Simultaneous Low Nonlinearity and High Power Confinement in Slot Waveguides

The effects of the slot waveguide structure and cladding material on the nonlinearity and the power confinement were systematically investigated by using the full vectorial model of the nonlinear effect and the finite element mode solver of the slot waveguide. The results show that the nonlinearity and the power confinement can be significantly affected by the silicon-arms width, the slot width, the thickness of the silicon layer and the cladding material. For the air-cladding slot waveguides with different structural parameters, the corresponding nonlinear coefficients are all above 20 W-1.m(-1) for the maximal power confinement factors, and the minimal nonlinear coefficients of 6.5 W-1.m(-1) are all obtained near the cut-off mode where the slot waveguides suffer from the leakages to the substrate. The low nonlinearity and the high power confinement can not be realized at the same time for the air-cladding slot waveguide. But the low nonlinearity and the high power confinement can be obtained simultaneously if the silica is coated on the slot waveguide, where the nonlinear coefficient can be as low as 4.12 W-1.m(-1) and the power confinement factor can be as high as 42%.