Polymer Ring Resonator with a Partially Tapered Waveguide for Biomedical Sensing: Computational Study.

Area of Science:

• Photonics and Materials Science
• Biomedical Engineering and Sensor Technology

Background:

• Ring resonators are established optical biosensors, valued for high Q-factor, sensitivity, and miniaturization potential.
• Existing designs offer good performance but have room for improvement in sensitivity and figure of merit for advanced biomedical sensing.

Purpose of the Study:

• To investigate the characteristics of a polymer ring resonator with a partially tapered waveguide for enhanced biomedical sensing.
• To develop a more sensitive biosensor with an improved figure of merit through increased field interaction in tapered segments.

Main Methods:

• Investigated polymer ring resonators with gradually reduced waveguide width (to half) in partially tapered segments.
• Analyzed sensitivity, Q-factor, and figure of merit variations with different numbers and angles of tapered sections.
• Compared performance of strip waveguides versus partially tapered waveguides (e.g., π/4 taper).

Main Results:

• Sensitivity increased from 84.6 to 101.74 [nm/RIU] with a π/4 partially tapered waveguide.
• Q-factor saw a minor reduction from 4.60 × 10³ to 4.36 × 10³.
• Figure of merit improved from 497 to 565 with approximately six π/4 tapered sections.
• A three-tapered design is suggested for optimal balance between performance and fabrication.

Conclusions:

• Partially tapered waveguides in polymer ring resonators significantly enhance biosensor sensitivity and figure of merit.
• The all-polymer device offers a low-cost, disposable solution compatible with roll-to-roll fabrication.
• This design is adaptable to silicon on isolator or polymer on silicon platforms for potentially higher Q-factors and sensitivity.