Optical frequency comb based system for photonic refractive index sensor interrogation

Area of Science:

• Integrated photonics
• Optical biosensing
• Metrology

Background:

• Integrated photonic biosensors offer label-free detection capabilities.
• Mach-Zehnder interferometers are commonly used in photonic biosensors for refractive index sensing.
• Accurate phase measurement is crucial for sensitive biosensing applications.

Purpose of the Study:

• To demonstrate the enhancement of integrated photonic biosensor functionality using an optical frequency comb.
• To develop a robust phase measurement technique for interferometric biosensors.
• To evaluate the impact of the proposed method on the sensor's limit of detection.

Main Methods:

• Utilized an optical frequency comb to sample the spectral response of a Mach-Zehnder interferometer.
• Arranged optical frequency comb line spacing to sample the interferometer's periodic response at 120° intervals.
• Combined spectral samples to achieve a single, accurate measurement of the interferometer phase.

Main Results:

• Developed a phase measurement approach that is accurate and independent of interferometer bias.
• Demonstrated robustness against intensity fluctuations common to optical frequency comb lines.
• Achieved benefits without degrading the lower limit of detection, measured at 3.70×10^-7 RIU in a silicon photonic refractive index sensor.

Conclusions:

• Optical frequency comb sampling provides an effective method for enhancing integrated photonic biosensor performance.
• The developed phase measurement technique offers high accuracy and robustness for interferometric biosensing.
• This approach maintains excellent sensitivity, making it suitable for demanding refractive index sensing applications.