Highly sensitive ion detection sensor based on an optical microfiber coupler operating near the dispersion turning...

Area of Science:

• Photonics and optical sensing
• Environmental monitoring and water quality analysis
• Nanomaterials and device fabrication

Background:

• Optical microfiber couplers (OMCs) offer potential for sensitive chemical detection.
• Refractive index (RI) sensitivity of OMCs is crucial for sensing applications.
• Enhancing OMC sensitivity near the dispersion turning point (DTP) is a promising research direction.

Purpose of the Study:

• To develop an OMC operating near the DTP for ultra-high sensitivity detection of calcium ions (Ca²⁺).
• To investigate the influence of DTP on the RI sensitivity of OMCs.
• To apply the developed OMC for practical Ca²⁺ concentration measurements in water.

Main Methods:

• Theoretical simulations to predict RI sensitivity enhancement near DTP.
• Fabrication of OMCs with optimized waist diameter (2.8 µm).
• Experimental verification of DTP's effect on OMC RI sensitivity.
• Application of OMC for Ca²⁺ detection in aqueous samples.

Main Results:

• Significant enhancement of RI sensitivity near the DTP was theoretically demonstrated.
• Experimental results confirmed the influence of DTP on OMC sensitivity.
• Maximum sensitivity of -1.055 nm/(10 mg/L) achieved for Ca²⁺ detection.
• A low detection limit of 0.095 mg/L for Ca²⁺ was established.

Conclusions:

• OMCs operating near the DTP enable ultra-high sensitivity detection of Ca²⁺.
• The DTP is a critical parameter for optimizing OMC-based RI sensing.
• This technology shows promise for accurate and sensitive water quality monitoring.