Reflectivity enhanced refractive index sensor based on a fiber-integrated Fabry-Perot microresonator

Area of Science:

• Photonics and Optical Sensing
• Materials Science and Engineering
• Nanotechnology

Background:

• Refractive index sensors are crucial for various applications, including chemical detection and biomedical diagnostics.
• Existing fiber-integrated sensors often face limitations in sensitivity and detection performance.
• Fabry-Perot resonators offer a promising platform for high-performance optical sensing.

Purpose of the Study:

• To develop and characterize a fiber-integrated refractive index sensor with significantly improved detection performance.
• To investigate the impact of resonator wall coating on sensor performance.
• To provide design rules and mathematical analysis for optimizing such sensors.

Main Methods:

• Implementation of a resonator using focused-ion beam milling of a step index fiber.
• Coating of resonator walls to enhance mirror reflectivity.
• Mathematical analysis and derivation of design rules for sensor optimization.

Main Results:

• Achieved a sensitivity of approximately 1.15 µm/RIU for the refractive index sensor.
• Demonstrated a significant improvement in mirror reflectivity by a factor of approximately 26 through resonator wall coating.
• Confirmed the sensor operates as an optimized Fabry-Perot resonator.

Conclusions:

• The developed fiber-integrated sensor exhibits strongly improved detection performance.
• Coating resonator walls is an effective strategy for enhancing mirror reflectivity and overall sensor performance.
• The performance of Fabry-Perot sensors is fundamentally limited by the detection limit function, influenced by cavity finesse and measurement capabilities.