Refractometer based on fiber Bragg grating Fabry-Pérot cavity embedded with a narrow microchannel

Area of Science:

• Optoelectronics
• Nanofabrication
• Chemical Engineering

Background:

• Optical fiber sensors offer remote and multiplexed sensing capabilities.
• Refractive index (RI) sensing is crucial for various applications, including chemical and biological detection.
• Existing fiber optic RI sensors face limitations in detection range and sensitivity.

Purpose of the Study:

• To develop a novel method for fabricating microchannels within optical fibers.
• To create high-performance fiber optic refractometers with enhanced RI detection capabilities.
• To investigate the relationship between microchannel dimensions and sensor performance.

Main Methods:

• Femtosecond (fs) laser inscription combined with chemical etching to create microchannels in optical fibers.
• Fabrication of Fabry-Pérot (FP) cavities using UV laser-written fiber Bragg gratings (FBGs).
• Integration of microchannels with FBG FP structures to form refractometers.

Main Results:

• Successfully inscribed microchannels with widths down to 1.2μm.
• Fabricated refractometers with 5μm and 35μm microchannels exhibiting linear response.
• Achieved a high refractive index (RI) detection range up to 1.7 with the 5μm microchannel device.
• Theoretical simulations showed excellent agreement with experimental results for the microchannel FBG FP structures.

Conclusions:

• Femtosecond laser inscription assisted chemical etching is an effective technique for fabricating sub-micron microchannels in optical fibers.
• The developed microchannel-based fiber optic refractometers demonstrate superior RI detection range compared to existing fiber grating sensors.
• The study validates the potential of these novel fiber optic sensors for advanced sensing applications.