The Center for Freeform Optics
An Industry/University Cooperative Research Center

Optimization of femtosecond laser processing of silicon via numerical modeling


optimization-of-femtoSurface processing of silicon using a 400-fs ytterbium fiber laser has been experimentally investigated. Processing was conducted using an average power of 20 W at laser repetition rates from 500 kHz – 2 MHz and scanning speeds up to 2.8 mm/s. Samples showed both effective material removal and detrimental surface artifacts resulting from high surface temperatures during the ablation process. A numerical model has been constructed to simulate the macroscopic surface heating mechanism in femtosecond laser processing. The model validates the experimental results, predicting the observed occurrence of oxidation and melting for un-optimized laser parameters. The surface-heating sensitivity to laser repetition rate, laser fluence, and scanning speed has been comprehensively analyzed, allowing for the first identification of optimized processing conditions to control surface heating and mitigate thermal artifacts in femtosecond laser processing. This work demonstrates a path for predicting deterministic femtosecond laser processing of silicon and other materials.

Optical Materials Express, Vol. 6, Issue 9, pp. 2745-2758 (2016) doi: 10.1364/OME.6.002745