Femtosecond Laser-induced Breakdown Research Articles

Discrimination of cow, goat, and sheep milk by femtosecond and nanosecond laser-induced breakdown spectroscopy

In the present work, femtosecond Laser Induced Breakdown Spectroscopy, fs-LIBS, is applied for the first time for the analysis of the inorganic content and the identification of the animal origin of milk samples (i.e., cow, goat, and sheep). The fs-LIBS spectra were analyzed by different machine learning algorithms (i.e., multivariate statistical analysis), and their performance was assessed. The obtained classification accuracies of the milk samples based on the animal origin were found to attain values up to 95 %, depending on the algorithm used. For comparison purposes, LIBS experiments were also carried out employing nanosecond laser pulses, ns-LIBS. The obtained results from both the fs- and ns-LIBS experiments were found to be in excellent agreement between them. The present findings, using fs laser excitation, demonstrate and extend the capabilities of LIBS technique, for the identification of the animal origin of milk samples, thus making fs- and/or ns-LIBS technique a powerful and useful tool for milk authentication, quality, and safety control related research.

Sensitivity, precision, and accuracy of fs-LIBS for heavy metal detection in flowing aqueous solutions.

This investigation employs femtosecond laser-induced breakdown spectroscopy (fs-LIBS) to measure the concentrations of chromium (Cr), lead (Pb), and copper (Cu) in flowing aqueous solutions. The fs pulsed laser excites the water, generating plasma in a dynamic setting that prevents liquid splashing-a notable advantage over static methods. The flowing water column maintains a stable liquid level, circumventing the laser focus irregularities due to liquid-level fluctuations. Calibration curves, based on a linear function, reveal limits of detection (LODs) as low as 0.0179 μg/mL for Cr, 0.1301 μg/mL for Pb, and 0.0120 μg/mL for Cu. The reliability of the experiment is confirmed by R2 values exceeding 0.99. These findings offer valuable insights for the analysis of trace heavy metals in flowing aqueous solutions using fs-LIBS, demonstrating the technique's potential for environmental monitoring.

Quantitative analysis of Th and U in graphite matrix using femtosecond laser-induced breakdown spectroscopy

Quantitative analysis of Th and U in graphite matrix using femtosecond laser-induced breakdown spectroscopy

Effect of Femtosecond Ultraviolet and Infrared Laser Wavelength on Plasma Characteristics of Metals, Ceramics and Glass Samples Using Femtosecond Laser-Induced Breakdown Spectroscopy.

In this work, we present studies on the effect of laser wavelengths on the laser-induced plasma characterization using a femtosecond (fs) ytterbium-doped potassium-gadolinium tungstate (Yb:KGW) laser. Plasma plumes of copper, steel, ceramics, and glass samples were induced using a multiple shot of 200 fs laser pulses with 1030 nm and 343 nm wavelengths at fixed laser fluence () and analyzed using the laser-induced breakdown spectroscopy (LIBS) technique. Time-resolved fs-LIBS measurements were performed on the same set of samples and under the same experimental conditions. For the calculation of plasma parameters, the set of spectral lines of Cu(I) (for copper sample), Fe(I) (for steel sample), and Ca(I), K(I) (for glass and ceramics samples) were observed. The plasma electron temperature and density were evaluated from the Boltzmann plots and Stark-broadening profiles of the plasma spectral lines, assuming the local thermodynamic equilibrium condition. Time-resolved plasma temperature and electron density for fs-LIBS using ultraviolet (UV) and infrared (IR) laser wavelengths were analyzed and no significant dependence on fs laser wavelength was observed for any of the samples. However, for all samples the signal-to-noise ratio (SNR) significantly increased using UV laser radiation: copper (), steel (), glass (), and ceramics (). Therefore, by using a fs UV laser wavelength for laser-induced breakdown spectroscopy experiments, for certain materials the SNR and at the same time the limit of detection can be significantly enhanced.

High-sensitivity analysis of trace elements in water using femtosecond LIBS with dry droplet pretreatment on a metallic substrate

Femtosecond LIBS with dry droplet pretreatment for detecting trace elements in water showed a significant decrease in LOD with increasing titration number, indicating that this method can achieve high sensitivity analysis of trace elements in water.

Identification of tumor tissue in thin pathological samples via femtosecond laser-induced breakdown spectroscopy and machine learning

In the treatment of most newly discovered solid cancerous tumors, surgery remains the first treatment option. An important factor in the success of these operations is the precise identification of oncological safety margins to ensure the complete removal of the tumor without affecting much of the neighboring healthy tissue. Here we report on the possibility of applying femtosecond Laser-Induced Breakdown Spectroscopy (LIBS) combined with Machine Learning algorithms as an alternative discrimination technique to differentiate cancerous tissue. The emission spectra following the ablation on thin fixed liver and breast postoperative samples were recorded with high spatial resolution; adjacent stained sections served as a reference for tissue identification by classical pathological analysis. In a proof of principle test performed on liver tissue, Artificial Neural Networks and Random Forest algorithms were able to differentiate both healthy and tumor tissue with a very high Classification Accuracy of around 0.95. The ability to identify unknown tissue was performed on breast samples from different patients, also providing a high level of discrimination. Our results show that LIBS with femtosecond lasers is a technique with potential to be used in clinical applications for rapid identification of tissue type in the intraoperative surgical field.

Discrimination of tooth composition through temporally shaped femtosecond laser-induced breakdown spectroscopy

Dental caries has attracted widespread concern because of its universality. However, the current diagnosis of dental caries depends largely on naked eyes and dentists' experience, which causes considerable randomness and inaccuracy in the diagnosis. In this study, temporally shaped double pulse (DP) femtosecond laser-induced breakdown spectroscopy (LIBS) has been used for tooth composition detection for the first time. Under the laser fluence of 20 J/cm2, the spectra intensity for DP LIBS with a pulse delay of 200 ps was 13 times higher than that of single pulse. For further prediction, the detection model based on DP LIBS and partial least squares discrimination analysis could discriminate dentin, enamel, and caries with a prediction accuracy of above 90%. This method may provide rapid and accurate feedback to dentists for real-time diagnosis in the future.

The effect of the duration of laser pulses on the spectral-temporal characteristics of laser plasma in femtosecond laser-induced breakdown spectroscopy of human hair

The effect of the duration of laser pulses of 40 and 650 fs with an energy of 1.1 mJ at a wavelength of 800 nm on the spectral-temporal characteristics of plasma during femtosecond laser-induced breakdown spectroscopy of human hair has been studied. The time dependences of the radiation line intensities of Ca I 422.6 nm, C I 193.1 nm, C I 247.8 nm, Ca II 396.8 nm, Mg II 279.5 nm, Zn II 206.2 nm and the continuous plasma spectrum in the range from 0 to 1 μs are obtained Keywords: emission spectrum, laser plasma, human hair.

Влияние длительности лазерных импульсов на спектрально-временные характеристики лазерной плазмы в фемтосекундной лазерной искровой спектроскопии волос человека

The effect of the duration of laser pulses of 40 and 650 fs with an energy of 1.1 mJ at a wavelength of 800 nm on the spectral-temporal characteristics of plasma during femtosecond laser-induced breakdown spectroscopy of human hair has been studied. The time dependences of the radiation line intensities of Ca I 422.6 nm, C I 193.1 nm, C I 247.8 nm, Ca II 396.8 nm, Mg II 279.5 nm, Zn II 206.2 nm and the continuous plasma spectrum in the range from 0 to 1 microseconds are obtained

Direct comparison of ns LIBS and fs LIBS with high spatial and temporal resolution in gases

Spatial resolution is one of the most critical parameters for spectroscopic measurements especially when used in gases. However, the lateral resolution of femtosecond (fs) laser-induced breakdown spectroscopy (LIBS) in gases has not been thoroughly investigated. Here, we directly compare the differences and connections between nanosecond (ns) LIBS and fs LIBS through spatio-temporally resolved spectroscopy. At the time period we measured, unlike the ns LIBS plasma, the fs LIBS plasma does not show detectable expansion, and we do not find composition transport due to turbulence inside the fs LIBS. In other words, the local spectral emission in the fs LIBS can correlate precisely to the composition at that location before the arrival of the laser, while ns LIBS cannot. This feature allows fs LIBS to have much higher lateral resolution than ns LIBS. Finally, this paper verified that fs LIBS can be used for one-dimensional measurements capability with its lateral resolution of 50 μm.

Assay measurement of gaseous UF6 using femtosecond laser-induced breakdown spectroscopy in the 424.4 nm spectral region

Most modern uranium enrichers use centrifuges to separate 235U [Uranium 235] and 238U [Uranium 238] in the gaseous form, UF6 [uranium hexafluoride]. Monitoring the enrichment level of the material being produced in a Gaseous Centrifuge Enrichment Plant (GCEP) or in a single centrifuge is important to the commercial enricher as well as those tasked with monitoring the enrichment activities of declared facilities, such as the International Atomic Energy Agency (IAEA). Here, methods for determining UF6 assay using a femtosecond laser-induced plasma are reported. These techniques resulted in assay measurements within 0.28% of the actual 235U content with a standard deviation of 0.90%, demonstrating the potential effectiveness and applicability of using femtosecond lasers in actual enrichment plants to measure UF6 assay through Laser-Induced Plasma Emission Spectroscopy (LIBS).

Controlling bubble generation by femtosecond laser-induced filamentation

Femtosecond laser-induced optical breakdown in liquids results in filamentation, which involves the formation and collapse of bubbles. In the present work, we elucidate spatio-temporal evolution, interaction, and dynamics of the filamentation-induced bubbles in a liquid pool as a function of a broad spectrum of laser pulse energies (∼1 to 800 µJ), liquid media (water, ethanol, and glycerol), and the number of laser pulses. Filament attributes such as length and diameter have been demarcated and accurately measured by employing multiple laser pulses and were observed to have a logarithmic dependence on laser energy, irrespective of the medium. The size distribution of persisting microbubbles is controlled by varying the pulse energy and the number of pulses. Our experimental results reveal that introducing consecutive pulses leads to strong interaction and coalescence of the pulsating bubbles via Bjerknes force due to laser-induced acoustic field generation. The successive pulses also influence the population density and size distribution of the micro-bubbles. We also explore the size, shape, and agglomeration of bubbles near the focal region by controlling the laser energy for different liquids. The insights from this work on filamentation-induced bubble dynamics can be of importance in diverse applications such as surface cleaning, fluid mixing and emulsification, and biomedical engineering.

Influence of distance from lens to sample surface on spectral sensitivity of femtosecond laser-induced breakdown spectroscopy with NaCl water film

Increasing the emission intensity of laser-induced breakdown spectroscopy (LIBS) is an effective way to improve the sensitivity of LIBS technology to elements analysis in liquid samples. In this work, the influence of the distance from lens to sample surface (DFLS) on the spectral emission of femtosecond laser-induced plasma of NaCl water film was studied by measuring Na atomic line. The results showed that the emission intensity of the spectral line presented the phenomenon of double peaks with an increase in the DFLS. The position for the highest spectral intensity was not geometric focal point of focusing lens, but was located in front of the geometric focal point. In addition, we carried out quantitative analysis on Na element with different concentrations, showing a calibration curve of Na element, and calculating limit of detection (LOD) and relative standard deviation (RSD) for different DFLSs. Subsequently, the changes in the LOD and RSD with the DFLS are discussed. With the increase of the DFLS, the LOD and RSD were greatly reduced. At the DFLS of 99.0 mm, the line intensity was highest, and the LOD and RSD were better. Therefore, it can be confirmed that femtosecond LIBS of water film can be optimized by changing the DFLS, the experiment shows great potential in real-time water quality monitoring.

Determination of the Elemental Composition of Aerosol by Femtosecond Laser-Induced Breakdown Spectroscopy

Determination of the Elemental Composition of Aerosol by Femtosecond Laser-Induced Breakdown Spectroscopy

Quantitative spectral analysis by femtosecond pulse laser-induced breakdown spectroscopy

Quantitative spectral analysis by femtosecond pulse laser-induced breakdown spectroscopy

Quantitative analysis of thorium in graphite using femtosecond laser-induced breakdown spectroscopy

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

Effect of Laser Pulse Repetition Rate on the Detection Limits of the Elemental Composition of Pollutants in Aqueous Solutions by Femtosecond Laser Induced Breakdown Spectroscopy

Effect of Laser Pulse Repetition Rate on the Detection Limits of the Elemental Composition of Pollutants in Aqueous Solutions by Femtosecond Laser Induced Breakdown Spectroscopy

Femtosecond Single-Pulse and Orthogonal Double-Pulse Laser-Induced Breakdown Spectroscopy (LIBS): Femtogram Mass Detection and Chemical Imaging with Micrometer Spatial Resolution.

Femtosecond laser-induced breakdown spectroscopy (fs-LIBS) is employed to detect tiny amounts of mass ablated from macroscopic specimens and to measure chemical images of microstructured samples with high spatial resolution. Frequency-doubled fs-pulses (length 400 fs, wavelength 520 nm) are tightly focused with a Schwarzschild microscope objective to ablate the sample surface. The optical emission of laser-induced plasma (LIP) is collected by the objective and measured with an echelle spectrometer equipped with an intensified charge-coupled device camera. A second fs-laser pulse (1040 nm) in orthogonal beam arrangement is reheating the LIP. The optimization of the experimental setup and measurement parameters enables us to record single-pulse fs-LIBS spectra of 5 nm thin metal layers with an ablated mass per pulse of 100 femtogram (fg) for Cu and 370 fg for Ag films. The orthogonal double-pulse fs-LIBS enhances the recorded emission line intensities (two to three times) and improves the contrast of chemical images in comparison to single-pulse measurements. The size of ablation craters (diameters as small as 1.5 µm) is not increased by the second laser pulse. The combination of minimally invasive sampling by a tightly focused low-energy fs-pulse and of strong enhancement of plasma emission by an orthogonal high-energy fs-pulse appears promising for future LIBS chemical imaging with high spatial resolution and with high spectrochemical sensitivity.

Evaluation of femtosecond laser-induced breakdown spectroscopy system as an offline coal analyzer

Developments in femtosecond laser induced breakdown spectroscopy (fs-LIBS) applications during the last two decades have further centered on innovative métier tie-in to the advantageous properties of femtosecond laser ablation (fs-LA) introduced into LIBS. Yet, for industrially-oriented application like coal analysis, no research has exposed to view the analytical capabilities of fs-LA in enhancing the physical processes of coal ablation and the impact into quantitative correlation of spectra and data modeling. In a huge coal market, fast and accurate analysis of coal property is eminently important for coal pricing, combustion optimization, and pollution reduction. Moreover, there is a thirst need of precision standardization for coal analyzers in use. In this letter, the analytical performance of a one-box femtosecond laser system is evaluated relative to an industrially applied coal analyzer based on five objectives/measures: spectral correlation, relative sensitivity factors, craters topology, plasma parameters, and repeatability. Despite high-threshold operation parameters of the fs system, competitive results are achieved compared to the optimized analytical conditions of the ns-coal analyzer. Studies targeting the in-field optimization of fs-LIBS systems for coal analysis can potentially provide insights into fs-plasma hydrodynamics under harsh conditions, instrumental customization, and pave the way for a competitive next-generation of coal analyzers.

Reduction of self-absorption in femtosecond laser-induced breakdown spectroscopy using spark discharge

The self-absorption effect of femtosecond laser-induced breakdown spectroscopy (LIBS) of aluminum with and without spark discharge is investigated in air. The measured time-resolved spectra show strong self-absorption/self-reversal in the absence of spark discharge. Still, when spark discharge is used to enhance the spectral intensity of LIBS, almost no self-reversal effect can be observed from time-resolved spectra. The results show that spark discharge can effectively reduce the self-absorption effect and improve spectral intensity in femtosecond-LIBS.