Shack-Hartmann Wavefront Sensing of Ultrashort Optical Vortices

Area of Science:

• Optics and Photonics
• Quantum Information Science

Background:

• Light beams with Orbital Angular Momentum (OAM), or optical vortices (OV), are crucial for quantum communication and light-matter interactions.
• Characterizing OV's amplitude, wavefront, and modal content in a single shot is a significant challenge.

Purpose of the Study:

• To report a novel method for single-shot characterization of ultrashort OV.
• To demonstrate the capability of Shack-Hartmann wavefront sensing for comprehensive OV analysis.

Main Methods:

• Utilized a Shack-Hartmann wavefront sensor to analyze ultrashort OV generated by spiral phase plates (SPPs).
• Reconstructed wavefronts and intensity distributions, comparing experimental data with numerical backpropagation.
• Employed Laguerre-Gauss (LG) decomposition for modal composition analysis.

Main Results:

• Successfully reconstructed the helical wavefronts of OV, confirming the topological charge.
• Achieved excellent agreement between experimental and numerical intensity distributions.
• Determined the radial and azimuthal mode composition of various OV, including asymmetric ones with fractional OAM.
• Demonstrated real-time topological charge measurement at 10Hz.

Conclusions:

• Shack-Hartmann wavefront sensing is a viable and powerful tool for single-shot characterization of ultrashort OV.
• The method provides accurate amplitude, wavefront, and modal content information.
• This technique can advance applications requiring precise control and understanding of structured light.