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Multiphysics Analysis and Optimization of a Thin-Film Lithium Niobate Phase Modulator for Fiber-Optic Gyroscopes
Hanyi Zhang1, Rong Fan1, Yin Cao1
1School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China.
Micromachines
|June 26, 2026
Summary
This study models lithium niobate phase modulators, unifying electro-optic, piezoelectric, thermo-optic, and pyroelectric effects for fiber-optic gyroscopes. Optimized designs achieve stable performance across wide temperature ranges, crucial for robust sensing applications.
Area of Science:
- Photonics and Optical Engineering
- Materials Science
- Sensing Technologies
Background:
- Lithium niobate on insulator (LNOI) is a key platform for compact, low-loss phase modulators.
- Existing LNOI device evaluation often decouples piezoelectric-photoelastic strain and thermo-optic drift, crucial for fiber-optic gyroscope (FOG) phase bias.
- Accurate modeling is needed to understand and mitigate environmental influences on modulator performance in FOGs.
Purpose of the Study:
- To establish a unified multiphysics model for X-cut thin-film lithium niobate (TFLN) ridge phase modulators.
- To quantitatively decompose the contributions of electro-optic, piezoelectric-photoelastic, thermo-optic, and pyroelectric effects.
- To optimize device geometry and electrode gap for enhanced modulation efficiency and environmental stability in FOG applications.
Main Methods:
- Developed a self-consistent multiphysics model coupling four key physical channels.
- Quantitatively decomposed the contributions of each mechanism under realistic FOG operating conditions.
- Systematically optimized slab thickness, ridge-top width, and electrode gap for performance and robustness.
Main Results:
- Achieved a half-wave voltage length (VπL) of 1.65 V·cm at a 4.4 μm electrode gap, maintaining an EO overlap factor near 0.55.
- Demonstrated temperature independence of VπL (≈1.65 V·cm, within ~0.3%) across 25–85 °C for the optimized geometry and electrode gap.
- Showed that thermal residuals are approximately 27% of the Pockels modulation depth under extreme temperature changes, absorbed by FOG servo electronics.
Conclusions:
- DC-coupled operation of TFLN sensor-grade modulators is viable across the full FOG temperature range without active stabilization.
- The optimized design provides quantitative guidelines for high-performance, environmentally stable TFLN phase modulators in compact FOG systems.
- This work enables robust and reliable sensing applications using LNOI-based phase modulators.
