RESUMEN
In this paper, an Ndâ¶YAG laser with 10ns pulse width and output wavelength of 1 064 nm was employed to ablate Gd metal target and Gd-doped glass target for plasma generation. The out-of-band (OOB) radiation of extreme ultraviolet sources with the two target configurations was comparatively studied. It has been found that the continuous radiation emitted by the plasma is the main component of the out-of-band radiation. The spectral distribution of the continuum emission matches that of blackbody radiation with a temperature of about 5 eV. And it is also found that the intensity of OOB radiation can be considerably decreased by using Gd-doped glass target. Optical Emission Spectroscopy (OES) has been used to analyze the temporal and spatial behaviors of electron temperature (Te) and density (Ne) of the Gd-doped glass target plasma, and experimental results show that temporal evolution of electron temperature and density of the plasma are found to be decayed exponentially with the increasing of delay time. At 125 ns after laser irradiation, electron temperature and density were 4 eV and 1.2×1018 cm-3 respectively, and then decreased to 1.5 eV and 8×1017 cm-3 with delaying time of 250 ns. On the other hand, spatial evolution of electron temperature and density show that both of them first increase and then decrease in the region of 1~10 mm from the target surface. The electron temperature and electron density achieves the maximum of 2.6 eV and 8.5×1017 cm-3, respectively, when the probe location away from the target surface 6 mm.
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In this paper, the concentration of copper element in the CuSO4 solution was measured by Laser Induced Breakdown Spectroscopy with aqueous jets. We used the CuSO4 solution with 7 kinds of concentration and adopted statistical exploratory data analysis method to get calibration curve of Cu, whose linear fitting coefficient R2 was larger than 0.98. The average RSD of LIBS was 6.96%, and the average LOD of Cu was determined to be 12 ppm. The values of relative error by analyzing Cu I 324.75 nm and Cu I 327.40 nm spectral lines were respectively 6.52% and 5.86%, with the method called leave-one-out cross validation. The experimental relative error had a greater value, which was 10.3%, when the concentration of Cu was 10 ppm. However, the relative error decreased to 1.1% for the concentration of 2000 ppm, which indicated that LIBS need to be studied on its accuracy further in detecting lower analytical concentrations. LIBS has the promising application in detecting heavy metal elements in the environmental wastewater pollution.
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Extreme ultraviolet lithography is one of the most promising technologies on the next generation of high-capacity integrated circuit manufacturing. However, techniques for ion debris mitigation have to be considered in the application of extreme ultraviolet source for lithography. In our paper the dynamics of ion debris from Sn plasma by using dual ns laser pulses were investigated. The results show that debris from plasma greatly depends on the energy of pre-pulse and the delay time between the two laser pulses. The energy of Sn ions debris was efficiently mitigated from 2. 47 to 0. 40 keV in the case of dual laser pulses, up to 6. 1 times lower than that by using single laser pulse. We also found that Sn ions debris can be mitigated at all angles by using the dual laser pulses method.
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The expansion dynamics of air plasma induced by 1,064 nm nanosecond laser pulse was studied by plasma fluorescence method. The time evolution images of air plasma expansion were acquired using the ICCD camera at different laser pulse energy, and the expansion velocity of air plasma was deduced based on the air plasma frontier expansion wave front distance at 150 mJ. The experimental results show that the plasma fluorescence was mainly distributed in the plasma expansion region, the plasma fluorescence intensity firstly increased then became weaker and the expansion area increased gradually with time evolution. The biggest expansion distance was 3. 76 mm with 300 mi at 20 ns. The plasma expansion speed was the order of magnitude of 10s m · s(-1) at the early stage of expansion process. The expansion speed of air plasma decayed rapidly within 16ns, then changed slowly with time. The time of air breakdown was close to the rising phase of laser pulse when the greater laser pulse energy was radiated.
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Laser-induced breakdown spectroscopy (LIBS) is a kind of spectroscopic technique for the qualitative and quantitative analysis of elements, which has been rising with the development of laser technique and optical detection technique in recent years. The present paper gives a review of the situation of the recent research progress in LIBS technique. The detailed latest application progress in LIBS in the metallurgy, environmental pollution detection, biomedicine, botany and space exploration field is shown.
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Laser induced plasma spectroscopy of alloy steel was produced by Nd : YAG pulsed laser at 1 064 nm, and the spectral signal was detected by high resolution and width controlled ICCD. Several Fe atomic spectral lines such as 404.581, 414.387, 427.176 and 438.355 nm were chosen for analysis, and the effects of different experimental parameters on LIBS spectral signal intensity were investigated. It is shown that the experimental parameters such as pulse energy, laser focus location and laser delay time have great influence on the LIBS signal. LIBS signals with high spectral intensity and signal-background ratio (SBR) as well as the optimum experiment conditions were obtained by optimizing these experiment parameters so as to make composition analysis of the alloy steel.
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The 355 nm laser pulse from THG (Third Harmonic Generation) of a Qswitched Nd3+ : YAG laser was used to ablate silicon mounted in air. The time-and space-resolved optical emission spectra were measured for different pulse energy in the wavelength range of 380-420 nm, the emission spectra of N+ was found for impact ionization of air near target surface on the early stage of plasma plume expansion. Under the model of local thermodynamic equilibrium, the electronic temperature of plasma was deduced to be in the range of 18 000-40 000 K using the Saha equation by the relative line intensities, and the electron density was deduced to be in the 10(17) cm(-3) scale by FWHM (the full width at half maximum) of Si spectral lines, the temporal and spatial evolution of the electronic temperature and electron density was given, showing that the electronic temperature and electron density exhibited second order exponential decreasing with laser delay time and a Lorentz distribution in space. The reason for the spatial position deviation of the maximum electron density from the maximum spectral intensity was analyzed. The relationship between the plasma plume parameters and laser pulse energy was discussed.
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This study investigates near-infrared region Ag2S quantum dots (QDs) and their nonlinear optical response under 532 nm nanosecond laser pulses. Our experimental result shows that nonlinear transmission is reduced from 0.084 to 0.04. The observed narrowing behavior of the output pulse width shows superior optical limiting. We discuss the physical mechanisms responsible for the nonlinear optical response of the QDs. The average size of the nanocrystals was 5.5 nm. Our results suggest the possibility of using these Ag2S QDs for photoelectric, biosensor, optical ranging, and self-adaptive technologies.
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This paper describes a debris-free laser plasma soft X-ray source with a gas target, which has high operating frequency and can produce strong soft X-ray radiation. The valve of this light source is drived by a piezoelectrical ceramic whose operating frequency is up to 400 Hz. In comparison with laser plasma soft X-ray sources using metal target, the light source is debris-free. And it has higher operating frequency than gas target soft X-ray sources whose nozzle is controlled by a solenoid valve. A channel electron multiplier (CEM) operating in analog mode is used to detect the soft X-ray generated by the laser plasma source, and the CEM's output is fed to to a charge-sensitive preamplifier for further amplification purpose. Output charges from the CEM are proportional to the amplitude of the preamplifier's output voltage. Spectra of CO2, Xe and Kr at 8-14 nm wavelength which can be used for soft X-ray projection lithography are measured. The spectrum for CO2 consists of separate spectral lines originate mainly from the transitions in Li-like and Be-like ions. The Xe spectrum originating mainly from 4d-5f, 4d-4f, 4d-6p and 4d-5p transitions in multiply charged xenon ions. The spectrum for Kr consists of separate spectral lines and continuous broad spectra originating mainly from the transitions in Cu-, Ni-, Co- and Fe-like ions.