  We investigate scatterer induced mode splitting in a composite microtoroidal
resonator (Q ~ 10^6) fabricated by coating a silica microtoroid (Q ~ 10^7) with
a thin poly(dimethylsiloxane) layer. We show that the two split modes in both
coated and uncoated silica microtoroids respond in the same way to the changes
in the environmental temperature. This provides a self-referencing scheme which
is robust to temperature perturbations. Together with the versatile
functionalities of polymer materials, mode splitting in polymer and polymer
coated microresonators offers an attractive sensing platform that is robust to
thermal noise.
