Analysis of Formation Mechanism of Microspike-Arrays on Tungsten Surface by Femtosecond Laser Irradiation

Abstract

Microspike-arrays are formed on a tungsten surface by irradiating femtosecond laser through a mask aperture in the air. Formation mechanism of such microspike-arrays was discussed with analysis of laser light diffraction. Intensity distribution diffracted through a mask aperture was calculated by using the Fresnel-Kirchhoff integral formula, not the Fresnel diffraction formula, because the distance between a mask aperture and a tungsten surface is almost as short as the size of a mask aperture. Assuming that the ablation rate depends on the diffracted intensity, ablation process by repetitive irradiation was analyzed. Estimated ablation results were consistent with the experimental results. Microspike-arrays have potential in application for such as emission cathodes in a Field Emission Display (FED).