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Proceedings Paper

Investigation of ultrashort pulse laser propulsion using time-resolved shadowgraphy and torsion pendulum
Author(s): Xiao-nong Zhu; Nan Zhang
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Paper Abstract

Laser pulses with different pulse durations between 50 fs and 12 ps are used to ablate different types of solid targets. With the help of time-resolved shadowgraphy, the ultrafast dynamics associated with femtosecond laser ablation of solid materials is experimentally investigated based on the commonly used pump-probe technique. It is revealed that both photothermal and photomechanical mechanisms exist in the ablation processes for laser fluence far above the target ablation threshold. From the recorded shadowgraphs, it is revealed that the material ejection due to femtosecond laser ablation of solid materials has a typical velocity of 105 - 104 m/s. Such high jet velocities can lead to specific impulse of 104 - 103 s, which is much higher than the upper limit of the specific impulse of chemical propulsion (500 s). The so-called ablative laser propulsion with high specific impulse can be thus realized. Momentum coupling coefficient is determined through using a homemade torsion pendulum with a minimum measurable momentum of ~2x10-9 N·s. The dependence of the ultrashort laser ablation generated momentum is investigated on laser energy fluence and pulse width. The main findings include: 1) As the pulse width increases, the laser generated momentum first increases rapidly and then remains almost constant; 2) For 50 fs pulses, optimal laser fluence exists that leads to the maximum momentum for aluminum and copper targets. At the optimal laser fluence, it is mostly the photomechanical mechanism that is responsible for material removal, and in this case the ablated material also has relatively lower jet velocity.

Paper Details

Date Published: 28 August 2009
PDF: 8 pages
Proc. SPIE 7382, International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging, 738208 (28 August 2009); doi: 10.1117/12.839584
Show Author Affiliations
Xiao-nong Zhu, Nankai Univ. (China)
Nan Zhang, Nankai Univ. (China)

Published in SPIE Proceedings Vol. 7382:
International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging
Farzin Amzajerdian; Chun-qing Gao; Tian-yu Xie, Editor(s)

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