Transmission Measurements Research Articles

Al–Au Thin Films for Thermally Stable and Highly Sensitive Plasmonic Sensors

Plasmonic sensors provide label-free detection of bio and chemical targets with ultrahigh sensitivity and accuracy. However, they usually lack the ability to operate at high temperatures, producing large measurement errors due to perturbations. Here, we report a surface plasmon resonance sensor based on Al–Au thin films, which outperforms its conventional Au counterpart by providing a temperature-stable response. We fabricate six metallic samples via the co-sputtering depositing method, obtaining four bimetallic thin films and two pure metals. Through spectroscopic ellipsometry, transmission measurements, and scanning electron microscopy images, we obtain their dielectric function and film morphology from room temperature to 200 °C, showing that the films containing Al do not undergo significant changes with increasing temperature. We experimentally and theoretically establish the dispersion relation of Al–Au alloys by varying the film chemical composition. Using the transfer matrix method, we evaluate the performance of the sensors by studying their response in the refractive index measurement of air, water, and a biological environment. We show that all alloys outperform their pure counterparts, achieving maximum theoretical sensitivities of 42411 nm/RIU and 162.7 °/RIU for a Au0.62Al0.38-based wavelength-dependent sensor and a Au0.85Al0.15-based angular-dependent sensor, respectively. We find that Au0.85Al0.15 is a particularly promising candidate for both wavelength- and angular-dependent sensors due to its high sensitivity (18967 nm/RIU and 162.7 °/RIU) and good peak definition. Furthermore, using partial density-of-state calculations assisted by machine learning, we obtain the dielectric function of the films, showing an excellent agreement with our experimental results. The alloying approach assisted by computational prediction of the samples’ physical properties has the potential to accelerate the discovery of novel materials for plasmonic sensors with high sensitivity and excellent functioning capabilities at elevated temperatures.

Measurement of Thin Carbon Films Absorption in the Visible Spectrum

The article is devoted to studying radiation absorption in the visible spectrum by thin carbon films. Two types of carbon films, diamond-like and graphite-like, with different structures, are investigated. The films are produced using laser vaporization of the initial material with a further coating of glass substrates. Measurements of light transmission through several samples of films with different thicknesses at three (or more) different areas are obtained for the wavelength range of 400-800 nm using the USB4000 compact fiber-optic spectrometer. The obtained results for the films with different thicknesses demonstrate scant differentiation of values (limiting to the same type of films). The imaginary parts of the films' complex refractive indices (absorption indices) are calculated. The comparison reveals the significant differences (by a factor of two or three) of the absolute values and trends of the absorption indices of diamondlike and graphite-like films. Both types of films are characterized by the expected increase in absorption when transitioning from the long-wavelength spectral region to the short-wavelength one. However, the rate of increase in absorption during such a transition is higher for the diamond-like films. These differences are related to the structure of the films.

Analytic solutions to closed and eclipsing aperture Z-scan power transmission

Analytical solutions are derived using a straightforward mathematical treatment that accurately describes the power of a T E M 00 Gaussian beam transmitted through or around a finite far-field aperture after propagation though a nonlinear refractive medium. These equations are arranged as a series of transmitted power orders, which allow closed and eclipsing aperture Z -scan experiments to be analyzed analytically without requiring numerical simulation. It is shown with this formulism that the power eclipsing an obscuring aperture can be expressed through a linear relationship of the power transmitted through a closed aperture of the same dimensions, which means that the theoretical measurement accuracy of the two methods is the same. A study of the sensitivity of the solutions to nonlinear phase shifts up to 4 π shows that the peak to valley change in normalized power transmission for both closed and eclipsing aperture decreases for phases beyond 3 π / 2 , which means for large phase shifts it is difficult to determine a nonlinear refraction coefficient from peak to valley transmission measurements alone. The solutions were experimentally verified with closed and eclipsing aperture Z -scan toluene measurements undertaken over a range of aperture radii, which agreed well with previously published empirical formulas. The solutions correctly model the observed changes and asymmetries, explained here through strong sample induced focusing, in the closed aperture Z -scan trace shape.

Silicon Nanodisk Huygens Metasurfaces for Portable and Low-Cost Refractive Index and Biomarker Sensing.

Biomarker detection and bulk refractive index sensing are important across multiple industries ranging from early medical diagnosis to chemical process quality control. The bulky size, high cost, and complex architecture of existing refractive index and biomarker sensing technologies limit their use to highly skilled environments like hospitals, large food processing plants, and research labs. Here, we demonstrate a compact and inexpensive refractive index sensor based on resonant dielectric photonic nanoantenna arrays or metasurfaces. These dielectric resonances support Mie dipole and asymmetric resonances that shift with changes in their external environment. A single-wavelength transmission measurement in a portable (<250 in.3), low-cost (<$4000) sensor shows sensitivity to 1.9 × 10–6 change in the fluid refractive index without the use of a spectrometer or other complex optics. Our sensor assembly allows for measurements using multiple metasurfaces with identical resonances or varying resonance types for enhanced diagnostics on the same chip. Furthermore, a 10 kDa culture filtrate peptide CFP-10, a marker for human tuberculosis, is detected with our sensor with 10 pM resolution. This system has the potential to enable facile, fast, and highly sensitive measurements with adequate limits of detection for personalized biomedical diagnoses.

A new in vitro method to predict in vivo photoprotection of skin hyperpigmentation induced by visible light.

BackgroundUltraviolet radiation is the main cause of skin pigmentation, but more recently visible light has been shown to be an important contributor especially in melano‐competent subjects. Photoprotection from visible light can improve several hyperpigmentation disorders. Recently, a visible light photoprotection assessment method has been proposed based on in vivo pigmentation; the visible light photoprotection factor (VL‐PF) is determined by assessment of the change in colorimetry parameter ITA over several days measured using a chromameter. Although in vivo methods remain the most representative of real life, in vitro methods are more suited to screening sunscreen formulations.ObjectiveThe aim of this study was to evaluate the correlation between in vivo and in vitro methods in assessing protection against visible light induced pigmentation.MethodsWe first analysed the in vitro protective properties of the 10 commercially available sunscreens using transmission measurements in the visible spectrum. Then, we performed a monocentric, double‐blind, randomized controlled study with intra‐individual comparisons in 20 healthy subjects and measure the VL‐PF in vivo of those sunscreens. The correlation between the VL‐PF and the percentage of blocked light was evaluated using the coefficient of determination R 2.ResultsA strong significant correlation was demonstrated between in vivo visible light protection factor and in vitro transmittance measurements, with the highest correlation factor at 420 nm and in the spectrum covering from 400 to 469 nm.ConclusionTransmittance measurements were found to be a good predictive tool to evaluate sunscreen visible light photoprotection efficacy and could be used to select formulations for final in vivo testing.

Structural and temperature-tuned band gap energy characteristics of PbMoO4 single crystals

PbMoO4 is one of the member of the molybdate materials and has been a significant research interest due to its photocatalytic and optoelectronic applications. In the present paper, the structural and optical properties of PbMoO4 single crystals grown by Czochralski technique were investigated. X-ray diffraction pattern presented well-defined and intensive peaks associated with tetragonal scheelite structure. Energy dispersive spectroscopy analyses presented the atomic compositional ratio of constituent elements as consistent with chemical formula of PbMoO4. Raman and infrared transmittance spectra were reported to give information about the vibrational characteristics of the compound. Room temperature transmission spectrum was analyzed by derivative spectroscopy technique and band gap energy was found as 3.07 eV. Temperature-tuned band gap energy characteristics of the single crystal were investigated by performing transmission measurements at different temperatures between 10 and 300 K. The analyses indicated that band gap energy of the PbMoO4 single crystal increases to 3.24 eV when the temperature was decreased to 10 K. Temperature-band gap energy dependency was studied considering Varshni and Bose-Einstein models. The successful fitting processes under the light of applied models presented various optical parameters like absolute zero band gap energy, variation rate of band gap with temperature and Debye temperature.

Temperature dependent bandgap in NaBi(WO4)2 single crystals

The double tungstates have been an attractive research interest due to their optoelectronic applications. In the present work, NaBi(WO4)2, one of the members of double tungstates family, was grown by Czochralski method as single crystal form and optically investigated. X-ray diffraction pattern presented three peaks associated with tetragonal scheelite crystalline structure. Optical properties of the crystal were studied by performing temperature-dependent transmission measurements between 10 and 300 K. The shift of the absorption edge to higher energies was observed with decrease of temperature. The analyses indicated that direct band gap energy increases from 3.50 to 3.60 eV when the temperature was decreased from room temperature to 10 K. The temperature dependency of bandgap was studied considering the Varshni model and fitting of the experimental data under the light of model presented the optical parameters of band gap energy at 0 K, rate of band gap change with temperature and Debye temperature as Eg(0) = 3.61 eV, γ = − 8.83 × 10−4 eV/K and β = 456 K, respectively. Urbach energies were also determined from the analyses as 122 and 113 meV for 10 and 300 K experimental data, respectively.

Nanosecond laser ablation of nitride ceramics in liquid

The work presents results on nanosecond laser ablation of nitride ceramics immersed in a liquid medium. AlN and Si3N4 ceramic plates were used targets, and double distilled water was used as a liquid medium. Radiation of a nanosecond Nd:YAG laser system was used in the ablation process with the purpose of studying the influence of the laser fluence and number of pulses on the target surface morphology. The morphology and phase composition of the structured surfaces were explored by scanning electron microscopy and X-ray diffraction measurements, respectively. The optical properties of the obtained colloids were investigated by transmission measurements in the UV-Vis spectral ranges.

Unified Detection of Attacks Involving Injection of False Control Commands and Measurements in Transmission Systems of Smart Grids

Transmission system operation and monitoring, in the context of smart grids, are heavily dependent on the correctness or aptness of supervisory control commands. These command channels are a part of the SCADA system, which is vulnerable to cyber-attacks. Maliciously injected commands can cause a wide range of issues including blackouts. However, the literature addressing this problem is limited. In order to fill this gap, a generalized framework is proposed to achieve simultaneous detection of attacks against various types of control devices/equipments used in transmission systems, even if they are carried out stealthily. First, generalized mathematical models of such stealthy attacks are presented. Then, based on these attack models, changes in the measurement covariance matrix that occur during an attack are exploited to formulate the proposed approach. We first mathematically characterize these changes using the eigenvectors and trace of the covariance matrix and then use them to develop a detection metric. It is observed that when the model of a false data injection (FDI) attack is considered, the developed detection metric is also capable of detecting such attacks. The algorithm that results from the detection metric is a generalized framework for detection of attacks against all types of transmission system controls and measurements. Moreover, the algorithm is non-iterative, computationally inexpensive, and independent of both the type of state estimation and communication technology used. The proposed algorithm is found to be effective, when tested on the IEEE 118-bus system.

Structural and optical properties of a layered ε-GaSe thin film under elastic deformation from flexible PET substrate

The present study focuses on the structural and optical characterizations of a GaSe thin-film consisting of few layers mechanically exfoliated from bulk GaSe on a flexible PET substrate. The XRD and the RAMAN spectroscopies confirm the high crystallinity of our material and show that it belongs to the hexagonal ε-GaSe polytype with a mean crystallite size of about 50 ​nm. The sample’s SEM images exhibit the two-dimensional nature of the layers. The optical transmission measurements clearly show two absorbing edges. They were assigned to an indirect band gap at 1.92 ​eV and to a direct one at 2.2 ​eV. The appreciable difference between the two gaps, of about 0.28 ​eV, is attributed to a compressive biaxial strain. A value, as high as 104 ​cm−1, of the absorption coefficient has been obtained which demonstrates the GaSe material’s great potential for optoelectronic applications.

Beyond 110 GHz Uni-Traveling Carrier Photodiodes on an InP-Membrane-on-Silicon Platform

In this work we have demonstrated a waveguide integrated uni-traveling carrier photodiode on an InP-membrane-on-silicon platform with 3 dB bandwidth beyond 110 GHz. With design optimization and an improved process, devices as small as <inline-formula><tex-math notation="LaTeX">$ \text{3}\times \text{2}\;\mu \text{m}^2$</tex-math></inline-formula> are successfully realized. An electrical equivalent circuit model based on measured S-parameters revealed ultra-small series resistance and junction capacitance as low as 6.5 <inline-formula><tex-math notation="LaTeX">$\Omega$</tex-math></inline-formula> and 4.4 fF, respectively, in the diodes. The model also provided insight in the photocurrent dependent characteristics in the bandwidth and resonsivity of the devices. Finally, data transmission measurements are demonstrated, showcasing the high speed telecommunication abilities of the UTC-PD.

Zr92(n,γ) and ( n ,tot) measurements at the GELINA and n_TOF facilities

Background: Stellar nucleosynthesis of elements heavier than iron is driven by neutron capture processes. Zr92 is positioned at a strategic point along the slow nucleosynthesis path, given its proximity to the neutron magic number N=50 and its position at the matching region between the weak and main slow processes. Purpose: In parallel with recent improved astronomical data, the extraction of accurate Maxwellian averaged cross sections (MACSs) derived from a more complete and accurate set of resonance parameters should allow for a better understanding of the stellar conditions at which nucleosynthesis takes place. Methods: Transmission and capture cross section measurements using enriched Zr92 metallic samples were performed at the time-of flight facilities GELINA of JRC-Geel (BE) and n_TOF of CERN (CH). The neutron beam passing through the samples was investigated in transmission measurements at GELINA using a Li-glass scintillator. The γ rays emitted during the neutron capture reactions were detected by C6D6 detectors at both GELINA and n_TOF. Results: Resonance parameters of individual resonances up to 81 keV were extracted from a combined resonance shape analysis of experimental transmissions and capture yields. For the majority of the resonances the parity was determined from an analysis of the transmission data obtained with different sample thicknesses. Average resonance parameters were calculated. Conclusions: Maxwellian averaged cross sections were extracted from resonances observed up to 81 keV. The MACS for kT=30keV is fully consistent with experimental data reported in the literature. The MACSs for kT≲15keV are in good agreement with those derived from the ENDF/B-VIII.0 library and recommended in the KADoNiS database. For kT higher than 30 keV differences are observed. A comparison with MACSs obtained with the cross sections recommended in the JEFF-3.3 and JENDL-4.0 libraries shows discrepancies even for kT≲15keV.5 MoreReceived 21 February 2020Revised 7 January 2022Accepted 7 February 2022DOI:https://doi.org/10.1103/PhysRevC.105.025805Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasHydrostatic stellar nucleosynthesisNeutron physicsNuclear astrophysicsNuclear reactionsRadiative captureResonance reactionsProperties90 ≤ A ≤ 149TechniquesNuclear data analysis & compilationNuclear Physics

Under-Ice Light Field in the Western Arctic Ocean During Late Summer

The Arctic is no longer a region dominated by thick multi-year ice (MYI), but by thinner, more dynamic, first-year-ice (FYI). This shift towards a seasonal ice cover has consequences for the under-ice light field, as sea-ice and its snow cover are a major factor influencing radiative transfer and thus, biological activity within- and under the ice. This work describes in situ measurements of light transmission through different types of sea-ice (MYI and FYI) performed during two expeditions to the Chukchi sea in August 2018 and 2019, as well as a simple characterisation of the biological state of the ice microbial system. Our analysis shows that, in late summer, two different states of FYI exist in this region: 1) FYI in an enhanced state of decay, and 2) robust FYI, more likely to survive the melt season. The two FYI types have different average ice thicknesses: 0.74 ± 0.07 m (N = 9) and 0.93 ± 0.11 m (N = 9), different average values of transmittance: 0.15 ± 0.04 compared to 0.09 ± 0.02, and different ice extinction coefficients: 1.49 ± 0.28 and 1.12 ± 0.19 m−1. The measurements performed over MYI present different characteristics with a higher average ice thickness of 1.56 ± 0.12 m, lower transmittance (0.05 ± 0.01) with ice extinction coefficients of 1.24 ± 0.26 m−1 (N = 12). All ice types show consistently low salinity, chlorophyll a concentrations and nutrients, which may be linked to the timing of the measurements and the flushing of melt-water through the ice. With continued Arctic warming, the summer ice will continue to retreat, and the decayed variant of FYI, with a higher scattering of light, but a reduced thickness, leading to an overall higher light transmittance, may become a more relevant ice type. Our results suggest that in this scenario, more light would reach the ice interior and the upper-ocean.

Dispersion of organic exciton polaritons—a novel undergraduate experiment

We report on an innovative and simple way to perform an experiment which utilizes the properties of a quantized electromagnetic field coupled to Frenkel excitons in organic materials, forming exciton–polaritons (EP). We present an optical setup, which allowed to perform precise measurements of transmission of organic optical cavities at different angles of incidence and to study the dispersion relation of EP. We provided the full theoretical background of EP and demonstrated that the experimental results are in good agreement with theoretical predictions. Furthermore, we extracted the strong coupling strength and the excitonic–photonic weights of organic cavity samples.

Prompt gamma-ray methods for industrial process evaluation: A simulation study

Abstract Radioisotope applications in industrial process inspection and evaluation using gamma-ray emitters provide otherwise unavailable information. Offering alternative gamma-ray sources can support the technology by complementing sources’ availability and radiation safety. This work proposes to replace gamma-ray from radioisotopes with prompt gamma-ray from the interaction of neutrons with stable isotopes injected into the industrial process or with the structural material of the industrial process equipment. Monte Carlo N-Particle Transport Code (MCNP5) was used to simulate the irradiation of two-phase flow pipes by 252Cf neutron source. Two simulations were run for each pipe, with and without mixing the liquid phase with the stable isotope 157Gd. The detected gamma-ray spectra were analysed, and images of the two phases inside the pipes were produced. The images were compared to images obtained from simulations of gamma transmission measurement using 60Co. Furthermore, results for prompt gamma computed tomography (CT) were presented and discussed. The studies’ outcomes indicate the potential of prompt gamma-ray to carry out the sealed sources applications of gamma transmission measurements and imaging.

Near-Nyquist-Limit Optical Communication and Ranging Method Based on Waveform Matched PPM

Deep-space optical communication and ranging technologies have attracted much attention for satellite-to-earth and moon-to-earth exploration. In integrated communication and ranging scenarios, non-integer oversampling factors are employed to improve the ranging performance, which can cause accumulated timing errors. We propose a novel pulse position modulation (PPM) symbol decision method based on waveform matching to reduce the impact of accumulated timing errors near the Nyquist sampling limit. Simulation results demonstrate that the ranging accuracy can reach 2.6 and 0.52 mm at sampling rates of 625 Msps and 2.5 Gsps, respectively. The proposed symbol decision method has a gain of over 1.1 dB compared with the traditional method at the bit error rate (BER) of less than 10−6. The experimental results verify that this method can achieve high-precision measurements of distance and reliable transmission of information.

Seismic monitoring of the STIMTEC hydraulic stimulation experiment in anisotropic metamorphic gneiss

Abstract. In 2018 and 2019, we performed STIMulation tests with characterising periodic pumping tests and high-resolution seismic monitoring for improving prognosis models and real-time monitoring TEChnologies for the creation of hydraulic conduits in crystalline rocks (STIMTEC). The STIMTEC underground research laboratory is located at 130 m depth in the Reiche Zeche mine in Freiberg, Germany. The experiment was designed to investigate the rock damage resulting from hydraulic stimulation and to link seismic activity and enhancement of hydraulic properties in strongly foliated metamorphic gneiss. We present results from active and passive seismic monitoring prior to and during hydraulic stimulations. We characterise the structural anisotropy and heterogeneity of the reservoir rocks at the STIMTEC site and the induced high-frequency (&gt;1 kHz) acoustic emission (AE) activity, associated with brittle deformation at the centimetre-to-decimetre scale. We derived the best velocity model per recording station from over 300 active ultrasonic transmission measurements for high-accuracy AE event location. The average P-wave anisotropy is 12 %, in agreement with values derived from laboratory tests on core material. We use a 16-station seismic monitoring network comprising AE sensors, accelerometers, one broadband sensor and one AE hydrophone. All instrumentation was removable, providing us with the flexibility to use existing boreholes for multiple purposes. This approach also allowed for optimising the (near)-real-time passive monitoring system during the experiment. To locate AE events, we tested the effect of different velocity models and inferred their location accuracy. Based on the known active ultrasonic transmission measurement points, we obtained an average relocation error of 0.26±0.06 m where the AE events occurred using a transverse isotropic velocity model per station. The uncertainty resulting from using a simplified velocity model increased to 0.5–2.6 m, depending on whether anisotropy was considered or not. Structural heterogeneity overprints anisotropy of the host rock and has a significant influence on velocity and attenuation, with up to 4 % and up to 50 % decrease on velocity and wave amplitude, respectively. Significant variations in seismic responses to stimulation were observed ranging from abundant AE events (several thousand per stimulated interval) to no activity with breakdown pressure values ranging between 6.4 and 15.6 MPa. Low-frequency seismic signals with varying amplitudes were observed for all stimulated intervals that are more correlated with the injection flow rate rather than the pressure curve. We discuss the observations from STIMTEC in context of similar experiments performed in underground research facilities to highlight the effect of small-scale rock, stress and structural heterogeneity and/or anisotropy observed at the decametre scale. The reservoir complexity at this scale supports our conclusion that field-scale experiments benefit from high-sensitivity, wide-bandwidth instrumentation and flexible monitoring approaches to adapt to unexpected challenges during all stages of the experiment.

First Offline Results from the S3 Low-Energy Branch

We present the first results obtained from the S3 Low-Energy Branch, the gas cell setup at SPIRAL2-GANIL, which will be installed behind the S3 spectrometer for atomic and nuclear spectroscopy studies of exotic nuclei. The installation is currently being commissioned offline, with the aim to establish optimum conditions for the operation of the radio frequency quadrupole ion guides, mass separation and ion bunching, providing high-efficiency and low-energy spatial spread for the isotopes of interest. Transmission and mass-resolving power measurements are presented for the different components of the S3-LEB setup. In addition, a single-longitudinal-mode, injection-locked, pumped pulsed-titanium–sapphire laser system has been recently implemented and is used for the first proof-of-principle measurements in an offline laser laboratory. Laser spectroscopy measurements of erbium, which is the commissioning case of the S3 spectrometer, are presented using the 4f126s23H6→4f12(3H)6s6p optical transition.

Pressure and Temperature Transformations of the Molecular Conformation and Crystal Structure of Ferrocene Fe2+(η5-C5H5)2–

X-ray diffraction, optical spectroscopy, and numerical calculations were carried out on pristine ferrocene Fe2+(η5-C5H5)2– single crystals under various pressure/temperature conditions. Structural data were obtained at room temperature and pressures up to 6.5 GPa as well as at ambient pressure and low temperatures up to 100 K. The iron–carbon bond length (l = 2.043 Å under ambient conditions) shows linear temperature dependence and quadratic pressure dependence with the coefficients ∂l/∂T = −2.84 × 10–5 Å K–1, ∂l/∂P = −1.36 × 10–3 Å GPa–1, and ∂2l/∂P2 = −3.04 × 10–4 Å GPa–2, respectively. Jumping of the Fc molecular configuration between D5h and D5d conformations decreases at high pressure/low temperature, leading to complete ordering in low-temperature (LT, <161.3 K) and high-pressure (HP, >3 GPa) phases. The initially large bandwidth of lattice phonon modes increases with pressure to a maximum at 2 GPa and decreases to the common value after molecular ordering at pressures P > 3 GPa. The electronic structure calculations in the HP phase at high pressure show a linear increase in the fundamental gap Eg with the pressure coefficient of 28 meV/GPa. Optical transmission measurements at high pressure demonstrate an almost 2 times smaller pressure coefficient of about 12 meV/GPa and an abrupt decrease in the gap by ∼14.5 meV at P = 2 GPa.

Polarization-controlled single-particle scattering imaging spectroscopy using waveguide excitation.

An imaging spectroscopic system that enables spatially-resolved detection of single-particle scattering with polarization-controlled waveguide excitation scheme is presented. The detected microscopic images of inhomogeneous nanostructures are recorded in a time sequence into a data cube based on a Michelson interferometer. The interferograms on selected pixels are Fourier-transformed into multiple spectra. The waveguide excitation scheme is presented for both transmission and reflection measurements while the dark-field excitation scheme is presented in transmission measurements for comparison. Gold nanoparticles, nanorods, and particles on film are utilized in the detection of polarization-dependent spectra. Measurement results are verified with the finite-difference time-domain (FDTD) simulations. The polarization-controlled coupling conditions in nanorods and particle-on-film systems are discussed with simulated field distributions around the nanostructures.