Silicon nitride waveguides with directly grown WS₂ for efficient second-harmonic generation.

Area of Science:

• Integrated photonics
• Materials science
• Nonlinear optics

Background:

• Silicon (Si) and silicon nitride (Si₃N₄) photonics offer potential for optoelectronics but lack light generation, detection, and second-order nonlinear properties.
• Existing methods for integrating 2D materials onto photonic devices are time-consuming, not scalable, and can damage materials or introduce impurities.

Purpose of the Study:

• To develop a scalable method for integrating 2D materials onto Si₃N₄ waveguides.
• To enhance the nonlinear optical properties of Si₃N₄ photonics through direct material growth.
• To enable new functionalities in integrated optoelectronic devices.

Main Methods:

• Direct growth of large-area homogeneous monolayer tungsten disulfide (WS₂) onto Si₃N₄ waveguides using physical vapor deposition.
• Controlled WS₂ growth along Si₃N₄ waveguides.
• Characterization of enhanced second-harmonic generation (SHG) in WS₂-covered Si₃N₄ waveguides.

Main Results:

• Achieved direct, large-area growth of monolayer WS₂ predominantly along Si₃N₄ waveguides.
• Observed significant enhancement of second-harmonic generation in Si₃N₄ waveguides with WS₂ coverage.
• Demonstrated a scalable and compatible method for integrating 2D materials, avoiding issues associated with transfer methods.

Conclusions:

• Directly grown WS₂ on Si₃N₄ waveguides imparts new nonlinear optical properties to integrated photonics.
• This physical vapor deposition method is a viable alternative to material transfer for large-scale integrated photonic fabrication.
• The findings lay the groundwork for on-chip integrated optical fabrication and advanced applications.