Abstract

Femtosecond laser ablation of positive ions from transparent, polished slides of single crystalline Al₂O₃ is studied by time-of-flight mass spectrometry The incident fluence from an amplified Ti:Sapphire laser could be varied between 0.5 J/cm² and 2.7 J/cm², the maximum being well below the single-shot damage threshold for Al₂O₃ at 3.0 J/cm². We investigated the emission of positive ions, negative ions, and electrons, usually averaging the signals over several hundred pulses. All experiments were conducted in the previously described 'strong etch' regime [1], i.e. after a preceding incubation the samples show a strong response to the incident radiation. In this regime, the ion emission is characterized by a stable average rate, consisting of stochastically alternating pulses with high and with low yield. Thus, sampling over 500 pulses for each data point leads stable, reliable, and reproducible results.

© 2000 IEEE