Performance of high-order spiral phase plate made by direct laser writing lithography

A computer-generated hologram about spiral phase light beam with four topological charges is realized, which is then inputted into spatial light modulators(SLMs). When a plane wave transits through the SLMs, a series of high-order optical vortices occur. In order to improve the diffraction efficiency, a spiral phase plate(SPP) with four topological charges is created by direct laser writing lithography. The theoretical depth of SPP is 1.073 m and the measured depth is 1.082 m, showing a manufacture error of no more than 0.83%.The efficiency and beam profile of Fraunhofer diffraction of the SPP are measured with a power meter and a CCD camera. The diffraction efficiency reaches 86% and the energy distribution is in a good agreement with theory.