We study the excitation of luminescence, photoionization, and laser-induced breakdown in a multi-component silicate photo-thermo-refractive (PTR) glass, and in fused silica. PTR glass is a high-purity homogeneous photosensitive alkalisilicate glass with intrinsic absorption edge at 5.8 eV (214 nm). Experiments are conducted with ultrashort laser pulses (100 fsec< τ < 1.5 psec) at the wavelengths 780 nm, 1430 nm, and 1550 nm. Filaments are observed inside both glasses and explained by a balance between Kerr self-focusing and free electron defocusing. Keldysh theory is used to model the formation of filaments and values of about 10¹³ W/cm² for laser intensity and 10¹⁹ cm^-3 for free-electron density are estimated. Laser-induced damage by pulses at 1430 nm and 1550 nm is detected in fused silica and PTR glass by third harmonic generation due to the formation of an interface between a damage site and the surrounding glass matrix. It is found that there is an intensity range where luminescence and photoionization in both glasses occurs without laserinduced damage.

Date Published: 30 December 2008
PDF: 10 pages
Proc. SPIE 7132, Laser-Induced Damage in Optical Materials: 2008, 713205 (30 December 2008); doi: 10.1117/12.804984

Published in SPIE Proceedings Vol. 7132:
Laser-Induced Damage in Optical Materials: 2008
Gregory J. Exarhos; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)