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In a femtosecond pump-probe experiment the pump pulse injects a modest density of free carriers by multiphoton absorption. Measuring the nonlinear absorption of the probe pulse we observe exciton-seeded multiphoton ionization. The excitons self-trap in SiO 2 in Ͻ300 fs following free-carrier injection and decay biexponentially with lifetimes of 34Ϯ 8 and 338Ϯ 67 ps at room temperature. The extent of the probe-pulse absorption provides a model-independent demonstration that avalanche ionization plays a significant role in free-carrier generation by laser pulses as short as 45 fs. Free-carriers injected into a dielectric from extremeultraviolet ͑XUV͒ sources created by high harmonic or attosecond pulse generation and then avalanched with a perfectly synchronized infrared ͑fundamental͒ probe pulse, can provide a route to nanoscale laser machining.

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Memory in nonlinear ionization of transparent solids Rajeev, P.; Gertsvolf, Marina; Simova, E.; Hnatovsky, C.; Taylor, R. S.; Bhardwaj, V. R.; Rayner, David; Corkum, Paul http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=fr L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D'UTILISER CE SITE WEB. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=12338175&lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=12338175&lang=fr READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1103/PhysRevLett.97.253001Physical Review Letters, 97, 25, p. 253001, 2006 We demonstrate a shot-to-shot reduction in the threshold laser intensity for ionization of bulk glasses illuminated by intense femtosecond pulses. For SiO 2 the threshold change serves as positive feedback reenforcing the process that produced it. This constitutes a memory in nonlinear ionization of the material. The threshold change saturates with the number of pulses incident at a given spot. Irrespective of the pulse energy, the magnitude of the saturated threshold change is constant ( 20%). However, the number of shots required to reach saturation does depend on the pulse energy. Recognition of a memory in ionization is vital to understand multishot optical or electrical breakdown phenomena in dielectrics.