Critical-angle-based sensor with improved figure of merit using dip detection.

Area of Science:

• Photonics
• Optical Sensing
• Materials Science

Background:

• One-dimensional photonic crystals (1D-PCs) offer unique optical properties.
• Prism-based sensors are crucial for refractive index (RI) detection.
• Total internal reflection (TIR) is a key sensing mechanism.

Purpose of the Study:

• To theoretically and experimentally investigate 1D-PC structures on prisms for RI sensing.
• To analyze the resonance behavior of 1D-PCs at the critical angle (θc).
• To evaluate the performance of the 1D-PC prism sensor as a TIR sensor.

Main Methods:

• Theoretical modeling and experimental validation of 1D-PC structures on prisms.
• Utilizing a diverging beam approach on an optical bench for sensor demonstration.
• Characterizing TE and TM resonances relative to the critical angle.

Main Results:

• Observed coinciding TE and TM resonances with θc for semi-infinite 1D-PCs.
• Demonstrated minimal deviation from θc for finite 1D-PCs.
• Achieved high sensitivity (120.9 deg/RIU) and a low detection limit (1.9×10⁻⁵ RIU) with a two-channel sensor.
• Showcased enhanced figure of merit by increasing 1D-PC periods.

Conclusions:

• 1D-PC prism structures function effectively as TIR refractive index sensors.
• The sensor offers advantages like narrow dip detection and enhanced figure of merit.
• The demonstrated sensor exhibits excellent sensitivity and a low detection limit for RI sensing applications.