Integrated Lab-on-a-Chip Optical Biosensor Using Ultrathin Silicon Waveguide SOI MMI Device.

Area of Science:

• Photonics and Nanotechnology
• Biomedical Engineering
• Materials Science

Background:

• Explores the use of sub-100 nm thick waveguides for advanced sensor applications.
• Focuses on the design and analysis of multimode interference (MMI) devices for biosensing.
• Validates design methodologies by comparing simulated and measured spectra of fabricated devices.

Discussion:

• Optimized MMI biosensor designs on sub-100 nm platforms using finite difference time domain (FDTD) simulations.
• Evaluates performance metrics including sensitivity, figure of merit (FOM), and limit of detection (LOD).
• Compares the trade-offs between sensor thickness, device length, and performance.

Key Insights:

• A 50-nm thick MMI sensor achieved a sensitivity of 420 nm/RIU and FOM of 133.
• A 70-nm thick sensor achieved a similar FOM of 134 with a shorter length (2.4 mm) and sensitivity of 330 nm/RIU.
• Demonstrated potential for detecting glucose (LOD < 10 mg dL⁻¹) and thin protein layers (1 nm).

Outlook:

• Ultrathin silicon-on-insulator (SOI) waveguides are promising for MMI-based biosensing.
• The simple MMI structure offers a scalable platform for various biomolecular detection applications.
• Further research can explore integration into complex lab-on-a-chip systems.