Generation of spiral optical vortex with varying OAM for micro-manipulation

Since the confirmation of orbital angular momentum (OAM) decades ago, numerous studies have led to a new understanding of optical effects and various applications. Here we propose a concept of the spiral optical vortex (SOV) which contains multiple OAM modes from inside to outside along the spiral intensity field. Theoretically, by linking the azimuthal spiral phase with the beam radius, the SOV can be generated. The corresponding OAM spectrum of the SOV are analyzed theoretically and measured experimentally. We also demonstrate the evolution characteristics of the SOV over the propagation distance. The OAM components of the SOV have also been investigated and measured based on the fundamental Laguerre-Gaussian mode experimentally. The experiment results show that the micro-particle can be transmitted along with the spiral intensity distribution of the SOV to the center. This proposal may paves a new way in the generation of the spiral light field and stimulate new applications in light field modulation and microparticles manipulation.