Surface-Modified Extrinsic Semi-Distributed Interferometers for Fiber-Optic Refractive Index Detection and...

Area of Science:

• Photonics and Sensing Technologies
• Nanomaterials Science
• Biomedical Engineering

Background:

• Semi-distributed interferometers offer refractive index sensing by utilizing random reflectivity in nanoparticle-doped fibers.
• Extending this, an extrinsic semi-distributed interferometer (ESDI) is proposed using a polydimethylsiloxane (PDMS) overlay on a fiber tip.

Purpose of the Study:

• To develop and characterize gold-sputtered and gold-nanoparticle-coated ESDI structures for enhanced refractive index sensing.
• To explore the potential of biofunctionalized ESDI probes for detecting specific biomolecules, such as vascular endothelial growth factor (VEGF).

Main Methods:

• Fabrication of extrinsic semi-distributed interferometers (ESDI) with PDMS overlays.
• Surface modification of ESDI structures with gold sputtering and gold nanoparticle coating.
• Performance evaluation for refractive index sensing, including sensitivity and resolution.
• Biofunctionalization of gold-sputtered probes for VEGF detection and sensitivity analysis.

Main Results:

• Gold-nanoparticle-coated ESDIs demonstrated superior refractive index sensing with an average sensitivity of 62.8 dB/RIU and a resolution of 3.9 × 10^-5 RIU.
• The refractive index sensing range was determined to be 1.34790-1.35981.
• Biofunctionalized gold-sputtered probes achieved a sensitivity of 0.0565 dB per 10× concentration increase for VEGF detection, with a limit of detection at 355 fM.

Conclusions:

• Extrinsic semi-distributed interferometers, particularly those coated with gold nanoparticles, offer a promising platform for high-performance refractive index sensing.
• The developed biofunctionalized probes show significant potential for sensitive and specific detection of biomarkers like VEGF in biological applications.