Time and space resolved visible spectroscopic imaging CO2 laser produced extreme ultraviolet emitting tin plasmas

Abstract

Experiments involving laser produced tin plasma have been carried out using a CO 2 laser with an energy of 800 mJ/pulse and a full width at half maximum (FWHM) of 80 ns in vacuum. Time-integrated extreme ultraviolet spectral measurement showed that the peak of the extreme ultraviolet lithography spectrum was located at 13.5 nm and the spectrum profile's FWHM of the unresolved transition arrays was 1.1 nm. Plasma parameters of the electron temperature and density measurements in both axial and radial directions at later times had been obtained from a two-dimensional time and space resolved image spectra analysis. The axial spatial distribution of the electron density showed a 1/d 2.6 decrease profile, and the radial spatial distribution of the electron density showed a 1/r 1.1 profile, in which d is the axial distance from the target surface and r is the radial distance. The electron density was found to maintain symmetry across the radial distance at all delay times. Near the plasma plume center, the electron temperature T e varied slightly with increasing axial or radial distance, which was related to collisional decoupling and reheating of the ionized species in the plasma at distances longer than 3 to 4 mm. The space averaged electron temperature was measured in the range of 3.4-1.0 eV, and the space averaged electron density was measured in the range of 2.0 Â 10 17 to 2.2 Â 10 16 cm À3 , as the time delay varied from 1.6 ls to 3.6 ls with respect to the pulse discharge. Time evolutions of the plasma temperature and density were found to have an apparent rise at a delay time of 2.4 ls in the corresponding time of the laser pulse tail peak. This suggests that plasma parameters and extreme ultraviolet emission intensity can be controlled by a double pulse combined laser.

Dynamics of femto- and nanosecond laser ablation plumes investigated using optical emission spectroscopy

“…A previous report showed similar trends for ns LPP, with a rapid drop in temperature after laser plasma generation with respect to time. 37,38 The time evolution of fs LPP shows a much different trend, the plasma decays slowly within the first 40 ns and then rapidly begins to drop, this profile was also reported by Xu et al 39 showing a slow decay and then a drop at similar times even though there was no explanation given for the unusual decay. Our previous studies 40 as well as ICCD imaging of fs plumes (see Figure 5) showed that plasma expansion is more collimated in the fs LPP compared to ns LPP.…”

“…All LPPs have preferential expansion of the material in the direction perpendicular to the target surface, irrespective of the angle of incidence of laser beam. 37 Figure 9 shows the temperature and electron density as a function of distance from the target. These measurements were performed in a time-integrated manner.…”

Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

“…30 Therefore, in the PIC simulation we use fictitious values keeping important physics to be the same. Table I displays the plasma simulation parameters 42,43 and a comparison with the reported experimental parameters for the similar experimental conditions used in the present experiment. Figure 13 displays the ion and electron motion and respective energies at real time $329 ns.…”

Imaging spectroscopy of Ag plasmas produced by infrared nanosecond laser ablation

“…Different authors [17][18][19][20][21][22][23][24][25][26][27][28][29][30] have previously described this kind of study. In order to study the plasma-plume expansion dynamics of different species, we plotted spectrally resolved 1D-spatial and 1D-spectral imaging mode for different delay times.…”