Effect of laser irradiance on the surface morphology and laser induced plasma parameters of zinc

Abstract

The effect of laser-irradiance on the surface morphology and laser induced breakdown spectroscopy of zinc has been investigated by employing Nd:YAG laser (wavelength λ = 1064 nm, pulse duration t ~ 10 ns, and repetition rate = 10 Hz) under ambient environment of argon at a pressure of 20 Torr. For this purpose, zinc targets were exposed to various laser irradiances ranging from 13 GW/cm2 to 100 GW/cm2. Scanning electron microscope analysis has been performed to analyze the surface modification of irradiated zinc targets. Scanning electron microscope analysis revealed the formation of various kinds of structures such as ripples, cones, cavities, and wave like ridges at the center and peripheral regions of ablated zinc. In the central ablated region with increasing laser irradiance, the growth of distinct and well defined ripples is observed. Further increase in irradiance makes the appearance of these ripples diffusive and narrow. In order to correlate the plasma parameters with the surface modification, laser induced breakdown spectroscopy analysis has also been performed. The electron temperature and number density of zinc plasma have been evaluated at various laser irradiances. For both plasma parameters, an increasing trend up to a certain value of laser irradiance is observed which is due to enhanced energy deposition. Afterword a decreasing trend is achieved which is attributed to the shielding effect. With further increase in irradiance a saturation stage comes and almost no change in plasma parameters is observed. This saturation is explainable on the basis of the formation of a self-regulating regime near the target surface. A strong correlation between surface modification and plasma parameters is established.

Laser-induced breakdown spectroscopy analysis of human deciduous teeth samples

“…1 The emission spectrum of laser induced tooth plasma collected under ambient environment of Ar at 20 Torr (a) overall (b) for emission lines of Ca I [22]. This absorption occurs through mainly two processes, i.e., inverse bremsstrahlung (IB) and direct photoionization (PI), and results in generation of plasma with increased temperature and number density of charged particles [23]. The pressure at 20 Torr of Ar is also sufficient for confinement of ablated species, and more energy deposition from laser to generated plasma causes enhancement of T e and N e .…”

Investigation of compositional analysis and physical properties for Ni-Cr-Nb alloys using laser-induced breakdown spectroscopy

“…Here, the natural logarithm of rescaled intensities of selected emission lines was plotted versus the upper state energy (E k ) to result in a straight line with the slope of (-1/k B T). For electron number density N e calculation, the Stark broadening of well resolved spectral lines can be used according to the relation [21,22]: (4) In Eq. ( 4), Δλ is the Lorentzian FWHM of the spectral line, ω s is the Stark broadening parameter, values of which can be found in scientific data tables, N r is the reference ---------------------------------------------- ------------------------E ------------------------N r = electron density equal to 10 16 (cm -3 ) for neural atoms and 10 17 (cm -3 ) for singly ionized states.…”

Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

“…The number of the cavities increases with increasing laser fluence up to a certain value and then decreases. Possible reason of this trend could be refilling of the cavities with the melted material [29]. Wrinkle formation can be described on the basis of many theories; interference between incident beam and scattered waves, surface plasmons [30,31] and capillary waves.…”