Generation of optical vortices from a spatial light modulator, vortex phase plate, and mode converter*

First introduced in 1992 by Prof. Allen et al., light with orbital angular momentum (OAM), also called the Laguerre–Gaussian mode, possesses an OAM of per photon. Its twisted phase wavefront is a manifestation of the azimuthal phase term in its wavefunction, while the phase singularities along the beam axis are defined as the optical vortices. The twisted light which possesses OAM can be generated by laser cavities, spiral phase plate, metalens, and spatial light modulator (SLM). In this work, we utilize a vortex phase plate, mode converter, and spatial light modulator to generate high-order vector vortex beams. The mode converter is used to transform the vortex beam with circular symmetry into rectangular symmetry and form the vortex array. This is a convenient and powerful method to produce and control the optical vortex array of the vector superposed optical field, which is composed of different orders of crossed Hermite-Gaussian bases with opposite helicity of circular polarization. The SLM provides an extra degree of freedom to increase and control the order of the bases in the vector superposed optical field, which can induce optical vortices of different sizes and quantities.