Decoupling bulk and surface characteristics with a bare tilted fiber Bragg grating.

Area of Science:

• Fiber optics
• Optical sensing
• Nanotechnology

Background:

• Tilted fiber Bragg gratings (TFBGs) offer advanced fiber-optic sensing capabilities.
• Cross-sensitivity to bulk and surface environments limits TFBG sensor accuracy.
• Decoupling environmental factors is crucial for precise sensing applications.

Purpose of the Study:

• To develop a theoretical method for decoupling bulk and surface sensing characteristics in bare TFBG sensors.
• To differentiate between bulk refractive index changes and surface-localized binding events.
• To enhance the specificity and accuracy of TFBG-based sensing platforms.

Main Methods:

• Utilized a bare TFBG sensor for theoretical analysis.
• Proposed a decoupling approach based on differential spectral responses.
• Analyzed the wavelength interval between P- and S-polarized resonances to represent mode dispersion.
• Investigated the response to bulk refractive index and surface film thickness.

Main Results:

• Successfully achieved theoretical decoupling of bulk and surface sensing environments.
• Demonstrated that the decoupling method maintains high sensing performance.
• Achieved bulk sensitivity exceeding 540 nm/RIU and surface sensitivity of 12 pm/nm.

Conclusions:

• The proposed differential spectral response method effectively decouples bulk RI and surface film thickness.
• This approach significantly improves the specificity of TFBG sensors.
• The findings pave the way for more robust and accurate fiber-optic sensing applications.