Nonlinear Metasurface for Simultaneous Control of Spin and Orbital Angular Momentum in Second Harmonic Generation

Area of Science:

• Optics and Photonics
• Materials Science
• Quantum Information

Background:

• Spin and orbital angular momentum (SAM and OAM) of light are crucial for advanced optical communications.
• Integrating SAM and OAM manipulation into nonlinear optical devices is challenging but offers increased communication capacity.
• Conventional nonlinear materials struggle to control both SAM and OAM in harmonic generation.

Purpose of the Study:

• To demonstrate the generation of spin-controlled orbital angular momentum (OAM) in harmonic generation processes.
• To overcome limitations in manipulating SAM and OAM of nonlinear optical signals.
• To explore new avenues for high-capacity optical communications using nonlinear photonic devices.

Main Methods:

• Utilized ultrathin photonic metasurfaces for generating spin-controlled OAM.
• Employed second harmonic generation (SHG) from gold meta-atoms with 3-fold rotational symmetry.
• Introduced nonlinear phase singularity into metasurface devices and used an on-chip interferometer to measure topological charges.

Main Results:

• Successfully generated and experimentally verified spin-controlled OAM in harmonic waves.
• Demonstrated the manipulation of OAM modes through SHG using engineered gold meta-atoms.
• Measured topological charges of spin-controlled OAM modes in SHG signals via an on-chip interferometer.

Conclusions:

• The proposed nonlinear photonic metasurface enables unprecedented control over the OAM of nonlinear optical signals.
• This work advances the understanding of nonlinear spin-orbit interactions in nanoscale photonic devices.
• The findings pave the way for novel optical communication systems with enhanced capacity and robustness.