A Highly Sensitive Fiber-Optic Fabry-Perot Interferometer Based on Internal Reflection Mirrors for Refractive Index...

Area of Science:

• Optoelectronics
• Fiber Optic Sensors
• Interferometry

Background:

• Refractive index (RI) sensing is crucial in various scientific and industrial applications.
• Existing fiber-optic sensors often face limitations in sensitivity, measurement range, or visibility.
• Fabry-Perot interferometers (FPIs) are known for their potential in high-resolution sensing.

Purpose of the Study:

• To propose and demonstrate a highly sensitive fiber-optic Fabry-Perot interferometer (FFPI) for wide-range refractive index (RI) measurements.
• To enhance fringe visibility and sensor performance using internal reflection mirrors within a micro-cavity.
• To achieve high RI resolution and sensitivity using gold thin films as mirrors.

Main Methods:

• Fabrication of a sensor head comprising a single-mode fiber (SMF) with an open micro-cavity.
• Sputtering gold thin films of varying thicknesses on the inner micro-cavity surfaces to act as a semi-transparent mirror (STM) and a total-reflection mirror (TRM).
• Experimental verification of the sensor's design, performance, and RI measurement capabilities.

Main Results:

• The fabricated FFPI sensor demonstrated strong interference fringe visibility exceeding 15 dB over a wide RI measurement range.
• The sensor achieved a high sensitivity greater than 1160 nm/RIU.
• An excellent RI resolution better than 1.0 × 10(-6) RIU was obtained.

Conclusions:

• The proposed FFPI design with internal reflection mirrors effectively enhances fringe visibility and sensing performance.
• The sensor exhibits high sensitivity and resolution, making it suitable for precise RI measurements across a broad spectrum.
• This novel FFPI sensor represents a significant advancement in optical sensing technology for various applications.