Cyclic Evolution of Synergized Spin and Orbital Angular Momenta.

Area of Science:

• Wave physics
• Quantum optics
• Acoustics

Background:

• Spin angular momentum (SAM) and orbital angular momentum (OAM) are fundamental properties of wave fields.
• Traditionally, SAM (polarization) and OAM (spatial phase) are treated as independent.
• Manipulating both simultaneously offers new possibilities for wave control.

Purpose of the Study:

• To demonstrate the synergistic coupling between SAM and OAM.
• To explore novel methods for simultaneous manipulation of polarization and spatial phase.
• To investigate the potential applications of this synergy in wave-based technologies.

Main Methods:

• Utilizing two orthogonal p-orbitals as eigenbases to generate OAM and manipulate polarization.
• Employing periodic modulation and directional coupling for synchronized SAM-OAM evolution.
• Designing an acoustic cavity array with dipole resonances to mimic p-orbitals for experimental validation.

Main Results:

• Achieved a full cyclic evolution of synchronized and synergized SAM-OAM with a nontrivial geometric phase, represented on a Möbius strip.
• Experimentally validated the concept using an acoustic cavity array, demonstrating precise control over pressure and velocity fields.
• Showcased a spin-orbital-Hall effect, revealing intricate locking between handedness, directionality, spin density, and spatial mode profile.

Conclusions:

• Unveiled a fundamental connection and synergy between SAM and OAM.
• The demonstrated SAM-OAM coupling opens new avenues for applications in optical trapping, information coding, and communications.
• This work provides a new paradigm for manipulating wave properties through combined spin and orbital angular momentum control.