Enhanced rotation sensing by nonlinear interactions in silicon microresonators.

We analyze the effect of the nonlinear Kerr index of refraction and two-photon absorption (TPA) in a rotating silicon microring resonator coupled to waveguides in an add-drop configuration. The nonlinear index of refraction leads to a bifurcation of the intensities of two counterpropagating modes in the nonrotating state. This bifurcation also significantly enhances the intensity difference between these modes due to the Sagnac-induced frequency splitting of the modes in the rotating resonator. Although silicon resonators have a very large Kerr index, they also suffer from large TPA at telecom wavelengths. It is shown that despite TPA, the Kerr nonlinear enhancement to the rotation sensitivity is still of the order of 10⁴. An analysis of typical detector noise indicates that a detection limit of <1  deg/h in a 1.4 mm radius resonator is achievable.