In this research, we investigated the effect of inter-pulse delay times on production of colloidal alumina nanoparticles by collinear double pulse laser ablation. In comparison to single pulse laser ablation, collinear double pulse laser ablation with inter-pulse delay times of 5, 10, 15 and 20 ns results in production of colloidal nanoparticles with smaller mean size and lower variance size distribution. In the case of 5 ns inter-pulse delay time, the highest concentration of nanoparticles was obtained due to more rapid cooling time of the plasma as a result of higher rate of nuclei generation than particle growth. The results also showed that the main pulse and the pre-pulse with 5 ns delay time have significant overlap and consequently such condition leads to maximum influence on the ablation.
In this paper, we investigate dynamics of optical breakdown in air induced by a pump- probe laser beam technique. The optical breakdown was generated by an Nd:YAG laser beam (operating at 10 ns pulse duration and 1064 nm wavelength). A small part of the beam was separated from the main beam by an optical splitter and was aligned to probe the breakdown plasma transversely. Monitoring the time resolved reflectivity from the breakdown plasma may give information on critical density and together with its transmittivity through the plasma provides information on plasma absorptivity. The results of this experiment can be also used to describe dynamics of breakdown plasma evolution.
In this paper, we present results of experimental investigation of the thermal lens effect in ethanol by a dual beam arrangement. The influence of thermal lens strength on a probe beam passing through this thermal lens medium was analyzed. Thermal lens was induced by focusing the beam of a high power diode laser in ethanol and the profile of a He-Ne laser as a probe beam was inspected. The comparison of the He-Ne laser beam profile in the condition of various diode laser beam powers shows that the beam quality of the probe can be significantly affected and the its deformed profile depends on the strength of thermal lens effect.
In this paper phase explosion in aluminum targets induced by Nd:YAG pulsed laser beam is studied. The phase
explosion occurs in ablation process when the Nd:YAG laser beam (single pulse) is focused on the surface of target in
ambient air. The phase explosion was investigated by monitoring the transmission of a cw laser probe beam through the
ablating region. Two different aluminum targets were used in this study; a thin film aluminum on a quartz substrate, and
a thick aluminum foil. The results show that the probe beam transmission through the ablated region is enhanced
significantly when the laser fluence is enough for the phase explosion to be occurred.
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