Research On The Charicteristic Of Polarization Conversion On Slot Waveguide

Slot waveguide is a talented micro-nano device constructing photonic circuits in the future all-optical communication. Because of the high confinement and high intensity, the micro-nano optical devices based on slot waveguide are widely applied in optical nonlinear effect, all-optical switch, optical modulation and optical signal processing. Considering that the slot waveguide is polarization dependent and the demand of polarization diversity, a polarization rotator which rotated polarization modes is highly demanded in the future all-optical communication.In this paper, three kinds of polarization rotator based on slot waveguide are presented. Using the mode evolution theory, the polarization modes rotation in linear polarization rotator is deduced. Nonlinear structure is introduced in the polarization rotator to minimize the size of polarization rotator. Symmetry deflection slots in different layers are induced and constructing cross slot waveguide, which transferring orthogonal polarization modes simultaneously. Micro-ring resonator is induced in polarization rotator, and constructing ultra-compact micro-ring polarization rotator transferring angular modes. A double ring resonator with dislocation is deduced with polarization mode evolution. The FDTD method is used and simulates the polarization modes transferring and rotation in the polarization rotators mentioned above.Firstly, nonlinear slot waveguide polarization rotator is induced. With the mode evolution theory, the linear polarization rotator and imperfect coupling are analyzed. The slow variation theory is used to explain the nonlinear slot polarization rotator increasing the coupling efficiency. Raised cosine function is used as the nonlinear function and optimized to minimize the size of nonlinear polarization rotator.Secondly, on the demand of polarization diversity, cross slot waveguide polarization rotator is designed with high confinement. Double deflected slot is introduced to increase the rotation of the device and further the polarization conversion efficiency. Cross slot waveguide polarization rotator is analyzed using mode evolution theory and optimized on the demand of polarization diversity.Finally, a polarization rotator based on micro-ring resonator is designed. Double ring slot waveguide polarization rotator consists of two vertically stacked micro-rings with dislocation. The coupling of polarized modes in the double rings with dislocation are analyzed to explain the polarization conversion of ring resonator. The resonant mode in micro-ring and the effect of slot waveguide coefficient is analyzed and optimized. Putting the traditional linear polarization rotator in a micro-ring, the angular transmission and conversion of polarized mode minimize the size of polarization rotator, and add wavelength-division multiplexing to the conversion spectrum.