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Proceedings Paper

Laser-induced microexplosions in transparent materials: microstructuring with nanojoules
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Paper Abstract

We tightly focus femtosecond laser pulses in the bulk of a transparent material. The high intensity at the focus causes nonlinear absorption of the laser energy, producing a microscopic plasma and damaging the material. The tight external focusing allows high intensity to be achieved with low energy, minimizing the effects of self-focusing. We report the thresholds for breakdown and critical self- focusing in fused silica using 110-fs pulses at both 400-nm and 800-nm wavelength. We find that permanent damage can be produced with only 10 nJ (25 nJ) for 400-m (800-nm) pulses, and that the threshold for critical self-focusing is 140 nJ for the 400-nm pulses and 580 nJ for the 800-nm pulses. The critical self-focusing thresholds are more than an order of magnitude above the breakdown thresholds, confirming that self-focusing does not play a dominant role in the damage formation. This lack of self-focusing allows a straightforward interpretation of the wavelength and bandgap dependence of bulk breakdown thresholds. The energies necessary for material damage are well within the range of a cavity-dumped oscillator, allowing for precision microstructuring of dielectrics with a high repetition-rate laser that is roughly one-third the cost of an amplified system.

Paper Details

Date Published: 4 June 1999
PDF: 5 pages
Proc. SPIE 3616, Commercial and Biomedical Applications of Ultrafast Lasers, (4 June 1999); doi: 10.1117/12.351827
Show Author Affiliations
Christopher B. Schaffer, Harvard Univ. (United States)
Andre Brodeur, Harvard Univ. (United States)
Nozomi Nishimura, Harvard Univ. (United States)
Eric Mazur, Harvard Univ. (United States)

Published in SPIE Proceedings Vol. 3616:
Commercial and Biomedical Applications of Ultrafast Lasers
Murray K. Reed; Joseph Neev, Editor(s)

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