Femtosecond Laser Ablated FBG with Composite Microstructure for Hydrogen Sensor Application

Area of Science:

• Materials Science
• Optical Engineering
• Chemical Sensing

Background:

• Fiber Bragg gratings (FBGs) are widely used optical sensors.
• Existing FBG sensors have limitations in sensitivity for certain applications.
• Hydrogen detection requires highly sensitive and stable sensing technologies.

Purpose of the Study:

• To develop a composite microstructure in an FBG for improved hydrogen detection.
• To investigate the effect of laser-ablated microstructures and film deposition on FBG sensitivity.
• To evaluate the performance of the novel FBG sensor for hydrogen sensing.

Main Methods:

• Fabrication of a composite microstructure on FBG cladding using femtosecond laser ablation (creating straight-trenches and spiral micro-pits).
• Sputtering a Palladium-Silver (Pd-Ag) film onto the laser-processed FBG surface to act as a hydrogen sensing transducer.
• Experimental testing to measure the hydrogen sensing performance and sensitivity of the fabricated FBG sensor.

Main Results:

• The composite microstructure FBG sensor achieved a highest sensitivity of 26.3 pm/%H.
• This represents a nearly sevenfold increase in sensitivity compared to a standard FBG.
• The developed sensor demonstrated good structure stability.

Conclusions:

• The composite microstructure FBG with Pd-Ag film deposition offers significantly enhanced hydrogen detection sensitivity.
• This novel sensor design shows great potential for practical engineering applications requiring high-sensitivity hydrogen sensing.
• The combination of laser-based microstructuring and thin-film deposition is an effective strategy for improving optical sensor performance.