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Proceedings Paper

Topographic imaging and velocity measurements of surface expansion during laser ablation of a metal layer on glass
Author(s): G. Rodriguez; A. R. Valenzuela; S. A. Clarke; K. A. Thomas
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Paper Abstract

We report on the development of novel high-speed techniques to measure the surface topography and instantaneous velocity of ablatively launched thin metal layers with sub-nanosecond temporal resolution. Applications for laser detonator technology require the understanding of laser fiber optical energy deposition and ablative launch of a thin metal layer into an explosive. Characterization of the ablation process requires a time-resolved diagnosis of the ejected material state (topography, velocity, density, pressure, etc.). A pulsed Nd:YAG fibercoupled laser is used to ablate a 250 nm layer of titanium deposited on a 500 μm thick fused silica substrate at fluences below 10 J/cm2. Time-resolved imaging of the free expansion of the metal surface is accomplished with Fourier plane imaging using a Shack-Hartmann lenticular array coupled to a fast framing camera. The imager performs topographical surface measurements by detecting changes in the optical wavefront of a reflected picosecond probe laser beam off the expanding surface. Consequently, single-event sub-nanosecond time-resolved "movies" of surface motion dynamics are captured. Crosscheck of the Shack-Hartmann imager is done using advanced velocimetry. A 1550 nm heterodyne laser-based Photonic Doppler Velocimeter is used to measure surface velocity. Using a 1550 nm single mode fiber laser, 10 GHz InGaAs detectors and telecom hardware, we directly record the resulting beat signal produced by the accelerated surface onto a fast digitizer. Free surface velocities as high as 6.5 μm/ns are recorded. Comparisons between the dynamic topography, surface velocimetry and laser hydrocode simulations are presented.

Paper Details

Date Published: 7 June 2006
PDF: 10 pages
Proc. SPIE 6261, High-Power Laser Ablation VI, 62610O (7 June 2006); doi: 10.1117/12.668999
Show Author Affiliations
G. Rodriguez, Los Alamos National Lab. (United States)
A. R. Valenzuela, Los Alamos National Lab. (United States)
S. A. Clarke, Los Alamos National Lab. (United States)
K. A. Thomas, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 6261:
High-Power Laser Ablation VI
Claude R. Phipps, Editor(s)

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