Atomic and Molecular Physics(DAMP)
Physique atomique et moléculaire (DPAM)

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Harold HAUGEN
McMaster University

Selected Studies of Femtosecond Laser Ablation and Modification of Semiconductors*

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Femtosecond lasers have become important tools for the micro-modification and micro-machining of materials. We outline a number of recent developments in our laboratory including the formation of sub-wavelength periodic structures on surfaces, the measurement of the ablation thresholds and ablation depths for InP over a wide range of laser wavelengths, and studies of the sub-surface modification of semiconductors using polarized photoluminescence (DOP) and cross-sectional transmission electron microscopic (TEM) techniques. Our work has demonstrated that high spatial frequency periodic structures significantly smaller than the light wavelength can be obtained in ultrafast laser irradiation of semiconductors, analogous to recent results reported in the literature for dielectrics. In addition, in experiments on the laser ablation of InP over a wide wavelength range, we have found a sudden increase of the crater depth with laser fluence near threshold, similar to spallation effects obtained via recently published theoretical models. Finally, observations using DOP and TEM revealed significant differences between nanosecond and femtosecond laser micro-machining of InP. In particular, ultrafast laser interactions lead to substantial damage in the vicinity of the laser-ablated features. Future directions for these on-going investigations will be discussed.

*Conducted in collaboration with A. Borowiec, G.A. Botton, D.M. Bruce, D.T. Cassidy, M. Couillard, and T.H.R. Crawford; McMaster University