Theoretical waveguide optimization in a Ti:LiNb0(3) Mach-Zehnder modulator by Mg diffusion

Area of Science:

• Materials Science
• Optical Engineering
• Photonics

Background:

• Titanium-diffused lithium niobate (Ti:LiNbO3) waveguides are crucial for integrated optics.
• Mach-Zehnder modulators based on Ti:LiNbO3 are widely used in optical communication systems.
• Optimizing waveguide characteristics is essential for device performance and miniaturization.

Purpose of the Study:

• To investigate the use of magnesium (Mg) diffusion in conjunction with titanium (Ti) diffusion to enhance Ti:LiNbO3 Mach-Zehnder modulator performance.
• To explore how double diffusion impacts key modulator parameters such as coupling loss, size, and modulating voltage.

Main Methods:

• Fabrication of Ti/Mg:LiNbO3 waveguides using a double diffusion process.
• Characterization of waveguide properties using Secondary Ion Mass Spectrometry (SIMS) and 771-line techniques.
• Numerical simulation employing a full vectorial beam-propagation method for optimization.

Main Results:

• Double diffusion reduces fiber-waveguide coupling loss.
• Increased bend radius is achievable without additional bend losses, enabling smaller modulator footprints.
• Improved lateral confinement of guided waves leads to a reduction in required modulating voltage.

Conclusions:

• Titanium/magnesium double diffusion is an effective technique for optimizing Ti:LiNbO3 Mach-Zehnder modulators.
• The method offers significant improvements in device performance, including reduced losses and lower operating voltage.
• This approach facilitates the development of more compact and efficient integrated optical modulators.