Title

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

Authors

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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