An analytical method to validate local thermodynamic equilibrium (LTE) in laser-induced plasmas is reported in this article. A more universal and general than Maxwellian electron energy distribution function (EEDF) is...
Understanding the laser-induced thermal damage mechanism is important to the development of high power continuous wave (CW) laser. In this paper, we monitor the evolution of damage via a self-build optical element testing platform and build a correspond theoretical model based on the temperature field and heat conduction theory. The waveband of optical coatings (ZnSe and YbF3) under test is dedicated for the mid-infrared. Using a 10 kW level mid-infrared CW laser, the thermal stress damage process of the optical coatings caused by surface contaminants is recorded. The Finite Element Method was employed to calculate the thermal damage mechanism of mid-infrared optical coatings. The calculated thermal damage mechanism agrees very well with our experiment. To the best of our knowledge, this is the first comprehensive study on thermal damage mechanism of mid-infrared coatings with surface contaminants induced by CW laser.
We present a non-contact optical investigation of laser-induced plasma at moderate Ar pressure ranging from 1 to 100 Pa. The significant shock front and spatial fractionation among the different charged ions are demonstrated at the pressure of 20 Pa. The collisions between Si IV ions and ambient Ar atoms generate distinct and excited Ar II ions, fresh Si III ions, and electrons at the dense layer. The electron density peaks at the position of the shock front, indicating that the collision that yields electrons is dominant over the recombination process in the region of the shock layer and its immediate vicinity.
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