Accurate analysis of multimode interference devices

The accurate analysis of multimode interference devices is demonstrated by using the least-squares boundary residual (LSBR) method. Accurate modal propagation constants and spatial field profiles in the multimode interference (MMI) section can be obtained by using the finite-element method. The accurate calculation of the excited modal coefficients is achieved by using the LSBR, which satisfies the continuity of the transverse field components more rigorously than the simple overlap integrals.