Matching Layers in Bragg Reflection Waveguides for Enhanced Nonlinear Interaction

Bragg reflection waveguides (BRWs) with matching layers placed between the core and claddings are proposed and analyzed as a means of enhancing the effective second-order optical nonlinearity. The addition of matching layers to conventional BRW structures provides extra degrees of freedom, which enable further optimization to enhance the nonlinear conversion efficiency. Pertinent parameters including overlap between modal profiles of the interacting waves, the group velocity mismatch and group velocity dispersion are examined. The structures studied in this work are designed using the GaAs-Al_xGa_1-x As material system. It is shown that, in comparison to phase-matched BRWs with no matching layers, the proposed structure benefits from relaxing the constraint over the phase-matched core thickness. For typical designs, it is shown that the new structure can provide over an order of magnitude enhancement in nonlinear coupling efficiency and 30% decrease in group velocity mismatch. It is also shown that the group velocity dispersion of the first and second harmonics are reduced by 10% and 52%, respectively.