Optical Vortex Harmonic Generation Enabled by Confinement-Induced Photonic Spin-Orbit Coupling.

Area of Science:

• Nanophotonics
• Nonlinear Optics
• Quantum Optics

Background:

• Photonic spin-orbit coupling (SOC) is significant in subwavelength waveguides, leading to spin-orbit entanglement.
• The role of confinement-induced SOC in nonlinear optical processes is largely unexplored.
• Conventional nonlinear optics typically requires specific conditions or materials.

Purpose of the Study:

• To experimentally demonstrate and theoretically analyze nonlinear optical frequency conversion driven by confinement-induced SOC.
• To explore the generation of structured light, specifically optical vortices, using this phenomenon.
• To investigate the potential for ultrafast all-optical switching applications.

Main Methods:

• Utilizing a silica optical nanofiber as the waveguide medium.
• Pumping the nanofiber with a spin-polarized Gaussian laser beam.
• Applying theoretical analysis to understand the underlying physics of the nonlinear process.

Main Results:

• Successfully generated a third-harmonic optical vortex with orbital angular momentum.
• Achieved an outcome typically forbidden in isotropic media under conventional nonlinear optical conditions.
• Demonstrated simple, cost-effective generation of optical vortices without specialized pump beams or materials.

Conclusions:

• Confinement-induced SOC enables unconventional nonlinear optical frequency conversion.
• This method provides a new route for generating optical vortices and enabling ultrafast all-optical switching.
• Opens avenues for exploring spin-orbit-coupled nanophotonic systems and novel light-matter interactions.