Color center formation in soda-lime glass with femtosecond laser pulses

Abstract

We show that exposure of soda-lime glass to ultrafast laser pulses at 800 nm causes coloration (darkening). We have characterized this coloring with time-resolved measurements of the transmission of 633 nm light through the glass during laser exposure. Reverse processes (partial bleaching) operate on time scales of μs to seconds. The competition between coloration after the femtosecond pulse and the subsequent transmission recovery limits the darkening that can be achieved at a given femtosecond pulse energy and repetition rate. The response of soda-lime glass to 400 and 267 nm ultrafast pulses is quite similar, although much lower pulse energies are required for darkening. We argue that darkening is due to absorption processes that produce mobile charge carriers, which then interact to produce trapped hole centers (H3+) that absorb strongly at 633 nm. Trapped electrons (that form E centers) are the likely cause of the accompanying loss of transmission in the near ultraviolet. Finally, we show that diffraction gratings can be rapidly and easily produced in this material using holographic methods.