Control of structural transitions in materials irradiated by temporally tailored ultrafast laser radiation

Abstract : Ultrafast lasers have emerged as promising tools to perform advanced processing of materials for a variety of applications. The additional option of programmable tailoring of laser pulse intensity envelopes offers the possibility to regulate in a synergetic manner the energy delivery and creates the premises to upgrade the degree of process control. This presentation will focus on several potential implementation of pulse tailoring methods in the temporal domain in material processing for different classes of materials. It will be shown that, for example, suitably tailored pulses on picosecond scales, incident on metal targets, are able to design the subsequent thermodynamic path. The modified hydrodynamics has consequences on regulating the life-time of the post-irradiation liquid and on the generation of nanoparticles from the liquid phase. Applied on low band-gap material, temporally tailored pulses may drive the material in hottest states with minimal energetic expenses. The kinetics of the ejected material (e.g. swift ions) is influenced by the pre-designed succession of phase transitions. Another potential implementation of ultrafast lasers lies in the possibility to design photonic functions by structuring materials of optical interest. The strong nonlinear localization of energy induces refractive index changes that are the building blocks of compact, integrated optical devices. Nevertheless, the result of the laser action depends essentially on the nature of the material and may result in specific electronic and structural changes associated with either increasing or decreasing the refractive index under light exposure. We will show that programmable spatio-temporal engineering of the laser pulse can assist in controlling the gradual development of a refractive index change in materials of optical interest. By exploiting thermal transients and thermo-mechanical consequences, one can design the balance of the laser-induced sequence of electronic and structural transformations under modulated excitation and define the end result of the laser action. Based on examples on fused silica (a-SiO2) and borosilicate (BK7) glasses we show that spatio-temporal pulse shaping has the potential to achieve a high degree of process control and to design the nature of the refractive index so that guiding structures can be induced in materials that does not allow it under normal excitation conditions.
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Contributor : Razvan Stoian <>
Submitted on : Sunday, July 20, 2008 - 11:14:47 AM
Last modification on : Wednesday, July 25, 2018 - 2:05:30 PM

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Razvan Stoian. Control of structural transitions in materials irradiated by temporally tailored ultrafast laser radiation. The International Congress on Applications of Lasers & Electro-Optics, ICALEO 2007, Oct 2007, Orlando, United States. ⟨ujm-00300790⟩

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