Propagation of optical vortices embedded with multiple wavefront singularities

Abstract

Optical vortices with the embedded wavefront singularities have attracted intensive attentions in many branches of modern physics, due to their important applications in optical tweezers, quantum entangles, optical testing, atmospheric propagations, etc. In this paper, optical vortices are generated by new types of custom designed wavefronts and their propagation in free-space is reported. Huygens–Fresnel diffraction integral is directly solved using the Gauss–Legendre quadrature method to estimate the diffraction pattern at some arbitrary plane. The variation of vorticity is demonstrated under diffraction. Evolution of phase singularities in wavefronts as the wavefront propagate is predicted for various near field distances. Simulations reveal that the exchange of the nature of topological charge occurs at a finite distance. Experimentally, the wavefronts have been generated using the phase-only spatial light modulator and their far-field diffraction patterns are recorded. The experimental result has been validated with the numerical simulation.

Keywords:

• optical vortices
• Huygens–Fresnel diffraction integral
• phase-only spatial light modulator

Acknowledgements

Authors are thankful to the reviewer for valuable suggestions. Authors also wish to acknowledge Director, IRDE for permitting to publish the work; Head of Photonics Design Centre, IRDE Dehradun for their encouragement and members of Adaptive Optics Division for their cooperation. Awakash Dixit is thankful to the DRDO, INDIA for the award of the research fellowship.