Liquid crystal based polarized low coherence interferometer for optical demodulation in sensors

Area of Science:

• Optics and Photonics
• Materials Science
• Sensor Technology

Background:

• Optimizing birefringent wedges in polarized low coherence interferometers (PLCI) is crucial for enhancing measurement resolution and sensitivity.
• Existing methods for demodulating Fabry-Perot (FP) cavity length often lack tunability and precision.

Purpose of the Study:

• To introduce and evaluate a liquid crystal (LC) wedge as a novel component in PLCI for demodulating FP cavity length.
• To demonstrate the LC wedge's capability to convert optical path difference into spatial fringe patterns for displacement sensing.
• To investigate the enhancement of sensing resolution through electric field modulation of interferogram fringes.

Main Methods:

• Incorporation of a nematic liquid crystal wedge into a PLCI setup.
• Utilizing the birefringence of the LC to spatially distribute optical path differences, creating localized interference fringes.
• Demodulating displacement by tracking fringe envelope centroids and considering birefringence dispersion.
• Conducting simulation studies to validate experimental findings.

Main Results:

• The LC wedge successfully demodulated FP cavity length by generating localized interference fringe patterns.
• Experimental and simulation results for displacement sensing showed high consistency and agreement with actual cavity length.
• The LC wedge demonstrated advantages over traditional birefringent crystals, offering high precision and tunable measurement ranges.

Conclusions:

• The liquid crystal wedge offers a promising, tunable, and high-precision alternative for displacement sensing in fiber optic applications.
• This approach enhances the resolution and adaptability of polarized low coherence interferometry.
• The developed method is suitable for robust fiber optic sensing applications requiring precise measurements.