Long-range surface plasmon triple-output Mach-Zehnder interferometers.

Area of Science:

• Photonics and optical sensing
• Integrated optics
• Plasmonics

Background:

• Mach-Zehnder interferometers (MZIs) are crucial for phase-based sensing.
• Improving the detection limits of MZIs is essential for advanced applications.
• Long-range surface plasmon-polariton waves offer unique light-matter interaction properties.

Purpose of the Study:

• To demonstrate a triple-output MZI utilizing long-range surface plasmon-polariton waves.
• To develop a theoretical model for three-waveguide coupling in the device.
• To enhance the detection limit and dynamic range for sensing applications.

Main Methods:

• Fabrication of a triple-output MZI cascaded with a triple coupler operating at ~1370 nm.
• Utilizing the thermo-optic effect for phase shifting.
• Theoretical modeling of three-waveguide coupling and device performance analysis.
• Experimental validation and comparison with theoretical predictions.

Main Results:

• Demonstrated sinusoidal output phase shifts separated by ~2π/3 rad, matching theoretical expectations.
• Proposed and analyzed four detection schemes to improve sensitivity.
• Achieved a minimum detectable phase shift of 7.3 mrad using power difference and normalization schemes.
• Obtained a 3x larger dynamic range and suppressed common perturbations.

Conclusions:

• The triple-output MZI shows significant potential for highly sensitive sensing.
• The developed theoretical model accurately predicts device performance.
• The enhanced dynamic range and reduced noise make the device suitable for (bio)chemical sensing.