Label-free biosensing with a multi-box sub-wavelength phase-shifted Bragg grating waveguide.

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Biotechnology and Biosensing

Background:

• Sub-wavelength grating (SWG) metamaterials offer advanced solutions for next-generation photonic integrated circuits.
• Silicon photonic planar biosensors utilizing SWG geometries are gaining traction for enhanced performance.
• Label-free biosensing platforms are crucial for real-time monitoring in various applications.

Purpose of the Study:

• To demonstrate a highly sensitive, label-free phase-shifted Bragg grating (PSBG) sensing configuration based on SWG metamaterials.
• To characterize the bulk and surface sensitivities of the proposed SWG-based PSBG sensor.
• To evaluate the sensor's performance for small molecule detection using an affinity assay.

Main Methods:

• Fabrication of a PSBG sensing configuration with sub-wavelength block arrays in both propagation and transverse directions.
• Characterization of bulk sensitivity using salt serial dilutions.
• Characterization of surface sensitivity using electrostatic polymers assays.
• Demonstration of small molecule detection via a biotin-streptavidin affinity assay.

Main Results:

• Achieved bulk sensitivity up to 579.2 nm/RIU and surface sensitivity up to 1914 pm/nm.
• The multi-box PSBG sensor exhibited a quality factor approximately 3-fold higher than microring-based counterparts.
• Demonstrated a minimum detectable concentration of biotin down to 10⁻¹² M, showcasing capability for small molecule monitoring.

Conclusions:

• The proposed SWG-based PSBG sensor offers a highly sensitive and effective platform for label-free biosensing.
• The enhanced quality factor and sensitivity enable improved detection limits for various analytes.
• This technology holds significant potential for advancing photonic integrated circuits and diagnostic applications.