Third Harmonic Generation Enhancement and Wavefront Control Using a Local High-Q Metasurface

Area of Science:

• Photonics and Nanotechnology
• Nonlinear Optics

Background:

• High quality factor (high-Q) optical nanostructures enhance nonlinear optical processes.
• However, field enhancement often leads to optical mode nonlocality, limiting spatial control.

Purpose of the Study:

• To achieve simultaneous strong enhancement and spatial control of third harmonic generation (THG).
• To overcome the trade-off between enhancement and local control in nonlinear optical processes.

Main Methods:

• Utilized a local high-Q metasurface based on higher-order Mie resonant modes.
• Investigated the spatial control and efficiency of third harmonic generation.

Main Results:

• Demonstrated third harmonic generation efficiency up to 3.25 × 10^-5.
• Achieved high-quality wavefront shaping with a third harmonic metalens.
• Observed a flatband, angle-independent THG response up to ±11° incident angle.

Conclusions:

• The developed metasurface offers simultaneous strong enhancement and local control for nonlinear optical processes.
• Efficient frequency conversion and precise spatial control pave the way for novel nonlinear optical devices.