Interferometry with sinusoidal phase modulation method for measuring the phase of optical vortex

The interferometry with sinusoidal phase modulation method (SPM) has been widely used in optical measurement for detecting the interference phase which traces the surface profile of objects. In this research, we employed the SPM interferometry to measure vortex beams (VBs), which have equiphasic wavefronts with spiral phase structure due to orbital angular momentum. It is increasingly important to accurately measure the phase distribution as well as the topological charge of the optical vortex. High-order VBs were generated by computer-generated holograms from a spatial light modulator. We have successfully measured the phase distribution of VB by interfering a Gaussian beam from a laser source using the SPM interferometry. The maximum standard deviation for determining of obtained topological charges was estimated to be approximately 0.016.