Novel S-Bend Resonator Based on a Multi-Mode Waveguide with Mode Discrimination for a Refractive Index Sensor

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Sensor Technology

Background:

• Conventional optical resonators often rely on single-mode waveguides, facing limitations in mass production due to high fabrication costs of nanoscale structures.
• Multi-mode waveguides are generally unsuitable for optical resonators due to modal dispersion and multi-peak output transmission, hindering performance.
• Existing refractive index sensors require improved sensitivity and cost-effective manufacturing methods.

Purpose of the Study:

• To propose and investigate a novel multi-mode waveguide-based optical resonator for integrated optical refractive index sensing.
• To overcome the limitations of conventional resonators by utilizing micro-scale multi-mode waveguides.
• To achieve high performance and cost-effective mass production for refractive index sensors.

Main Methods:

• Design of an S-bend resonator based on a micro-scale multi-mode waveguide.
• Exploitation of mode discrimination through bending loss to suppress higher-order modes.
• Utilized the variational finite-difference time-domain (VFDTD) method for performance analysis.

Main Results:

• The proposed S-bend resonator effectively removes higher-order modes, yielding a single-peak output transmission.
• Achieved a high Q-factor of 2.3 × 10^3.
• Demonstrated a sensitivity of 52 nm/RIU (refractive index unit), suitable for refractive index sensing applications.

Conclusions:

• The multi-mode waveguide-based S-bend resonator offers a viable alternative to conventional designs for integrated optical sensors.
• The developed resonator exhibits promising performance metrics, including high Q-factor and sensitivity.
• This approach facilitates cost-effective mass production of refractive index sensors.