Probe Setup Research Articles

Making liquid crystals twitch under metamaterial-enhanced terahertz illumination: toward strong optical nonlinearity.

We provide the first direct experimental evidence for the reorientation of liquid crystals by polarized radiation from a conventional, low power, oscillator-based terahertz time-domain spectrometer. Using a terahertz pump - optical probe setup, we observed that the reorientation occurs locally through the resonant amplification of the terahertz field in a specially designed planar metamaterial, adjacent to the liquid crystal layer, and increases with increasing incident terahertz intensity. Our work thus demonstrates that it is possible to induce strong optical nonlinearity in liquid crystals in the terahertz part of the spectrum, paving the way toward the development of new all-optical active terahertz devices as well as electric field sensors for localized resonant systems.

Magnetic Hysteresis Cycle Measurements With a New Needle Probe Setup

Magnetic Hysteresis Cycle Measurements With a New Needle Probe Setup

Ultrafast laser-enabled optoacoustic characterization of three-dimensional, nanoscopic interior features of microchips

The recent advances in micromanufacturing have been pushing boundaries of the new generation of semiconductor devices, which, in the meantime, brings new challenges in the material and structural characterization – a key step to ensure the device quality through the micromanufacturing process. An ultrafast laser-enable optoacoustic characterization methodology is developed, targeting in situ calibration and delineation of the three-dimensional (3-D), nanoscopic interior features of opaque semiconductor chips. With the guidance of ultrafast electron–phonon coupling effect and velocity-perturbated optical interference, a femtosecond-laser pump–probe set-up based on Sagnac interferometer is configured to generate and acquire picosecond ultrasonic bulk waves (P-UBWs) traversing the microchips. The interior features of the microchips shift the phase of acquired P-UBW signals, reflected in the perturbed probe laser beam. The phase shifts are calibrated to compute signal correlation of P-UBW signals between different acquiring positions, whereby to delineate the interior features in an intuitive manner. The approach is experimentally validated by characterizing nanoscopic, invisible interior aurum(Au)-gratings with periodically varied depths in typical microchips. Results highlight that the 3-D nanoscopic features of the microchips can be revealed with a microscopic and a nanoscopic spatial resolution, respectively along the transverse and depth directions of the chip, where the Au-gratings become “visible” with a depth variance of a few tens of nanometers only. This proposed approach has provided a fast, nondestructive approach to “see” through an opaque microchip with a nanoscopic resolution.

Influence of Salt Concentration and Type on Dielectric Permittivity of Rocks

Summary Ionic properties and concentration significantly influence the response of brine-saturated rocks to electromagnetic disturbance. However, the dielectric permittivity response of rocks under different ionic conditions is poorly described. This significantly limits the potential information that could be gained from dielectric permittivity measurements about the pore geometry and fluid content. The influence of salt concentration and type on broadband dielectric permittivity must be reliably quantified to enhance interpretation of dielectric permittivity measurements. The main objective of this paper is to quantify the influence of salt type and concentration on dielectric permittivity via experimental measurements and pore-scale simulations. We examine the impact of salt concentration and type on the dielectric permittivity of pore- and core-scale Berea sandstone (BS) samples. First, we perform frequency-domain dielectric permittivity simulations to quantify the response of the pore-scale models to electric field excitation. The frequency-domain dielectric permittivity simulator solves Maxwell’s equations under quasistatic conditions at discrete frequencies. We simulate the dielectric permittivity in the frequency range of 20 MHz to 3 GHz. We perform the simulations in samples saturated with NaCl, KCl, and MgCl2 brines. The salt concentration of the brine solutions ranges between 10 PPT and 100 PPT (parts per thousand). We fully saturate the samples with different brine solutions at varying salt concentrations for the core-scale analysis. In the core-scale domain, we use the brine solutions and salt concentrations assumed in the pore-scale analysis. The dielectric permittivity measurements were conducted using a network analyzer with a high-temperature coaxial probe setup in the frequency range of 300 MHz to 3 GHz. We observed that relative permittivity at 1 GHz increases with increasing salt concentration, irrespective of the brine type. However, the type of salt significantly controls the magnitude of the decrease in relative permittivity. After increasing the salt concentration from 10 PPT to 100 PPT, relative permittivity at 1 GHz increased by 11% and 7% when the samples were saturated with KCl and NaCl brine solutions, respectively; at 20 MHz, the same increase in salt concentration caused rock relative permittivity to increase by only 1% and 5% in the samples saturated with KCl and NaCl brines, respectively. The lower sensitivity of relative permittivity to salt concentration at 20 MHz compared to 1 GHz can be attributed to the combined influence of interfacial and orientational polarizations on rock dielectric permittivity. The impact of salt type on relative permittivity was negligible in samples saturated with 10 PPT brine solutions. Results demonstrated that taking the influence of salt concentration and type into account is critical for reliable interpretation of dielectric permittivity measurements. The novel contribution of this work is the documentation of how the saturating brine type influences the complex dielectric permittivity of the rocks. This work illuminates the extent to which the relative permittivity can be used for petrophysical analysis in cases where the formation brine salt concentration is uncertain. Additionally, the outcomes of this work will contribute to enhanced interpretation of dielectric permittivity measurements in formations with variable salt concentrations of formation water.

Silver vanadate and cerium oxide decorated graphene oxide ternary heterostructure nanocomposites: structural, electrochemical, and optoelectrical properties

In the present work, we synthesized a novel ternary heterostructure nanocomposite comprising Silver Vanadate and Cerium Oxide Decorated Graphene Oxide (AgVO3-CeO2/GO) using a straightforward and cost-effective method. Six samples, including GO, CeO2, CeO2/GO, AgVO3, AgVO3/GO, and CeO2-AgVO3/GO, were prepared. The structural, morphological, electrochemical, and optoelectrical properties of these samples were thoroughly investigated. X-ray diffraction (XRD) demonstrated the presence of graphene oxide, cerium oxide, and silver vanadate phases, while transmission electron microscopy (TEM) showed the single crystalline nature of AgVO3 and the dispersion of CeO2 and AgVO3 nanoparticles within the GO matrix. The heterojunctions between different components facilitated efficient charge transfer and enhanced optoelectronic performance. External quantum efficiency was measured using a 532 nm laser beam, and the electrical properties were evaluated under dark and illuminated conditions with a two-point probe setup. The inclusion of CeO2 and AgVO3 nanoparticles in the GO matrix improved charge transport and interfacial charge transfer processes. These findings highlight the potential of these materials for various optoelectronic applications, including photodetection, sensing, and energy harvesting, with further optimization potentially leading to high-performance devices with enhanced functionality and efficiency.

Characteristics of fluctuations in the equatorial and polar directions of a compact dipole plasma driven at steady state

The fluctuations in the plasma potential (Vs̃) and electron density (Nẽ) are measured in the steady-state dipole plasma confined in a spherical vacuum chamber using a single permanent dipole magnet. Measurements are made from a radial distance r = 0.5–17 cm, from the surface of the magnet in the equatorial (θ=90°) and polar (θ=180°) directions, using a 4-pin probe setup, and have been characterized by power spectra, cross-phase, cross-coherence, induced transport, and energy spectra. The fluctuations are stronger near the surface of the dipole magnet for θ=90°, thereafter their magnitude decreases gradually with the radial distance. However, a peaked profile of potential fluctuations with the peak around r = 9 cm is observed for θ=180°. The locations of strong fluctuations are around the locations of smaller values of the electron neutral collision frequency. Frequency-resolved power spectra show that the fluctuations in the dipole plasma, predominantly, belong to the very low-frequency range. The values of cross-phase (≤45°) and |Vs̃/Te|/|Nẽ/Ne|≤1 indicate the presence of drift wave instability in both planes, where Te and Ne are equilibrium values of the electron temperature and density. The radial variation of fluctuation-induced electron flux (Γr) verifies the “inward diffusion” of electrons in the equatorial plane.

Enhancing electrical properties of SiHfBCN ceramics through Cu-catalyzed polymer-derived ceramic synthesis

In this study, we employed Cu-catalyzed polymer-derived ceramic methods at lower temperatures to synthesize SiHfBCN ceramics. The SiHfBCN-Cu single-source precursors were characterized using Fourier Transform-Infrared Spectrometry and thermal gravimetric analysis, while X-ray diffraction, X-ray photoelectron spectroscopy, Raman Spectrometer, transmission electron microscopy, and a four-point probe setup were utilized to investigate composition, microstructural evolution, and electrical conductivity. Our analysis revealed that the electrical conductivity of SiHfBCN-Cu ceramics, annealed at 1500 °C, reached an impressive 2409.6 S·m-¹. This improvement was attributed to the influence of pyrolysis temperature and Cu content, resulting in the formation of in-situ abundant graphite-like carbon, Cu nano crystallites and Hf1-xCuxC@C and SiC@C nanoparticles with core-shell structures constructed a three-dimensional conductive network. Importantly, Cu-catalyzed SiHfBCN ceramics at lower temperatures produced an abundance of graphite-like carbon ribbons, effectively enhancing their electrical conductivity. These findings highlight the potential of Cu-catalyzed SiHfBCN ceramics as high-temperature sensors for in-situ measurements in extreme environments.

Ultrasound-driven piezoelectret-based nanogenerator stimulates vagus nerve for myocardial infarction treatment

Myocardial infarction (MI) stands as the predominant cause of morbidity and mortality within the spectrum of cardiovascular diseases, with an unfavorable long-term prognosis. Vagus nerve stimulation (VNS) emerges as a potential clinically significant intervention for alleviating myocardial remodeling after MI, offering promise as a therapeutic approach. However, challenges persist in addressing the fundamental issues of flexibility, miniaturization, and the long-term use of VNS devices. Here, we devised an implantable ultrasound-driven piezoelectret-based nanogenerator (UPN) as a wireless-powered and battery-free vagus nerve stimulator. The UPN with the features of flexibility and lightweight exhibited a maximum output of 10.68 V and 261 μA (peak to peak) under an ultrasonic probe setup at 700 mW cm−2. In the in vivo efficacy study, VNS therapy resulted in a notable improvement in cardiac function with the treatment of UPN, a 20.42 % enhancement in left ventricular ejection fraction and an 11.76 % increase in fractional shortening on the 28th day were realized. Concomitantly, inflammatory responses, myocardial fibrosis, and sympathetic nerve remodeling witnessed a significant reduction. Particularly noteworthy is the observed therapeutic effect linked to the inhibition of the IL-17 and TNF signaling pathways. In summary, this study introduces a novel strategy for nerve stimulation, offering a potential avenue for treating chronic inflammatory diseases.

A Near Fourier-Limited Pulse-Preserving Monochromator for Extreme-Ultraviolet Pulses in the Few-Fs Regime

We present a pulse-preserving multilayer-based extreme-ultraviolet (XUV) monochromator providing ultra-narrow bandwidth (ΔE<0.6eV, Ec=92eV) and compact footprint (28×10cm2) for easy integration into high-harmonic generation (HHG) or free-electron laser (FEL) sources. The temporal resolution of the novel design supports pulse durations of typical pump–probe setups in the femtosecond and attosecond regime, depending on the mirror design and focusing geometries over the tuning range of the monochromator. The theoretical design is analyzed and experimentally characterized in a laser-driven HHG setup.

The Liquid Jet Endstation for Hard X-ray Scattering and Spectroscopy at the Linac Coherent Light Source

The ability to study chemical dynamics on ultrafast timescales has greatly advanced with the introduction of X-ray free electron lasers (XFELs) providing short pulses of intense X-rays tailored to probe atomic structure and electronic configuration. Fully exploiting the full potential of XFELs requires specialized experimental endstations along with the development of techniques and methods to successfully carry out experiments. The liquid jet endstation (LJE) at the Linac Coherent Light Source (LCLS) has been developed to study photochemistry and biochemistry in solution systems using a combination of X-ray solution scattering (XSS), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES). The pump–probe setup utilizes an optical laser to excite the sample, which is subsequently probed by a hard X-ray pulse to resolve structural and electronic dynamics at their intrinsic femtosecond timescales. The LJE ensures reliable sample delivery to the X-ray interaction point via various liquid jets, enabling rapid replenishment of thin samples with millimolar concentrations and low sample volumes at the 120 Hz repetition rate of the LCLS beam. This paper provides a detailed description of the LJE design and of the techniques it enables, with an emphasis on the diagnostics required for real-time monitoring of the liquid jet and on the spatiotemporal overlap methods used to optimize the signal. Additionally, various scientific examples are discussed, highlighting the versatility of the LJE.

WaveGate: a versatile tool for temporal shaping of synchrotron beams.

We present a full performance characterization of a solid state pulse picker for hard x-ray pulses at synchrotrons. The device is called WaveGate. Specifically, we quantify its efficiency (>30 %), timing capabilities (switching times between 100 ns and ms), on-off contrast (>104) and influence on the coherence properties of the incident x-ray beam. In addition, we discuss the implementation of the WaveGate in an optical pump - x-ray probe setup. Even if single pulse selection is performed by external detector gating, the WaveGate drastically increases the efficiency of a measurement. Finally, we introduce advanced timing schemes that can be realized by modulating the time structure of the synchrotron beam.

Collected Current by a Double Langmuir Probe Setup With Plasma Flow

Collected Current by a Double Langmuir Probe Setup With Plasma Flow

Programmable Cone Shell Configuration Based Depth-Sensitive Fluorescence Spectroscopy With Flexible Target Depth and Depth Sensitivity

Depthsensitivefluorescencespectroscopycanextract the depth dependent distribution of fluorophores, which is closely associated with disease progresses in layered tissues. However, the conventional contact fiber-optic probe or non-contact lens setup based fluorescence measurements often suffer from insufficient depth sensitivity for precise diagnosis. Although a modified non-contactlenssetup, usingaxiconlensinsteadof conventional convex lens, has successfully achieved improved depth sensitivity by forming a cone-shell configuration, challenges remain in incompletely flexible target depth and limited depth sensitivity. In this study, a programmable cone shell configuration based depth-sensitive fluorescence spectroscopy was proposed and tested on a two-layered agar phantom. According to the experimental results, the target depth can be altered arbitrarily by digitally tuning the ring beam radius, even switching between two distant target depths. In addition to better depth sensitivity than conventional methods, its capability of flexibly narrowing the ring beam width can promote further improvement on depth sensitivity. Various aspects can benefit from its capabilities of flexibly switching among different target depths and depth sensitivities, thus the proposed programmable cone shell configuration based depth-sensitive fluorescence spectroscopy is expected to promote its wider applications in biomedicine.

Ultrastable, high-repetition-rate attosecond beamline for time-resolved XUV–IR coincidence spectroscopy

The implementation of attosecond photoelectron–photoion coincidence spectroscopy for the investigation of atomic and molecular dynamics calls for a high-repetition-rate driving source combined with experimental setups characterized by excellent stability for data acquisition over time intervals ranging from a few hours up to a few days. This requirement is crucial for the investigation of processes characterized by low cross sections and for the characterization of fully differential photoelectron(s) and photoion(s) angular and energy distributions. We demonstrate that the implementation of industrial-grade lasers, combined with a careful design of the delay line implemented in the pump–probe setup, allows one to reach ultrastable experimental conditions leading to an error in the estimation of the time delays of only 12 as over an acquisition time of 6.5 h. This result opens up new possibilities for the investigation of attosecond dynamics in simple quantum systems.

Real-Time Monitoring Platform for Ocular Drug Delivery.

Real-time measurement is important in modern dissolution testing to aid in parallel drug characterisation and quality control (QC). The development of a real-time monitoring platform (microfluidic system, a novel eye movement platform with temperature sensors and accelerometers and a concentration probe setup) in conjunction with an in vitro model of the human eye (PK-Eye™) is reported. The importance of surface membrane permeability when modelling the PK-Eye™ was determined with a "pursing model" (a simplified setup of the hyaloid membrane). Parallel microfluidic control of PK-Eye™ models from a single source of pressure was performed with a ratio of 1:6 (pressure source:models) demonstrating scalability and reproducibility of pressure-flow data. Pore size and exposed surface area helped obtain a physiological range of intraocular pressure (IOP) within the models, demonstrating the need to reproduce in vitro dimensions as closely as possible to the real eye. Variation of aqueous humour flow rate throughout the day was demonstrated with a developed circadian rhythm program. Capabilities of different eye movements were programmed and achieved with an in-house eye movement platform. A concentration probe recorded the real-time concentration monitoring of injected albumin-conjugated Alexa Fluor 488 (Alexa albumin), which displayed constant release profiles. These results demonstrate the possibility of real-time monitoring of a pharmaceutical model for preclinical testing of ocular formulations.

GHz adhesion dynamics of gold nanoparticles down to 40 nm in diameter

We investigate the acoustic vibrations of single gold nanoparticles on a glass substrate using time-resolved optical spectroscopy. Using a two-color pump–probe setup, we measure the transient change of a particle's reflectivity induced by an optical pump pulse. Our measurements identify both the axial mode, which corresponds to an oscillation of the distance between nanoparticle and substrate, and the particle's fundamental breathing mode, an oscillation of particle diameter. We investigate the scaling of the axial mode frequency with the radial mode frequency. Our analysis reveals that the scaling established for larger particles extends down to diameters of 40 nm. This finding strongly suggests that continuum models of contact mechanics hold for contact areas comprising only a few thousand atoms.

Laguerre–Gaussian vortex beam for reduced thermal effects in nonlinear optical studies

Interaction of an intense laser beam with a material induces many thermal effects. In this work, thermo-optic effects induced by fundamental Gaussian and Laguerre–Gaussian vortex (LGV) laser beams in a sample in nonlinear optical (NLO) experiments are compared and their impact on the accuracy of determining the nonlinear susceptibility is examined. A solution of saturable absorber dye IR 26 in dichloroethane with the technique of z-scan to determine its third order nonlinear susceptibility was used as a model system. The LGV beams were generated by passing the Hermite–Gaussian beams from an Ar-ion laser through a cylindrical lens mode converter. Pump–probe setup was used to study the thermo-optic effects. Experiments and simulations suggest that the LGV beam is advantageous to reduce the thermal effects.

Investigation of the Conductive Properties of ZnO Thin Films Using Liquid Probes and Creation of a Setup Using Liquid Probes EGaIn for Studing the Conductive Properties of Thin Films

The use of liquid probes based on indium–gallium eutectic (EGaIn) with the possibility of positioning is an important problem for the study of thin films. This work is centered on the creation of a setup for measuring the current–voltage characteristics with the use of a liquid eutectic electrode. A technique for obtaining a cone-shaped liquid EGaIn electrode, a 3D assembly model and an algorithm for the operation of a probe setup for obtaining the current–voltage characteristics using liquid contacts are presented.

Multidetection scheme for transient-grating-based spectroscopy.

Time-resolved optical spectroscopy represents an effective non-invasive approach to investigate the interplay of different degrees of freedom, which plays a key role in the development of novel functional materials. Here, we present magneto-acoustic data on Ni thin films on SiO2 as obtained by a versatile pump-probe setup that combines transient grating spectroscopy with time-resolved magnetic polarimetry. The possibility to easily switch from a pulsed to continuous wave probe allows probing of acoustic and magnetization dynamics on a broad time scale, in both transmission and reflection geometry.

Analog wavelet-like transform based on stimulated Brillouin scattering.

A photonics-enabled analog wavelet-like transform system, characterized by multiscale time-frequency analysis (TFA), is proposed based on a typical stimulated Brillouin scattering (SBS) pump-probe setup using an optical nonlinear frequency-sweep signal. The periodic SBS-based frequency-to-time mapping (FTTM) is implemented by using a periodic nonlinear frequency-sweep optical signal with a time-varying chirp rate. The frequency-domain information of the signal under test (SUT) in different periods is mapped to the time domain via the FTTM in the form of low-speed electrical pulses, which is then spliced to analyze the time-frequency relationship of the SUT in real-time. The time-varying chirp rate in each sweep period makes the signals with different frequencies have different frequency resolutions in the FTTM process, which is very similar to the characteristics of the wavelet transform, so we call it a wavelet-like transform. An experiment is carried out. Multiscale TFA of a variety of RF signals is carried out in a 4-GHz bandwidth limited only by the equipment.