High-sensitivity H₂S gas sensor based on asymmetric modes in long-period fiber grating

Area of Science:

• Fiber optic sensing
• Chemical sensors
• Materials science

Background:

• Hydrogen sulfide (H2S) is a toxic gas requiring sensitive detection methods.
• Long-period fiber gratings (LPFGs) offer potential for gas sensing applications.
• Coating LPFGs with sensitive materials can enhance gas detection capabilities.

Purpose of the Study:

• To propose and characterize a novel LPFG sensor coated with zinc oxide (ZnO) for H2S detection.
• To investigate the sensor's performance based on asymmetric cladding modes and ZnO film sensitivity.
• To determine the optimal ZnO film thickness for enhanced H2S sensitivity.

Main Methods:

• Fabrication of an LPFG in an asymmetric dual-core fiber (ADCF).
• Coating the ADCF-LPFG with a zinc oxide (ZnO) film.
• Simulation to determine the optimal ZnO film thickness (120 nm).
• Experimental characterization of H2S and temperature sensitivity.

Main Results:

• The sensor achieved a maximum H2S sensitivity of 63.21 pm/ppm over a concentration range of 4.93-41.6 ppm.
• Excellent stability (0.0011%) and a detection limit of 2.432 ppm for H2S were recorded.
• The sensor exhibited a temperature sensitivity of -83.17 pm/°C within the 10-40°C range.

Conclusions:

• The developed ZnO-coated ADCF-LPFG sensor demonstrates high sensitivity and stability for H2S detection.
• The sensor's compact structure and ability to measure both H2S and temperature show significant potential for simultaneous sensing.
• This technology offers a promising solution for environmental monitoring and industrial safety applications.