Slow light Mach-Zehnder interferometer as label-free biosensor with scalable sensitivity

Area of Science:

• Photonics
• Biosensing
• Nanotechnology

Background:

• Mach-Zehnder interferometers (MZIs) are widely used in optical sensing.
• Enhancing the sensitivity of MZI-based biosensors is crucial for detecting low concentrations of analytes.
• Photonic crystals offer unique light-manipulating properties.

Purpose of the Study:

• To design, fabricate, and characterize a novel label-free MZI optical biosensor.
• To incorporate a highly dispersive one-dimensional (1D) photonic crystal to enhance sensor sensitivity.
• To demonstrate the sensor's capability for bulk refractive index and nucleic acid detection.

Main Methods:

• Integration of a slow light 1D photonic crystal into one arm of an MZI.
• Numerical simulations to predict sensor sensitivity based on photonic crystal length.
• Experimental fabrication and characterization of the MZI biosensor.
• Performance evaluation using bulk refractive index measurements and nucleic acid detection.

Main Results:

• The sensitivity of the slow light MZI biosensor scales with the length of the photonic crystal region.
• Numerical simulations predicted a sensitivity of 115,000 rad/RIU-cm for a 16 μm slow light region.
• Experimental bulk refractive index detection sensitivity reached 84,000 rad/RIU-cm.
• Successful demonstration of nucleic acid detection using the fabricated biosensor.

Conclusions:

• The developed slow light MZI optical biosensor offers significantly higher sensitivity compared to traditional MZIs.
• The sensor's sensitivity is directly correlated with the length of the incorporated photonic crystal.
• This technology holds promise for advanced label-free biosensing applications, including nucleic acid detection.