Analytical time-domain model of partially coherent phase-shift cavity ringdown spectroscopy for sensor design and...

Area of Science:

• Photonics and Spectroscopy
• Optical Sensing Technologies
• Materials Science for Sensors

Background:

• High-quality optical cavities offer high sensitivity for sensing applications.
• Current systems often require expensive, bulky tunable lasers and active frequency tracking.
• Partially coherent phase-shift cavity ringdown spectroscopy (PS-CRDS) offers a simpler, time-domain alternative.

Purpose of the Study:

• To develop a closed-form analytical time-domain model for PS-CRDS that accounts for partial source coherence.
• To enable the use of low-cost, partially coherent sources like laser diodes and LEDs.
• To provide practical design guidelines for integrated PS-CRDS sensors.

Main Methods:

• Developed a new analytical time-domain model for PS-CRDS.
• Explicitly incorporated partial source coherence into the model.
• Quantified the impact of source linewidth, modulation frequency, and cavity parameters on performance metrics.

Main Results:

• Demonstrated robust absorption detection using partially coherent sources with only a modest sensitivity reduction.
• Showed that performance metrics saturate when source linewidth exceeds the cavity free spectral range, indicating wide design tolerance.
• The model accurately predicts phase sensitivity, signal strength, and signal-to-noise ratio (SNR).

Conclusions:

• Partially coherent sources are viable for PS-CRDS, supporting integrated, low-cost sensor designs.
• The developed model provides practical guidelines for optimizing PS-CRDS sensor performance.
• This work facilitates the development of compact silicon photonic microring biosensors.