Third optical harmonic generation reveals circular anisotropy in tilted silicon nanowire array.

Area of Science:

• Nanophotonics
• Nonlinear Optics
• Condensed Matter Physics

Background:

• Silicon nanowires (SiNWs) exhibit unique optical properties due to their size and crystalline structure.
• Third-harmonic (TH) generation is a nonlinear optical process sensitive to material and structural symmetries.
• The photonic spin Hall effect describes the spin-dependent deflection of light.

Purpose of the Study:

• To investigate the circular anisotropy of TH generation in tilted SiNW arrays.
• To explore the role of the photonic spin Hall effect in TH generation.
• To understand the influence of polarization and orientation on TH signals.

Main Methods:

• Fabrication of SiNW arrays tilted at 45° to a silicon substrate.
• Numerical simulations of light scattering for single SiNWs and array approximations.
• Experimental measurement of TH generation with varying incident polarization and array orientation.

Main Results:

• Simulations revealed asymmetric scattering diagrams, indicative of the photonic spin Hall effect.
• The TH signal showed significant dependence on incident light polarization.
• Experimental TH measurements confirmed the polarization and orientation dependence despite strong scattering.

Conclusions:

• Circular anisotropy in TH generation is achievable in tilted SiNW arrays.
• The photonic spin Hall effect, mediated by a synthetic gauge field, governs this anisotropy.
• SiNWs offer a platform for controlling nonlinear optical responses through spin-photon coupling.