van der Waals NbOCl₂ Nanodisks for Enhanced Second-Harmonic Generation

Area of Science:

• Materials Science
• Nanophotonics
• Quantum Optics

Background:

• Niobium oxide dichloride (NbOCl₂) is a van der Waals crystal with notable second-harmonic generation (SHG) properties.
• High SHG efficiency is essential for applications in quantum light sources, photon modulators, and sensors.
• Improving SHG in NbOCl₂ is key for its integration into photonic systems.

Purpose of the Study:

• To enhance the second-harmonic generation (SHG) efficiency of niobium oxide dichloride (NbOCl₂) using dielectric metasurfaces.
• To investigate the role of nanostructure geometry and optical resonance in boosting SHG.
• To demonstrate a viable strategy for developing efficient nonlinear optical components in integrated nanophotonics.

Main Methods:

• Fabrication of patterned NbOCl₂ nanodisks.
• Utilization of dielectric metasurfaces for optical resonance.
• Precise tuning of geometric parameters to match excitation wavelength.
• Measurement of second-harmonic emission enhancement.

Main Results:

• A remarkable 25-fold enhancement in second-harmonic emission at 400 nm was achieved in NbOCl₂ nanodisks compared to unpatterned films.
• Optical resonance near the excitation wavelength was successfully engineered through geometric parameter tuning.
• Strong field enhancement within the nanodisks at nanophotonic resonances was identified as the mechanism for increased SHG.

Conclusions:

• Dielectric metasurfaces effectively boost SHG in patterned NbOCl₂ nanodisks.
• This approach offers a significant improvement in nonlinear optical conversion efficiency for van der Waals materials.
• The findings pave the way for efficient nonlinear optical components in integrated nanophotonics.