A refractive index sensor design based on grating-assisted coupling between a strip waveguide and a slot waveguide.

Area of Science:

• Photonics and Optical Sensing
• Integrated Optics
• Nanophotonics

Background:

• Refractive index sensors are crucial for various applications, including chemical detection and environmental monitoring.
• Existing sensor designs face limitations in sensitivity and operational stability.
• Waveguide-based sensors offer miniaturization and integration potential.

Purpose of the Study:

• To design and investigate a novel refractive index sensor based on grating-assisted light coupling.
• To explore the relationship between waveguide parameters and sensor sensitivity.
• To evaluate the sensor's performance, including sensitivity and temperature dependence.

Main Methods:

• Design of a sensor utilizing a strip waveguide and a slot waveguide for light coupling.
• Analysis of grating-assisted coupling mechanism for refractive index sensing.
• Systematic investigation of slot-waveguide parameters and their impact on sensitivity.
• Evaluation of temperature dependence with and without an isolation layer.

Main Results:

• The sensor demonstrates a baseline sensitivity of ~1.46 × 10^3 nm/RIU.
• Sensitivity is significantly enhanced, nearly doubling when the strip waveguide is isolated.
• Extraordinarily high sensitivity (on the order of 10^5 nm/RIU) is achieved when group indices of the waveguides are closely matched.
• A polymer isolation layer effectively minimizes temperature dependence.

Conclusions:

• The proposed grating-assisted coupled waveguide sensor offers a promising platform for high-sensitivity refractive index sensing.
• Optimization of waveguide parameters, particularly group indices, is key to achieving ultra-high sensitivity.
• The sensor exhibits low temperature dependence, making it suitable for stable real-world applications.