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Sub-micron machining of semiconductors: femtosecond surface ripples on GaAs by 2 μm laser light

In recent years, a major interest in surface as well as bulk property modification of semiconductors using laser irradiation has developed. A.Kar et al. [1][2] and E.Mazur et al. [3] have shown introduction and control of dopants by long-pulse laser irradiation and increased absorption due to femtosecond irradiation respectively. With the development of mid-IR sources, a new avenue of irradiation can be established in a spectral region where the semiconductor material is highly transparent to the laser radiation. The characterization of the light-matter-interaction in this regime is of major interest. We will present a study on GaAs and its property changes due to pulsed laser irradiation ranging from the visible to the mid-IR region of the spectrum. Long-pulse as well as ultra-short pulse radiation is used to modify the material. Parameters such as ablation threshold, radiation penetration depth and thermal diffusion will be discussed.