Microfabrication of Au film using optical vortex beam

Abstract

We fabricate Au microneedle structures by irradiating nanosecond optical vortex pulse, possessing orbital angular momentum (OAM), to Au thin film. Twisted microneedle associated with the handed-ness of optical vortex is formed. The partial liquid motion of the molten Au film and the OAM transfer effects play a role to establish a twisted Au microneedle. An Au microsphere on a twisted pillar is also achieved. Non-twisted structure is fabricated with picosecond optical vortex pulse irradiation due to unoptimized condition such as laser fluence, film thickness and unavoidable imperfections of the optical vortex.