Nonlinear photoionization and laser-induced damage in silicate glasses by infrared ultrashort laser pulses

    Authors

    L. A. Siiman; J. Lumeau;L. B. Glebov

    Comments

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    Abbreviated Journal Title

    Appl. Phys. B-Lasers Opt.

    Keywords

    THERMO-REFRACTIVE GLASS; WHITE-LIGHT CONTINUUM; SMALL-SCALE FILAMENTS; FEMTOSECOND LASER; TRANSPARENT MATERIALS; INDUCED BREAKDOWN; FUSED-SILICA; WAVE-GUIDES; IONIZATION; SOLIDS; Optics; Physics, Applied

    Abstract

    We show that photoionization of wide band gap silicate glasses by infrared ultrashort laser pulses can occur without laser-induced damage. Two glasses are studied, fused silica and a multi-component silicate photo-thermo-refractive (PTR) glass. Experiments are performed by low numerical aperture focusing of ultrashort laser pulses (100 fsec < tau < 1.5 psec) at the wavelengths 780 nm, 1430 nm, and 1550 nm. Filaments form inside both glasses and are visibly observable due to intrinsic luminescence. Keldysh's theory of nonlinear photoionization is used to model the formation of filaments and values of about 10(13) W cm(-2) for the laser intensity and 10(19) cm(-3) for the free electron density are estimated for stable filaments to arise. Laser-induced damage is studied by the generation of a third harmonic from an interface created between a damage site and the surrounding glass matrix. It is found that third harmonic generation occurs only after several thousands of laser shots indicating that damage is not a single-shot phenomena. The ability to photoionize PTR glass without damage by ultrashort laser pulses offers a new approach for fabricating diffractive optical elements in photosensitive glass.

    Journal Title

    Applied Physics B-Lasers and Optics

    Volume

    96

    Issue/Number

    1

    Publication Date

    1-1-2009

    Document Type

    Article

    Language

    English

    First Page

    127

    Last Page

    134

    WOS Identifier

    WOS:000266813000020

    ISSN

    0946-2171

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