Dynamic spatiotemporal beams that combine two independent and controllable orbital-angular-momenta using multiple optical-frequency-comb lines

Abstract

Novel forms of beam generation and propagation based on orbital angular momentum (OAM) have recently gained significant interest. In terms of changes in time, OAM can be manifest at a given distance in different forms, including: (1) a Gaussian-like beam dot that revolves around a central axis, and (2) a Laguerre-Gaussian (LG ';p) beam with a helical phasefront rotating around its own beam center. Here we explore the generation of dynamic spatiotemporal beams that combine these two forms of orbital-angular-momenta by coherently adding multiple frequency comb lines. Each line carries a superposition of multiple LG ';p modes such that each line is composed of a different ' value and multiple p values. We simulate the generated beams and find that the following can be achieved: (a) mode purity up to 99%, and (b) control of the helical phasefront from 2π-6π and the revolving speed from 0.2-0.6 THz. This approach might be useful for generating spatiotemporal beams with even more sophisticated dynamic properties.

Generation and Detection of Structured Light: A Review

“…(F-H) Spatiotemporal structured light. Reprinted from Chong et al [13], Rego et al [14], and Zhao et al [15]. Spatial-structured light beams are, obviously, light fields with spatially inhomogeneous distributions/trajectories.…”

“…Pulse with time-varying orbital angular momentum has been successfully demonstrated in the process of high-harmonic generation [14], providing the ability for controlling magnetic, topological, and quantum excitations and for manipulating molecules and nanostructures on their natural time and length scales. Dynamic spatiotemporal beams, with two independent orbital angular momentum, are also proposed [15]. In addition, the study of group velocities [33] and anomalous refraction [34] of spatiotemporal beams paves the way to fabricate a new free-space optical delay line [35].…”

“…In the last few years, spatiotemporal light beams with inhomogeneous structures in the spatiotemporal domain have become a frontier research field. Various spatiotemporal light beams have been proposed and demonstrated in the experiment [13][14][15][33][34][35]. However, tailoring the spatiotemporal structure of light beams is not that easy due to the ultrahigh value of light speed.…”

Spatiotemporal Helicon Wavepackets

“…Note that more complex fluence and phase profiles could be easily generated by choosing a superposition of multiple higher-order modes at the phase-matched discrete frequencies. This would provide simultaneous revolving and rotating of such profiles in the x-y plane during propagation [24].…”

Geometric-phase-based shearing interferometry for broadband vortex state decoding

“…It has been established that photons can possess spin and orbital angular momenta (SAM and OAM) 1 , 2 . SAM is important in that it directly relates to the polarization of light in scalar and vector optical fields, which is an essential state variable in both classical and quantum optical systems 3 , 4 . OAM is associated with an optical vortex which gives rise to a twisted wavefront and such a structured field possesses a helical phase expressed as exp( imϕ ), where m is the topological charge and ϕ is the azimuthal angle 5 , 6 .…”