond the good quality of the mirrors, they demonstrate the very good reliability of such a measurement. Moreover, they show that compared to a classical single reflection measurement, multireflection experiment enables us to increase the accuracy of the reflectivity value measured on the extended plateau

Maxwell’s Demon: Entropy, Information, Computing

About 120 years ago, James Clerk Maxwell introduced his now legendary hypothetical "demon" as a challenge to the integrity of the second law of thermodynamics. Fascination with the demon persisted throughout the development of statistical and quantum physics, information theory, and computer science--and linkages have been established between Maxwell's demon and each of these disciplines. The demon's seductive quality makes it appealing to physical scientists, engineers, computer scientists, biologists, psychologists, and historians and philosophers of science. Until now its important source material has been scattered throughout diverse journals. This book brings under one cover twenty-five reprints, including seminal works by Maxwell and William Thomson; historical reviews by Martin Klein, Edward Daub, and Peter Heimann; information theoretic contributions by Leo Szilard, Leon Brillouin, Dennis Gabor, and Jerome Rothstein; and innovations by Rolf Landauer and Charles Bennett illustrating linkages with the limits of computation. An introductory chapter summarizes the demon's life, from Maxwell's illustration of the second law's statistical nature to the most recent "exorcism" of the demon based on a need periodically to erase its memory. An annotated chronological bibliography is included. Originally published in 1990. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.