Enhanced second harmonic generation by an atomically thin MoS₂ sheet attached to a resonant metasurface

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Two-dimensional transition metal dichalcogenides (TMDs) exhibit significant nonlinear optical properties due to broken inversion symmetry.
• Nonlinear light-matter interactions in TMDs are limited by their atomic thinness.
• Resonant metasurfaces can enhance light-matter interactions for thin nonlinear materials.

Purpose of the Study:

• To overcome the limitation of thin 2D materials in nonlinear optics.
• To demonstrate methods for simultaneously tuning metasurface resonances to fundamental and second harmonic frequencies.
• To enhance nonlinear optical responses in 2D materials integrated with photonic crystals.

Main Methods:

• Investigated the integration of 2D transition metal dichalcogenides (e.g., MoS2) with silicon nitride photonic crystal metasurfaces.
• Developed and numerically simulated two independent methods to achieve simultaneous resonance tuning.
• Utilized numerical simulations to quantify the enhancement of second-harmonic generation.

Main Results:

• Achieved simultaneous resonance tuning for enhanced nonlinear optical effects.
• Demonstrated a 20-fold enhancement in second-harmonic generation compared to single-resonant designs.
• Showcased a 170-fold enhancement in second-harmonic generation with optimized designs.

Conclusions:

• The proposed methods effectively enhance nonlinear optical responses in 2D materials integrated with resonant metasurfaces.
• The approach offers a viable strategy for overcoming the inherent limitations of atomically thin nonlinear materials.
• The demonstrated techniques are applicable to various dielectric metasurfaces and nonlinear 2D materials.