Rapid online analysis of trace elements in steel using a mobile fiber-optic laser-induced breakdown spectroscopy system

A mobile fiber-optic laser-induced breakdown spectrometer(FO-LIBS) prototype was developed to rapidly detect a large quantity of steel material online and quantitatively analyze the trace elements in a large-diameter steel tube.Twenty-four standard samples and a polynomial fitting method were used to establish calibration curve models.The R^2 factors of the calibration curves were all above 0.99,except for Cu,indicating the elements’ strong self-absorption effect.Five special steel materials were rapidly detected in the steel mill.The average absolute errors of Mn,Cr,Ni,V,Cu,and Mo in the special steel materials were 0.039,0.440,0.033,0.057,0.003,and0.07 wt%,respectively,and their average relative errors fluctuated from 2.9% to 15.7%.The results demonstrated that the performance of this mobile FO-LIBS prototype can be compared with that of most conventional LIBS systems,but the more robust and flexible characteristics of the FO-LIBS prototype provide a feasible approach for promoting LIBS from the laboratory to the industry.

All optical method for measuring the carrier envelope phase from half-cycle cutoffs

An all optical method is demonstrated for measuring the carrier-envelope phase （CEP） of few-cycle laser pulses. It is found that, in the few-cycle regime, the high harmonic spectrum generated from asymmetric molecules shows several half-cycle cutoffs that change their positions as the CEP varies. Such half-cycle cutoffs represent the fingerprint of different quantum trajectories and the waveform of the driving pulse. In this case, the CEP can be accurately measured from the half-cycle cutoffs.

Classification of steel based on laser-induced breakdown spectroscopy combined with restricted Boltzmann machine and support vector machine

In recent years,a laser-induced breakdown spectrometer(LIBS)combined with machine learning has been widely developed for steel classification.However,the much redundant information of LIBS spectra increases the computation complexity for classification.In this work,restricted Boltzmann machines(RBM)and principal component analysis(PCA)were used for dimension reduction of datasets,respectively.Then,a support vector machine(SVM)was adopted to process feature information.Two models(RBM-SVM and PCA-SVM)are compared in terms of performance.After optimization,the accuracy of the RBM-SVM model can achieve 100%,and the maximum dimension reduction time is 33.18 s,which is nearly half of that of the PCA model(53.19 s).These results preliminarily indicate that LIBS combined with RBM-SVM has great potential in the real-time classification of steel.

Portable fiber-optic laser-induced breakdown spectroscopy system for the quantitative analysis of minor elements in steel

In this paper, we developed a portable laser-induced breakdown spectroscopy(LIBS) using an optical fiber to deliver laser energy and used it to quantitatively analyze minor elements in steel.The R^2 factors of calibration curves of elements Mn, Ti, V, and Cr in pig iron were 0.9965,0.9983, 0.9963, and 0.991, respectively, and their root mean square errors of cross-validation were 0.0501, 0.0054, 0.0205, and 0.0245 wt%, respectively. Six test samples were used for the validation of the performance of the calibration curves established by the portable LIBS. The average relative errors of elements Mn, Ti, V, and Cr were 2.5%, 11.7%, 13.0%, and 5.6%,respectively. These results were comparable with most results reported in traditional LIBS in steel or other matrices. However, the portable LIBS is flexible, compact, and robust, providing a promising prospect in industrial application.

Dynamically tunable multiband plasmon-induced transparency effect based on graphene nanoribbon waveguide coupled with rectangle cavities system

A dynamically tunable multiband plasmon-induced transparency(PIT) effect in a series of rectangle cavities coupled with a graphene nanoribbon waveguide system is investigated theoretically and numerically by tuning the Fermi level of the graphene rectangle cavity. A single-PIT effect is realized using two different methods: one is the direct destructive interference between bright and dark modes, and the other is the indirect coupling through a graphene nanoribbon waveguide. Moreover, dual-PIT effect is obtained by three rectangle cavities side-coupled with a graphene nanoribbon waveguide.Results show that the magnitude of the dual-PIT window can be controlled between 0.21 and 0.74, and the corresponding group index is controlled between 143.2 and 108.6. Furthermore, the triple-PIT effect is achieved by the combination of bright–dark mode coupling and the cavities side-coupled with waveguide mechanism. Thus, sharp PIT windows can be formed, a high transmission is maintained between 0.51 and 0.74, and the corresponding group index is controlled between161.4 and 115.8. Compared with previously proposed graphene-based PIT effects, the size of the introduced structure is less than 0.5 μm2. Particularly, the slow light effect is crucial in the current research. Therefore, a novel approach is introduced toward the realization of optical sensors, optical filters, and slow light and light storage devices with ultra-compact,multiband, and dynamic tunable.

An ultrafast and low-power slow light tuning mechanism for compact aperture-coupled disk resonators

An ultrafast and low-power slow light tuning mechanism based on plasmon-induced transparency(PIT)for two disk cavities aperture-coupled to a metal-dielectric-metal plasmonic waveguide system is investigated numerically and analytically.The optical Kerr effect is enhanced by the local electromagnetic field of surface plasmon polaritons,slow light,and graphene-Ag composite material structures with a large effective Kerr nonlinear coefficient.Through the dynamic adjustment of the frequency of the disk nanocavity,the group velocity is controlled between c/53.2 and c/15.1 with the pump light intensity increased from 0.41 MW/cm^2 to 2.05 MW/cm^2.Alternatively,through the dynamic adjustment of the propagation phase of the plasmonic waveguide,the group velocity is controlled between c/2.8 and c/14.8 with the pump light intensity increased from 5.88 MW/cm^2 to 11.76 MW/cm^2.The phase shift multiplication of the PIT effect is observed.Calculation results indicate that the entire structure is ultracompact and has a footprint of less than 0.8μm^2.An ultrafast responsive time in the order of 1 ps is reached due to the ultrafast carrier relaxation dynamics of graphene.All findings are comprehensively analyzed through finite-difference time-domain simulations and with a coupling-mode equation system.The results can serve as a reference for the design and fabrication of nanoscale integration photonic devices with low power consumption and ultrafast nonlinear responses.

Attosecond manipulation of ionization and efficient broadband supercontinuum generation in stretched molecules

We theoretically investigate the high-order harmonic generation from stretched molecules in a linearly polarized intense field. By adopting an infrared pulse combined with an ultraviolet （UV） attosecond pulse, the ionization process can be controlled effectively. In this excitation scheme, the harmonic spectrum beyond Ip ＋ 3.17Up is significantly enhanced by two orders, where Ip and Up = e^2E0^2/（4mew^2） are the ionization and ponderomotive potential, then smooth broadband supercontinuum with the bandwidth of about 120 eV is obtained, which leads to an isolated sub-60- as attosecond pulse with a high signal-noise ratio. Moreover, the bandwidth of the supercontinuum is weakly dependent on the location and pulse duration of the UV pulse.

Thermal stress concentration points and stress mutations in nano-multilayer film structures

In the multilayer film-substrate system,thermal stress concentration and stress mutations cause film buckling,delamination and cracking,leading to device failure.In this paper,we investigated a multilayer film system composed of a substrate and three film layers.The thermal stress distribution inside the structure was calculated by the finite element method,revealing significant thermal stress differences between the layers.This is mainly due to the mismatch of the coefficient of thermal expansion between materials.Different materials respond differently to changes in external temperature,leading to compression between layers.There are obvious thermal stress concentration points at the corners of the base layer and the transition layer,which is due to the sudden change of the shape at the geometric section of the structure,resulting in a sudden increase in local stress.To address this issue,we chamfered the substrate and added an intermediate layer between the substrate and the transition layer to assess whether these modifications could reduce or eliminate the thermal stress concentration points and extend the service life of the multilayer structure.The results indicate that chamfering and adding the intermediate layer effectively reduce stress discontinuities and mitigate thermal stress concentration points,thereby improving interlayer bonding strength.

Multi-functional metasurface:ultra-wideband/multi-band absorption switching by adjusting guided-mode resonance and local surface plasmon resonance effects

This study introduces an innovative dual-tunable absorption film with the capability to switch between ultra-wideband and narrowband absorption.By manipulating the temperature,the film can achieve multi-band absorption within the 30-45 THz range or ultra-wideband absorption spanning 30-130 THz,with an absorption rate exceeding 0.9.Furthermore,the structural parameters of the absorption film are optimized using the particle swarm optimization(PSO)algorithm to ensure the optimal absorption response.The absorption response of the film is primarily attributed to the coupling of guided-mode resonance and local surface plasmon resonance effects.The film's symmetric structure enables polarization incoherence and allows for tuning through various means such as doping/voltage,temperature and structural parameters.In the case of a multi-band absorption response,the film exhibits good sensitivity to refractive index changes in multiple absorption modes.Additionally,the absorption spectrum of the film remains effective even at large incidence angles,making it highly promising for applications in fields such as biosensing and infrared stealth.

Simulation study of multi-layer titanium nitride nanodisk broadband solar absorber and thermal emitter

Solar energy has always been a kind of energy with large reserves and wide application.It is well utilized through solar absorbers.In our study,the finite difference time domain method(FDTD)is used to simulate the absorber composed of refractory metal materials,and its absorption performance and thermal emission performance are obtained.The ultra-wide band of 200 nm-3000 nm reaches 95.93%absorption efficiency,of which the bandwidth absorption efficiency of2533 nm(200 nm-2733 nm)is greater than 90%.The absorption efficiency in the whole spectrum range(200 nm-2733 nm)is 97.17%on average.The multilayer nanodisk structure of the absorber allows it to undergo strong surface plasmon resonance and near-field coupling when irradiated by incident light.The thermal emission performance of the absorber enables it to also be applied to the thermal emitter.The thermal emission efficiency of 95.37%can be achieved at a high temperature of up to 1500 K.Moreover,the changes of polarization and incident angle do not cause significant changes in absorption.Under the gradual change of polarization angle(0°-90°),the absorption spectrum maintains a high degree of consistency.As the incident angle increases from 0°to 60°,there is still 85%absorption efficiency.The high absorption efficiency and excellent thermal radiation intensity of ultra-wideband enable it to be deeply used in energy absorption and conversion applications.

Temperature-dependent optical properties of low-loss plasmonic SrMoO_(3)thin films

SrMoO_(3)(SMO)thin films are deposited on LaAlO_(3)substrates by magnetron sputtering.The effects of ambient temperature on the structural,electrical,and optical properties of the films are investigated.As the temperature increases from 23℃ to 800℃,the SMO film exhibits high crystallinity and low electrical resistivity,and the real part of dielectric functions becomes less negative in the visible and near-IR wavelength range,and the epsilon near zero(ENZ)wavelength increases from460 nm to 890 nm.The optical loss of the SMO film is significantly lower than that of Au,and its plasmonic performance is comparable to or even higher than TiN in the temperature range of 23℃ to 600℃.These studies are critical for the design of high-temperature SMO-based plasmonic devices.