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This paper investigates the impact of a sample structure on the amplitude of time-domain Brillouin scattering (TDBS) oscillations using silicon wafers with different oxide layer thicknesses as an example. According to the calculation results based on transfer matrix theory and Green's function, along with experimental results, we discovered that the amplitude of TDBS exhibits dual peaks corresponding to the thickness of the silicon dioxide layer, highlighting the TDBS's acute sensitivity to an internal sample structure. Furthermore, our computational results indicate that both the roughness of the sample and the non-monochromatic nature of the probe light affect the time-domain Brillouin scattering signal, underscoring the significant role of interference effects in TDBS detection. The outcomes of this study suggest that by precisely designing the thickness of the transducer layer, the time-domain Brillouin scattering signal can be enhanced, and it may be possible to determine the roughness of the sample using the amplitude of the time-domain Brillouin oscillation. This is beneficial for improving the detection accuracy of time-domain Brillouin scattering and for extracting a broader range of physical information from TDBS oscillations. [ABSTRACT FROM AUTHOR]

Picosecond ultrasonics is a technique where coherent acoustic phonons are generated with frequencies in the GHz frequency range. When optical detection is operated in a transparent medium, the interaction of these phonons with the probe pulses yields oscillations in the time domain that reveal Brillouin scattering. Their frequency is at the Brillouin frequency shift, commensurate with the phonon velocity. As the pump–probe experiments are time-resolved, changes in the Brillouin frequency with time can be attributed to changes in sound velocity with depth. As sound velocity is temperature-dependent in liquids, we show that the picosecond ultrasonics technique can be used for temperature depth profiling in liquids. In this work, the concept is proved using the pump absorption itself as a heat source and confronting measured changes in Brillouin frequency with depth with data resulting from the derivation of a 3D modeling of the temperature rise in the liquid. We demonstrate the remote depth profiling of temperature, with measured data spaced at a distance less than the optical wavelength. [ABSTRACT FROM AUTHOR]

We report on the field evolution of the microwave spin wave modes in magnonic crystals made of square antidot lattices etched in a thin film of the Co2MnSi Heusler alloy and having a lateral size s of 200 nm and an edge-to-edge separation d of 600 or 800 nm. The spin wave modes are investigated combining ferromagnetic resonance, Brillouin light scattering experiments, and micromagnetic simulations of the static and dynamic magnetic states as a function of the applied field. We show that for applied fields ≥10 mT, when the magnetization is quasi-saturated across the crystals, the two samples show similar behavior and the two most intense modes in the spin waves spectra correspond to a mode extending in the channels comprised between the antidot and a mode localized in the region between the antidots. For smaller fields, we observe a difference of the measured spectra as a function of d. This is attributed to the fact that for d = 800 nm, the magnetization remains partially uniform in the channel between the antidots because of the Heusler cubic crystal anisotropy, while for d = 600 nm, the magnetic edge domains around the antidots spread into the channels. Moreover, this anisotropy also allows different remanent states when initializing the crystals with a small magnetic field along two perpendicular directions. This leads to an efficient excitation or extinction of the spin wave modes, making possible to achieve reconfigurable microwave devices exploiting an antidot geometry in a metallic ferromagnetic with a low damping coefficient. [ABSTRACT FROM AUTHOR]

Since it was first predicted 100 years ago, Raman scattering has been a cornerstone of molecular spectroscopy with a widespread impact on science and technology. Nearly all theoretical frameworks have employed Raman cross sections (σRaman) to characterize and quantify molecular Raman response. The recently introduced absolute stimulated Raman scattering cross section (σSRS), on the other hand, provides an alternative way of interpreting molecular responses under two coherent laser sources. However, the theoretical connection between σRaman and σSRS remains unclear. Herein, we are inspired by Einstein's A and B coefficients for spontaneous and stimulated emissions and derived an analogous equation [Eq. (16)] for Raman scattering from an approach along quantum electrodynamics. Equation (16) decomposes Raman cross sections into a contribution from the vacuum electromagnetic field and an underlying molecular response captured by stimulated Raman cross sections (in the unit of Göppert–Mayer). This theoretical relation is supported by recent experimental measurements on methanol as a model compound. Foremost, it provides a connection between experimentally defined σRaman and σSRS under certain approximations. In addition, it quantitatively shows that it is the weak vacuum field of the Stokes channel that makes Raman cross sections appear so small, corroborating the conventional Raman theory. Moreover, it suggests stimulated Raman cross sections to be a vacuum-decoupled intrinsic quantity for characterizing molecular response during Raman scattering. Remarkably, stimulated Raman cross sections turn out to be not weak when compared to two-photon absorption, narrowing the conventional gap of cross sections between spontaneous Raman and UV–vis absorption by more than 1010 folds. [ABSTRACT FROM AUTHOR]

In this paper, we develop a method that combines optical birefringence properties and time-domain Brillouin scattering microscopy to determine in situ the optical axis orientation of each single micrometer size grain in a polycrystalline sample. We illustrate the method by investigating the room temperature multiferroic material BiFeO3 where the optical axis coincides with the ferroelectric polarization direction. We are able to find the grain orientation and also provide the sound velocity (longitudinal and transverse) since the method is based on the Brillouin scattering process. These advances open interesting perspectives for probing the anisotropy of a micrometer size grain with an extension to the evaluation of the ferroelastic domain orientation in a non-contact and non-destructive manner. [ABSTRACT FROM AUTHOR]

The development of a generalized machine learning approach based on distributed detection and quantification of cracks by optical fibers is described in this article. A Brillouin scattering optical fiber sensor system was employed to develop, test, and verify the method. The main components of the approach described herein consist of an unsupervised crack identification module based on the iForest algorithm and a crack quantification component by the one-dimensional convolutional neural network method. The main attribute of this model is the versatility for application in various types of structures. The proposed method does not require further application-dependent training or calibration as long as the structural applications employ the same optical fiber type and installation adhesives. The effectiveness of the proposed method was verified by two experiments involving a 15-m steel beam in the laboratory and monitoring a twin set of 332-m-long, five-span continuous box girder concrete bridges. Regarding crack detection capabilities, it was possible to detect 107 out of 112 cracks in the laboratory beam and 20 out of the 21 in the bridges. The resolution of crack opening displacements for the steel beam and concrete bridges were 20.6 and 21.7 µm, respectively. The verification experiments further indicated the generality of the approach in applications to various types of structures and materials. [ABSTRACT FROM AUTHOR]

Polymer colloidal crystals (PCCs) have been widely explored as acoustic and optical metamaterials and as templates for nanolithography. However, fabrication impurities and fragility of the self‐assembled structures are critical bottlenecks for the device's efficiency and applications. We have demonstrated that temperature‐assisted pressure [T,p]$T,p]$ annealing results in the mechanical strengthening of PCCs, which improves with the annealing temperature. Here, the enhancement of elastic properties and morphological features of self‐assembled PCC's is evaluated using Brillouin light scattering and scanning electron microscopy. The pressure‐induced effects on the vibrational modes of PCCs are also illustrated at temperatures well below the polymer glass transition. While the PCCs colloid constituents display reversibility, the PCC material is strongly irreversible in the performed thermodynamic cycle. The effective elastic modulus enhances from 0.7 GPa for the pristine sample to 0.8 GPa, solely by pressure annealing at room temperature. [T,p]$T,p]$ annealing at higher temperatures leads to a maximum effective elastic modulus of 1.7 GPa, more than twice the value in the pristine sample. Above a cross‐over pressure, pc(≈${{p}_{c\ }}(\approx $725 bar at 348 K), the PCCs respond elastically and, hence, reversibly to pressure changes. [ABSTRACT FROM AUTHOR]

A crack‐free and high structural quality Sr2Nb2O7 single crystals are grown by the optical float zone method using optimized growth parameters. The Laue pattern confirms the single crystalline nature of the grown crystal. Temperature‐dependent Raman and Brillouin light scattering studies reveal a significant shift in phonon modes across normal to incommensurate phase transition (Tn‐in) which occurs ≈488 K. In the temperature range from 900 down to 500 K, two optical phonon modes ≈63 (B1 mode) and 54 cm−1 (A1 mode) are observed. The frequency of A1 mode strongly decreases with an increase in temperature above the Tn‐in while the frequency of this mode almost remains constant below the Tn‐in. In contrast, the frequency of B1 phonon mode is found to increase with temperature in the range of 500–900 K but it does not display a significant shift below the phase transition temperature. In addition, in the in‐commensurate phase (T< 488 K), a new optical phonon mode (M1) at ≈35 cm−1 also begins to appear and exhibits strong stiffening behavior with an increase in temperature in the range of 300–488 K. Moreover, the anomalous behavior of the acoustic phonon across Tn‐in are further probed using Brilliouin scattering. Longitudinal acoustic phonon mode at 41 GHz exhibits a strong change in slope near Tn‐in. In addition, the transverse acoustic modes at 28.6 and 22.4 GHz also exhibit strong anomalies with minimum frequency near Tn‐in. The inelastic light scattering studies provide valuable information on the phase transition. [ABSTRACT FROM AUTHOR]

Ferroelectric and antiferroelectric materials are technologically important by the richness of applications such as piezoelectric, pyroelectric, electro-optic, elasto-optic, and nonlinear optic effects. Especially, oxides with a perovskite structure are very important. Its chemical formula is ABO3, where A is a cation with a larger ionic radius, and B is a cation with a smaller ionic radius. Various elements are available in A- and B-sites. For example, the large piezoelectricity of well-known Pb(ZrxTi1−x)O3 (PZT) solid solutions was found in a morphotropic phase boundary (MPB). The very high dielectric constant, colossal piezoelectric effect, and large electro-optic effect are induced by ferroelectric phase transitions. Such excellent functionalities are closely related to lattice dynamical instability. The vibrational spectroscopy, i.e., Raman scattering, Brillouin scattering, far-infrared, and terahertz time-domain spectroscopy, is a powerful tool for lattice dynamical anomalies. This paper intended a brief review of vibrational spectroscopy on ferroelectric phase transitions of advanced perovskite oxides. [ABSTRACT FROM AUTHOR]

Strontium-barium niobate (SrxBa(1−x)Nb2O6) films can be considered as a promising material for microwave applications due to high dielectric nonlinearity and relatively low losses. Since strontium-barium niobate has a disordered structure that determines its unique electrical properties, the identification of structural features of the SrxBa(1−x)Nb2O6 films is the key to their successful use. The SrxBa(1−x)Nb2O6 films were synthesized on a sapphire substrate by magnetron sputtering. The structure of the films was studied by both traditional methods of electron microscopy, X-ray diffraction, and the rarely used for thin films investigation Brillouin light scattering method, which was the focus of our study. We show that Brillouin light scattering is an excellent nondestructive method for studying the structural features of thin ferroelectric strontium-barium niobate films. An analysis of the features of the Brillouin light scattering spectra in thin-film structures and their comparison with the spectra of bulk crystals allowed us to determine with high accuracy the thickness of the films under study and their structural features determined by the resonant scattering of acoustic waves. [ABSTRACT FROM AUTHOR]

Brillouin scattering provides a unique approach in diverse applications ranging from sensing to signal processing and beyond. The recent advancement in Brillouin scattering research has been driven by the development of integrated photonic platforms. However, the realization of efficient Brillouin scattering with substantial gains at low pump powers within compact devices is still a challenge. Here, a chalcogenide metasurface is proposed and demonstrated as a promising candidate for facilitating spontaneous Brillouin scattering. By employing Ge25Sb10S65 materials with remarkable photoelastic properties and leveraging the capacity of metasurfaces to effectively confine light waves through quasi‐bound states in the continuum, alongside their ability to confine acoustic waves via mechanical resonances, a substantial Brillouin gain of up to 27.7 dB at a low pump power of 23 mW is achieved within a metasurface with a compact dimension of <0.03 cm. The superior performance of chalcogenide metasurfaces‐based Brillouin scattering may hold profound potential to advance Brillouin scattering research and find wide applications. [ABSTRACT FROM AUTHOR]

A multimodal spectroscopic approach is proposed to correlate the mechanical and chemical properties of plastic materials in art and design objects, at both surface and subsurface levels, to obtain information about their conservation state and to monitor their degradation. The approach was used to investigate the photo-oxidation of acrylonitrile butadiene styrene (ABS), a plastic commonly found in many artistic and design applications, using ABS-based LEGO bricks as model samples. The modifications of the chemical and viscoelastic properties of ABS during photoaging were monitored by correlative Brillouin and Raman microspectroscopy (BRaMS), combined with portable and noninvasive broad-range external reflection infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) relaxometry, directly applicable in museums. BRaMS enabled combined measurements of Brillouin light scattering and Raman spectroscopy in a microspectroscopic setup, providing for the coincident probe of the chemical and mechanical changes of ABS at the sample surface. NMR relaxometry allowed for noninvasive measurements of relaxation times and depth profiles which are directly related to the molecular mobility of the material. Complementary chemical information was acquired by external reflection IR spectroscopy. The simultaneous probe of the chemical and mechanical properties by this multimodal spectroscopic approach enabled us to define a decay model of ABS in terms of compositional changes and variation of stiffness and rigidity occurring with photodegradation. The knowledge acquired on LEGO samples has been used to rate the conservation state of ABS design objects noninvasively investigated by external reflection Fourier transform IR spectroscopy and NMR relaxometry offered by the MObile LABoratory (MOLAB) platform of the European Research Infrastructure of Heritage Science. [ABSTRACT FROM AUTHOR]

Few known material systems can simultaneously guide optical and elastic fields through total internal reflection. This natural limit has restricted the realization of strong optoacoustic effects to highly specialized and purpose-built platforms, which employ either exotic materials or complex waveguide designs. Here, we apply the concept of Anti-Resonant Reflecting Acoustic Waveguides (ARRAWs) as a potential solution to this issue. ARRAWs confine the elastic field to a high-elastic-velocity core via the anti-resonances of a cladding layer of lower elastic velocity. We numerically study the appearance and dispersion of ARRAW-guided modes in a conventional silicon-on-insulator rib waveguide geometry. Applying the technique to the problem of efficient backward stimulated Brillouin scattering, we predict that ARRAW guidance, in conjunction with conventional optical confinement, can produce Brillouin gains comparable with those of more exotic geometries. [ABSTRACT FROM AUTHOR]

We investigate two-phonon parametric opto-mechanical generation in a solid state optical cavity pumped with two resonant counter-propagating coherent optical fields. We show that the optical frequencies of the fields must differ by more than the characteristic frequency of the stimulated Brillouin scattering in the material to support the parametric process. The optical harmonics associated with the subsequent optical scattering over the sound waves can be utilized for the excitation of low noise microwave signals. [ABSTRACT FROM AUTHOR]

Asymmetric (Pt/Co/X) multilayers where X is Ta or W have been investigated. Both structures showed a tailed hysteresis loop indicating the existence of skyrmions. The interfacial Dzyaloshinskii–Moriya interaction (iDMI) extracted from Brillouin light scattering revealed that sample with W has a value of −0.52 mJ/m2, which is ∼2.5 times larger than Ta case. In addition to iDMI, the perpendicular magnetic anisotropy is also stronger for W case due to the orbital hybridization at the interface. From magnetic force microscopy, W sample showed a change from unusual rod-like domains to skyrmions, while the change was from labyrinth domains to skyrmions in Ta-based structure. [ABSTRACT FROM AUTHOR]

The biomechanical properties of cells and tissues play an important role in our fundamental understanding of the structures and functions of biological systems at both the cellular and subcellular levels. Recently, Brillouin microscopy, which offers a label-free spectroscopic means of assessing viscoelastic properties in vivo, has emerged as a powerful way to interrogate those properties on a microscopic level in living tissues. However, susceptibility to photodamage and photobleaching, particularly when high-intensity laser beams are used to induce Brillouin scattering, poses a significant challenge. This article introduces a transformative approach designed to mitigate photodamage in biological and biomedical studies, enabling nondestructive, labelfree assessments of mechanical properties in live biological samples. By leveraging quantum-light-enhanced stimulated Brillouin scattering (SBS) imaging contrast, the signal-to-noise ratio is significantly elevated, thereby increasing sample viability and extending interrogation times without compromising the integrity of living samples. The tangible impact of this methodology is evidenced by a notable three-fold increase in sample viability observed after subjecting the samples to three hours of continuous squeezed-light illumination, surpassing the traditional coherent lightbased approaches. The quantum-enhanced SBS imaging holds promise across diverse fields, such as cancer biology and neuroscience where preserving sample vitality is of paramount significance. By mitigating concerns regarding photodamage and photobleaching associated with high-intensity lasers, this technological breakthrough expands our horizons for exploring the mechanical properties of live biological systems, paving the way for an era of research and clinical applications. [ABSTRACT FROM AUTHOR]

Hydrogen may be recycled into the Earth's lower mantle by subduction and stabilized in solid solutions between phase H (MgSiO4H2), δ-AlOOH, ε-FeOOH, and SiO2 post-stishovite. In high-pressure oxyhydroxide phases, hydrogen is incorporated following the typical (OHO) sequence, adopting the asymmetric configuration O-H⋯O that evolves into a symmetric disordered state upon compression. Moreover, these iron-bearing aluminum oxyhydroxides [δ-(Al,Fe)OOH] present a structural phase transition from P21nm to Pnnm as pressure increases. Here, the single-crystal elasticity of the P21nm phase of δ-(Al0.97Fe0.03)OOH has been experimentally determined across the P21nm→Pnnm transition up to 7.94(2) GPa by simultaneous single-crystal X-ray diffraction (XRD) and Brillouin scattering at high pressures. The transition appears to be continuous, and it can be described with a second-, fourth-, and sixth-order terms Landau potential. Our results reveal an enhanced unit-cell volume compressibility, which is linked to an increase of the b- and a-axes linear compressibility in the P21nm phase of δ-(Al0.97Fe0.03)OOH prior to the transition. In addition, we observed the presence of elastic softening in the P21nm phase that mostly impacts the elastic stiffness coefficients c12, c22, and c23. The observed elastic anomalies cause a significant change in the pressure dependence of the adiabatic bulk modulus (KS). These results provide a better understanding of the relation between elasticity, P21nm→Pnnm structural phase transition, and hydrogen dynamics in δ-(Al0.97Fe0.03)OOH, which may be applied to other O-H⋯O-bettring phases. [ABSTRACT FROM AUTHOR]

To control the spin wave (SW) propagation, external energy sources such as magnetic fields, electric currents, or complex nanopatterning are used, which can be challenging at the deep nanoscale level. In this work, we overcome such limitations by demonstrating SW propagation in Pt/Co multilayers at a remanent state controlled by stripe domain patterns, using Brillouin light scattering and micromagnetic simulations. We show that parallel stripes with a periodicity around 100 nm exhibit reconfigurability, as the stripes can be rotated by applying the in-plane field without damaging their shape. This allows us to study SW propagation perpendicular and parallel to the stripes. We observe multimodal SW spectra—three bands in perpendicular and five in parallel geometry. Numerical results allow us to identify all observed modes and to explain the differences between two configurations by the unequal contribution of all three magnetization components in the SW dynamics. We find that the experimentally measured non-reciprocal dispersion (for the wavevector perpendicular to the stripes) is not the breaking of time-symmetry but the asymmetry in intensity of the measured signals of two different low-frequency modes, which is due to the inhomogeneous SW amplitude distribution over the multilayer thickness and the limited light penetration depth. Our results pave the way for easy reprogrammability and high energy efficiency in nanomagnonics. [ABSTRACT FROM AUTHOR]

Driven by a large number of emerging diversified services, in the 5G and beyond era, concurrent direct inter-ONU and upstream communications inside a PON-based mobile access network are highly desirable to provide dynamic, ultra-dense, and fast ONU-to-ONU (without involving an OLT) and ONU-to-OLT connections. To cost-effectively deliver highly dynamic and low latency direct inter-ONU communications, this paper proposes and experimentally demonstrates novel concurrent direct inter-ONU and upstream communications in an upstream 27 km, >62.47 Gbit/s IMDD PON. For supporting inter-ONU communications between a large number of ONUs, an advanced passive remote node is also proposed. Based on different passive optical components, this remote node can be implemented using two approaches, which can, respectively, reduce the inter-ONU signal power losses by >12.2 dB and >16.6 dB (for 128 ONUs) in comparison with existing inter-ONU communication techniques' remote nodes. In each ONU and OLT, a single pair of cascaded IFFT/FFT-based point-to-multipoint (P2MP) flexible optical transceivers are employed to simultaneously and dynamically establish multiple ONU-to-ONU and ONU-to-OLT communications according to actual users' requirements. Experimental results show that the proposed network has excellent robustness against various transmission system impairments, including chromatic dispersion, the Rayleigh and Brillouin backscattering effects, and the channel interference effects. For each ONU, dynamic channel allocation can be made without compromising its overall performance. [ABSTRACT FROM AUTHOR]

We present a novel method of modeling the contact between a metal and a two-dimensional semiconductor. Using Au on MoS 2 as an example, we self-consistently solve the Schrödinger and Poisson equations and obtain the charge density in the contact. We consider open boundary conditions using the quantum transmitting boundary method and model the electron current through the contact region. We then investigate the effect of effective Schottky barrier height, electrostatic doping, and length of the overlap region on the contact resistance in a top contact geometry. By using data from experiments or from ab initio calculations for the fitting of parameters, such as the effective Schottky barrier height, the model can be used to efficiently obtain the contact resistance and, therefore, the quality of the contact. Furthermore, we investigate the effect of sampling of the Brillouin zone in the transverse direction on the numerical calculation of key quantities, such as contact resistance and free charge density. Additionally, we show that the boundary conditions applied to the Poisson equation during the calculation of the free charge density have a significant impact on the calculated contact resistance and that the impact is more pronounced in heterostructures with a larger Schottky barrier. We found that the contact resistance may be significantly underestimated, by up to one order of magnitude, when the height of the simulation domain is not large enough. [ABSTRACT FROM AUTHOR]

We employed high-pressure Brillouin scattering to study the pressure dependencies of acoustic modes of glycerol up to 14 GPa at 300 K. We observed longitudinal acoustic velocities and transverse acoustic velocities for the first time from 5 to 14 GPa. The results allow the determination of a complete set of elastic properties and an accurate determination of the pressure–volume (P–V) equation of state (EOS). EOS parameters, K0 = 14.9 ± 1.8 GPa and K′0 = 5.6 ± 0.5, were determined from fits to the data from ambient pressure to 14 GPa. Direct volume measurements of the P–V EOS are consistent with those determined by Brillouin scattering. A deviation from a Cauchy-like relationship for elastic properties was observed, and the pressure dependencies of the photoelastic constants and relaxation times were documented from 5 to 14 GPa. These results have broad implications for glass-forming liquids, viscoelastic theory, and mode coupling theory. [ABSTRACT FROM AUTHOR]

A modified Brillouin intensity measurement method was developed in this study. A means of adjusting a modern Brillouin scattering system to apply the methods presented in previous literature was identified, an analysis model of the geometric factors for a given light path in a Brillouin scattering system was proposed, and ambiguous discussions in the literature due to the idealized modeling of geometric factors were addressed. The proposed model was expanded into a 60° platelet symmetric geometry by measuring the elastic and elasto-optical coefficients of MgO, KTaO3, and TeO2 samples. To avoid deviation, the geometric factor in experiments was considered, and various ways to circumvent it were identified. [ABSTRACT FROM AUTHOR]

We report the adiabatic elastic constants of single-crystal thorium dioxide over a temperature range of 77–350 K. Time-domain Brillouin scattering, an all-optical, non-contact picosecond ultrasonic technique, is used to generate and detect coherent acoustic phonons that propagate in the bulk perpendicular to the surface of the crystal. These coherent acoustic lattice vibrations have been monitored in two hydrothermally grown single-crystal thorium dioxide samples along the (100) and (311) crystallographic directions. The three independent elastic constants of the cubic crystal (C11, C12, and C44) are determined from the measured bulk acoustic velocities. The longitudinal wave along the (100) orientation provided a direct measurement of C11. Measurement of C44 and C12 was achieved by enhancing the intensity of quasi-shear mode in a (311) oriented crystal by adjusting the polarization angle relative to the crystal axes. We find the magnitude of softening of the three elastic constants to be ∼2.5% over the measured temperature range. Good agreement is found between the measured elastic constants with previously reported values at room temperature, and between the measured temperature-dependent bulk modulus with calculated values. We find that semi-empirical models capturing lattice anharmonicity adequately reproduce the observed trend. We also determine the acoustic Grüneisen anharmonicity parameter from the experimentally derived temperature-dependent bulk modulus and previously reported temperature-dependent values of volumetric thermal expansion coefficient and heat capacity. This work presents measurements of the temperature-dependent elasticity in single-crystal thorium dioxide at cryogenic temperature and provides a basis for testing ab initio theoretical models and evaluating the impact of anharmonicity on thermophysical properties. [ABSTRACT FROM AUTHOR]

The need to develop synthetic bone substitutes with structures, properties, and functions similar to bone and capable of preventing microbial infections is still an ongoing challenge. This research is focused on the preparation and characterization of three-dimensional porous scaffolds based on hydroxyapatite (HA)-functionalized calcium carbonate loaded with silver nanoparticles and simvastatin (SIMV). The scaffolds were prepared using the foam replica method, with a polyurethane (PU) sponge as a template, followed by successive polymer removal and sintering. The scaffolds were then coated with poly(lactic-co-glycolic) acid (PLGA) to improve mechanical properties and structural integrity, and loaded with silver nanoparticles and SIMV. The scaffolds were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), ATR FT-IR, and silver and SIMV loading. Moreover, the samples were analyzed by Brillouin and Raman microscopy. Finally, in vitro bioactivity, SIMV and silver release, and antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis were evaluated. From the Brillouin spectra, samples showed characteristics analogous to those of bone tissue. They exhibited new hydroxyapatite growth, as evidenced by SEM, and good antimicrobial activity against the tested bacteria. In conclusion, the obtained results demonstrate the potential of the scaffolds for application in bone repair. [ABSTRACT FROM AUTHOR]

Pressure dependences of the highest and lowest possible longitudinal sound velocities in single crystals of the B1 and B2 phases of NaCl were extracted from examination of their polycrystalline samples using the technique of time-domain Brillouin scattering. Based on the data collected up to 41 GPa, we largely extended the pressure range where single-crystal elastic moduli, Cij(P), and elastic anisotropy of the two cubic phases are measured, especially the experimental data for the B2 phase formed upon the reconstructive phase transition. The B1 phase of NaCl exhibits strong and growing anisotropy with increasing pressure, while that of the B2 phase is much weaker. Comparing with the previous experimental Cij(P) of other compounds exhibiting or expected to exhibit the B1–B2 phase transition, such as CaO, MgO, and (Mg1−x, Fex)O, we concluded that the transition is initiated by the shear instability due to violation of the Born stability criterion [C44(P)–P] > 0 and predicted the presently-not-verified transition pressures for MgO and (Mg1−x, Fex)O. [ABSTRACT FROM AUTHOR]

Cadmium zinc telluride (CdxZn1-xTe) is frequently used material for the production of nuclear radiation detectors and solar cells. Therefore, the characterization of its quality by different methods is very important. This work is devoted to the development of a technique for mapping the poly-crystalline structure of CdxZn1-xTe, alternative to the X-ray technique usually used for this goal. In comparison with X-ray, the non-destructive and contactless picosecond laser ultrasonic technique provides numerous advantages, including simplicity of the analysis of the results and possibility to work with very compact laser spots (about 1 µm) probing the sample. As a step to achieve this goal, picosecond laser ultrasonics is applied in this work to study the samples in the form of 8 mm-diameter discs of 1 mm thickness including several connected disoriented crystals of CdxZn1-xTe. The experimental study is performed using classical pump-probe experimental set-up based on Tsunami femtosecond laser and delay line with moving retro-reflector. The sound velocities of the samples have been evaluated from frequency spectra of obtained signals, using the literature data on the index of refraction. Then, the value of the longitudinal sound velocity in the direction perpendicular to the sample surface is traced as a function of Zn concentration. Finally, measured sound velocities are compared with their available theoretical evaluation, using statistical analysis. [ABSTRACT FROM AUTHOR]

This work presents a Brillouin amplification performance comparison of seed generation techniques using double-sideband suppressed carrier (DSB-SC) and single-sideband suppressed carrier (SSB-SC) modulations. The SSB-SC is obtained using an optical bandpass filter (OBPF) and in-phase and quadrature Mach-Zehnder modulator (IQ-MZM). All three techniques provide high amplification performance with optical signal-to-noise ratio (OSNR) enhancement of 37.47 dB, 33.14 dB, and 32.67 dB using DSB-SC, SSB-SC/OBPF, and SSB-SC/IQ-MZM, respectively. The best seed generation technique is using the DSB with a signal amplification of 62.47 dB. The technique presents ~4 dB higher OSNR enhancement due to the dual-energy transfer obtained from the beating process of the DSB than SSB. A ~3 dB OSNR reduction is found when pump linewidth (LW) was changed from 1kHz to 50 MHz, which suggests using a low-cost pump source whenever the OSNR reduction is not critical. The work also shows that the three techniques required 10 dBm stimulated Brillouin scattering threshold (SBST) to stimulate the process. An additional analysis of DSB-SC shows that a high-carrier suppression during the seed generation technique using MZMs is insignificant to the amplification performance. The high-carrier suppression produces a high seed signal power that distorts the Brillouin gain spectrum (BGS) and the pump depletion region, hence reducing the Brillouin gain (BG). Since carrier suppression is not a primary consideration, a cost-effective MZM with a modest extinction ratio requirement is allowed. The relaxed requirement of the pump's linewidth and MZM's extinction ratio suggest a cost-effective development of the SBSbased optical amplifier with narrow filter bandwidth. [ABSTRACT FROM AUTHOR]

Brillouin spectroscopy has become an important tool for mapping the mechanical properties of biological samples. Recently, stimulated Brillouin scattering (SBS) measurements have emerged in this field as a promising technology for lower noise and higher speed measurements. However, further improvements are fundamentally limited by constraints on the optical power level that can be used in biological samples, which effectively caps the gain and signal-to-noise ratio (SNR) of SBS biological measurements. This limitation is compounded by practical limits on the optical probe power due to detector saturation thresholds. As a result, SBS-based measurements in biological samples have provided minimal improvements (in noise and imaging speed) compared with spontaneous Brillouin microscopy, despite the potential advantages of the nonlinear scattering process. Here, we consider how a SBS spectrometer can circumvent this fundamental trade-off in the low-gain regime by leveraging the polarization dependence of the SBS interaction to effectively filter the signal from the background light via the polarization pulling effect. We present an analytic model of the polarization pulling detection scheme and describe the trade-space unique to Brillouin microscopy applications. We show that an optimized receiver design could provide >25× improvement in SNR compared to a standard SBS receiver in most typical experimental conditions. We then experimentally validate this model using optical fiber as a simplified test bed. With our experimental parameters, we find that the polarization pulling scheme provides 100× higher SNR than a standard SBS receiver, enabling 100× faster measurements in the low-gain regime. Finally, we discuss the potential for this proposed spectrometer design to benefit low-gain spectroscopy applications such as Brillouin microscopy by enabling pixel dwell times as short as 10 μs. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering offers a broad range of applications, including lasers, sensors, and microwave photonics, most of which require strong Brillouin gain within a narrow bandwidth. Here, we experimentally report the first measurement of stimulated Brillouin scattering in silica optical nanofibers from both hybrid and surface acoustic waves. Using a pump–probe technique in the radio frequency domain, we measured a Brillouin gain as high as 15 m−1 W−1 and linewidth to 16 MHz for the L03 hybrid acoustic mode near 9 GHz using a 990-nm diameter nanofiber. This gain is 65 times larger than the highest gain obtained in standard single-mode fibers. In addition, we report a Brillouin gain of up to 5 m−1 W−1 from surface acoustic waves around 5 GHz. We further demonstrate a nanofiber-based Brillouin laser with a threshold of 350 mW. Our results create opportunities for advanced Brillouin-based applications utilizing optical nanofibers. [ABSTRACT FROM AUTHOR]

Distributed optical fiber sensors with the capability of dynamic temperature and strain discrimination can be used for various applications, including perimeter security, structural health monitoring, and seismic sensing, as they can access the tolerance of the structures and sites to natural hazards, such as earthquakes, fires, and overflows. Here, we propose a hybrid Brillouin/Rayleigh sensing system that combines distributed phase matching measurement via Brillouin dynamic grating and inhomogeneity-induced Rayleigh scatting in polarization-maintaining fiber. Due to the high birefringence of polarization-maintaining fibers imposed by the stress-rods, the detection of Brillouin dynamic gratings results in opposite signs of spectral shifts under the changed temperature and strain, giving a high discrimination accuracy. In addition, the usage of a single chirped probe pulse signal allows a single end detection system for Rayleigh of the probe wave and idler wave from stimulated Brillouin scattering enhanced four-wave mixing, which simplified the sensing system significantly. Driven by the high spatial resolution ability of distributed phase matching measurement without phonon lifetime limitation, an intensity-based analysis approach for Rayleigh traces is carried out to resolve the external perturbation applied in a short section that is smaller than the spatial distinctness associated pulse width. In the proof-of-concept experiments, a simultaneous strain and temperature variation within a 40 cm fiber section are successfully discriminated with noise equivalent discrimination errors for strain and temperature of 112.2 nɛ and 10.9 m °C. The spatial resolution here is 2 m, and the maximum system's sampling rate is up to 100 kHz without average, corresponding to the sensing distance of 1 km. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) is an effective method for compensating wavefront aberrations in high-energy lasers due to its phase conjugation property. However, SBS phase conjugate mirrors (SBS-PCMs) under high-power pumping often suffer from significant spatial aberrations and decreased energy reflectivity, indicating instability in the nonlinear gain. Here, a nonlinear gain modulation method is proposed to realize the stable output. Experiments show that the energy reflectivity of SBS decreased due to the thermal effect in high-repetition-rate pumped SBS-PCMs. The nonlinear gain modulation was accomplished with simultaneous adaptation of radial and axial focusing parameters resulting in a higher SBS gain under short-focus conditions. The feasibility of the method was experimentally confirmed by obtaining SBS energy reflectivity stabilized at 60%, while the root mean squares of steady-state Stokes energy and pulse time delay enhanced to 1.97% and 1.81%, respectively, in an HT-230 medium. This scheme ensures stable and efficient SBS output under high-power pumping, which is of great significance for expanding the application of SBS-PCMs in high-repetition-rate laser systems. [ABSTRACT FROM AUTHOR]

Surface acoustic wave devices are ubiquitously used for signal processing and filtering, as well as mechanical, chemical, and biological sensing and show promise as quantum transducers. While surface acoustic waves (SAWs) are primarily excited and driven using electromechanical coupling and interdigital transducers, there is a strong desire for novel methods that enable the coherent excitation and detection of SAWs all-optically interfacing with photonic integrated circuits. In this work, we numerically model and experimentally demonstrate SAW excitation in integrated photonic waveguides made from GeAsSe glass via backward stimulated Brillouin scattering (SBS). We measure a Brillouin gain coefficient of 203 W−1 m−1 for the surface acoustic resonance at 3.81 GHz, with a linewidth narrowed to 20 MHz. Experimental access to this new regime of SBS not only opens up opportunities for novel on-chip sensing applications by harnessing the waveguide surface but also paves the way for strong Brillouin interactions in materials lacking sufficient acoustic guidance in the waveguide core, as well as the excitation of SAWs in non-piezoelectric materials. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the corneal biomechanical metrics of Chinese adults with myopia and identify relevant factors of Brillouin microscopy. Methods: In this cross-sectional study, corneal biomechanics in Chinese adults with myopia were quantified and analyzed using Brillouin microscopy and the Corvis ST (CST) (Oculus Optikgeräte GmbH) and analyzed. Univariate linear regression was used with potential factors including age, sex, spherical equivalent (SE), intraocular pressure (IOP), central corneal thickness (CCT), and mean keratometry (Kmean). Results: The study included 87 eyes of 87 participants (mean age: 24.47 ± 6.27 years). Central, Mean, maximum (Max), minimum (Min), standard deviation, and Max–Min Brillouin modulus (BM) values obtained from Brillouin microscopy exhibited values of 2.826 ± 0.039, 2.827 ± 0.027, 2.864 ± 0.034, 2.790 ± 0.038, 0.108 ± 0.042, and 0.074 ± 0.041 GPa, respectively. No significant correlations were found between BM parameters and age, sex, SE, IOP, or CCT. However, the Mean (β = −0.251, P =.019), Min (β = −0.315, P =.003), and Max–Min (β = 0.229, P =.033) BM values were significantly associated with Kmean. The Central, Mean, Min, and Max BM values negatively correlated with the Tomographic Biomechanical Index measured by CST (Spearman's r = −0.24, −0.35, −0.29, and −0.23, respectively, all P <.05). Conclusions: Brillouin microscopy accurately reflects corneal biomechanical parameters in Chinese adults with myopia, independent of IOP and CCT, with a good correlation with CST. Concurrent evaluation of the corneal curvature is imperative when employing Brillouin microscopy in clinical practice. [J Refract Surg. 2024;40(10):e768–e776.] [ABSTRACT FROM AUTHOR]

We report on experimental observation of unidirectional propagation of zero-momentum magnons in synthetic antiferromagnet consisting of strained CoFeB/Ru/CoFeB trilayer. Inherent non-reciprocity of spin waves in synthetic antiferromagnets with uniaxial anisotropy results in smooth and monotonous dispersion relation around Gamma point, where the direction of the phase velocity is reversed, while the group velocity direction is conserved. The experimental observation of this phenomenon by intensity-, phase-, and time-resolved Brillouin light scattering microscopy is corroborated by analytical models and micromagnetic simulations. [ABSTRACT FROM AUTHOR]

The existing long-distance transmission line perception mainly focuses on the measurement and analysis of electrical parameters. When the line is subject to wind vibration, icing or galloping, the changes of electrical parameters are not obvious and difficult to capture, resulting in poor performance of long-distance transmission line fault state perception. In this regard, the long-distance transmission line condition sensing based on distributed optical fiber sensing technology is studied. This method designs corresponding sensing methods for four working conditions: using the back Brillouin scattering sensor and phase sensitive Rayleigh scattering sensor in the optical fiber sensing technology to form a multi parameter distributed optical fiber sensing device, which is used to sense the surface temperature, vibration, strain and other data of the long-distance transmission line; By analyzing the linear relationship between fiber Brillouin frequency shift and Brillouin power and fiber strain and temperature, the sensing results of icing thickness of long-distance transmission lines are obtained; By calculating the amplitude and phase information of the detection signal, the sensing results of long-distance transmission line vibration are obtained; By calculating the time difference of polarization mutation signal at both ends of long-distance transmission line, combined with the propagation speed of optical signal and the length of long-distance transmission line, the perception result of lightning fault location of long-distance transmission line can be obtained. The experimental results show that this method can more accurately collect the real-time operation data of long-distance transmission lines, and can effectively perceive the galloping, wind vibration and lightning fault location of long-distance transmission lines. [ABSTRACT FROM AUTHOR]

We investigated the magnon hybridization behavior in FeNi films, which were deposited on the yttrium-iron garnet (YIG) films by using Brillouin light scattering. Nonreciprocal magnon hybridizations have been detected not only on the mode densities but also the dispersion relations. The perpendicular standing spin wave mode confined in the thickness direction hybridized with the top surface magnetostatic surface spin wave at smaller wave vectors range while hybridized with the bottom surface mode at larger wave vectors range. The dipolar interaction between the FeNi layer and the YIG layer should be the main reason for the nonreciprocal hybridization of the two modes in the FeNi layer. The nonreciprocal hybridization characteristics of FeNi/YIG double-layer magnetic films enrich the nonreciprocal magnon hybridization system and might have potential application in constructing spin wave-based devices. [ABSTRACT FROM AUTHOR]

In this study, we concentrate on the seismic signature of subducted sediments and suggest the formation of the L‐discontinuity beneath the ancient craton related to migrated sediment dehydration. We first determined the single‐crystal elasticity of topaz, the product of sediment dehydration, at high pressures and temperatures by Brillouin scattering. Using the derived elastic parameters, we establish the velocity and density profiles of subducted sediments in the upper mantle. According to our modeling results, 8.5–17.5 vol.% sediments intruding into the upper mantle will induce a 2%–4% low‐VS anomaly at 210–260 km. Meanwhile, continuous heating will lead to the dehydration of phengite in sediments. The dehydration of this amount sediments can generate a 3%–6% ISS with negative Clapeyron slopes, satisfying the observed L‐discontinuity in northern Finland and northern America without the anisotropy changes but accompanied by low‐velocity anomalies. Our study thus provides new insights into the origin of the L‐discontinuity. Plain Language Summary: The origin of the global seismic discontinuities in the Earth's mantle has been well understood, but the formation mechanism of some local seismic discontinuities is still vague. Lehmann discontinuity (L‐discontinuity) is one of the regional discontinuities in the upper mantle with a 2%–6% impendence contrast (ISS) and negative Clapeyron slope. However, the deformation mechanism changes of olivine cannot explain the formation of the L‐discontinuity without the anisotropy changes. Here, we emphasize the significance of the migration and dehydration of the subducted sediments in the origin of the L‐discontinuity beneath the ancient craton. We determined the single‐crystal elasticity of topaz, the product of the sediment dehydration, and then investigated the seismic signature of subducted sediments. Our modeling results indicated that ∼17.5 vol.% sediments intruding into the upper mantle would lead to ∼4% low‐VS anomalies at 210–260 km. After the continuous heating, these intruding sediments would dehydrate by the reaction with the negative Clapeyron slopes, thus producing significant ISS. Therefore, the migration and dehydration of the subducted sediments can reasonably interpret the seismic characteristics of the L‐discontinuity beneath the cratonic regions such as northern Finland and northern America. Our results deepen the understanding of the origin of the L‐discontinuity. Key Points: Single‐crystal elasticity of topaz under high pressure and temperature has been investigated by Brillouin scatteringThe obtained elasticity parameters are used to model the density and velocity profiles of the subducted sedimentsWe suggest the formation of the L‐discontinuity beneath the ancient craton related to migrated sediment dehydration [ABSTRACT FROM AUTHOR]

Photons with zero rest mass are impossible to be stopped. However, a pulse of light can be slowed down and even halted through strong light-matter interaction in a dispersive medium in atomic systems. Exceptional point (EP), a non-Hermitian singularity point, can introduce an abrupt transition in dispersion. Here we experimentally observe room-temperature storing light near an exceptional point induced by nonlinear Brillouin scattering in a chip-scale 90-μm-radius optical microcavity, the smallest platform up to date to store light. Through nonlinear coupling, a Parity-Time (PT) symmetry can be constructed in optical-acoustical hybrid modes, where Brillouin scattering-induced absorption (BSIA) can lead to both slow light and fast light of incoming pulses. A subtle transition of slow-to-fast light reveals a critical point for storing a light pulse up to half a millisecond. This compact and room-temperature scheme of storing light paves the way for practical applications in all-optical communications and quantum information processing. Exceptional point introduces the ability to control and tune light propagation. Here the authors demonstrate a 90-μm-radius optical microcavity to store light, induced by nonlinear Brillouin scattering at room temperature. [ABSTRACT FROM AUTHOR]

Brillouin light scattering (BLS) is the inelastic scattering of light from elementary excitations with periodic density modulation. The characteristics of non‐contact, high sensitivity, and high resolution in energy, wavevector, time, space, and phase make the BLS spectrometer widely used in investigating many intriguing physical phenomena, including the acoustic phonon confinement effects, Bose‐Einstein condensation (BEC), supercurrent, and soliton formation. Generally, the quick and correct assignment of the signals in the BLS spectra is a prerequisite for further investigations. Herein, we experimentally identify the high‐order spurious signals in the BLS spectra, which make the interpretation of the spectra difficult. The additional signals are demonstrated to originate from the laser and the temperature‐controlled laser filter used for laser filtering. Our results would contribute to the rapid assignment of the signals from the sample after excluding the spurious signals reported here. Moreover, the series of high‐order modes spaced by the free spectral range can serve as a weak broadband light source, which has great potential for investigating the optical responses of materials. [ABSTRACT FROM AUTHOR]

The ultrafast dynamics of the antiferrodistortive phase transition in perovskite SrTiO3 is monitored via time-domain Brillouin scattering. Using femtosecond optical pulses, we initiate a thermally driven tetragonal-to-cubic structural transformation and detect the crystal phase through changes in the frequency of Brillouin oscillations (BO) induced by propagating acoustic phonons. Coupling the measured BO frequency with a spatiotemporal heat diffusion model, we demonstrate that, for a sample kept in the tetragonal phase, deposition of sufficient thermal energy induces a rapid transformation of the heat-affected region to the cubic phase. The initial phase change is followed by a slower reverse cubic-to-tetragonal phase transformation occurring on a timescale of hundreds of picoseconds. We attribute this ultrafast phase transformation in the perovskite to a structural resemblance between atomic displacements of the R-point soft optic mode of the cubic phase and the tetragonal phase, both characterized by anti-phase rotation of oxygen octahedra. The structural relaxation time exhibits a strong temperature dependence consistent with the prediction of the equation of motion describing collective oxygen octahedra rotation based on the energy landscape of the phenomenological Landau theory of phase transitions. Evidence of such a fast structural transition in perovskites can open up new avenues in information processing and energy storage sectors. [ABSTRACT FROM AUTHOR]

The scattered-light time-history diagnostic (SLTD) suite measures time-resolved scattered light in three wavelength bands: stimulated Brillouin scattering (350–352 nm), stimulated Raman scattering (430–760 nm), and plasma emission at half the laser frequency (695–735 nm), at 15 locations around the National Ignition Facility (NIF) target chamber. The SLTD, along with the full-aperture backscatter station (FABS), collects scattered light from direct- and indirect-drive inertial confinement fusion experiments. The SLTD calibration was revisited after a discrepancy between FABS and SLTD measurements was observed on NIF polar direct-drive [Skupsky et al., Phys. Plasmas 11, 2763 (2004)] experiments. An integrated calibration of the SLTD was performed for the first time, and individual components were also calibrated for the wavelengths of 351, 527, and 532 nm. The optical transmission of the instrument was measured to be (1.12 ± 0.04) × 10−7 and (1.96 ± 0.11) × 10−7 for the wavelengths of 351 and 532 nm, respectively. The revised calibration at 351 nm brings the SLTD measured scattered energy in agreement with the FABS measured scattered energy after additionally accounting for the degradation of an optical element in FABS. This decreased the inferred absorption by 7% for a representative experiment. However, discrepancies remain between FABS and SLTD measurements in the SRS band (532 nm). [ABSTRACT FROM AUTHOR]

The use of magnetic fields to improve the performance of hohlraum-driven implosions on the National Ignition Facility (NIF) is discussed. The focus is on magnetically insulated inertial confinement fusion, where the primary field effect is to reduce electron-thermal and alpha-particle loss from the compressed hotspot (magnetic pressure is of secondary importance). We summarize the requirements to achieve this state. The design of recent NIF magnetized hohlraum experiments is presented. These are close to earlier shots in the three-shock, high-adiabat (BigFoot) campaign, subject to the constraints that magnetized NIF targets must be fielded at room-temperature, and use ≲ 1 MJ of laser energy to avoid the risk of optics damage from stimulated Brillouin scattering. We present results from the original magnetized hohlraum platform, as well as a later variant that gives a higher hotspot temperature. In both platforms, imposed fields (at the capsule center) of up to 28 T increase the fusion yield and hotspot temperature. Integrated radiation-magneto-hydrodynamic modeling with the Lasnex code of these shots is shown, where laser power multipliers and a saturation clamp on cross-beam energy transfer are developed to match the time of peak capsule emission and the P 2 Legendre moment of the hotspot x-ray image. The resulting fusion yield and ion temperature agree decently with the measured relative effects of the field, although the absolute simulated yields are higher than the data by 2.0 − 2.7 ×. The tuned parameters and yield discrepancy are comparable for experiments with and without an imposed field, indicating the model adequately captures the field effects. Self-generated and imposed fields are added sequentially to simulations of one BigFoot NIF shot to understand how they alter target dynamics. [ABSTRACT FROM AUTHOR]

The combination of the dark fiber in existing Optical Fiber Composite Overhead Ground Wire (OPGW) with Distributed Optical Fiber Sensing (DOFS) technology can be used to enable online monitoring and provide early warnings of anomalies in high-voltage transmission lines. Accurate mapping of the optical cable length to the geographic coordinates of actual towers is a key factor in achieving this goal. This paper discusses the principle of using a DOFS system for transmission line tower positioning and presents four available positioning features. To overcome the limitations of single physical parameter positioning, this paper presents a self-developed hybrid DOFS that simultaneously captures Rayleigh backscattering and Brillouin scattering signals. Several physical parameters, including temperature, strain, and vibration, are acquired synchronously. Through hybrid multi-parameter analysis, the rapid and accurate positioning of OPGW line towers is achieved. Experimental results have shown that the proposed method, based on the hybrid DOFS system, can locate up to 82 towers, while the traditional method could only identify 12. The hybrid system was able to complete 80% of the tension towers in 40 h. This paper presents a novel multi-parameter localization method that has the potential to significantly improve the efficiency and reliability of grid operation and maintenance. [ABSTRACT FROM AUTHOR]

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The ultrafast dynamics of the antiferrodistortive phase transition in perovskite SrTiO3 is monitored via time-domain Brillouin scattering. Using femtosecond optical pulses, we initiate a thermally driven tetragonal-to-cubic structural transformation and detect the crystal phase through changes in the frequency of Brillouin oscillations (BO) induced by propagating acoustic phonons. Coupling the measured BO frequency with a spatiotemporal heat diffusion model, we demonstrate that, for a sample kept in the tetragonal phase, deposition of sufficient thermal energy induces a rapid transformation of the heat-affected region to the cubic phase. The initial phase change is followed by a slower reverse cubic-to-tetragonal phase transformation occurring on a timescale of hundreds of picoseconds. We attribute this ultrafast phase transformation in the perovskite to a structural resemblance between atomic displacements of the R-point soft optic mode of the cubic phase and the tetragonal phase, both characterized by anti-phase rotation of oxygen octahedra. The structural relaxation time exhibits a strong temperature dependence consistent with the prediction of the equation of motion describing collective oxygen octahedra rotation based on the energy landscape of the phenomenological Landau theory of phase transitions. Evidence of such a fast structural transition in perovskites can open up new avenues in information processing and energy storage sectors. [ABSTRACT FROM AUTHOR]

Background: The brain and spinal cord formation is initiated in the earliest stages of mammalian pregnancy in a highly organized process known as neurulation. Environmental or genetic interferences can impair neurulation, resulting in clinically significant birth defects known collectively as neural tube defects. The Fuz gene encodes a subunit of the CPLANE complex, a macromolecular planar polarity effector required for ciliogenesis. Ablation of Fuz in mouse embryos results in exencephaly and spina bifida, including dysmorphic craniofacial structures due to defective cilia formation and impaired Sonic Hedgehog signaling. Results: We demonstrate that knocking Fuz out during embryonic mouse development results in a hypoplastic hindbrain phenotype, displaying abnormal rhombomeres with reduced length and width. This phenotype is associated with persistent reduction of ventral neuroepithelial stiffness in a notochord adjacent area at the level of the rhombomere 5. The formation of cranial and paravertebral ganglia is also impaired in these embryos. Conclusions: This study reveals that hypoplastic hindbrain development, identified by abnormal rhombomere morphology and persistent loss of ventral neuroepithelial stiffness, precedes exencephaly in Fuz ablated murine mutants, indicating that the gene Fuz has a critical function sustaining normal neural tube development and neuronal differentiation. Key Findings: Disruption of Fuz in mice embryos generates hypoplastic hindbrain and abnormal rhombomeres.Fuz mutant embryos exhibit persistent loss of ventral neural fold stiffness.Cranial and paravertebral ganglia development are reduced in Fuz ablated embryos.Fuz ablated embryos exhibit abnormal Sox10 positive neural crest migration. [ABSTRACT FROM AUTHOR]

Blood plasma viscosity (PV) is an established biomarker for numerous diseases. Measurement of the shear PV using conventional rheological techniques is, however, time consuming and requires significant plasma volumes. Here, we show that Brillouin light scattering (BLS) and angle-resolved spectroscopy measurements of the longitudinal PV from microliter-sized plasma volumes can serve as a proxy for the shear PV measured using conventional viscometers. This is not trivial given the distinct frequency regime probed and the longitudinal viscosity, a combination of the shear and bulk viscosity, representing a unique material property on account of the latter. We demonstrate this for plasma from healthy persons and patients suffering from different severities of COVID-19 (CoV), which has been associated with an increased shear PV. We further show that the additional information contained in the BLS-measured effective longitudinal PV and its temperature scaling can provide unique insight into the chemical constituents and physical properties of plasma that can be of diagnostic value. In particular, we find that changes in the effective longitudinal viscosity are consistent with an increased suspension concentration in CoV patient samples at elevated temperatures that is correlated with disease severity and progression. This is supported by results from rapid BLS spatial-mapping, angle-resolved BLS measurements, changes in the elastic scattering, and anomalies in the temperature scaling of the shear viscosity. Finally, we introduce a compact BLS probe to rapidly perform measurements in plastic transport tubes. Our results open a broad avenue for PV diagnostics based on the high-frequency effective longitudinal PV and show that BLS can provide a means for its implementation. [ABSTRACT FROM AUTHOR]

New strategies for converting signals between optical and microwave domains could play a pivotal role in advancing both classical and quantum technologies. Traditional approaches to optical-to-microwave transduction typically perturb or destroy the information encoded on intensity of the light field, eliminating the possibility for further processing or distribution of these signals. In this paper, we introduce an optical-to-microwave conversion method that allows for both detection and spectral analysis of microwave photonic signals without degradation of their information content. This functionality is demonstrated using an optomechanical waveguide integrated with a piezoelectric transducer. Efficient electromechanical and optomechanical coupling within this system permits bidirectional optical-to-microwave conversion with a quantum efficiency of up to −54.16 dB. Leveraging the preservation of the optical field envelope in intramodal Brillouin scattering, we demonstrate a multi-channel microwave photonic filter by transmitting an optical signal through a series of electro-optomechanical waveguide segments, each with distinct resonance frequencies. Such electro-optomechanical systems could offer flexible strategies for remote sensing, channelization, and spectrum analysis in microwave photonics. The authors showcase an optical-to-microwave conversion method using an optomechanical waveguide integrated with a piezoelectric transducer. The presented system allows bidirectional optical-to-microwave conversion with a quantum efficiency of up to—54.16 dB. [ABSTRACT FROM AUTHOR]