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Copper plasma generated at different filament-copper interaction points was characterized by spectroscopic, acoustic, and imaging measurements. The longitudinal variation of the filament intensity was qualitatively determined by acoustic measurements in air. The maximum plasma temperature was measured at the location of peak filament intensity, cor...
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... As intensity-clamped limits are approached under longer focusing conditions through laser filamentation [31], particle excitation is naturally expected to experience a similar limitation through laser-particle energy coupling which explains the reduced emission intensities at longer focal lengths in Fig. 3(b). This is unlike filament interactions with bulk solid samples, where the entire pulse energy is deposited directly onto the sample surface resulting in stronger Cu emissions [32]. Here, only a small portion of the filament is expected to interact and transfer energy to the particle given the relative size difference between the filaments (∼100 µm) and the particle (<5 µm). ...
Excitation from optically trapped particles is examined through laser-induced breakdown spectroscopy following interactions with mJ-level fs pulses. Optical emissions from sub-ng ablation of precisely positioned cupric oxide microparticles are used as a method to spatially resolve laser–particle interactions resulting in excitation. External focusing lenses are often used to change the dynamics of nonlinear self-focusing of fs pulses to form laser filaments or, alternatively, to form very intense air plasmas. Given the significant implications external focusing has on laser propagation and plasma conditions, single-particle emissions are studied with focusing lenses ranging from 50 to 300 mm. It is shown that, while single particles are less excited at longer focal lengths due to limited energy transfer through laser–particle interactions, the cooler plasma results in a lower thermal background to reveal resolved single-shot emission peaks. By developing an understanding in the fundamental interaction that occurs between single particles and fs pulses and filaments, practical improvements can be made for atmospheric remote sensing of low-concentration aerosols.
... Through mechanisms such as energy reservoir regeneration [17][18][19] and fog-clearing hysteresis [20][21][22], fs laser filaments have been demonstrated to be tolerant to instabilities from atmospheric turbulence and attenuation in aerosolized environments, making them promising for standoff characterization of airborne particles. While filaments can form spontaneously from collimated laser beams of sufficient peak power, they can also be produced within confined laboratory spaces using an external focusing lens by forcing early filamentation [23][24][25]. External focusing affects the filament length, diameter, and electron density, having implications on aerosol measurements which are highly dependent on both plasma geometry and collisional plasma-particle energy transfer by free electrons [1,26,27]. ...
The bulk aerosol emissions excited by externally focused femtosecond laser filaments are characterized using time-resolved plasma imaging and spectroscopy. Images of N2 and $\text {N}_2^+$ N 2 + plasma fluorescence are used to characterize the filament dimensions. Emission profiles from bulk Sr aerosols are studied, showing that several localized emission regions in the filament begin to develop for lower repetition rates and higher pulse energies. Plasma temperature and electron density profiles are determined using particle emissions along the length of short- and long-focused filaments, and results are compared for on-axis and side-collected spectra. The use of on-axis collection enables the sampling of light emitted over the entire length of the filament; however, the necessary back-propagation of light makes on-axis collection susceptible to self-absorption as the optical path is extended through the filament plasma column formed in bulk aerosols.
... It is a challenge to diagnose the high-intensity zone produced by femtosecond laser pulse filamentation [12], since almost any material inserted into a high-intensity laser beam will be destroyed. By a feat of the induced abundant physical effects during filamentation, various indirect methods such as optical interferometry [13], acoustic [14,15], imaging [16], fluorescence [17], and plasma conductivity [18] have been utilized to diagnose the plasma. Due to the advantages of fast, non-destructive, and high-resolution, the acoustic diagnosis based on observable photoacoustic effects demonstrates tremendous potential in measuring filamentation. ...
The promising application of femtosecond laser filamentation in atmospheric remote sensing brings imperative demand for diagnosing the spatiotemporal dynamics of filamentation. Acoustic emission (AE) during filamentation opens a door to give the insight into the dynamic evolution of filaments in air. In particular, the frequency features of the acoustic emission provide relevant information on the conversion of laser energy to acoustic energy. Here, the acoustic emission of femtosecond laser filament manipulated by energy and the focal lengths was measured quantitatively by a broadband microphone, and the acoustic parameters were compared and analyzed. Our results showed that the acoustic power presents a squared dependence on the laser energy and the bandwidth of the acoustic spectrum showed a significant positive correlation with laser energy deposition. It was found that the spectrum of the acoustic pulse emitted from the middle of the filament has a larger bandwidth compared to those emitted from the ends of the filament and the spectrum of the acoustic pulse is also an indicator of the filament intensity distribution. These findings are helpful for studying the plasma filament properties and complex dynamic processes through acoustic parameters and allow the optimization of remote applications.
... The high laser intensity and electron density in the plasma channel make it challenging to measure the filament directly [39]. By a feat of the induced abundant physical effects, various indirect methods such as optical interferometry [40], acoustic [41][42][43][44], imaging [45], fluorescence [43,46], and plasma conductivity [47] have been utilized to characterize the plasma. Due to the advantages of fast, non-destructive, and high-resolution, the acoustic diagnosis based on observable photoacoustic effects demonstrates tremendous potential in measuring longdistance filamentation. ...
The promising application of femtosecond laser filamentation in atmospheric remote sensing brings imperative demand for diagnosing and controlling the spatiotemporal dynamics of long-distance filamentation. Here, the acoustic method was adopted to quantitatively diagnose the long-distance filamentation of femtosecond pulses manipulated by energy and temporal domain. The onset and length of filament can be conveniently obtained from a simple analytic formula based on reasonable approximation and further demonstrated by the experimental results. The influence of pulse energy and initial pulse chirp under three different focal lengths (∼10 m, 20 m, and 30 m) on the filamentation in the air were studied experimentally. These findings provide a guiding significance for the optimal control of the long-distance propagation of filament, thereby laying a firm foundation for femtosecond laser-based atmospheric remote sensing.
... The fs filaments can propagate and deliver energies over very long distances without any diffraction effects in contrast to the conventional nanosecond (ns) pulses and makes it very desirable for remote sensing applications [25]. These unique features of the fs laser pulse propagation have demonstrated over the range of a few kilometers [26,27]. Most of the FIBS studies have been focused on the capability of standoff measurements and the recognition of atomic and molecular spectra. ...
We present the spatial and temporal characterization of the copper (Cu) plasma produced by the femtosecond laser filaments. The filaments of various lengths and intensities were generated with the aid of three different focusing lenses. Further, the filamentation induced breakdown spectroscopy (FIBS) measurements were carried out for each filament at three different positions along the length of the filament. The filaments were spatially characterized by estimating the plasma temperature and electron density. Our investigation has demonstrated that the centre of the filament is the best to obtain a maximum signal. Both the spectral line intensity and their persistence time are highest for the center of the filament. The enhanced persistence and the scalability of the spectral line intensity tested across different focusing geometries can boost the application of this technique in various fields.
... Filamentation has been combined with various analytical spectroscopy techniques [25,48,49,84,102,103,110,119,126,148,196,209,210,225,233,256,257] and sensing methods [48,56,123,145,259] in order to extend the excitation distance. ...
... Numerous works investigate filament ablation using the fundamental 800-nm wavelength from Ti:sapphire laser systems [49,84,103,247,256]; however, fewer groups have studied the near-UV and mid-IR wavelength regions. This section presents recent work investigating the effects of filament laser wavelength on metal ablation, comparing wavelengths ranging from the near-UV (400 nm) to the mid-IR (2-µm) spectral domains. ...
Laser-based optical spectroscopy is an emerging technology which fulfills the criteria for safe, efficient, and economical measurement of various materials, including those relevant to nuclear energy and nuclear security. The primary spectroscopy techniques discussed in this work include laser-induced breakdown spectroscopy (LIBS), laser-induced fluorescence (LIF) spectroscopy, and laser ablation-laser absorption spectroscopy (LA-LAS). All-in-one advantages of these methods include capabilities for in-situ, rapid, and remote measurements, fieldable/portable systems, and sensitivity to various forms of the target: any state of matter, solid, liquid, gas; and any form or abundance of the target constituents -- radioactive, nonradioactive, elemental, ionic, molecular, and even isotopic. This work demonstrates the use of laser-based optical spectroscopy for detection and classification of various materials, in particular uranium and its compounds. Optical emission spectroscopy is used to identify a characteristic visible-range signature from heavier gas-phase uranium oxide species in a laser-produced plasma (LPP), for the first time. This signature, as well as improved understanding of the evolution of uranium oxides in LPPs, have implications for in-situ distinction of uranium isotopes using LIBS and LA-LAS, relevant to nuclear security and safety. Further, this work investigates the propagation of intense laser pulses in nonlinear media, such as air, which results in filamentation. Filamentation presents a promising mode for extended delivery of the laser excitation source. This nonlinear propagation regime can augment analytical spectroscopy methods to enable remote sensing at distances that could potentially extend to several hundreds of meters or even kilometers. The transient structures associated with filamentation in gases have been demonstrated in previous work to be useful for waveguiding optical signals also. Filament-driven guiding may be applied not only to the delivery of the excitation source but also to collection of distant optical signals. Fundamental aspects of filamentation are experimentally studied, including the onset of multi-filamentation for high-peak-power lasers and multi-filament interactions during target ablation. Filamentation is combined with analytical spectroscopy techniques including LIBS and LIF to demonstrate standoff excitation and detection of nuclear materials relevant to nuclear security and safety (namely, uranium and its compounds like uranyl fluoride, vital to uranium enrichment processes). Finally, this work demonstrates that the lasting thermal structures left in the gas following dissipation of the filament plasma can be used to improve analytical performance of the LIBS technique. The refractive index change of gas traversed by the filament is used as an anti-guide to suppress time-varying optical signals, such as unwanted backgrounds from an LPP. Furthermore, two filament waveguide structures are concatenated to improve collection of the spectroscopic emission from an LPP, enabling prospects for scalability of such waveguides to greater distances using a series of laser pulses.
... In hazardous environments, telescope systems or fiber optic transmission can be used to conduct long-distance contactless analysis of toxic and hazardous substances, including nuclear radiation environments, explosive analysis, isotope analysis, environmental analysis, and soil contamination analysis. [11][12][13][14][15][16] Ghebregziabher et al. [17] reported the characteristics of copper plasma induced by the filament and studied the spec-tral intensity, plasma temperature, electron density, and signalto-background ratios (SBR) trends at different locations of the filament. Harilal et al. [10] studied plasma temperature clamping by ablating brass and obtained the spatial evolution of radiation intensity and electron density propagating along the filament channel. ...
Ultrafast laser filament-induced breakdown spectroscopy (FIBS) is a potential technique for quantitative analysis of trace elements. In this work, we investigate the effect of the distance between focusing lens and target surface on the FIBS quantitative analysis of Mn element in aluminum alloys, and several major parameters are calculated such as the linear correlation coefficient ( R ² ), limits of detection (LOD), relative standard deviation (RSD), and root-mean-square error of cross-validations (RMSECV). The results show that the quantitative analysis parameter values before and after filament position are different. The optimal value can be obtained at the filament region, the average values of total 23 positions of R ² , LOD, RSD, and RMAECV were 99.45%, 1.41 mg/kg, 7.12%, and 0.56%, respectively. Besides, the spatial distributions of quantitative analysis parameter values in filament region are noticeable, and this is essentially due to intensity clamping effect in a filament.
... Finally, MSE data have been useful for investigations like initiation of a formation of an arc at a plasma-wall contact [160] and quick creation of approximate spectra of dense cool plasmas in the optical wavelength range [161]. Data from [87] have been used in papers dealing with propagation distance-resolved characteristics of filament-induced Cu plasma [162], heterogeneous (Cu-Ti) colliding plasma dynamic [163] and initiation process of vacuum breakdown between copper u and copper-chrome electrodes [164]. Data from [17] have been used in a paper dealing with the zone of compression of a magnetoplasma compressor as a source of extreme ultraviolet radiation [165]. ...
The aim of this paper is to analyze the various uses of Stark broadening data for non-hydrogenic lines emitted from plasma, obtained with the modified semiempirical method formulated 40 years ago (1980), which are continuously implemented in the STARK-B database. In such a way one can identify research fields where they are applied and better see the needs of users in order to better plan future work. This is done by analysis of citations of the modified semiempirical method and the corresponding data in international scientific journals, excluding cases when they are used for comparison with other experimental or theoretical Stark broadening data or for development of the theory of Stark broadening. On the basis of our analysis, one can conclude that the principal applications of such data are in astronomy (white dwarfs, A and B stars, and opacity), investigations of laser produced plasmas, laser design and optimization and their applications in industry and technology (ablation, laser melting, deposition, plasma during electrolytic oxidation, laser micro sintering), as well as for the determination of radiative properties of various plasmas, plasma diagnostics, and investigations of regularities and systematic trends of Stark broadening parameters.
... The ionization and thermal properties of magnesium and aluminum were summarized in Table 1. Usually, ionized metal atoms that have been stripped out of the outermost electrons, such as singly (Cu + ) and doubly (Cu 2+ ), took a large part of cations in the plasma [31,32]. According to Table 1, compared with aluminum, magnesium was easier to be fused, vaporized and ionized to utilize the energy from carbon layer and transfer energy to the posterior aluminum layer. ...
Laser-driven flyer technology not only has been widely applied in micro-scale material processing and dynamic high-pressure physics but also possesses obvious advantages in improving the instantaneity and safety of shock initiation. To investigate the launch and impact characteristics between different flyers, six types of typical laser-driven flyers were designed and prepared via magnetron sputtering. The photonic Doppler velocimetry (PDV) and a self-made polyvinylidene fluoride (PVDF) stress sensor were used to collect the velocities and impact stresses of flyers driven by ns-pulsed laser, so that the kinetic energy coupling efficiency and shock initiation property were able to be obtained. Comparisons of characteristics between different flyers were implemented. The effect of nanothermite formed between aluminum and copper oxide layers was verified. The kinetic energy coupling relationship with laser and factors that influenced impact stress of flyers were discussed as well. The results are of significance in optimizing the launch and impact characteristics of laser-driven flyers for practical application.
... evolutions of emission intensity and the electron density along the filament channel propagation. Ghebregziabher et al. [20] reported the propagation distance-dependent characteristics of filament-induced copper plasma, and the trends of spectral intensity, plasma temperature, electron density and SBR in the different position of filament propagation were studied. Yang et al. [21] measured the spectral intensity of produced Cu plasma along the filament channel and obtained the distribution of Cu(I) intensity versus the distance between sample and focused lens. ...
In this paper, the spatially-resolved characteristics, such as emission intensity, plasma temperature, and electron density, of femtosecond filament induced soil plasma were experimentally studied, and the spatial evolution of the limit of detection (LOD) was obtained along the filament channel propagation. The experiment results show that the spectrum intensity and LOD of Pb I 405.78 nm trended opposingly along the filament channel propagation, the maximum spectrum intensity and the minimum LOD are obtained at a certain distance along the filament channel, and the minimum LOD value for Pb element is 1.31 ± 0.04 ppm.
