[Paper Review] Ultrafast bursts of tailored spatiotemporal vortex pulses

Xin Liu, Chunhao Liang+3 more|arXiv (Cornell University)|Jul 29, 2024

Fluid Dynamics and Turbulent Flows6 citations

TL;DR

The authors experimentally generate ultrafast spatiotemporal vortex bursts with picosecond switchable transverse OAM, enabling tailored spatiotemporal Laguerre-Gaussian wavepackets and chirality control.

ABSTRACT

Orbital angular momentums (OAMs) of light can be categorized into longitudinal OAM (L-OAM) and transverse OAM (T-OAM). Light carrying time-varying L-OAM, known as self-torqued light, was recently discovered during harmonic generation and has been extensively developed within the context of optical frequency combs (OFCs). Meanwhile, ultrafast bursts of optical pulses, analogous to OFCs, are sought for various light-matter interaction, spectroscopic and nonlinear applications. However, achieving transiently switchable T-OAM of light on request, namely spatiotemporal vortex pulse bursts, with independently controlled spatiotemporal profile of each comb tooth, remain unrealized thus far. In this work, the experimental generation of spatiotemporal vortex bursts featured with controllable time-dependent characteristics is reported. The resultant bursts comprised of spatiotemporal optical vortex comb teeth have picosecond timescale switchable T-OAMs with defined arrangement, manifesting as spatiotemporal torquing of light. We also show ultrafast control of T-OAM chirality, yielding pulse bursts with staggered azimuthal local momentum density, resembling Kármán vortex streets. This approach enables the tailoring of more intricate spatiotemporal wavepacket bursts, such as high-purity modes variation in both radial and azimuthal quantum numbers of spatiotemporal Laguerre-Gaussian wavepackets over time, which may facilitate a host of novel applications in ultrafast light-mater interactions, high-dimensional quantum entanglements, space-time photonic topologies as well as spatiotemporal metrology and photography.

Motivation & Objective

• Motivate the need for transiently switchable transverse OAM (T-OAM) in ultrafast pulses.
• Demonstrate experimental generation of spatiotemporal vortex bursts with controllable time-dependent characteristics.
• Show independent control of spatiotemporal profiles for each comb tooth within a vortex pulse burst.
• Explore the ability to tailor radial and azimuthal mode content over time for high-purity spatiotemporal wavepackets.

Proposed method

• Generate spatiotemporal optical vortex comb teeth with controllable time-dependent T-OAM.
• Achieve picosecond-scale switchable T-OAM with a defined spatial arrangement of the vortex teeth.
• Manipulate T-OAM chirality to produce bursts with staggered azimuthal local momentum density.
• Tailor spatiotemporal Laguerre-Gaussian wavepackets by varying radial and azimuthal quantum numbers over time.

Experimental results

Research questions

• RQ1 Can spatiotemporal vortex bursts be generated with independently controllable spatiotemporal profiles for each comb tooth?
• RQ2 Is picosecond-scale switching of transverse OAM achievable and controllable in real time?
• RQ3 Can the chirality of T-OAM be ultrafastly controlled to create spatially varying momentum densities akin to Kármán vortex streets?
• RQ4 Can high-purity spatiotemporal Laguerre-Gaussian modes be engineered to vary in both radial and azimuthal quantum numbers over time?

Key findings

• Spatiotemporal vortex bursts composed of vortex comb teeth with picosecond switchable T-OAM and a defined arrangement.
• Ultrafast control of T-OAM chirality yields pulse bursts with staggered azimuthal local momentum density, resembling Kármán vortex streets.
• Ability to tailor high-purity spatiotemporal Laguerre-Gaussian wavepackets by varying radial and azimuthal quantum numbers over time.