Refractive Index Measurement Using SOI Photodiode with SP Antenna toward SOI CMOS-Compatible Integrated Optical...

Area of Science:

• Photonics and Biosensing
• Integrated Optics
• Nanophotonics

Background:

• Optical biosensors are crucial for detecting biomolecular interactions.
• Surface Plasmon Resonance (SPR) sensors are established but can be complex.
• Silicon-on-Insulator (SOI) technology offers a platform for integrated photonic devices.

Purpose of the Study:

• To develop a novel optical biosensor combining SOI photodiodes with surface plasmon antennas.
• To demonstrate sensitive refractive index (RI) detection.
• To explore the potential for high-throughput, label-free biosensing.

Main Methods:

• Fabrication of a silicon-on-insulator (SOI) p-n junction photodiode integrated with a surface plasmon (SP) antenna.
• Utilizing phase-matching conditions between diffracted light and waveguide modes for sensitivity.
• Evaluating refractive index detection limit using bulk solutions.
• Employing finite-difference time-domain (FDTD) simulations to assess biomolecular interaction detection.

Main Results:

• Observed sharp peaks in spectroscopic light sensitivity when phase-matching conditions were met.
• Achieved a refractive index detection limit of 1.11 × 10^-5 RIU.
• Simulations indicated potential for detecting intermolecular bonds and biomolecular interactions.
• Demonstrated feasibility of large-scale integration on a single chip using CMOS fabrication.

Conclusions:

• The proposed SOI photodiode with an SP antenna functions as a sensitive optical biosensor.
• The sensor performance is comparable to traditional SPR sensors.
• This technology provides a foundation for high-throughput, label-free biosensing applications.