3D Printing of Micro-Optic Spiral Phase Plates for the Generation of Optical Vortex Beams

Optical vortex is a type of structured beam with helical phase wavefronts that carry orbital-angular momentum (OAM) with different topological charge numbers. Optical vortex beams are of use in a wide range of areas ranging from communications to biomedical applications. In this letter, we demonstrate that microscale polymer spiral phase plates (SPPs) with different topological charges can be fabricated through two-photon polymerization by femtosecond 3D direct laser writing. These micro-optical SPPs can modify input light beams carrying no OAM into optical vortex beams carrying an OAM of lh per photon. Intensity patterns and interferograms of the vortex beams are experimentally obtained, showing good agreement with numerical simulations. The two-photon direct laser writing technique with a high resolution of 100 nm enables easy fabrication of micro-optic devices such as SPPs with broad applications in mesoscale photonic devices.