Micromachining on the Chrome Stainless Mold Steel Using the Femtosecond Laser

The femtosecond laser is able to minimize the collateral damages which limit the application of the long pulsed laser ablation. In spite of its advantage over the long pulsed laser, the application of femtosecond laser on the metals had been limited due to the high thermal diffusivity of metals. In order to examine the feasibility of femtosecond laser-induced micromachining on stainless mold steel, we tested the femtosecond laser-induced ablation on the chrome stainless mold steel using various laser parameters. The damage threshold fluence and laser-induced morphological change on the mold steel were examined using the SEM. The single pulse induced damage threshold was measured about 84 mJ/cm(2). We were able to fabricate the grating-like structures using the femtosecond laser on the chrome stainless mold steel under the beam scanning mode. The gratings with pitches as small as 2 mu m were fabricated using the direct laser writing and the width of fabricated gratings was as small as 1.2 mu m. We were also able to observe the femtosecond laser-induced ripple structure on the surface of the mold steel. The ripple structure is characterized as the repetitive lines with a few hundred nanometers pitch and the orientation is governed by the polarization of incident laser beam. The continuous ripples over the entire gratings can be used for the nano scale fabrication on the mole steel using the direction laser writing.