Helical Surface Relief Formation by Two-Photon Polymerization Reaction Using a Femtosecond Optical Vortex Beam

Optical vortices possess a helical phase wavefront with central phase dislocation and orbital angular momentum. We demonstrated three-dimensional microstructure formation using a femtosecond optical vortex beam. Two-photon polymerization of photocurable resin was induced by long-term exposure, resulting in the fabrication of cylindrical structures. The ring shape represents the intensity profile of optical vortex beam, and the diameter and height of the structures are related to the laser power. Periodic helical surface relief was observed on the inner surface. Significantly, the helical direction of the surface relief is consistent with the direction in which the orbital angular momentum acts and changes depending on the sign of the topological charge. Our proposed method can form three-dimensional microstructures with helical periodic surface relief, and the pitch is smaller than the diffraction limit without laser scanning. This method paves the way for further applications in optical devices such as three-dimensional chiral metamaterials.