Structural changes in BK7 glass upon exposure to femtosecond laser pulses
Article first published online: 28 SEP 2010
Copyright © 2010 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 42, Issue 4, pages 715–718, April 2011
How to Cite
Little, D. J., Ams, M., Gross, S., Dekker, P., Miese, C. T., Fuerbach, A. and Withford, M. J. (2011), Structural changes in BK7 glass upon exposure to femtosecond laser pulses. J. Raman Spectrosc., 42: 715–718. doi: 10.1002/jrs.2770
- Issue published online: 19 APR 2011
- Article first published online: 28 SEP 2010
- Manuscript Accepted: 5 JUL 2010
- Manuscript Received: 28 APR 2010
- femtosecond laser;
- Raman microscopy;
- borosilicate glass;
- cumulative heating
A general picture of refractive index change mechanisms in glass modified by a femtosecond laser has proven elusive. In this paper, Raman microscopy was used in conjunction with refractive near-field profilometry to analyse the structure of borosilicate glass (Schott BK7) modified by a femtosecond laser and determine the mechanism of the observed refractive index change. For a pulse repetition rate of 1 kHz, it was determined that the refractive index change was due to an elevated population of non-bridging oxygen atoms, resulting in more ionic bonds forming within the glass network and increasing the molar refractivity of the glass. For a pulse repetition rate of 5.1 MHz, the dominant mechanism of refractive index change was densification and rarefaction of the glass network. Different refractive index change mechanisms were attributed to different thermal conditions imparted to the glass under different pulse repetition rates. Implications for device fabrication are also discussed. These findings constitute an important step toward a complete overview of femtosecond-laser-induced refractive index change in glass. Copyright © 2010 John Wiley & Sons, Ltd.