Theory of polarization rotation and conversion in vertically coupled microresonators

Two orthogonally polarized waveguide modes cap exchange power through an in termediate level, if the polarization state of that level is tilted with re spect to the polarization states of the waveguide, Microrings with modest s idewall angles support such tilted modes. Ultracompact, wavelength selectiv e polarization rotators might be achieved. Simple analytic expressions are derived for polarization rotation by vertically-coupled resonators in terms of geometrical factors.