Leaky mode integrated optical fibre refractometer.

Area of Science:

• Optoelectronics and Photonics
• Materials Science
• Sensor Technology

Background:

• Integrated optical fiber (IOF) platforms offer robust solutions for sensing in demanding conditions.
• Monitoring external refractive indices beyond the core waveguide index is crucial for advanced applications.
• Fabrication of optical quality, ruggedized glass layers is key for integrated optical devices.

Purpose of the Study:

• To present a novel refractometer capable of measuring external refractive indices greater than the waveguide core index.
• To demonstrate the application of this refractometer on an integrated optical fiber platform for harsh environment sensing.
• To analyze the performance and potential development routes for the developed refractometer.

Main Methods:

• Fabrication of an integrated optical fiber using flame hydrolysis deposition.
• Direct UV writing of multiple fiber Bragg gratings (FBGs) into an etched optical fiber.
• Quantification of propagation loss via linear regression analysis of FBG back-reflected power.
• Numerical simulations using the transfer matrix method.

Main Results:

• The developed refractometer achieves a sensitivity of approximately 350 dB/cm/RIU at a refractive index of 1.451 (1550 nm).
• Propagation loss was effectively quantified by monitoring FBG back-reflected power.
• Successful integration of FBGs onto an etched optical fiber for sensing.

Conclusions:

• The presented refractometer design is effective for measuring high external refractive indices in harsh environments.
• The integrated optical fiber platform provides a rugged and reliable sensing solution.
• Further development can enhance the sensitivity and expand the application range of the refractometer.