Linewidth-related residual intensity modulation in lithium niobate phase modulators

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Residual Intensity Modulation (RIM) is a critical performance parameter in lithium niobate (LiNbO3) phase modulators.
• Understanding RIM is essential for optimizing modulator performance with various laser sources.

Purpose of the Study:

• To present a modified theoretical model for Residual Intensity Modulation (RIM) in lithium niobate phase modulators.
• To validate the model's applicability for both narrow and wide linewidth lasers.
• To differentiate the dominant causes of RIM based on laser linewidth.

Main Methods:

• Developed a modified model incorporating optical propagation loss and optical interference effects.
• Experimentally measured RIM using lasers with varying linewidths.
• Validated the model by comparing theoretical predictions with experimental data using R-square values.

Main Results:

• The modified model accurately predicts RIM for both narrow and wide linewidth lasers (R-square > 0.995).
• For narrow linewidth lasers, optical interference is the primary cause of RIM.
• For wide linewidth lasers, optical propagation loss becomes the dominant factor causing RIM.

Conclusions:

• The proposed model provides a unified framework for understanding RIM in LiNbO3 phase modulators across different laser linewidths.
• The findings highlight the distinct physical mechanisms driving RIM depending on the spectral characteristics of the input laser.
• This research offers insights for designing and optimizing optical modulators for specific laser applications.