Polarization independent guided-wave optical modulators and switches

New low-voltage designs for polarization-independent interferometric optical modulators and coupled waveguide switches are described. Operation of these devices is based on TE-TM mode coupling via off-diagonal elements of the electrooptic tensor. Using a coupled mode analysis, it is shown that the refractive index change-length product is the same as for single-polarization modulators and switches which utilize diagonal electrooptic tensor elements. It is estimated that the use of TE-TM coupling can reduce the voltage-length product for polarization independent operation by a factor of 2 in LiNbO3and a factor of 2.9 in LiTaO3.