Mode control of Ti-diffused LiNbO(3) slab optical waveguide

Area of Science:

• Materials Science
• Photonics
• Solid-State Physics

Background:

• Optical waveguides are crucial components in integrated optics and photonic devices.
• Lithium niobate (LiNbO3) is a widely used material for fabricating optical waveguides due to its excellent electro-optic properties.
• Titanium (Ti) indiffusion is a standard technique for creating optical waveguides in LiNbO3.

Purpose of the Study:

• To investigate the relationship between fabrication conditions and the optical properties of Ti-diffused LiNbO3 slab waveguides.
• To determine how to control the refractive index profile, including surface index change and diffusion depth.
• To achieve specific waveguide parameters, such as the number of TE modes and effective indices, for targeted laser wavelengths.

Main Methods:

• Fabrication of optical waveguides via thermal diffusion of titanium (Ti) into LiNbO3 single crystals.
• Systematic variation of diffusion conditions to study their impact on waveguide characteristics.
• Characterization of the refractive index profile and optical modes supported by the fabricated slab waveguides.

Main Results:

• Established clear relationships between diffusion parameters and the resulting refractive index profiles of Ti-LiNbO3 waveguides.
• Identified specific fabrication conditions to achieve desired waveguide properties for 0.6328 µm (He-Ne laser) and 0.8730 µm (GaAs-GaAlAs DH laser) wavelengths.
• Demonstrated that adjusting the thickness of the evaporated Ti film is sufficient to control the number of modes and effective indices.

Conclusions:

• The thickness of the evaporated Ti film is a critical parameter for precisely controlling the optical characteristics of Ti-diffused LiNbO3 slab waveguides.
• This study provides a method for fabricating waveguides with tailored properties for specific laser applications.
• The findings facilitate the design and production of customized optical waveguides for photonic integrated circuits.