Efficient Second-Harmonic Generation in Adapted-Width Waveguides Based on Periodically Poled Thin-Film Lithium...

Area of Science:

• Photonics and Quantum Information Science
• Nonlinear Optics
• Materials Science

Background:

• Periodically poled thin-film lithium niobate (PPTFLN) is crucial for quantum information and photonic signal processing.
• Nanophotonic waveguides offer high normalized conversion efficiency (NCE) due to optical mode confinement.
• Inhomogeneity in thin-film lithium niobate (TFLN) limits power conversion efficiency by causing phase errors.

Purpose of the Study:

• To theoretically present a novel approach to overcome phase errors in PPTFLN devices.
• To enhance the power conversion efficiency of second harmonic generation (SHG) in nanophotonic waveguides.
• To simplify fabrication processes for highly efficient nonlinear optical devices.

Main Methods:

• Dispersion engineering to adjust waveguide structure.
• Local waveguide width adjustment based on thickness variations.
• Application of adapted waveguide design to etched and loaded PPTFLN waveguides.

Main Results:

• Achieved ultrahigh power conversion efficiency for SHG: 2.1 × 10^4 %W^-1 (etched) and 6936 %W^-1 (loaded).
• Eliminated phase errors through precise waveguide width engineering.
• Demonstrated a simplified approach using standard periodic poling with a single period.

Conclusions:

• The proposed dispersion engineering method effectively eliminates phase errors in PPTFLN waveguides.
• The approach significantly enhances power conversion efficiency for SHG, surpassing existing methods.
• This work offers a simplified, manufacturable pathway for highly efficient second-order nonlinear optical processes using PPTFLN.