Guided-Mode-Leaky-Mode-Guided-Mode Fiber Interferometer and Its High Sensitivity Refractive Index Sensing Technology

Area of Science:

• Optoelectronics
• Optical Sensing
• Interferometry

Background:

• Mach-Zehnder interferometers (MZIs) are widely used for sensing applications.
• Optimizing MZI structures is crucial for enhancing sensitivity and resolution.
• Guided-mode and leaky-mode interference offer unique spectral characteristics for sensing.

Purpose of the Study:

• To propose and experimentally validate a cascaded symmetrical dual-taper Mach-Zehnder interferometer.
• To analyze the interference spectrum characteristics and optimize sensor parameters for high spectral contrast.
• To investigate the refractive index sensitivity and measurement resolution of the proposed sensor.

Main Methods:

• Finite Difference-Beam Propagation Method (FD-BPM) for spectral characteristic analysis.
• Fabrication and experimental testing of the dual-taper MZI sensor.
• Refractive index sensitivity measurements using NaCl solutions.

Main Results:

• Optimized parameters (taper waist diameter 24 μm, dual-taper length 837 μm, taper distance 5.5 cm) yield high spectral contrast (0.8).
• Achieved a high refractive index sensitivity of 62.78 nm/RIU in the refractive index range of 1.3333-1.3792.
• Demonstrated a measurement resolution of 1.6 × 10⁻⁵ RIU.

Conclusions:

• The cascaded symmetrical dual-taper MZI sensor exhibits high sensitivity and stability.
• The sensor is well-suited for high-precision measurements in low refractive index environments.
• Simulation results are in strong agreement with experimental findings, validating the sensor's design.