Optical whispering-gallery mode (WGM) microresonators have proven their ability to enhance light-matter interactionand hence are widely used for sensing. In contrast to the traditional approach of using symmetric adiabatic tapers tocouple light into the resonators, we use an asymmetric non-adiabatically tapered fiber to couple light from two fibermodes into a microresonator. Previously it was shown that dissipative sensing of an absorbing analyte can be moresensitive than dispersive sensing, and that dissipative sensing based on dip depth change can be more sensitive thandissipative sensing based on linewidth change. In this report, we demonstrate an enhancement in sensitivity by threeorders of magnitude for dissipative sensing based on dip depth change. The enhancement factor is independent of thequality factor Q of the WGM and is determined solely by the values of the throughput power in the absence of analytewhen the two fiber modes are in and out of phase at the point where they couple into the WGM.
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