Answers are grounded in this paper and cite their sources.
The combination of selective chemical etching and atomic force microscopy has been used for the first time to make ultra-high spatial resolution (20 nm) index of refraction profiles of femtosecond laser modified structures in silica glass.
No takes yet. Share an insight, caveat, or question.
Taylor et al. (2003) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: