Self‐Referencing 3D Characterization of Ultrafast Optical‐Vortex Beams Using Tilted Interference TERMITES Technique

Abstract

Femtosecond light pulses carrying optical angular momentums (OAMs), possessing intriguing properties of helical phase fronts and ultrafast temporal profiles, enable many applications in nonlinear optics, strong‐field physics, and laser micromachining. While generation of OAM‐carrying ultrafast pulses and their interactions with matters are intensively studied in experiments, 3D characterization of ultrafast OAM‐carrying light beams in spatiotemporal domain has, however, proved difficult to achieve. Conventional measurement schemes rely on the use of a reference pulsed light beam, which needs to be well characterized in its phase front and to have sufficient overlap and coherence with the beam under test, largely limiting practical applications of these schemes. Here a self‐referencing set‐up is demonstrated based on a tilted interferometer that can be used to measure complete spatiotemporal information of OAM‐carrying femtosecond pulses with different topological charges. Through scanning one interferometer arm, the spectral phase over the pulse spatial profile can be obtained using the tilted interference signal, and the temporal envelope of the light field at one particular position around its phase singularity can be retrieved simultaneously, enabling 3D beam reconstruction. This self‐referencing technique, capable of measuring spatiotemporal ultrafast optical‐vortex beams, may find many applications in fields of nonlinear optics and light–matter interactions.

Polarization-Dependent Distortion of the Vortex Light Field Generated Using a Vortex Retarder

“…We used Eq. ( 3) as the initial condition in the Collins integral formula and thereby derived the electric field expression at any given propagation distance along the axis [22][23][24]:…”

“…The mainstream passive methods for generating vortex light beams include spiral phase plates [16,17], forked diffraction gratings [18,19] and Pancharatnam-Berry phase optical elements (PBOEs) [20], etc. Among these, vortex retarders (VRs), as one of the PBOEs, are widely used in various applications due to their significant advantages, including increased insensitivity to chromatic aberration, which is particularly beneficial for scenarios requiring broadband light sources [21,22]. In VRs, the fast axis orientation is uniformly radial and varies continuously along the azimuthal direction, specifically following the following rule [21,22]:…”