Circularly Polarized High-Harmonic Beams Carrying Self-Torque or Time-Dependent Orbital Angular Momentum

Area of Science:

• Structured light
• Ultrafast optics
• Quantum optics

Background:

• Self-torque is an intrinsic property of light beams with time-dependent orbital angular momentum.
• Extreme-ultraviolet (EUV) beams with self-torque are generated via high-order harmonic generation (HHG) using infrared vortex beams.
• Previous methods limited EUV self-torque beams to linear polarization due to efficiency losses.

Purpose of the Study:

• To theoretically demonstrate control over the polarization state of EUV beams with self-torque.
• To overcome limitations in manipulating the polarization of EUV beams carrying self-torque.
• To enable custom polarization states for EUV beams with time-dependent orbital angular momentum.

Main Methods:

• Utilizing two distinct driving schemes in high-order harmonic generation (HHG).
• Employing advanced numerical simulations to model the process.
• Deriving selection rules for angular momentum conservation.

Main Results:

• Demonstrated tunability of EUV self-torque beams from linear to circular polarization.
• Identified driving schemes that circumvent efficiency limitations.
• Achieved precise control over the angular momentum properties of the generated harmonics.

Conclusions:

• The ability to control polarization states of EUV self-torque beams opens new avenues for ultrafast light-matter interactions.
• Applications in areas requiring dichroic or chiral properties, such as magnetic materials and chiral molecules, can be expanded.
• This work provides a pathway for engineering complex light fields for advanced scientific research.