Ultraprecise Resonance Wavelength Determination for Optofluidic Sensing Applications

We propose an ultraprecise resonance wavelength determination algorithm for optofluidic sensing applications, which can be expected to overcome the defect that the quality factor of the capillary resonator is deteriorated by the severe absorption in water. A parameter proportional to sinusoidal value of electrical field phase shift before and after the interaction with the capillary is constructed to determine the resonance wavelength of the optofluidic capillary. It is numerically demonstrated that this algorithm can narrow the full-width at half-maximum (FWHM) of resonance peak down to ~5% of the FWHM of transmission spectrum, which makes an ultraprecise peak determination feasible. Besides, this algorithm can reduce the FWHM of resonance peak to at least one quarter of FWHM of transmission spectrum in a rather wide region spans from undercoupling to overcoupling, and can be widely used in whisper-gallery mode-based sensor to improve the sensing precision conveniently.