LiNbO(3) waveguide second-harmonic-generation device phase matched with a fan-out domain-inverted grating

Area of Science:

• Nonlinear Optics
• Integrated Photonics
• Materials Science (Lithium Niobate)

Background:

• Optical second-harmonic generation (SHG) is crucial for frequency conversion in lasers and photonics.
• Lithium Niobate (LiNbO3) is a key material for nonlinear optical devices due to its strong electro-optic and nonlinear properties.
• Achieving efficient quasi-phase matching (QPM) in waveguide devices is often limited by fabrication tolerances and residual phase mismatch.

Purpose of the Study:

• To propose and demonstrate a novel LiNbO3 waveguide optical second-harmonic-generation (SHG) device.
• To design a ferroelectric domain-inverted grating in a fan pattern for enhanced quasi-phase matching (QPM).
• To create a device structure with built-in redundancy to mitigate phase mismatch from fabrication errors.

Main Methods:

• Fabrication of a 3-mm interaction length LiNbO3 waveguide device.
• Utilized domain inversion via Titanium (Ti) indiffusion for grating formation.
• Formed channel waveguides using annealed proton exchange (APE) and reactive ion etching (RIE).

Main Results:

• Successfully fabricated the proposed LiNbO3 waveguide SHG device.
• The fan-patterned grating design effectively absorbed residual phase mismatch.
• Achieved a normalized second-harmonic generation (SHG) efficiency of 17%/W when pumped by a continuous-wave (cw) Nd:YAG laser.

Conclusions:

• The proposed fan-patterned domain-inverted grating in LiNbO3 waveguides offers a robust approach for efficient optical SHG.
• The device demonstrates significant tolerance to fabrication imperfections, leading to high normalized efficiency.
• This technology holds promise for advanced frequency conversion applications in integrated photonics.