Shack-Hartmann Wavefront Sensing of Ultrashort Optical Vortices

• Published in: Sensors (Basel, Switzerland) Vol. 22; no. 1; p. 132
• Main Authors: Pandey, Alok Kumar, Larrieu, Tanguy, Dovillaire, Guillaume, Kazamias, Sophie, Guilbaud, Olivier
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 25.12.2021; MDPI
• Subjects: Amplitudes; Angular momentum; Electron beams; Energy; Light beams; Optics; orbital angular momentum; Phase plates; Physics; Sensors; Shack-Hartmann sensors; shack-hartmann wavefront sensing; Single shot characterization; structured light; Topology; ultrashort optical vortices; Vortices; Wave front sensors; Wave fronts; shack-hartmann wavefront sensing; orbital angular momentum; structured light; ultrashort optical vortices
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s22010132

Light beams carrying Orbital Angular Momentum (OAM), also known as optical vortices (OV), have led to fascinating new developments in fields ranging from quantum communication to novel light-matter interaction aspects. Even though several techniques have emerged to synthesize these structured-beams, their detection, in particular, single-shot amplitude, wavefront, and modal content characterization, remains a challenging task. Here, we report the single-shot amplitude, wavefront, and modal content characterization of ultrashort OV using a Shack-Hartmann wavefront sensor. These vortex beams are obtained using spiral phase plates (SPPs) that are frequently used for high-intensity applications. The reconstructed wavefronts display a helical structure compatible with the topological charge induced by the SPPs. We affirm the accuracy of the optical field reconstruction by the wavefront sensor through an excellent agreement between the numerically backpropagated and experimentally obtained intensity distribution at the waist. Consequently, through Laguerre-Gauss (LG) decomposition of the reconstructed fields, we reveal the radial and azimuthal mode composition of vortex beams under different conditions. The potential of our method is further illustrated by characterizing asymmetric Gaussian vortices carrying fractional average OAM, and a realtime topological charge measurement at a 10Hz repetition rate. These results can promote Shack-Hartmann wavefront sensing as a single-shot OV characterization tool.