Plasmonics co-integrated with silicon nitride photonics for high-sensitivity interferometric biosensing

Area of Science:

• Photonics
• Plasmonics
• Integrated Optics

Background:

• Mach-Zehnder interferometers (MZI) are sensitive optical sensors.
• Plasmonic waveguides offer unique light-matter interaction for sensing.
• Integrating plasmonic and photonic components presents challenges in loss compensation.

Purpose of the Study:

• To develop a photonic integrated Mach-Zehnder interferometric sensor.
• To utilize a plasmonic stripe waveguide for refractive index sensing.
• To optimize interferometer operation using a photonic variable optical attenuator and phase shifter.

Main Methods:

• Fabrication of a hybrid plasmonic-photonic integrated sensor.
• Utilizing Surface-Plasmon-Polariton (SPP) mode propagation in the sensing arm.
• Employing a variable optical attenuator in the reference arm for loss compensation.
• Characterizing the sensor's response to changes in refractive index.

Main Results:

• Achieved a bulk sensitivity of 1930 nm/RIU.
• Measured an extinction ratio exceeding 35 dB.
• Demonstrated optimized interference through co-integration of plasmonic and photonic waveguides.

Conclusions:

• The co-integration of plasmonic and photonic waveguides in an MZI sensor is functionally beneficial.
• The developed sensor effectively detects refractive index changes.
• The variable optical attenuation is crucial for optimizing MZI performance with plasmonic components.