Sensitivity Enhancement of Polymer Optical Fiber Surface Plasmon Resonance Sensor Utilizing ITO Overlayer.

Area of Science:

• Photonics and Optical Sensing
• Materials Science for Sensors
• Nanotechnology for Biosensing

Background:

• Surface Plasmon Resonance (SPR) sensors are crucial for label-free biomolecular detection.
• Polymer Optical Fiber (POF) offers advantages in flexibility and cost for sensor fabrication.
• Enhancing SPR sensor sensitivity is key for detecting low-concentration analytes.

Purpose of the Study:

• To investigate the sensitivity enhancement of SPR sensors using a cladding etched multimode POF.
• To evaluate the effect of an indium tin oxide (ITO) overlayer on SPR sensor performance.
• To determine the optimal ITO thickness for maximizing sensor sensitivity and figure of merit.

Main Methods:

• Fabrication of a cladding etched multimode POF SPR sensor.
• Coating the POF with a gold layer followed by an ITO overlayer of varying thicknesses.
• Characterization of sensor performance, including refractive index sensitivity, figure of merit, and resolution.
• Assessment of long-term stability and repeatability in a hydrated environment.

Main Results:

• The POF SPR sensor with an ITO overlayer demonstrated significantly higher sensitivity compared to gold-only coatings.
• Optimal sensitivity was achieved with a 25 nm ITO layer, yielding a refractive index sensitivity of 2258 nm/RIU.
• The sensor exhibited a figure of merit of 10.13 RIU⁻¹ and a resolution of 2.74×10⁻⁴ RIU.
• Long-term stability tests showed minimal wavelength drift (1.2 nm) and good repeatability.

Conclusions:

• The ITO overlayer effectively enhances the sensitivity of POF SPR sensors.
• The proposed sensor design offers a simple fabrication process with a large interaction area.
• This enhanced POF SPR sensor is a promising platform for high-sensitivity biosensing applications.