Comparison of Linear and Nonlinear Regimes in MMI couplers

In this paper, linear and nonlinear characteristics of the multimode interference couplers are investigated. When the intense input field is launched from the access waveguide, the linear modes of multimode waveguide, which are determined by using the planar waveguide theory, can be influenced and therefore Kerr nonlinear effect will be appeared. In fact, by varying the intensity of the input field, the refractive index of the region and therefore the intensity distribution of the light in MMI region will be changed. To determine the guided modes in nonlinear medium, the set of coupled wave equations in this region is analyzed and then is solved by numerical method. In addition, the guided modes in linear model are obtained by EIM method. Coupling and transmission coefficients of MMI coupler for these regimes are obtained and their results are compared. In addition, comparison of wave propagation along the waveguide for these regimes is done and it is shown that there are some differences in their intensity distribution of the field.

Keywords:

MMI Coupler , Self-Imaging , Kerr Nonlinear Effect , Refractive Index