Abstract:We have investigated the thermal stability of femtosecond laser modification inside fused silica. Raman and FL spectroscopy show that fslaser induced non-bridging oxygen hole center (NBOHC) defects completely disappear at 300 °C, whereas changes in Si-O ring structures only anneal out after heat treatment at 800-900 °C. After annealing at 900 °C optical waveguides written inside the glass had completely disappeared whereas more significant damage induced in the glass remained. The results are related to different types of bond rearrangements in the glass network. 354(2-9), 416-424 (2008). 14. Y. Bellouard, E. Barthel, A. A. Said, M. Dugan, and P. Bado, "Scanning thermal microscopy and Raman analysis of bulk fused silica exposed to low-energy femtosecond laser pulses," Opt. Express 16(24), 19520-19534 (2008 4196-4202 (1986). 20. R. Brüning and D. Cottrell, "X-ray and neutron scattering observations of structural relaxation of vitreous silica," J. Non-Cryst. Solids 325(1-3), 6-15 (2003).
The light-energy coupling during femtosecond laser processing of glass is mediated by non-linear ionization mechanisms through the formation of an electron plasma. Its transient optical properties provide information about the density, temperature and scattering rate of the excited electrons. In turn, these properties strongly condition the features and size of the permanent optical modification near the focal volume that are desirable to fabricate photonic devices, such as optical waveguides inside transparent materials. Here, we report on the spectral response of a fs-laser-induced electron plasma inside fused silica by measuring its transient transmission using a broadband probe. We model the interaction of the probe beam with the plasma by combining Drude-Sommerfeld model with Gaussian optics. In this manner, we take into account both the laser-plasma interaction and the influence of the chromatic aberration inherent to a broadband-based system. We find good agreement between experiments at several processing energies and simulations and provide an estimate of the dielectric function of the excited material.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.