Extremely sensitive multi-order mode refractive index sensor using TiO₂ nanograss film and weakly bounded waveguide...

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Refractive index (RI) sensors are crucial for detecting chemical and biological analytes.
• Developing highly sensitive and cost-effective RI sensors remains a key challenge.
• Titanium dioxide (TiO2) nanostructures offer unique optical properties for sensing applications.

Purpose of the Study:

• To fabricate and characterize an extremely sensitive multi-order mode refractive index sensor.
• To investigate the relationship between resonant waveguide modes and sensor sensitivity.
• To evaluate the sensor's performance, including sensitivity and figure of merit.

Main Methods:

• Fabrication of a sensor by coupling titanium dioxide nanograss film coated FTO conductive glass with a Kretschmann prism.
• Theoretical analysis using resonant waveguide modes to determine optimal operating conditions.
• Experimental measurements of refractive index sensitivity for p-polarized and s-polarized light.

Main Results:

• The sensor demonstrated a maximum RI sensitivity of 2938.21 nm/RI unit (RIU) for p-polarized light in the 1st order mode.
• A sensitivity of 1484.39 nm/RIU was achieved for s-polarized light.
• The sensor achieved a maximum figure of merit (FOM) of 77.77.

Conclusions:

• The developed TiO2 nanograss film sensor exhibits ultra-high sensitivity and a high FOM.
• Theoretical analysis confirmed that weakly-bounded modes yield maximum sensitivity.
• The sensor shows significant potential for applications in environmental monitoring, immune analysis, and nucleic acid testing.