TEA CO2 Laser Research Articles

Optimization of some input parameters of a pulsed TEA CO2 laser based on the generalized Landau-Teller equations

Optimization of some input parameters of a pulsed TEA CO2 laser based on the generalized Landau-Teller equations

Application of laser-induced breakdown spectroscopy for the analysis of pig bones

An application of the laser-induced breakdown spectroscopy technique (LIBS) for the elemental analysis of pig shoulder bone samples is reported. Measurements were performed using a compact laboratory-made LIBS system based on the TEA CO2 laser and time-integrated signal detection. The recorded spectra consisted of well-defined atomic and single-charged ionic lines of bone matrix elements (Ca and P) and other constituent elements (e.g. Mg, Zn, Na, K, and C) with a good signal-to-noise ratio suitable for chemical analysis. Based on the elemental composition of bone samples measured by inductively coupled plasma emission spectroscopy, limits of detection (LOD) of LIBS analysis were estimated for several elements. LOD ranged from 2.2 ppm (K) to 16 ppm (Zn). Carbon and Hα spectral lines were used for plasma diagnostics by measuring Stark widths. Optical profilometry was used to assess the capability of LIBS for depth profile analysis. For laser fluence between 13.0 and 18.2 J cm−2, the ablation rate per pulse ranged from 6 to 10 μm.

Remote sensing of air pollution incorporating integrated-path differential-absorption and coherent-Doppler lidar

An innovative complex lidar system deployed on an airborne rotorcraft platform for remote sensing of atmospheric pollution is proposed and demonstrated. The system incorporates integrated-path differential absorption lidar (DIAL) and coherent-doppler lidar (CDL) techniques using a dual tunable TEA CO2 laser in the 9–11 μm band and a 1.55 μm fiber laser. By combining the principles of differential absorption detection and pulsed coherent detection, the system enables agile and remote sensing of atmospheric pollution. Extensive static tests validate the system’s real-time detection capabilities, including the measurement of concentration-path-length product (CL), front distance, and path wind speed of air pollution plumes over long distances exceeding 4 km. Flight experiments is conducted with the helicopter. Scanning of the pollutant concentration and the wind field is carried out in an approximately 1 km slant range over scanning angle ranges from 45° to 65°, with a radial resolution of 30 m and 10 s. The test results demonstrate the system’s ability to spatially map atmospheric pollution plumes and predict their motion and dispersion patterns, thereby ensuring the protection of public safety.

The TEA CO2 Laser as a Promising tool for Elemental Analysis of Restored Teeth and Evaluation of Restoration Constituent Penetration into Dental Tissues

The TEA CO2 Laser as a Promising tool for Elemental Analysis of Restored Teeth and Evaluation of Restoration Constituent Penetration into Dental Tissues

The role of multi-photon dissociation of high pressure SF6 gas in TEA CO2 lasers pulse shaping

High pressure SF6 gas has been irradiated by intense TEA CO2 laser pulses with different wavelengths around 10.6μm and then, temporal variations of the transmitted laser pulses have been characterized at different energy fluences and gas pressures. It has been shown that for every fluence above the multi-photon dissociation threshold of SF6 molecules, there is a certain cut-off pressure at which the pulse spike is completely quenched. While, the pulse tail escapes with an appreciable fraction of its initial energy. FTIR spectra of the irradiated gases together with other experimental evidences have clearly revealed the occurrence of laser induced multi-photon dissociation of SF6 molecules, that should be considered as the main responsible for the observed pulse shaping effects.

Thermal stability and compensation of compact dual-path TEA CO2laser resonant cavities

Thermal stability and compensation of compact dual-path TEA CO2laser resonant cavities

Remote sensing of gaseous SF6 plume in troposphere using CO2 laser based DIAL according to ringing effect compensation

A TEA-CO2 laser based DIAL is employed to determine the range resolved hexafluoride (SF6) concentration. An algorithm is developed here in favor of the lidar signal processing to improve the data assessment against the undesired ringing effect. The latter is known as a lidar waveform defect that arises from multiple reflections of transmission line during the data acquisition, detection and recording. Before retrieval of SF6 parameters, namely concentration and extinction coefficient, the noise removal is initially carried out by means of the wavelet thresholding. Then, the ringing effect is significantly suppressed according to the developed Gaussian decomposition method. Furthermore, the plume concentration is measured regarding the signal processing of the neighboring lines of the 32SF6 absorption band within the spectral range of 10.247–10.6 µm. The 32SF6 concentration is determined by improving the accuracy of the signal processing. The 3D visualization of the SF6 diffusion is carried out in time and distance domains through the lower troposphere too. Horizontal atmospheric extinction profiles are successively obtained based on the near boundary method (NBM) with the spatial resolution 3.75 m. Moreover, the extinction profiles are recorded in three typical meteorological conditions i.e. 2 × 10−4 m−1 (morning-still), 6 × 10−4 m−1 (afternoon-snow) and 7 × 10−4 m−1 (night-rainy). We have shown that developed Gaussian decomposition method certainly improves DIAL-data processing.

Temporal behavior of the high-power pulsed gas terahertz laser pumped by a fundamental mode TEA CO2 laser.

Optically pumped gas molecular terahertz (THz) lasers are promising for generating high-power and high-beam-quality coherent THz radiation. However, for pulsed gas THz lasers, the temporal behavior of the output THz pulse has rarely been investigated. In this study, the temporal behavior of a pulsed gas THz pumped by a fundamental-mode TEA CO2 laser has been presented for the first time both in simulation and experiment. A modified laser kinetics model based on the density matrix rate equation was used to simulate the temporal behavior and output pulse energy of a pulsed gas THz laser at different gas pressures. The results clearly show that the working gas pressure and pump pulse energy have critical influences on the output THz pulse shape. Three typical pulse shapes were obtained, and the THz pulse splitting caused by gain switching was quantitatively simulated and explained based on the laser dynamic process. Besides, with an incident pump pulse energy of 342 mJ, the maximum output THz pulse energy of 2.31 mJ was obtained at 385 µm, which corresponds to a photon conversion efficiency of approximately 56.1%, and to our knowledge, this is the highest efficiency for D2O gas THz laser. The experimental results agreed well with those of the numerical simulation for the entire working gas pressure range, indicating that our model is a powerful tool and paves the way for designing and optimizing high-power pulsed gas lasers.

Some experimental studies on the UV spark pin-array pre-ionization in TEA CO2 laser

The output characteristics of a UV pin array pre-ionized transversely excited atmospheric CO2 laser have been experimentally studied in detail. The effects of the applied voltage and capacitance of the main capacitors on the laser performance was investigated. By increasing the voltage at a constant capacitance, not only the laser output energy increases, but also the pulse build-up time, width and tail length decrease. Also, the stability conditions of the discharge were investigated and the cross section of the laser output beam at different input energies was compared.

Development of a dielectric corona pre-ionized TEA CO2 laser with CO2-rich gas mixture suitable for second harmonic generation

A simple dielectric corona pre-ionized TEA CO2 laser, which is suitable for SHG applications, has been developed with the help of high concentration of carbon dioxide. The intense, very uniform UV pre-ionization and low-inductance discharge circuit permit the best laser performance with a gas mixture rich in CO2. In order to achieve the most acceptable combination of the peak power, output energy and pulse duration, not only N2:CO2 ratio varies in favor of CO2 but also helium concentration is significantly reduced. When CO2 concentration varied from 20 to 53% in the experiment, a more symmetrical, shorter output pulse (a FWHM of ∼60 ns) with a significantly lower tail and a lower energy (∼700 mJ) was obtained with a rich gas mixture of CO2:N2:He = 10:1:8 than a lean gas mixture of 1:1:3 while the peak output power was virtually kept constant (∼5.8 MW). The effect of the laser gas mixture on optimizing the energy and time parameters of SH waveform has been studied numerically. The calculations show that for the rich gas mixture the residual tail of the SH pulse is completely eliminated by the nonlinear conversion and the corresponding waveform has a lower total duration (∼600 ns). Moreover, the energy conversion efficiency can be increased by 29% with the rich mixture compared to the lean mixture.

Quantitative Analysis of Coal by Laser-Induced Breakdown Spectroscopy Using TEA CO2 Laser as the Excitation Source

Quantitative Analysis of Coal by Laser-Induced Breakdown Spectroscopy Using TEA CO2 Laser as the Excitation Source

Investigation of Laser Damage Thresholds of an Output Coupler for TEA CO2 Laser

Investigation of Laser Damage Thresholds of an Output Coupler for TEA CO2 Laser

Laser-induced breakdown spectroscopy analysis of water solutions deposited on PTFE surface: Influence of copper oxide nanoparticles and NELIBS effect

The analytical potential of LIBS for the analysis of liquid solutions was evaluated using two experimental setups, one based on a TEA CO2 laser and the other in which Nd:YAG laser was used. Polytetrafluoroethylene (PTFE) was used as a substrate on which a 10 μL drop of analyte solutions with different concentrations of analyte elements, Be, Cr, Ni, Co, Pb, Tl, and V, were deposited and dried. The samples were deposited either directly on the PTFE or over the pre-deposited layer of copper oxide nanoparticles to study the influence of nanoparticles (NPs) on the ablation and plasma excitation. The obtained results imply that the presence of Cu oxide NPs does not significantly affect the analytical performance of LIBS based on TEA CO2 laser for analysis of solutions. At the same time, it was shown that plasma created by TEA CO2 laser radiation efficiently excited ablated material, making metal elements detectable in the sub-ppm concentration range. On the other hand, Cu oxide NPs significantly influence the formation and the analytical properties of plasma induced by Nd:YAG laser. Without the presence of NPs, the intensities of analyte lines were very low, unsuitable for spectrochemical analysis. At the optimal surface concentration of NPs, 0.36 mg/cm2, the intensity of analyte lines was increased more than ten times. Limits of detection of Be and Cr were 5.3 ppb and 33 ppb, with good linearity of curves of growth.

Analytical model to determine the relevant parameters governing the transferred momentum to spherical indenters by laser-induced shock waves

Rapid material development is a new approach to reduce the time and cost intensity. It is based on small and simple sample geometries. Many conventional test methods such as hardness measurements or tensile tests are not suitable for this approach, because they either require a sample geometry adapted to the test method or they are time-consuming. Thus, research is being conducted on a novel impact-based method, which allows short time indentations and correlations with mechanical material properties such as hardness and tensile strength: With a high intensity pulsed TEA-CO2 laser, a shock wave is generated on top of a spherical indenter. The momentum of the shock wave pushes the indenter inside a sample. From the induced indentations, characteristic values such as indentation depth and indentation diameter are extracted, which correlate well with the material hardness and tensile strength. Still, the process dynamics are not fully understood. Thus, a model is developed to determine the main parameters that govern the interaction between laser-induced shock wave as well as indenter and accordingly, significantly affect the forming energy. The model is validated by experimental results. From the findings of the analytical model and the conducted experiments, fundamental correlations with respect to the available forming energy are determined. The main parameters influencing the available forming energy are pulse energy, pulse duration, laser spot area, density of the ambient medium and indenter mass.

Numerical simulation and experimental study of pulsed CO2 laser-induced micro-channels on poly-ether sulfone (PES) polymer

TEA CO2 laser pulses were used to create micro-channels on PES samples with various low fluences and scanning speeds in 16–50 J/cm2 and 23–45 µm/s ranges, respectively. Different micro-channels were created with 142–342 µm widths and 85–440 µm depths which has been 3-dimensionally simulated using ABAQUS software based on the finite element method and CIN heat source. The sharp spike (~85 ns FWHM) and long tail (~3.8 µs) parts of the laser pulses were mathematically modeled with individual Gaussian profiles. A good agreement has been found between the simulated and experimental results. Namely, the maximum relative errors of the depth and opening width of the grooves remain below 11.5% and 12.3%, respectively. However, the corresponding mean values of these relative errors do not exceed 4.1% and 7.5%, respectively.

Preliminary evaluation of chemical component in the 2004 indian ocean giant tsunami impacted soil using a Co2 Laser Induced Breakdown Spectroscopy (LIBS)

Preliminary evaluation of chemical component in soil impacted by 2004 Indian Ocean giant tsunami using LIBS has been carried out. The sampling of the tsunami impacted soil was carried out in several points in Aceh, Indonesia. In this study, the sample soil was pretreated to turn into pellets. The beam of a TEA CO2 laser (10.6 µm, 3 J, 200 ns, 10 Hz) is sent onto surface of pellet using focusing lens under air at atmospheric pressure for producing a plasma. The emission spectral lines from plasma that generated were discovered when testing with Optical Multichannel Analyzer (OMA) system. It shows many emission lines because of various elements could clearly be detected and be identified. It was found that both the tsunami impacted and unimpacted soil sample contain chemical signatures of tsunami event such as saltwater signal (Na), carbonate markers (Ca, Mg, Sr), terestrial markers (Fe, Mn, Si Ti, Ba), and other heavy metal elements. However, it is found that emission intensities of the spectral lines are far higher for the tsunami impacted soil samples compared to the case of tsunami unimpacted soil. The qualitative observation finding implies that the chemical elements such as calcium (Ca), then followed by magnesium (Mg), and sodium (Na) are good candidate for chemical proxies of tsunami event. Since the measurement allows to simultaneously observe these elements in a single measurement, thus LIBS is a potential, simultaneous, efficient, and versatile spectroscopic technique not only for analyzing chemical component in soil affected by the tsunami but also to identify the tsunami impacted soil from the impacted soilThe first section in your paper.

Emission Characteristics of Hydrogen and Carbon in Various Ambient Gases using Pulsed-CO2 Laser-Induced Breakdown Spectroscopy

Background:Hydrogen (H) and Carbon (C) are major elements that occur in various materials, including organic matter. The identification and analysis of C and H are necessary for several fields. LIBS is an excellent method for such analysis because it is rapid, and can be conducted remotely. The technique has been employed for the analysis of H in zircaloy metals. However, few studies on the emission characteristics of H and C in various gases have been undertaken because of the difficulty of identifying H and C using standard LIBS techniques. In this work, the emission characteristics of H and C were studied using pulsed CO2 LIBS. H and C elements were obtained from ethanol vapor. Various gas environments were employed, including Nitrogen (N2), Argon (Ar), and Helium (He) gases, in order to study the stability of the laser-induced plasma, the plasma lifetime, and the excitation mechanisms of H and C.Methods:The LIBS system used in this work consisted of a pulsed TEA CO2 laser (Shibuya SQ 2000), pulse generator, and optical multichannel analyzer. In this work, the laser with a wavelength of 10.6 µm, pulse duration of 200 ns, and pulse energy of 3 J, was used as the irradiation source. The laser energy used was 1.5 J. The laser was irradiated, and focused, using a 200 mm zinc selenide (ZnSe) lens, onto a metal surface in order to initiate and induce a luminous plasma. The sample used in this study was ethanol vapor, obtained from ethanol (99.5%, Merck). For this purpose, 10 mL ethanol was poured into a glass beaker, and this was placed into a closed chamber that could be evacuated by ambient gases including N2, Ar, and He gases.Results:Identification of H emission line has been successfully carried out using this present technique demonstrated in various gases including N2, Ar, and He. From the results, it was observed that in N2 gas, the Hα I 656.3 nm emission line was clearly expressed, with a wide, full-width halfmaximum, and quite a low emission intensity.Conclusion:The emission characteristics of H and C in laser-induced plasma, produced in various ambient gases, including N2, Ar, and He, were studied. The emission spectra of Hα and Hβ were expressed clearly, with high intensity and low background emission, in He, while they were broad and had high background emissions in N2 and Ar. Based on the time-resolved emissions, the Hα emission had a longer lifetime in Ar and He. It was assumed that the metastable atoms of Arand He were predominant in the excitation process of H and C. The characteristics of the H and C emissions in various gases are important in selecting a suitable ambient gas for the study of light atomic emission in the medical field, which mostly deals with organic materials containing H, C, and oxygen.

EUV spectroscopy of optically thin germanium plasmas in the 9-18 nm region

SynopsisEUV spectra have been recorded from optically-thin germanium laser produced plasmas created using a high-powered TEA CO2 laser. The Cowan suite of atomic codes has been used to identify previously unidentified lines in Ge VI-XI. The absence in the spectra of Δn=0 transitions for ion stages lower than Ge9+ has been interpreted by calculating line strength ratios for of Δn=0 to Δn=1 transitions for the relevant ion stages.

Tailoring the Pressure Profile of TEA-CO2 Laser-Induced Shock Waves for Mechanical Forming and Separation Processes

For laser shock processes, the acting pressure can be increased by confining the propagation of the laser-induced plasma. Water or glass is commonly used as confinement for laser shock waves induced by Nd:YAG-lasers. This is not possible for the longer wavelength of TEA-CO2 lasers due to higher absorption coefficients. Instead, the acting pressure can be manipulated with a pressure cell above the workpiece. Two different pressure cells were designed to test the versatility of this concept. A cylindrical pressure cell design was used to confine the propagation of the laser-induced plasma and a parabolic pressure cell design was used to reflect the shock wave back to the workpiece. The effect of the pressure cells was analysed by time-resolved force measurements and evaluated for maximum force and force duration. This study shows that the cylindrical pressure cell strongly increases the maximum force while the parabolic pressure cell maximises the duration of force application. Furthermore, the pressure cells have been applied to the laser shock-based processes laser shock punching and LiSE hardness measurement. The cylindrical pressure cell strongly enhances the results of both processes, while the parabolic pressure cell shows only a minor effect.

An original LIBS system based on TEA CO2 laser as a tool for determination of glass surface hardness

This study was carried out to examine the applicability of original laser-induced breakdown spectroscopy (LIBS) setup for determination of the surface hardness of lead glass as a function of its chemical composition. For this purpose, a set of five lead glass samples with different amount of ZrO2 was prepared. The LIBS measurements were carried out using TEA CO2 laser in the air at atmospheric pressure and without sample preparation. A ratio of the intensity between the Zr(II) 355.66 nm and Zr(I) 360.12 nm emission lines has been used to examine the hardness of the material. In addition, the surface hardness of glass samples was determined by Vickers’s indentation tests. Obtained results indicate a linear relationship of the measurements of hardness in glass samples between the LIBS and Vickers method. To show that LIBS based on TEA CO2 laser is an almost nondestructive technique, profilometric surface analysis was used. The proposed LIBS system is suitable not only for a spectrochemical analysis but also as an easy to use and cost-effective way to measure the surface hardness for all types and shapes of glass samples which are in some cases difficult to examine by standard Vicker’s method.