Self-organized microvoid array perpendicular to the femtosecond laser beam in CaF2 crystals

Abstract

Microvoid arrays were self-organized when femtosecond laser beam was tightly focused at a fixed point inside CaF2 crystal sample. Expect the void array grown below the focal point which had been reported before, we found another void array grown vertical to the laser propagation direction. This result has potential application in the fabrication of integrated micro-optic elements and photonic crystals. The possible mechanism of the phenomenon was proposed and verified experimentally. A figure is presented. Optical microscope photograph of X-Z plane (a), X-Y plain (b) and Z-Y plane (c) in CaF2 sample after irradiation. Laser beam was focused 600 μm beneath the horizontal surface (X-Y place) with pulse energy of 50 μJ through a 100× objective. 125 pulses were launched at the focus. © 2008 by Astro Ltd.