C. Vazquez et al., 3-DIMENSIONAL METHOD FOR SIMULATION OF MULTIMODE INTERFERENCE COUPLERS, Journal of lightwave technology, 13(11), 1995, pp. 2296-2299
A three-dimensional (3-D) method for modeling multimode interference d
evices based on a finite element formulation is presented as an altern
ative to models having one-dimensional cross-sections only, The method
is tested for couplers with two different strongly confined waveguide
s structures. The results show that full treatment of two-dimensional
cross-section is of special importance for design and simulation of wa
veguide devices for which the effective index approximation is no long
er valid. For deep rib waveguide geometries, excess loss greater than
15 dB can be obtained if the 3-D method is not used in the design of t
he couplers.