Modal phase matching in z-cut dual-layered lithium niobate rib waveguide for second harmonic generation

Area of Science:

• Photonics and Nonlinear Optics
• Materials Science
• Integrated Optics

Background:

• Thin-film lithium niobate (TFLN) is a key material for integrated nonlinear photonics.
• Efficient second harmonic generation (SHG) is crucial for optical frequency conversion.
• Modal phase matching (MPM) offers a route to enhance nonlinear processes in waveguides.

Purpose of the Study:

• To investigate modal phase matching in z-cut TFLN rib waveguides.
• To explore the impact of waveguide geometry on SHG efficiency.
• To optimize TFLN waveguides for high-performance nonlinear optical devices.

Main Methods:

• Systematic analysis of waveguide cross-sectional dimensions (width, height, etch depth).
• Investigation of geometrical dispersion engineering for phase-matching.
• Experimental demonstration of second harmonic generation in TFLN rib waveguides.

Main Results:

• Phase-matching wavelength is highly sensitive to waveguide thickness variations.
• Optimized TFLN waveguides achieve SHG conversion efficiencies of ~10³% W^-1cm^-2.
• Geometrical dispersion engineering effectively controls phase-matching conditions.

Conclusions:

• Precise control of waveguide thickness is critical for efficient SHG in TFLN.
• MPM in z-cut TFLN rib waveguides is a viable strategy for on-chip frequency conversion.
• This work advances the development of integrated nonlinear photonic devices.