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13 March 2019 Dynamics of different ablation regimes during femtosecond laser processing of silicon (Conference Presentation)
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Femtosecond laser ablation has a wide variety of applications, from re-shaping the cornea of the eye to micro-machining electronic devices. It is imperative to understand the dynamics of ablation from energy absorption to surface vaporization. In this work, time- and space-resolved microscopy is used to analyze the ablation dynamics induced by femtosecond laser pulses in single-crystalline silicon. These dynamics are revealed by capturing the surface images generated with probe pulse reflection at a variable delay time relative to the pump pulse. When the peak fluence of the incident laser pulse is near the ablation threshold, the transient surface reflectivity initially changes from low to high due to electron-hole plasma formation and then exhibits dynamic Newton-ring patterns with increasing numbers of fringes. When the peak fluence exceeds two times the ablation threshold, surface reflectivity first increases, then significantly decreases (to a level lower than the initial value), and increases again with a growing Newton-ring pattern resulting from thermally induced material expansion. Finally, a crater is formed with two side bumps within which the absorption depth is reduced with spatial fluence level over two times the ablation threshold. The time-resolved silicon images and analyses describing the evolution of transient reflectivity and morphological will be presented.
Conference Presentation
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Jie Qiao and Tao Feng "Dynamics of different ablation regimes during femtosecond laser processing of silicon (Conference Presentation)", Proc. SPIE 10905, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXIV, 109050T (13 March 2019); doi: 10.1117/12.2508733;

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