title: Formation of optical bullets in laser-driven plasma bubble accelerators.
abstract: Electron density bubbles--wake structures generated in plasma of density n(e) approximately 10(19) cm(-3) by the light pressure of intense ultrashort laser pulses--are shown to reshape weak copropagating probe pulses into optical "bullets." The bullets are reconstructed using frequency-domain interferometric techniques in order to visualize bubble formation. Bullets are confined in three dimensions to plasma-wavelength size, and exhibit higher intensity, broader spectrum and flatter temporal phase than surrounding probe light, evidence of their compression by the bubble. Bullets observed at 0.8 approximately < n(e) approximately < 1.2x10(19) cm(-3) provide the first observation of bubble formation below the electron capture threshold. At higher n(e), bullets appear with high shot-to-shot stability together with relativistic electrons that vary widely in spectrum, and help relate bubble formation to fast electron generation.
authors.affiliation: Department of Physics, University of Texas at Austin, Austin, Texas 78712-1081, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Dong
authors.forename: S A
authors.initials: SA
authors.lastname: Reed
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authors.initials: SA
authors.lastname: Yi
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authors.lastname: Kalmykov
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authors.lastname: Shvets
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authors.lastname: Matlis
authors.forename: W P
authors.initials: WP
authors.lastname: Leemans
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authors.lastname: McGuffey
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authors.lastname: Bulanov
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authors.lastname: Kalintchenko
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authors.lastname: Krushelnick
authors.forename: A
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authors.lastname: Maksimchuk
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authors.lastname: Matsuoka
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authors.lastname: Thomas
authors.forename: V
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authors.lastname: Yanovsky