Coupled optical microcavities: an enhanced refractometric sensing configuration.

We theoretically investigate the application of coupled optical microcavities as refractive index sensors. Coupled microcavities support a very sharp asymmetrical Fano resonance, which gives rise to faster changes in output transmission than the changes from a single cavity. With the output transmission at a fixed wavelength that varies much faster than it does in a single-cavity resonance, the result is enhanced sensitivity of the device to the changes in refractive index. In addition, it is observed that both thermal and optical Kerr effects can be utilized to improve the sensitivity.