Simultaneous measurement of quality factor and wavelength shift by phase shift microcavity ring down spectroscopy

TL;DR

This paper demonstrates a novel method using phase shift cavity ring down spectroscopy to simultaneously measure the quality factor and wavelength shift in microcavity biosensors, improving detection robustness against laser intensity noise.

Contribution

It introduces the first simultaneous measurement technique of quality factor and wavelength shift in microcavities using phase shift cavity ring down spectroscopy.

Findings

Successful measurement of disassociation curves in biotin-streptavidin reactions

Good agreement with previous results on kinetics

Application of the method in liquid-phase biosensing

Abstract

Optical resonant microcavities with ultra high quality factors are widely used for biosensing. Until now, the primary method of detection has been based upon tracking the resonant wavelength shift as a function of biodetection events. One of the sources of noise in all resonant-wavelength shift measurements is the noise due to intensity fluctuations of the laser source. An alternative approach is to track the change in the quality factor of the optical cavity by using phase shift cavity ring down spectroscopy, a technique which is insensitive to the intensity fluctuations of the laser source. Here, using biotinylated microtoroid resonant cavities, we show simultaneous measurement of the quality factor and the wavelength shift by using phase shift cavity ring down spectroscopy. These measurements were performed for disassociation phase of biotin-streptavidin reaction. We found that the disassociation curves are in good agreement with the previously published results. Hence, we demonstrate not only the application of phase shift cavity ring down spectroscopy to microcavities in the liquid phase but also simultaneous measurement of the quality factor and the wavelength shift for the microcavity biosensors in the application of kinetics measurements.