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Proceedings Paper

Terahertz-frequency electrical conductivity measurements of ultrashort laser-ablated plasmas
Author(s): K. Y. Kim; B. Yellampelle; J. H. Glownia; A. J. Taylor; G. Rodriguez
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Paper Abstract

We investigate the phase transitions of intense ultrashort laser-heated solids, from the cold solid to the hot dense plasma state, by measuring the complex electrical conductivity (or refractive index) transients at terahertz (1 THz = 1012 Hz) frequencies. Using optical-pump, terahertz-probe spectroscopy, we measured the phase shifts and absorption of terahertz probe pulses that were reflected from the warm dense plasma. To characterize the THz field, we developed and used a single-shot, high-temporal-resolution THz diagnostic capable of measuring free-space electromagnetic pulse fields in time and space. Due to relatively large focal spot sizes of the THz probe (~mm), mainly limited by the diffraction properties of THz radiation, the optical pump pulse was weakly focused onto the target in order to overfill the THz probe spot size with a peak intensity of ~1013 W/cm2. In contrast to the previous measurements of conductivities at optical frequencies, our THz non-contact probe method can directly measure quasi-DC electrical conductivities, providing insight into the transport nature of warm dense matter and any present discrepancies with the Drude model. In case of warm dense aluminum, we observe a noticeable deviation from the Drude model even in the ~1013 W/cm2 laser intensity regime. In addition, we observe strong coherent THz emission produced by a current surge in the laser-produced plasma.

Paper Details

Date Published: 7 June 2006
PDF: 9 pages
Proc. SPIE 6261, High-Power Laser Ablation VI, 62612Q (7 June 2006); doi: 10.1117/12.668945
Show Author Affiliations
K. Y. Kim, Los Alamos National Lab. (United States)
B. Yellampelle, Los Alamos National Lab. (United States)
J. H. Glownia, Los Alamos National Lab. (United States)
A. J. Taylor, Los Alamos National Lab. (United States)
G. Rodriguez, 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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