Compact Slot Microring Resonator for Sensitive and Label-Free Optical Sensing

Area of Science:

• Photonics
• Optical Biosensing
• Nanotechnology

Background:

• Label-free optical biosensing is crucial for real-time biological analysis.
• Traditional microring resonators have limitations in sensitivity and size.
• Silicon-on-insulator platforms offer advantages for integrated photonic devices.

Purpose of the Study:

• To propose and analyze a novel all-pass slot microring resonator (SMRR) for enhanced optical biosensing.
• To investigate the performance of the SMRR for label-free detection of sodium chloride (NaCl) solutions.
• To optimize the SMRR design for improved light-matter interaction and sensing capabilities.

Main Methods:

• Design and simulation of an asymmetric-slot microring waveguide and a bent asymmetric directional coupler.
• Utilizing the three-dimensional finite-difference time-domain (3D-FDTD) method to determine optimal slot width (140 nm).
• Numerical calculations to evaluate concentration and refractive index sensitivity, and detection limit.

Main Results:

• The proposed SMRR sensor exhibits a concentration sensitivity of 725.71 pm/% for NaCl solutions.
• A high refractive index sensitivity of 403 nm/RIU was achieved, approximately six times greater than traditional microring resonators.
• A low detection limit of 0.129% was demonstrated, highlighting the sensor's precision.

Conclusions:

• The novel SMRR demonstrates superior sensing performance compared to conventional microring resonators.
• Its compact footprint (10 µm × 10 µm) and high sensitivity make it suitable for integrated biosensing applications.
• The SMRR is a promising platform for developing advanced label-free optical biosensors.