Second harmonic generation in nano-structured thin-film lithium niobate waveguides

Area of Science:

• Photonics and Materials Science
• Integrated Optics
• Nonlinear Optics

Background:

• Integrated thin-film lithium niobate is a key platform for advanced photonic devices.
• Efficient wavelength conversion is crucial for optical communication and signal processing.

Purpose of the Study:

• To demonstrate efficient, phase-matched second harmonic generation (SHG) in sub-micron thin-film lithium niobate waveguides.
• To explore both modal phase matching and quasi-phase matching techniques for SHG in these waveguides.

Main Methods:

• Fabrication of lithographically-defined thin-film lithium niobate nanowaveguides with sub-micron dimensions.
• Theoretical proposal and experimental demonstration of modal phase matching in fixed-width waveguides.
• Theoretical proposal and experimental demonstration of quasi-phase matching in periodically grooved waveguides.

Main Results:

• Achieved efficient, phase-matched second harmonic generation in the fabricated waveguides.
• Demonstrated both modal phase matching and quasi-phase matching experimentally.
• Obtained low-loss (~3.0 dB/cm) nanowaveguides with high normalized conversion efficiencies up to 41% W^-1cm^-2.

Conclusions:

• Thin-film lithium niobate nanowaveguides are highly effective for efficient wavelength conversion.
• The demonstrated techniques enable high-performance nonlinear photonic devices for integrated systems.
• This work advances the development of next-generation, mass-producible photonic systems.