Strip-loaded Mach-Zehnder interferometer for absolute refractive index sensing

Area of Science:

• Photonics and optical sensing
• Integrated optics
• Chemical sensing technologies

Background:

• Mach-Zehnder interferometers (MZIs) are crucial for optical sensing.
• Conventional MZI designs face limitations in sensitivity and analyte interaction.
• Developing enhanced MZIs for precise refractive index measurement is essential.

Purpose of the Study:

• To design, fabricate, and characterize a novel strip-loaded MZI for liquid refractive index measurement.
• To enhance MZI sensitivity by using the analyte as a loading strip.
• To demonstrate superior performance compared to conventional MZI designs.

Main Methods:

• Fabrication of a strip-loaded waveguide using TiO2 thin film and nLOF resist on a SiO2 wafer.
• Implementation of a large opening in the sensing region to maximize analyte interaction.
• Characterization using ethanol-water solutions to determine homogeneous sensitivity.

Main Results:

• Achieved a high confinement factor (~23%) in the cladding for effective evanescent field interaction.
• Demonstrated a homogeneous sensitivity of 0.128.
• Enabled monitoring of refractive index changes as small as 10^-4.

Conclusions:

• The novel strip-loaded MZI design significantly enhances sensitivity for refractive index measurements.
• The design effectively utilizes the analyte as a loading strip, surpassing conventional approaches.
• This technology offers a promising platform for advanced optical sensing applications.