Etching and forward transfer of fused silica in solid-phase by femtosecond laser-induced solid etching (LISE)

We present a femtosecond laser-based technique for etching and forward transfer of bulk transparent materials in solid-phase. Femtosecond laser pulses with were focused through a fused silica block onto an absorbing thin film of Cr. A constraining Si wafer was pressed into tight contact with the Cr film to prevent lift-off of the film. A combination of the high temperature and pressure of the Cr, and compressive stress from the Si, resulted in etching of smooth features from the fused silica by cracking. Unlike in conventional ablative or chemical etching, the silica was removed from the bulk as single solid-phase pieces which could be collected on the Si. Using this so-called laser-induced solid etching (LISE) technique, 1-2 m deep pits and channels have been produced in the silica surface, and corresponding dots and lines deposited on the Si. The threshold fluence for etching was found to be with duration pulses. The morphology of the etched features are investigated as functions of fluence and exposure to multiple pulses.