In-Fiber Closed Cavity Interferometric High-Resolution Aqueous Solution and Alcohol Gas Refractometer

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Nanomaterials

Background:

• Optical fiber sensors offer sensitive detection methods.
• Measuring low refractive index (RI) solutions and gas concentrations requires high-performance sensors.
• Single-mode thin-core single-mode (STS) interferometers can be adapted for refractometry.

Purpose of the Study:

• To demonstrate an optical fiber interferometric refractometer for alcohol gas and low RI solution measurement.
• To investigate the impact of air cavity size and graphene integration on sensor performance.
• To compare the sensitivity of single-cavity, graphene-filled, and double-cavity sensor structures.

Main Methods:

• Fabrication of an STS interferometric structure with an embedded air cavity.
• Excitation of high-order cladding modes for enhanced low RI sensitivity.
• Experimental analysis of air cavity diameter effects on alcohol gas sensitivity.
• Integration of graphene into the air cavity to boost sensor sensitivity.
• Characterization of single-cavity, graphene-filled, and double-cavity sensor structures.

Main Results:

• Sensor sensitivity to alcohol gas concentration increased with enlarged air cavity diameter.
• Graphene-filled cavity achieved a measured sensitivity of -1206.1 pm/% for alcohol gas.
• Linear RI sensitivities were -54.593 nm/RIU (single-cavity), -85.561 nm/RIU (graphene-filled), and 359.77 nm/RIU (double-cavity).
• The developed sensors are compact and easy to prepare.

Conclusions:

• The optical fiber refractometer effectively measures alcohol gas concentration and low RI solutions.
• Graphene integration significantly enhances sensor sensitivity.
• The double-cavity structure exhibits the highest RI sensitivity among the tested configurations.