Ultrafast Laser Pulse Tailoring in Pure Water

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Authors
  1. Fournier, G.R.
Corporate Authors
Defence R&D Canada - Valcartier, Valcartier QUE (CAN)
Abstract
Some experimental measurements of femtosecond laser pulses propagating in water have shown an apparent absorption coefficient that is much smaller by more than an order of magnitude than even that measured using picosecond pulses in the same water with the same apparatus. The effect was found to be linear since the power density in the experiments was kept well below the threshold of any known non-linear mechanism. The lasers used in the experiments had transform limited pulses centered around 800 nm. The measured effect can be .explained' by viewing the phenomenon from the spectral perspective where the coherent laser pulse spectrum can be considered as inhomogeneous and subjected to a form of hole burning by the absorbing medium. This means that the absorption eats away the central portion of the laser spectrum and leaves two separate spectra that beat against one another. This way of looking at the process resolves also the apparently contradictory results to that of Fox and Osterberg, which were obtained by workers at the University of Nebraska and more recently at Texas A&M. An interesting consequence of this spectral analysis is that the apparent reduction in absorption can be directly related to the initial and evolving temporal pulse shape of the laser. The absorption curve can thus be used to infer details of the laser pulse shape. It also turns out that the temporal shape and breakup of the laser pulse can be modified in a controllable fashion by pure water or with
Report Number
DRDC-VALCARTIER-SL-2009-158 — Scientific Literature
Date of publication
25 May 2009
Number of Pages
5
DSTKIM No
CA032963
CANDIS No
532197
Format(s):
Document Image stored on Optical Disk

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