Dynamics of femtosecond laser processing in glass

Denise M. Krol, University of California-Davis, DMR 0801786

Femtosecond (fs) laser processing of glass is a powerful novel method to modify the properties of glass with 3-D spatial selectivity. In earlier studies we have shown that fs-laser modification in silica glass results in the appearance of a 650 nm fluorescence band, which is associated with the formation of non-bridging-oxygen hole center (NBOHC) defects. In addition, there is a change in the Raman spectrum reflecting an increase in the relative concentration of three-membered Si-O rings in the glass network which is associated with an increase in the density of the glass. Studies of thermal annealing of the fs-laser written structures reveal that NBOHC defects anneal out at much lower temperatures than the changes in network structure (see figure). These results are important with respect to the stability of fs-laser written devices and they give us further insight into the mechanism of fs-laser modification in glass.

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D2 Raman peak intensity vs temperature

650 nm fluorescence intensity vs temperature

Dynamics of femtosecond laser processing in glass

Denise M. Krol, University of California-Davis, DMR 0801786

This summer we hosted Lu Siyuan, an undergraduate student from the Optical Engineering program at Zhejiang University in China. He participated in The Global Research Experience in Advanced Technologies (GREAT) Summer Research Program at UC Davis. In our lab Lu worked together with Ph D student Neil Troy on the spectroscopic characterization of structural changes in various glass samples after indentation.

Our work on fs-laser waveguide writing in rare-earth doped phosphate glasses, which was carried out in collaboration with Professor R. K. Brow’s group at MST, Rolla resulted in a provisional patent application ““Femtosecond laser induced positive refractive index changes inside polyphosphate glass”.

Ph.D. students Neil Troy and Luke Fletcher in the lab. Insert: visiting undergraduate student Lu Siyuan